Autoclave #3 manual

1.0 Introduction

This document describes the functions and operation of the autoclave hardware and Programmable logic controller (PLC) functions. The purpose and emphasis of this manual is provide the level of detail necessary to operate and maintain the autoclave control system. The level of discussion presupposes that the reader is familiar with the purpose and normal operation of the autoclave, that he/she is familiar with the Process and Control diagrams, and has access to the vender manuals and design documents.

This manual describes the functions of the system from the electro-mechanical process control devices, instrumentation, and operation. The other two major components, commonly known as the "Computer", are the TDC 3000 terminals and communications network, and the HP data collection computer. The TDC provides the operator interface,

custom graphics and the trending and reports that are available from the operator's consoles. The HP computer provides the process recipes, supervisory functions, and calculated part temperature. These functions also include the cure definition, initialization, and the run data report generation for QC.

1.1 HP-TDC-PLC operation

Several functions require all three of the major physical components. An example of the three components working together is the vacuum leak test. It is usually started during initialization by the HP computer, which then transmits the request across the TDC communications network to the PLC, which then performs the valve changes for the test. The PLC reads the vacuum transmitters and provides the data which can be read by either the TDC or the HP Computer. The HP then decides whether the test has passed or failed. This document concentrates on the functions provided by the PLC.

1.2 Functional Description Format

The functional descriptions include a description of the high level function, operator controls and operation, and down to the details of the actual valve and instrument operations (where it is necessary). There is a certain amount of overlap between this section and the chapter with detailed program descriptions. Section ??.?, PLC Program, is used as an adjunct to the documentation capabilities of the Honeywell Ms-Dos Loader package. The line comments in the program will often refer to the section in this document where additional information can be found.

1.3 Reference Designations

References to the physical components, such as valves and gauges, are made with the standardized reference designations that are detailed on page 1 of the Process and Control (P&Cs) diagrams. The three digit tag number is consistent through the documentation package. This number may be followed through the wiring diagrams to the PLC modules. One part of the wire number is the field device and the other part is the terminal strip or module that it connects to. The thermocouples and analog outputs (from the PLC's viewpoint) connect directly to the modules. All other field devices connect to the back panel terminal strips.

1.4 TDC and PLC Tags

The hardware tag numbers are carried through the PLC to the TDC with minor modifications. The hardware pressure transmitters are "PT"s, while the TDC calls them "PI"s. Thermocouples are temperature elements in hardware and "TI"s on the consoles. The leading number on the TDC Tag is not shown on the P&Cs since these drawings are specific to the Autoclave.

The switches in the TDC are called "Hand Indicating Switch". The Tag name is built from the prefatory autoclave number, "HIS", and the most relevant item tag number. For example, the Blowdown Switch, which locks the 4 inch vent valve open, is named "3HIS302". The switches on the TDC may be mapped to one or two points in the PLC. The TDC designation, "OP%" is the output from the TDC to the PLC. In the case of a switch it is a contact in the PLC program. The TDC designation "PV" is the input to the TDC from the PLC. The PLC program will set the on/off state of this element with a coil. In the case where the PV and OP% have the same PLC address, it is generally only a PLC contact. (Note that this differs from the operator interface switches in the #6 Modicon. Refer to the PLC Programming notes in the appendix for more details.)Tags, PLC vs. TDC

1.5 PID Loop Tags

An array of ten addresses per PID loop have been allocated for interface to the TDC. Six of the ten are configured as points on the highway. The PV (PICxxx), OP (aka Process Demand), and SP are analog inputs. These are read only points that yield a scaled indication on the TDC. The three tuning constants are counters, which simply pass the non negative, 16 bit, integer number. Since counters can not pass a decimal point, the tuning constants values are entered times one hundred, IE. a gain of 1 is entered as 100. The PID loops are written by Bill Ware of Honeywell in ladder logic. They have additional tables of variables used in the calculations. The most significant items are the SP (written to) and the PV, which are in engineering units times 10, such as PSI, Degrees F. and In Hg.

1.6 Control Point Tables Format

The start of each functional description includes a list of the major control points that are related to the operation of the function, and are configured on the highway. Each point includes the TDC Tag name, which may be one or two PLC tags, the PLC address, and a description of the function. The list may have points in common with other functions. A detailed description of the points as they relate to the function or internal programming is given in the text.

1.7 PID Control Addressing

1.7.1 PID Loop Tags vs. Loop number

The PID routine is written in ladder logic. It uses several tables of values that are accessed by indirect address operations. The actual datum address is determined by the beginning address of the particular table plus the loop number. The correlation is:

LOOP #      LOOP TAG    FUNCTION
1     3PIC300     Autoclave Pressure
2     3TIC500     Part temperature
3     3TIC540     Air temperature
4     3FIC600     Circulation Blower Horsepower
            control
5     3PIC450     Header 1 (West) vacuum
6     3PIC460     Header 2 (East) vacuum
7     3PIC440     (AWACS) Back pressure

1.7.2 TDC Interface Tables

The formatted data items on the TDC screens are usually done with the point type Analog Input, (AI). This allows the display to have a decimal point and/or a negative sign. Since the PLC uses integer arithmetic (without a decimal point) and the TDC Highway can not pass a negative number, this point type allows the transfer of real numbers. This point type expects the register value to be in the range of 0 to 4095 counts. The configured TDC low and high end engineering units are obtained from the point detail display, second page. The TDC configured parameters for each loop are in a group of 10 successive registers. The effective address is calculated as 10 times the loop number plus the starting address. The table below gives this correllation. The Point Type "XX" means that this point is not configured on the Highway.

HIGHWAY INTERFACE TAGS
Parameter Point Type Start Addr.

PV in Engn. Units (read only)       XX    6141
Process demand (Output)       AO    6142
SP in Engn. Units (PLC writes)            XX    6143
K Proportional gain .01 - 99.9            C     6144
T1 Integral gain Min/Repeat         C     6145
T2 Deriv. gain (rate) Minutes       C     6146
Low end PLC engn units        XX    6147
High end PLC engn units       XX    6148
A/D input bias (4 mA offset)        XX    6149
SP in 0-4K counts read only         AI    6150
T3 Tuning, rate decay time          C     6620

The low and high end Engineering Units values in this table is used only within the PLC. The TDC and the HP maintain their own copies of these values. Also, the smart transmitters are generally set up with these same scaling values.

1.7.3 PLC PID Parameter Tables

The TDC interface tables are written to and from another set of tables. These are not configured on the TDC Highway. They are accessed with indirect address registers. The effective address is calculated as Loop Number plus Starting Table Address. These items and two coils are given below.

PID TABLES
Parameter Starting Address

Output (Process Demand)       5970
A/D raw analog input          5520
PV in engn units (X 10)       6020
MCC Manual Control Command (PD in Man.)   5190
Scan flag         1900
Auto (On) / Manual Mode flag        1650
Proportional term (K X error)       5920
Integral term           5720
Derivitive term (Rate action)       5570

The last three values are useful for watching the effects of the tuning constants. Refer to volume 1 of the Honeywell 626-1202 Manual for an explanation of how all of this works.

1.8 PLC & TDC Data Tables

The three methods of getting analog information into the PLC (and to HP and TDC) from real I/O are Thermocouple Modules, Analog Input Modules, and the Novatech RTU. The highway can not access any of these devices directly, so the PLC "Pulls" the data, massages the values, and puts them into tables. The starting address of these tables are given as a guide to where they are located in the tag listings. These addresses can be "Searched" for in the PLC program to find rungs that show the table.

Start of Operator switches and indicators       1000
Open current loop status                  1101
PID Deviation alarms                1200
Vacuum valves, source select              1401
Solvent extraction valves select                1451
Deviation alarms limits (Engn. X 10)            4111
Cure specification (downloaded)                 4201
Cure specs, same table, used by PLC in run            4701
Analog Inputs, (rescaled 0 to 4095)       4330
RTU data table (0 to 4095)                4350
Thermocouple inputs                 4400
Thermoucouple channel open status         4501
RTU channel status (register values)            7950
RTU channel status (coils)                1550
Search for 1566 and 1582
RTU channel ignore bad channel registes         5101

1.9 Contacts

These venders and representatives have been involved in the Autoclave Modernization Project. They can provide technical and/or repair information.

Honeywell:

Mike Keser, PLC expert, sales representative, and a helpful soul.
He does not handle this area any more, but can frequently answer technical questions off the top of his head. (503) 526-5113.

Repairs of PLC hardware, L.A. (800) 423-3704 Give them a P.O. number for repairs and priority orders for replacement.

Repairs and parts for Smart Transmitters and other Honeywell products: (800) 223-8947.

Mark Michaels, TDC equipment sales representative and service. Bellevue: 453-7559. His voice message box is 559. (He has the telephone number for Service Dispatch) Steve Buck is the TDC Technical service representative for this area.

Honeywell ICD, PLC headquarters in York Pa. (717) 848-1151 The next four people can be reached with this number. The accuracy of the information from some of the people at this office leaves room for improvement.

Bill Ware, PID routines author and most knowledgeable person in the PLC (IPC) division at York, Penn.

Scott Young, MiniCop Basic Program author and general PLC information. Contact at York, Penn. Ask for Marketing.

Tom Deller, Technical Services, York, Penn. PLC classes and documentation.

Les Furguson, Mgr. of MS-DOS Loader/Terminal software. Feel free to call him at any hour of the day or night if you encounter problems with the Loader software.

TDC Technical Support, Consultation fees paid through July 1989. Daytime, Az. hours. (800) TAC-PMSD Tell them the System Number is "HWJ".

Bud Gaynot (215)641-3402, Dick Lucas (X3405) Engineers for smart transmitters at Ft. Worth, Penn. They are very interested the quality of the smart transmitters. They will want a Detailed description of problems and/or failures of any Smart Transmitters.

Worcester "Wooster" and SVF Motor Operated Valves:
Industrial Valve and Fitting Co. 922-3175

AUSCO Valves:
Automatic Switch Co, Bellevue 454-6167
Larry Blane, George Ross, Jack Mosteller

Fischer Valves and Flow Sensors:
PCE Pacific Co. of Bellevue, 823-2112
Tom Fritsler is very knowledgeable about all of the green valves. Get the Serial Number off of the valve, along with the other ratings on the plate before calling him. (They keep records of all valves by serial number.)

ISI, Woodinville, HP software:
481-6325 Contacts: Ken Roberts, Michael Robbins. Normally coordinate these calls through Rob Stitt in Facilities Engineering, X1-3427

Novatech, RTU manufacturer. Information contact: Arlen Nipper , Bob Sardou (913) 491-3248 Office hours in Kansas City, 8 am. to 5 pm.
Honeywell sold their equipment as an "Off the Shelf" item, but has not done very well with support and/or information. Novatech is a small company which will be much more helpfull than York, Pa.

Thermoflux, heating system manufacturer on AC #3 and AC #5. Bob Moon,(918) 747-9394

2.0 Functional Descriptions;

.2.1 Pressurization System

2.1.1 Pressure Control PointsPressure Control Points

3HIS300     Backup pressure control
3PC300S     Setpoint for backup pressure
3HIS302     Open and lock blowdown valve
3HIS320     Close and lock N2 gas blocking valve
3HIS310     Air/Gas select
3PIC300     Pressure PV in use by PID controller
3PC300SP    Read only Set Point
3PC300OP    Read only Process demand
3PI301      Pressure gauge #1
3PI302      Pressure gauge #2
3HIS301     Select pressure gauge #2
3QAD301     Pressure gauges differ by > 2%

2.1.2 Pressure System Overview

The autoclave may be pressurized with either plant air or with nitrogen. The plant air pressure is regulated down to about 100 to 110 PSI. The nitrogen source is directly off the accumulators, so that this pressure can vary from a low of 160 PSI to a high of 365 PSI. The control valves for filling the autoclave are located at the south east corner of the chamber. The 1 inch and the 4 inch vent control valves are located on top. The autoclave has two safety relief valves that will open at about 225, depending on temperature, and a rupture disk that is currently 225 PSI at 350 degrees. A high pressure limit switch is located by the door controls. It will shut down the fill valves and open the vents until the pressure returns below the limit, which is a drop of about 25 PSI. Under fault conditions of a stuck open fill valve, it will cycle on and off; this will be a noticeably dramatic event.

2.1.2 Pressure System Operation

The pressure system is automatically controlled during a normal run by the cure specifications. Operator intervention is only necessary to handle exceptional circumstances, but even Backup will not allow pressure in the autoclave if the equipment and controls are not ready. Equipment Ready and Operator Controls Ready are necessary to start a run.

means that the door is closed and locked, there is no Man-In-Autoclave alarm, nor is the Emergency Stop button pushed in. The Ping Pong Valve closed status is part of the Operator Controls Ready indicator. The manual section entitled "Startup" lists the complete definition of these indicators.

Initialization on the HP Computer will set the autoclave to use nitrogen. Closing the door will turn on the automatic purge switch. The start-up screen also contains the Auto Switch To Air on Cooldown switch. It should be left on. Ocassionally, these controls will end up set incorrectly. The Equipment Status screen will tell you what is preventing startup.

2.1.3 Pressure Startup

The normal cycle starts with pressurization to the Vent Bags Pressure. The pressure ramp is put on hold until the bags are actually vented. If the bags do not vent for some reason, then pressure will not continue. This hold can not be turned off by the operator. The Post Pressurization Leak Test, abbreviated PPLT, is ocassionally used after pressure is applied, but before the bags vent. The system turns on Operator Hold when this specified pressure (setpoint) is reached. The operator is expected to initiate the test and to turn off the hold after it is complete.

2.1.4 Pressure Holds and Restarts

The hold on the temperature system is generally released when the pressure is at the first (and usually only) soak pressure. If the pressure does not come up to this setpoint, then the temperature hold may not be released. The temperature hold release may be specified in the cure to release at a number of minutes into any pressure segment. If the temperature hold does not release as expected, check the cure specification pages. Pressure may be held by temperature and released when either the Part Temperature reaches the specification, or at a number of minutes into a temperature segment. Since pressure can hold and release temperature, and temperature can hold and release pressure, it is possible to devise a cure specification that will lock up. No parts use this lockup cure at present, but the option exists if it becomes necessary.

Most cures call for continuous pressure over the entire cycle, but more than one pressure ramp and soak level may be specified. The run moniter shows the presure segment number and the soak time remaining. These segments and times are what is specified on the Cure screens. Odd segments are ramps and Even segments are soaks.

2.1.5 Auto Switch to Air

The Auto Switch To Air on Cooldown function uses the cure specification to select Air during the last cooldown ramp. The pressure in the autoclave must be below 100 PSI, and the Part Temperature must be below 280 degrees. The switch to air is accompanied by the sound of the nitrogen blocking valve closing. This event also initiates the Purge function. Refer to the Purge discussion below.

2.1.6 Blowdown and Blocking Valves

The Blowdown can occur for several reasons. The normal blowdown occurs when the last temperature soak at room temperature is completed. The pressure soak timer may also time out, although this is rarely used. The Emergency Stop Button will blowdown, but Man-In-Autoclave will not. Unintentional intervention may also cause blowdown and/or termination of the cure cycle. That is the right autoclave that you have up on the screen, isn't it? Turning off the power to the PLC will cause termination of the run, as will putting it into Program Mode.

The Blowdown Switch and the Nitrogen Blocking Valve Switch on the Startup Screen are there for emergency use. Normally, they need not be touched. The Blowdown switch will over ride the automatic functions and open the vents and close the fill valves. The Nitrogen Blocking valve will close this valve and keep it closed. Before starting a run, the Blowdown Switch indicater will say "BLOW", and the output will say "CLOSE". The indicator will change to "CLOSE" once the run is started. The blocking valve output will indicate "OPEN" and the indicator will say "CLOSED" before the run. At the start of the run, the indicator will change to "OPEN" if nitrogen has been selected. Stated simply, you can force the blowdown valve open but you can not force it closed. You can force the Nitrogen Blocking Valve closed, but you can not force it open.

Pressure Backup will not allow pressure if the equipment and controls are not correct. It is used primarily for testing, but it is necessary to put pressure and temperature into backup if the run gets trashed by a power bump, ESTOP, or other operational anomolies.

2.1.7 Pressure Gauges

Two Pressure gauges are provided for controlling autoclave pressure. The alarm 3QAD301 indicates that these two transmitters read differently by more than 2%. If you get this alarm, look at the two readings on the Bypass screen. A failure of the gauge being used to control pressure will cause one of two events: either full pressurization or complete venting. The switch that selects which gauge to use is also on this screen, it is 3HIS301. These gauges are operated in analog mode and do not go through the RTU. This means that the readings will go seriously amuck if someone connects the Smart Field Communicator, (SFC) to the gauge. If this occurs during a run, switch to the other gauge and go discuss family lineage with them.

2.1.8 Nitrogen Blocking Valve

An open/close blocking valve is provided in addition to the nitrogen control valve. Valves EV323 (blocking) and PCV321 (control) are in series and have a vent valve, EV322 in the line between them. The blocking valve will open only when nitrogen has been selected, the door is closed and locked, and neither Man-In-Autoclave or ESTOP are in alarm. Since the autoclave will sit for extended periods in this condition, a setpoint of more than 0.4 psi must be selected. This will prevent unintentional leakage of nitrogen into the autoclave while a load is being initialized and checked. A noticeable delay before the blocking valve opens is partially due to the time it takes to close the vent valve. This is a motor operated valve of the type discussed below. A failure of this valve, or of the Open status switch in it will prevent the Safe To Open indication, and hence the door open functions from operating.

2.1.9 Pressure Valves Adjustment

Adjustment and maintenance of these valves is relatively simple. As with all the pneumatic valves on the autoclave, the I/P adjustment is for closed at 4 mA. and open at 20 mA. An additional tweaking may be necessary. The air fill valve must be guaranteed off at 4 mA. This means that it will not start to open until about 5 mA. Listen to it. The nitrogen fill valve is not as critical since it has the blocking valve in series. It should start to open at 4.5 to 5 mA. The blocking valve has no adjustments. The two vent valves are located on top of the autoclave. The one inch vent valve, PCV301, is the main trim valve. It starts to open at a process demand of less than 50%. The TDC point is 3PC300OP. It will open completely at a non critical PD of about 30%. The 4 inch vent will start to open at this percentage and will be fully open at 0%. The overlap of these two valves is not critical.

2.1.10 Pressure Trouble

OVER PRESSURE Startup screen, Close the Blocking Valve, 3HIS320.
Open the Blowdown valve, 3HIS302.
ESTOP Button blows down and terminates the run
At the autoclave, turn off the control air for the control valves. The control air valve on the blocking valve will NOT close it.

Rupture disk blown
Close the blocking valve and switch to nitrogen. The inlet pipe has a check valve that will hold AC pressure for a few minutes.

Won't start run:
Check Equipment Ready and Operator Controls Ready. The Blocking Valve Switch (OP is CLOSED), and the Blowdown Switch (OP is OPEN) will prevent pressurization.

Cycle Run but no Pressure:
Look at the Run Monitor Screen. Is the pressure loop at 100% or at 0%? 100% means that the controls are trying to pressurize; some valve is probably closed off. 0% is usually caused by something wrong being detected by the control system, or possibly a pressure transmitter reading full scale. What is the AC pressure? Do the two transmitters agree? Try the other pressure transmitter. If the controlling transmitter is stuck at zero, then full pressure will be put into the autoclave. If the transmitter is stuck above the current pressure, then the autoclave will vent.
PS Be sure to control pressure with the other transmitter any time you use the Smart Field Communicator (SFC) on the pressure transmitters. Better still, don't do it in a Run and set the Blowdown Switch to BLOW.

2.2 Purge Autoclave Atmosphere

2.2.1 Purge Control Points

PLC Inputs:
3HIS313P    Auto Purge to Air       1830
~~3HIS320P                Manual Purge           deleted     1831~~
3HIS310     AIR/GAS fill            1001
3HIS313     Auto Sw to Air on Cooldown          1123
3FC302      Purge rate in % of valve opening

Status:
3QI302      Purge cycle is operating            1030
3QI302A     Purge cycle is complete       1031
3AI302      Percent oxygen in AC 0-25%          4330
3QI302      Oxygen reading is valid             1009
3QI300A     Ready to Open Door            1006

2.2.2 Purge Operation

The purge functions are provided as a safety precaution to exchange the nitrogen atmosphere inside the autoclave for a more normal mixture of oxygen and nitrogen. Normal atmosphere contains about 21 % oxygen; unconsciousness will result at 10 to 12 % oxygen. The system is not foolproof. The Purge-To-Air switch is normally on. It will switch on when the door is closed and locked. The purge cycle may be started or stopped anytime that the door is locked and air is selected by changing the switch 3HIS313P.Oxygen Analyzer, Flow

The purge cycle will bring the oxygen back to 19.5%, but caution should be exercised when relying on the oxygen analyzer reading. The analyzer requires low pressure in the autoclave to get the air flow through the instrument. Normal operation of the purge system will provide a valid measurement, however the blowdown switch, ESTOP, high pressure in the autoclave or turning 3HIS313P off will terminate purge cycle. Electrical, mechanical, and operator failures can give false readings. The oxygen percentage indication will read zero unless the valid status indicator is on. Automatic Purge to air function is enabled when the switch 3HIS313P is on. It is normally initiated when the autoclave is switched to air. The auto switch to air on cool down, 3HIS313, is normally left on, which will initiate the purge cycle at the correct time and temperature. This will select air when the temperature, pressure, and cool down ramp allow plant air. Note that after initialization, the Air/Nitrogen switch, 3HIS310, will automatically switch to nitrogen.

IF THE AUTOCLAVE IS NOT SWITCHED TO AIR, THEN IT WILL NOT PURGE.
A purge cycle may be terminated by turning 3HIS313P off. It may be started by turning this switch on. If this switch is left off when the door is locked, then it will automatically turn on and a purge cycle will take place if air is currently selected.

2.2.3 Purge, Add Air

The normal purge cycle starts when the autoclave gets switched to Air during cool down. The vent valve will open slightly and allow plant air to replace the nitrogen while the autoclave is pressurized, because the pressure is still being controlled to the setpoint. Purge Cycle Operating, 3QI302, comes on. The pressure setpoint will go to zero at the end of the run. When the pressure reaches 1 1/2 psi, the 4 inch vent is constricted and plant air is turned on. The oxygen analyzer air sample line is then opened. In two minutes, the status 3QI302, Oxygen Reading is Valid, will come on, indicating that the purge-fill-sample state has existed for enough time to obtain a valid reading. When the oxygen level reaches 19.5%, the status 3QI302A, Purge Cycle Complete, will be turned on and the air venting will stop. The Ready to open door indication on the TDC will come on only after a completed purge cycle. The Safe-To-Open-Door indicator light, on the door controls, means ONLY that the pressure is out of the AC. It does NOT indicate anything about the atmosphere inside. The indication O₂ Reading is Valid and the Purge Cycle Complete will be reset to off once the door is opened.

2.2.4 Manual Purge to Air or Gas

This function has been removed for safety reasons.

2.2.5 Purge Caution

Caution should be exercised when using and interpreting the indications. The oxygen analyzer does not give a continual valid indication. Note that the Auto Purge to Air will initiate a purge cycle when the pressure source is switched to air, but nothing prevents the operator from switching back to nitrogen and stopping the cycle. This event may also occur when the PLC stops processing for a moment.

A serious hazard exists if this system is not functioning properly. It is depended upon when the Stop Before Precure is used. The operator will generally climb in the autoclave to check and fix bag leaks. The temptation is to rush the process, and purging takes additional time. Failures of the system have been noted that can aggravate the situation. The flow regulator on the sensor has been plugged with the floating ball, the valve, the fuel cell has died and then adjusted for atmospheric percentage. Both these failure modes can lead to low oxygen content.

2.3 Man in Autoclave

Details in this section to be supplied.

2.3.1 Man In Autoclave Emergency Switch

Autoclave;

1.    DO NOT BLOW DOWN   DO NOT HIT ESTOP
2.    Call EMERGENCY 1-2222 AND GIVE THEM THIS INFORMATION:
            MAN TRAPPED IN AUTOCLAVE
            LOCATION: AUTOCLAVE # 3 BUILDING 17-05   COLUMN J-16
            NEAREST OUTSIDE DOOR: # 15
            AUTOCLAVE PRESSURE: ??? PSI--ATMOSPHERE: AIR or N2
            AMOUNT OF TIME TRAPPED UNDER PRESSURE
3.    FOLLOW INSTRUCTIONS

2.3.2 MAN IN AUTOCLAVE ALARM WILL DO THIS

The alarm will automatically switch to Local temperature control, setpoint 70 deg F. [3his501], TEMP: [3tic540], SP: [3tic540s]
Pressure is set to local and current Autoclave pressure is the setpoint [3his300], PV: [3pic300], SP: [3pic300s]
Switch to air if press is less than Plant Air Pressure [3his310]
Purge to air is initiated when enabled and Air is switched on. This will dilute the nitrogen atmosphere. Note that the oxygen analyzer reading is not valid while under pressure. [3his320p]
Purge Rate: [3fc300] O2%: [3ai304] [3qi304] Blowdown switch will terminate purge. [3his302]
NOTE THAT THE PURGE FUNCTION WILL DELAY THE DOOR OPENING BECAUSE AIR IS BEING ADDED TO THE AUTOCLAVE. THE BLOWDOWN SWITCH AND ESTOP BUTTON WILL TERMINATE THE PURGE FUNCTION.

2.3.3 Hyperbaric Unit

The local decompression chamber is located at the Virginia Mason Hospital at 925 Seneca Street, Seattle 98101. This is located one block to the north of the Emergency Room. The head of the unit is Dr. Zell. The 24 hour consultation line is 583-6543; the Emergency Room number is 583-6433.

2.4 EMERGENCY STOP PUSHBUTTON

2.4.1 ESTOP WILL DO

1.    Combustion and Circulation blowers will turn off
2.    Blowdown valve will open and zero pressure setpoints
3.    Terminate cure cycle
4.    Close liquid nitrogen MOVs and Pneumatic Control Valves
5.    Vent bags

2.4.2 ESTOP Differences

Emergency Stop behaves differently in Autoclave #3 in that it does not put on full cooling. The Emergency Stop switch is pushed in to open the contacts for an alarm condition. The first line of logic in the PLC program reads the switch and sets coil 525, "NESTOP" when out of alarm. This line may be reached rapidly with the CTRL HOME keys combination and forced off for an alarm. Note that forcing this coil or switch off will cause an alarm in the entire program, but forcing 525 off in any other line will affect only that line.

2.4.3 ESTOP Details

The combustion and circulation motors are turned off with this alarm. The motor starter is turned off, (Provided the MCC control switch is in the AUTO position). When the starter's "M" contact drops out, and since the starting failure timer has timed out, the TDC motor run switches, 3HIS600 & 3HIS601 are then turned off. This prevents the motors from immediately starting when ESTOP is reset. (Refer to the line with coil 86, the timer in the following line and the reset in the next.) The autoclave is blown down by closing air and nitrogen valves, and opening both vent valves 100%. This occurs at the lines that push the analog values to the 4-20 mA drivers. Refer to coil 531 for the Gas Blocking Valve details, 3EV323. NESTOP is in both this line, and the line of logic that operates the solenoid for the Gas Blocking Valve. This will immediately close the blocking valve, regardless of the state of the (3EV322) vent line. Refer to the P & C diagrams, page 3.

2.4.4 PLC NESTOP

NESTOP shows up in several places in the Ramp-Soak generator logic. It will set the pressure demand counter to zero, zero the manual setpoint, and terminate the Cure Cycle. This prevents pressure from coming back on after the button is reset. The automatic purge cycle is cancelled. This occurs because the purge requires that the large vent valve be restricted in order to obtain the 1 psi pressure necessary to operate the oxygen analyzer. The heating & cooling system has the low and high level NESTOP redundancy built into it. The temperature Ramp-Soak cycle is terminated, which puts the control loops into Setpoint Tracking, where SP is set to the PV. The natural gas and liquid nitrogen valves pneumatic are both closed. Note that unlike Autocalve #2, full cooling is Not turned on. The two liquid nitrogen source valves, 3EV570 and 3EV571, are both closed. If they are in the process of changing, they will complete the change, timeout, and then the open one will close and prevent any further movement. Cooling after an ESTOP has been cleared will require the Circulation Blower to be restarted and the temperature controls put into backup.

2.4.5 ESTOP Thermoflux

The Thermoflux enable signal is the discrete output for the Combustion Blower. It has an NESTOP in it to shut down the heating system in case the combustion blower has been put into local "Hand" on position, or if the starter contactor gets stuck.

2.5 Temperature Control

Temperature control is the most complicated function in the system. The automation systems will make substantial allowances for normal variation and abnormal events, however, judgement by the operator is required. Operator intervention can entail enabling and disabling thermocouples on the HP Computer, adjusting the setpoint bias, or the extreme case of running the autoclave in backup. Such an extreme situation as is rarely necessary. In fact, once the cycle is started, the PLC at the autoclave will finish a run even if it is completely disconnected from the control room and computer. In this section, the major components and how they interact are described, followed by the operator controls and when and how they are used. Failure modes and how to manage them are described, and finally the technical details of the heating and cooling system.

2.5.2 Block diagram

PART Ö‑‑‑‑‑‑‑‑‑Ì AIR Ö‑‑‑‑‑‑‑‑‑Ì     Ö‑‑‑‑‑‑‑‑‑Ì     Ö‑‑‑‑‑‑‑‑‑Ì
   SP >° 3PIC500 ° SP ° 3PIC540 °     ° HEATING ° AIR ° PARTS °
       °         û‑‑‑‑>À         û‑‑‑‑>À   &     ° TMP °   IN    °
       ° PART   °     °   AIR   °     ° COOLING û‑‑Ú‑>À   AC    °
   Ö‑‑>À CONTROL ° Ö‑>é CONTROL °     ° SYSTEMS ° ° °         °
   °   Û‑‑‑‑‑‑‑‑‑ì ° Û‑‑‑‑‑‑‑‑‑ì     Û‑‑‑‑‑‑‑‑‑ì ° Û‑é‑‑‑‑‑é‑ì
   °   Ö‑‑‑‑‑‑‑‑‑Ì Û‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑ì    °.....°
   °   ° 3TYC500 °                                       °     °
   Û‑<‑À   HP    û<‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑Ù‑‑‑‑‑ì
       ° PART   °                                   THERMOCOUPLES
       ° TEMP   °
       Û‑‑‑‑‑‑‑‑‑ì
       COMPUTER GENERATED
       FEEDBACK

2.5.3 Part and Air Temperature Control Loops

This diagram is a simplifed version of the Logic Diagrams for this system. This does not show any of the controls or configurations that are possible. This is how temperature control normally works.

The upper left box is the Part Temperature Control Loop. The setpoint is generated within the PLC by the Ramp/Soak Generator. It may be entered directly by the operator in "Backup". The other input, on the lower left, is the Part Temperature Feedback. This value normally comes from the HP Computer. The output of this loop becomes the Air Temperature Setpoint. This is called "Cascade" Loops. The Part Loop has very "Slow Tuning", because it takes a long time for the heat to "Soak" into the parts. The Air Loop tuning is relatively "Fast Tuning". It does not take very long to change the temperature of the air. These two loops normally work together to generate the "Process Demand" for the heating and cooling hardware. This is the "Output" of the Air Loop, where above 50% is calling for additional heat, and below 50% is cooling.

2.5.4 Outputs to heating and cooling

Four control valves configure the Thermoflux unti for either heating or cooling. Two of these valves are the 18 inch butterfly valves that direct the circulation air through either the heating chamber or the cooling heat exchanger. The natural gas valve controls the amount of heating and the liquid nitrogen valve controls the cooling. The details are discussed later in this section. The output of the Air temperature control loop is always connected to the heating and cooling valves. The inputs to the Air Loop can be changed.

2.5.6 Temperature feedback, HP and/or PLC

Feedback from the process is what makes for a Closed Loop control system. The measurement of the process is fed back into the control loop. If it is too low, the output of the loop will call for more heat (or less cooling) until the SP and PV are equal. If the PV is greater than the SP, then the output will decrease (less heat or more cooling). Notice that this is exactly opposit of what adjusting the set point does. The PV for the Part Loop may be selected from two sources, either the (normal) HP Computer generated Part Temperature, or Autoclave Air temperature. These two values will generally differ by several degrees. This means that the heating and cooling will get bumped when the feedback is changed. The HP generated feedback is usually either "High TC wire less 10 Degrees", or the "Average" of the enabled thermocouples. The former is the feedback during a Ramp Segemnt, and the latter is the feedback while in a soak. When a wire is disabled on the HP screen, its value is not used in the temperature calculation. This is why disabling a hot wire will decrease the feedback temperature and cause more heating to come on. (Except during a ramp where the affected TC is not the Highest controlling TC).

2.5.7 Parts and thermocouples

The HP Computer does several things with the thermocouple data. The displays and reports generated are the subject of another book, so this discussion is limited to the effects of the "Part Temperature Feedback" on the operation of the PLC based control structure. The HP feedback allows better control of the parts' temperature than does simple Air temperature feedback. The dirty things that thermocouples will do can be managed by enabling and disabling TC. When a TC is loose or is on a very light part, it will follow the air temperature. This will give too high a reading and can be ignored by disabling it. Thermocouples that become "Open" or become by wandering around will also be disabled. If all of the part thermocouples are disabled, then the HP will provide air temperature for the part temperature feedback. During the beginning of a soak, the heavy parts will not be as hot as the light parts. This will decrease the average temperature and cause more heat to be applied, which can make the light parts exceed their maximum temperature specification. In this case, the feedback can be increased by disabling the "Slow" wire, or by enabling a hot wire. Either way will increase the feedback and reduce the amount of heating.

2.5.8 Setpoint Bias and Feedback control

The other method of adjusting the autoclave temperature is with the Setpoint Bias Control. This is a number of degrees that is added to or subtracted from the Part Temperature Setpoint. The primary difference between this method and enable/disable TCs is that the bias is used when most or all of the parts need to be adjusted, while the individual TCs are used to achieve a compromise between different sized parts.

2.5.9 Modes of Operation

The normal mode of operation is as shown in the above block diagram The setpoint for the part loop comes from the Ramp Soak Generator, "Computer", the PV comes from the HP Computer, "Part". The output from the Part Loop creates the setpoint for the Air Loop, and its feedback is from the usual thermocouple. Here are the options:

Part Temperatue Setpoint:
COMPUTER                From the ramp soak generator in PLC
LOCAL                   Operator provides setpoint
COMPUTER + BIAS         Value added or subtracted to SP
LOCAL + BIAS            Bias has no effect

Part Temperature Feedback:
COMPUTER                HP provides feedback, TCs can be
                        enabled or disabled. There are
                        differences between ramps and soaks.
AIR                     Directly off air temperature,
                        requires more operator use of Bias.
3HSTYC5A OVERRIDE Tells HP to use Air temperature for
                        feedback when it would normally not.
3HSTYC5B OVERRIDE Tells HP to use Part Temp. feedback
                        when it would normally not.
                        (The last two require a password)

Air Temperature Setpoint:
CASCADE           SP derived from Part Loop output
LOCAL             SP entered by Operator. This setting
                  allows the most direct control over
                  air temperature.
3HIS500S          Ramp Soak Generator Setpoint is sent
                  directly to Air Temp Setpoint. This
                  bypasses the Part Loop and the HP.

Air Temperature Feedback:
3TI551 Normal TC to use
3TI552 Alternate Air Temp TC

2.5.10 Computer Shed

The HP Computer sets a switch in the PLC to ON about every 6 seconds. The PLC resets a watch dog timer and clears the switch. If the Keep Alive Bit is not set back on in 33 seconds, the timer turns on "Computer Shedded". This alarm will switch the Part Temperature feedback to Air temperature. (The other condition where the HP does not provide feedback is when it is not in a run. That is why the Bypass Screen indicates "AIR" for the Part Feedback before the run starts.) The other event that will occur with the computer shedded is a hold will be put on in the last cool down soak segment. This is so that the pressure will stay until the parts are cool enough and the operator releases the hold.

The operator must put on the hold at the start of a soak segment when the computer does not do it. The computer normally turns the hold on until the enabled TC wires are within the cure specification. Since the HP also maintains the TC to Part correllation and produces the QC reports, these functions can not be provided. Refer the section "Running the AC without the Computer" for the methodology.

2.5.11 Trouble

This section will assist in isolating the trouble to the general part of the system. The details of trouble shooting the Thermoflux system are in the following sections. Trouble with the HP system is covered in other documents. This paragraph is intended as a general guide to problem solving and not as a comprehensive trouble shooting flow chart.

Refer to the simple block diagram 9 paragraphs back for this discussion. The first order of business is to observe the data presented by the Run Moniter and to look for what is normal and abnormal. If the temperature is seriously wrong, then consider putting the Air Loop in local and adjusting the setpoint. If you give a local setpoint that is about the same as the PV, then the output will go to 50%, which is calling for neither heating or cooling.

The PVs to the Part and Air loops are frequently a source of problems. If an Air thermocouple goes open, then it will read 1100 degrees and put on full cooling. A local setpoint will not cure this problem, but, there are two air TCs to choose from. Compare the two thermocouple readings and use the one that looks more normal. Hint: A third TC in the autoclave has a digital readout inside the PLC cabinet. Choose which one agrees with it.

The Part Loop PV comes from either the HP or from Air temperature. The HP can be shedded, rebooted, or fouled up in a number of ways. Once upon a time, it got a power bump and thought that the run was over, so it stopped calculating Part temperature. Since the PV stayed low, the control system put on full heating in an attempt to bring it up. In this case, simply switch to air feedback and use the setpoint bias and hold controls to finish the run without the computer. Beware of perfectly stable readings, the world does not work that way.

The Emergency Stop Button will cancel the run. If it is still possible to save after the butten is reset, then it will have to be done without the computer. The Startup Screen has the switches "Computer Bypass" and "Cycle Run Bypess" on it. Changing both of these to ready, restarting the fans, and restarting the cycle should get it going again. This method will work only if it was in the initial ramp up or early in the first soak when it got trashed.

The Setpoint generator for the Part Loop is fairly reliable, but it can have some problems. If it will not continue past Vent Bag Pressure, observe the bag vacuums. If they do not vent, the hold will not release. The cure specifications can also cause it to go into perpetual hold. It is possible to specify Pressure to Hold Temperature, and Temperature to Hold Pressure at the same time. In this case, dump the run and start over again.

Several other problems and unusual operational events have occured in the past. If you notice something that does not seem correct, or is causing problems, PLEASE write them down in the so that they can be delt with.

2.5.12 Heating System by Thermoflux

The heating and cooling unit on Autoclave #3 was manufactured by Thermoflux, Inc. of Tulsa, Oklahoma. The contact person there who knows about #3 and #5 systems is Bob Moon. His number is 918 747-9394. #3 operates quite differently than #5; #3 heats air directly with natural gas and cools the air with liquid nitrogen. (#5 heats and cools an intermediate antifreeze solution.) Note that in this discussion, "PLC" refers to the main autoclave (Honeywell) programmable logic controller, while, "SLC" refers to the Thermoflux (Allen-Bradley) "Slick 100" controller on the Thermoflux unit.

2.5.13 Thermoflux Documents

A binder with the field components data sheets and Thermoflux drawings is located in the upstairs computer room. It contains the As-Built electrical diagram and the current SLC controller program printout. (The original hand drawn Thermoflux program drawing is obsolete.) Refer the Boeing P&C drawing, page 5 for the correct instrumentation and control system.

2.5.14 Thermoflux SLC Program

The controller in the cabinet located at the South East corner of the heating unit runs the natural gas solenoid safety valves, the pilot light and ignition, and the over temperature shutdown functions. The main autoclave PLC controls the pneumatic natural gas and liquid valves, the combustion and circulation motors, and the 18 inch butterfly valves that direct the air through the heating and cooling exchangers.The majority of the SLC program is a First Fault detection and latch. Only the first fault that has caused a shutdown is latched and indicated by the output lights (on the two lower expansion units), and on the TDC. The last 20 rungs of the program control the pilot light ignition and gas check valves enables.

PilotLight;Purge Thermoflux combustion;Purple Peepers;

The startup of the Thermoflux heating unit is enabled by the PLC by giving discrete outputs to the SLC controller which indicate that the Combustion and Circulation Blowers are running. (These outputs have additional permissives in addition to the motor "M" contacts, such as ESTOP and Man-In-Autoclave.) The SLC looks at the annubar flow sensor in the Process Air piping, and a pressure switch on the combustion air to verify the air circulation. If these conditions are met, then the SLC starts a two minute Purge timer. At the end of the purge cycle, it will open the solenoid valve for the pilot light and turn on the spark for 10 seconds. It verifies the pilot light with two "Purple Peepers", which are wired in parallel.

If the pilot fails to light, then the 2 minute purge and pilot lighting sequence is repeated. It will attempt 5 pilot sequences before giving up with a Flame Failure Alarm. The indication on the TDC is 5 reports of Purge Cycle Operating On/Off, followed by a Flame Failure. The Thermoflux must be reset before it will try another startup. Do not confuse the Thermoflux purge cycle with the autoclave chamber purge cycle.

The natural gas line has two normally closed solenoid valves in series with a normally open vent line between them. When they are deenergized, the series valves are closed and the vent line valve is open. After the pilot is lighted, the 18 inch valve to the cooling exchanger, FCV601, must close to 15-20 % open and make the "closed" switch contact, 3ZSC601, before the SLC will open the natural gas check valves. The natural gas flow can then be controlled by the autoclave PLC. The cooling exchanger, liquid nitrogen cryogenic control valve, and the 18 inch valve are totally under control of the PLC.

Some of the obsolete documents show a low temperature switch in place of the cooling exchanger exhaust gas thermocouple, 3TE580. This TC now goes directly to the PLC. The logic and alarm has been removed from the SLC, even though it still shows up on the Thermoflux alarm screen. Resetting Thermoflux will have no effect on the exhaust gas temperature alarm, (3QA608).

NOTE: The thermocouple channel 3TI580 is the only channel in the world with hardware scaling different from the standard (32-1100) range. It has the zero offset pot lowered to give (minus) -169 to 900 degrees. This is the last TC module in the rack and CAN NOT be interchanged or swapped with any other module without a hardware adjustment.

2.5.16 Heating System Alarms

Several additional permissives must be met in order to run the heating system. Any one of the following alarm will shut off heating:

3QA600      Flame Failure (after 5 retrys)
3QA601      Local Shutdown button or local power failure
3QA602      Loss of Combustion Air, (Motor off, leak in the low
            pressure switch, bad switch PSL601, or
            misadjustment.
3QA603      High Chamber Temperature, or open thermocouple
3QA604      High Tube wall Temperature, or open TC.
            Note: This will probably go away, TC defective,
            wires twisted together as of 12/88
3QA605      High Fuel Gas Pressure, or defective switch
3QA606      Low Fuel Gas Pressure
3QA607      Low Discharge Air Flow, IE. circulation blower
3QA608      Low Cooling Discharge Temperature, will not shut
            down Thermoflux. Thermoflux program and wiring
            changed.

2.5.17 Thermoflux Published Limits

The revised edition (2/89) of the Thermoflux manual lists the following calibration values.
TSH602      Chamber Temperature, max            1800 Deg. F
TSH603      Tube Wall Temperature, max          950 Deg. F
TSL600      LN₂ Exhaust Temperature, min 20 Deg. F
PSH600      Fuel Gas Pressure, max        15 Inches W.C.
PSL600      Fuel Gas Pressure, min        1 Inch W.C.
PSL601      Combustion Air Pressure, min        3 Inches W.C.
PSL600      Process Air Pressure, min           2 Inches W.C.

The initial published regulator settings differ from what Bob Moon actually set them to during startup. These values are subject to whim.

REGULATOR               PUBLISHED         ACTUAL
PRV605      Fuel Gas    7 Inches W.C.     16 Inches W.C.
PRV606      Pilot       1 PSIG            0.9 PSIG

2.5.18 Specific Heating Problems

Several specific failures have been observed. The following list is in addition to the one page trouble shooting guide provided by Thermoflux.

The combustion air loss detection is a pressure switch that opens when the pressure between the combustion blower and the regulation baffle drops below a certain amount. The low pressure switch is set as low as it can go and the baffle is partially closed. Reducing the restriction will cause regular alarms and shutdown, even though it is getting air. A leak in the line will cause an alarm. (This alarm will appear every time the motor is shut off, but should be fixed before the AC is retired.

The pneumatic gas control valve will open 100% if the rod to the pneumatic actuator comes loose. This causes uncontrolled heating. It is attached with a couple 1/4 " screws that tend to work loose.

The pilot will fail to light if the gas pressure is out of range. The correct setting for the pilot light regulator is 0.9 PSI. If the locking nut on the adjustment shaft is not secure, it will vibrate out to a lower pressure. Adjust while it is operating, or during the 10 seconds that the gas is flowing during the attempts to light the pilot after a purge cycle. It will do 5 attempts to light the pilot and then give up with a "Flame Failure" Alarm.

The two Purple Peepers that detect the ultraviolet light from the fire are wired in parallel. The outputs go to a receiver in the SLC cabinet. If these devices are suspect, unbolt one from the chamber and hold a flame in front of it. It should light the Flame Relay which is connected to input LED # 003, on the top SLC unit. One of the two should give a flame indication, even if the other is defective. If one is defective but the other is good, and you are getting flame detection problems, try swapping the physical locations. One position has a better view of the pilot light than the other. A shorted sensor will render the good sensor inoperative. The Flame Relay has a test connector that supports a microamp meter made by Honeywell. This piece of test equipment might prove to be worth procuring.

The enable signals for starting the Thermoflux heater are discrete PLC outputs that indicate that the two blower motors are running. There are additional permissives in the PLC coils besides the motors' MCC M contacts. The discrete outputs are wired to the coils of Thermoflux CR4 and CR7. They should energize the relays after the motors start, (and the reduced voltage blower starter finishes). The input LEDs on the SLC will light.

The program in the SLC is backed up in EEPROM which requires no battery power for retention. Observe the caution to remove power before messing with the module. It should not ever need removal.

The chamber temperature and tube wall temperature thermocouples have both failed. The improved reliability of using redundant Chamber TCs and high limit controllers should be implemented. With the two alarms wired in parallel, then both TCs would have to read high or fail before Thermoflux is shut down. Currently, an open thermocouple will stop heating.

The main natural gas regulator is set for 16 inches of mercury. This pressure will rise when the blocking valves are off, so, be sure to set it while in heating. If this pressure changes, try to find out why before attempting to adjust it.

2.6 Liquid Nitrogen Cooling

Cooling for the autoclave is accomplished by the evaporation of liquid nitrogen. The liquid source may be from either the low pressure or the high pressure system. Normally, the high pressure system is the source and the evaporated gas is returned to the accumulator tanks. The volume and rate of gas returned to the tanks is about sufficient to supply the entire autoclave area. The accumulators will increase in pressure at about 0.4 PSI per minute at full cooling.

2.6.1 Cooling Exhaust Recirculation

Nitrogen flow depends on the "Differential Pressure" between the liquid nitrogen and the exhaust gas. This differential can vary over a wide range and is also dependent on the rate of flow. The low pressure evaporator is usually connected to the accumulators with a pressure of about 160 PSI. The high pressure system runs at 330 to 350 PSI. This configuration guarantees a minimum of 160 PSI accumulator pressure without #3 working, and a high pressure that is the High Pressure System less about 25-35 PSI.

The accumulators are precharged to high pressure prior to an autoclave # 6 high pressure run, which prevents #3 from recycling the cooling exhust nitrogen. Under conditions of low differential pressure, the exchanger exhaust gas is vented through a chimney. Several configurations are possible by using the automatic and manual controls. The most common configuration is the high pressure system used as the liquid source and the accumulators are the destination for the exhaust gas. The source may be selected with the switch 3HIS570, "Use Low Pressure LN2 System". The vent control may be operated either automatically or manually. The switch 3HIS580 will select automatic control when it is on. In manual, 3HIS580V will either open or close the vent. In automatic, the vent will open in proportion to cooling demand when the differential pressure drops below the low limit of 3QA580, and will close when the differential pressure exceeds the alarm deadband. The venting action is indicated by the indicator on 3HIS580V changing from CLOSED to OPEN. Switch 3HIS580 should be left in Auto. Check the state of these switches in group 252 in the advent of a cooling failure. The cooling will fail if the switches are left in the Manual & Closed positions and the accumulators reach a high pressure. It will also fail if the liquid nitrogen hand valves are turned off. It is guaranteed to fail if the liquid nitrogen tank is run dry, (dry is a few inches left on the TDC indicators).

2.6.2 LN₂ Flow

The manual open/close switch has no effect in auto. The High Pressure liquid nitrogen tanks should be selected with the switch 3HIS570 in the HIGH (off) position. The differential pressure between the liquid nitrogen and the exhaust gas can vary from as little 30 PSI (before the vent opens) to as much as 355 PSI with the high pressure system selected and the vent open. The flow rates and hence the cooling capacity will vary with the differential pressure. The amount of valve opening for a given air temperature loop cooling demand, 3TC540OP, is modified by the differential pressure. The lower the pressure, the more the valve opens. This will aid in maintaining a consistent cooling capacity for a given process demand.

2.6.3 LN₂ Adaptive Gain

Several variables are considered in the operation of the liquid nitrogen control valve. The efficiency of the cooling will vary with the autoclave temperature, the mode of operation, and the differential pressure across the control valve. A prime consideration is to maintain a constant (gain) relationship between the heating and cooling functions. The relationship between temperature and cooling is primarily due to the difference between the air temperature and the minus 360 degree liquid. At high temperatures, the cooling is excessive for small changes of process demand, while at low temperatures, the efficiency of the cooling heat exchanger will not extract sufficient heat from the liquid. The extraction of BTUs from the autoclave is a function of the amount of liquid passing through the heat exchanger. The volumetric rate is a function of the differential pressure across the cooling valve. This differential can vary over a wide range.

The second approximation of the real world accounts for the differential pressure. Since the flow rate is proportional to this pressure, then the valve drive can be scaled to account for the difference between the measured line pressure and the accumulator pressure. 3PDI580, differential pressure = 3PI580 - 3PI321 (LN2 Pressure minus Accumulator Pressure), which is clamped at zero for a negative number. The amount of additional gain provided by this function is determined by a PLC constant called Kpdi. The equation in the PLC is 3EV580 = 3EV580' X Kpdi / 3PDI580. This constant gives a 100% output for 25 PSI differential pressure and the Air Loop PD (3PC54OP) at 40%. A Kpdi of 600 would give an additional gain of 3 with 100% @ 25 PSI, or 100% at 34%. These constants give somewhat less gain under the ideal situation of a 350 PSI high pressure tank, no line drop, and a 160 PSI accumulator pressure. For 0-100% valve movement for 50-0% PD under this condition would use a Kpdi constant of 1556. At very low differential pressures, the cyrogenic LN2 valve is essentially an on/off valve.

The third approximation deals with the very efficient cooling at high temperatures, which leads to instability in soaks, where the cooling capacity exceeds the heating capacity. Temperature trim can be accomplished by simply valving some air through the cooling exchanger and letting it radiate the heat. Any liquid flow will cause too much cooling. The way this is handled is to vary the b offset in the mX + b equation by the temperature in the autoclave. The variable "LN2 b" is calculated as an additional offset to the nominal 50% ("b" offset) Air Temperature Process Demand, (3TC540op). The present constants will start to open the liquid valve when the TC540PD is at 42%, when the autoclave is at the maximum temperature. In other words, at maximum autoclave temperature, there is an 8% deadband before liquid nitrogen is applied. The deadband is reduced for lower temperatures. This method minimizes the potential instability during a soak due to the high thermal capacity of the liquid verses that of the air. Otherwise, this condition will show up as a radical fluxuations in air temperature due to the variation of the PD while in soak.

The process (sub)equation is calculated to set the 50% valve opening to a specific TC540PD percentage. The present constant is set to give 50% cryogenic valve opening at a air PD of 35%. This is somewhat more cooling than would be with a linear equation at this PD, but is substantially less than linear between 35% and 50% PD. The constant is calculated by using the PCV580 value, which is assumed to be twice the deviation of the 540PD from 50% PD. Figure [4, page 2] of this discussion shows the graph and calculation for the constant. The equation is: EV580 X EV580 / Ksq.

A non linear valve action that approximates the desired response is obtained by squaring the PCV580 LN₂ drive and dividing by a constant. This equation gives a curve with very low gain (slope) around the Air Loop 50% point, and increasing gain as the PD decreases. Therefore the liquid flow is minimal during a soak and maximum during a low temperature cooldown. The trends of autoclave temperature vs. process demand show the air temperature lagging the setpoint when the air temperature drops below about 175 degrees. This is when the cooling exchanger is least efficient. The inefficiency will cause excessively low exchanger exhaust temperature while cooling at low temperature. The alarm point 3QA508 indicates that the exhust temperature has reached -100 degrees and that the LN₂ MOVs have shut off. This is a normal operational event. The alarm point 3QAL608 indicates that the exhast temperature has reached 120 degrees below zero. Something is wrong if this occurs.

2.6.5 Configured LN2 Points

3PI321      4351 Plant Nitrogen pressure scaled 0 to 500 PSI
3PI580      4340 LN2 Pressure
3PDI580     4348 Accumulator minus LN2 pressure "Differential"
3HIS570     1441 Use Low Press LN2 system
3QA580      1442 Low LN2 differential pressure:
            on at 45, off at 50 psi.
3HIS580     1443 Auto / manual LN2 vent control
3HIS580V    1444 Manual Open / close LN2 vent control
3QA608            -100 degree Exhaust Temperature
3QA608L           -120 degree Exhaust Alarm

2.7 MOTOR OPERATED VALVES

This discussion of the Worcester Motor Operated Valves, MOVs, precedes the functional descriptions of the systems where they are being used. This information should be kept in mind whenever troubleshooting a problem.

2.7.1 Motor Operated Valve Operation

The Worcester Motor Operated Valves, MOVs, consist of a small shaded pole motor, a gear train, a SPDT limit switch, and a ball valve. The motor drives the stem through 180 degrees for each open & close cycle; the direction of travel does not reverse, and the next 180 degrees performs another open/close cycle. References to "direction" in this discussion refer to the Open and Close functions, not the direction of the stem travel. The limit switch changes between the Open and the Close wires at 90 degrees of travel and stops the motor. This requires that the power remain on for the entire amount of time that the motor is moving, otherwise, the valve will stop at an indeterminate position and will not be able to continue until power is restored for the same direction.

2.7.2 MOV Timers and Failures

Each MOV requires a timer and a lockout for the Open/Close to guarantee full travel. A fault has occurred where the stem packing locking nuts tighten up with use and stops the motor. This will burn up the motor if the power remains on all of the time. The limit switch adjustment can also cause malfunction if it is set so that it can not open or close. The motor will then continue to turn until the power is removed. A similar fault will occur if the wires get tucked under the switch and prevent proper action. The software drivers for the MOVs provide the functions of Minimum On Time, mutually exclusive Open/Close arbitration, and de-energizing the power after the cycle. A couple of the most critical valves do not have the de-energizing feature. A discussion of the MOVs by functional group follows.

2.7.3 Pressure System MOVs

Page 3 of the P & C diagrams shows the pressure vessel related valves. 3EV301 is the low pressure switch line valve. It opens when the line when the AC pressure is less than 0.4 PSI and closes it at more than 0.6 PSI. Motor drive output coils addresses are 80 and 81. The timer for this valve is shared by 3EV322, the Oxygen Analyzer line valve; outputs at 82 and 83. These valves have different pressure thresholds where they operate. The power is not removed from them when they are not operating, except when pressure is within their respective dead bands. (This is because they are in very critical applications.) The pressure MOV driver code is sealed in with the timer at 534, which is set for an on time of 10 seconds. The Open and Close outputs are made mutually exclusive by having the normally closed contact for the opposite direction in series with the coils.

2.7.4 Blocking Valve Vent MOV

The nitrogen blocking valve, 3EV323, and its vent valve 3EV322 are interlocked, even though the blocking valve is solenoid operated. The internal coil 531 is the "Request" for the blocking valve to open. It has the permissives for the door, nitrogen selection, high pressure and etc. A change of state will run the 8 second MOV timer. The blocking valve will open only when the timer finishes moving the vent MOV. This allows time for the vent valve to close before the high pressure nitrogen is allowed in the line, and thus preventing the volumous egress of nitrogen through the vent valve.

2.7.5 Liquid Nitrogen Source Select MOVs

The two MOVs that select either the high or low pressure liquid nitrogen system are 3EV570 (low), and 3EV571 (high pressure). The output coils are 292 through 295, and their timer is at 538. The high or low source is selected with 3HIS570, which selects the low pressure system. This switch is normally off, which selects the high pressure system. Refer to the liquid nitrogen vent control section of this document. Both of these valves will close with either low temperature in the heat exchanger exhaust, (-100 deg F.), or with Emergency Stop.

2.7.6 Vacuum System MOVs

The 96 MOVs in the vacuum racks have several inter-related functions. The section of program logic follows the other valves. Refer to page 4 of the P & C diagrams. The "A" valves connect the autoclave lines to the Pressure transmitter, the "B" valves connect the pressure transmitter to the vacuum header, and the "C" valve is the solvent extraction valve. There are 3 valves for each of the 32 lines. Any line can be used as either a source line (with vacuum or pressure applied through the A and B valves), a probe line (with A open and B closed), or in calibrate (with B closed and A open). The Source/Probe selection is done with the switches 3HIS401 through 3HIS416 for the West side, and 3HIS421 through 3HIS436 for the East side. Turning this switch on will define the line as a source.

2.7.7 Leak Test, Line Test and Calibrate MOVs

Leak Test, 3HIS417, and Line Test, 3HIS418 are used for the integrity tests. Line test will open all of the B valves to supply vacuum to the lines, regardless of the state of the Source/Probe switches. Leak Test will close all of the B valves, regardless of the Source/Probe state. Calibrate, 3HIS400 will close all of the A valves and open all of the B valves. Since Leak Test + Calibrate, and Line Test + Calibrate are mutually exclusive, these function combinations are locked out. The first one selected will get the valves, the second will occur when the first is turned off. Line Test and Leak test are used together. The normal sequence is to turn on Line Test to draw down the lines, the computer verifies this and then turns on Leak Test. A leak is detected by the loss of vacuum. When these two switches are turned off, the Source/Probe configuration returns.

2.7.8 PLC Program Vacuum MOVs

The MOVs are engergized only when a function change is requested. The state of the Source/Probe switches and the solvent extraction switches are compared with their last state (when any valves changed). If a change occurs when not in Calibrate or Leak Test, or when the valves are in motion, then the valves will be changed and the new configuration will be used for the next comparison. The C valves are used for the solvent extraction system and are discussed below.

Since the state of the Source/Probe switch does not necessarily reflect the actual position of the valves (during Line Test, Leak Test, and Calibrate), a couple logic lines write the valve status to the PLC addresses 100 coil addresses above the control addresses. These are used as the PV input to the 3HIS4xx switches on the TDC. The switch inputs and outputs will disagree while in Leak Test or Line Test.

The actual valve drive and configuration is done within a skip block, NSKR number 8300. It is executed on either the positive or negative going transition of the (single) valve timer. When the timer turns on, the valves are driven, and when it turns off, the power is removed. The Loader display does not display the state of the contacts and coils if it is not being executed, so use the MULTI element display to view individual valve coils (accessed by Shift F5 or with the Data Display Shift F2, F8).

The logic for the 98 valves consists of one line for each wire, or 186 lines of code. (The alternate methodology was to use fewer lines by using memory mapped words, but that would have been very difficult to trouble shoot.) The sequence is always the same, and is in ascending sequence for each vacuum line, A valve, B valve, C valve. Each line contains all of the permissives for opening or closing that valve.

Two other MOVs are used for calibration or AWACS Back Pressure. They are 3EV450 and 3EV460. They valve in the "Calibration Air" 3PIC440, pressure to the two headers. They may be operated independently, so that one header may have pressure while the other has vacuum. This is used in the AWACs cures for back pressure. The operation and interlocks are similar to the other MOVs. Refer to the AWACS section for more details.

5/8/89 CALIBRATION INTERFACE

Add new control points:
      3HIS440C Pressure Calibration 1447
      3HIS450C Vacuum   Calibration 1448
      3HIS441C Vent     Calibration 1449

Turning on any of these switches will turn off the other two.
Calibration on is indicated by coil 632, be it Pressure, Vacuum, or Vent.
Calibration can not be initiated during a run. A run can not be started if calibration is on.

Operator Controls Not in Backup (3QI126) is false if calibration is on.

3HIS440C opens both headers to pressure header.

3HIS400A and 3HIS420A, back pressure header switches are still functional.

Plumbing back pressure is done with these two switches, and with Line Test, 3HIS418.

2.7.10 Vacuum System Hardware

Back in the dark ages, before automation, each platen in each of the 4 autoclaves had a separate vacuum pump. The pumps are now joined together via manifolds above and behind the pumps and on the floor in front of the pumps. The two pipes leading to the autoclave vacuum rack are joined at this point. Each of the two "Part" or "Bag" Vacuum headers is an independent system. The numbering is from 3PI401 through 3PI416 for the West side racks, and 3PI421 through 3PI426 for the East side racks. Each line may be either a probe or a source. The switches to select a source line match the transducers and are labeled 3HIS401 through 3HIS426. The solvent extraction switches are labeled 3EXT4xx. They are configured as switches on the TDC but do not conform to the "HIS" nomenclature because they are normally operated in the automatic mode and are operated manually only during mainenance operations.

The source vacuum level is controlled with valves PCV450, source, and PCV451, vent valves, (PCV460 and PCV461 on header 2--East). The vent is opened about 20% while controlling vacuum. This "Leak Constant" provides flow through the vacuum source valve, which makes the system more controllable. The nature of a control valve is to control flow as a function of the valve opening. The vacuum system provides little or no flow under most conditions, so the Leak Constants, valve adjustments and PID tuning constants are very critical.

Very slight movements of the vacuum source valve result in large changes in the header vacuum level. The PID control loop output varies over only a few percent for normal operation. This is the equivalent of having a huge gain in the system. As a result, the PID tuning constants are very "Slow". The gain of the pneumatic system will also vary with part bag leaks, which will alter the flow through the valves. A squared output function provides for variable gain at the valve. The PID output will open the source valve above 50% and opens the vent valve below 50%. The value above 50% is squared and divided by a constant so that the range is limited to the 0-4k counts for the D/A converters. This non-linear function provides a very slight change in valve drive current for a change in PID output while the PID is around 50%. This variable gain allows the PID to control for normal operation, yet provides the large gain at the high PID output end that is necessary when controlling with bag leaks.

2.8.2 Vacuum Valve Adjustment

The vacuum valve I/P adjustments are critical. Two facets of the control valves are a slow PID update rate, and valve stem hysteresis (or deadband). The deadband means that the source valves must be adjusted so that they are guaranteed closed at 4.25 mA. The vent valves on Autoclave #3 close with increasing control current, they are adjusted the same as the source valves to guarantee close at 4.25mA. Note that the vent valves on #2 fail open (current to close) while the vent valves on #3 fail closed. This is the adjustment procedure:

1. Disconnect the wires to the source valve. Put the 4-20 Transmation on the source valve. Zero the leak constant on the TDC, put the vacuum into backup with a 30 inch setpoint. This closes the vent valve; the header must not leak.

2. Vent the header by gently touching the lever on the Vent I/P that has the zero screw on it. The valve will open and bleed the header.

3. Increase the current on the source valve until the header vacuum starts to increase, as is indicated by the local gauge. Note this current value. Decrease the current until the vacuum stops increasing when the source valve is closed. Note this value. The valve should open at about 5 mA, and close at 4.25 mA. Vent the header and repeat as necessary to achieve these values. The valve closing current is critical. Excessive deadband will be caused if the stem packing nuts are too tight. Adjust the I/P Zero control and repeat as necessary.

4. Move the current source to the vent valve, and give it 4mA to close. Bump the source valve to put vacuum into the header. Increase the vent current until the vacuum level starts to drop and note the current reading. Decrease the current until the drop stops and the vent valve is closed. It should open at about 5mA and be closed at 4.25mA. Adjust the zero control on the I/P and repeat the test as necessary.

5. The Span control on the I/P should not be adjusted. It is not critical. It may be checked by visually verifying the current necessary to open the valve all the way.

6. Please record the current values obtained in the maintenance section of a Trouble Report. This will provide a record of any changes in the valve operation that may lead to problems. Return the Leak Constant values to their previous levels.

2.7.11 Vacuum Cure

The two vacuum headers may be operated with separate cure specifications. Autoclave #3 has additional features over autoclave #2. Awacs back pressure has been implemented and the Thermoplastic Solvent Extraction (aka. ATF) system is included. Note that extreme care must be exercised while loading an AWACS dome into #3 to avoid spatial distortion of the part. The tag names in the next paragraphs refer to the configured points on header 1, the East header operates the same but the tag names use the 460 series tags.

The normal cure (non AWACS) has four vacuum levels configured. The first level, known as segment 1, is put on the lines with initialization. This is when the cure table is down loaded from the HP to the PLC. The second segment is dedicated to the integrity Leak Test. The level is loaded into the set point when the switch 3YS401 is turned on by the HP Computer. The HP then turns on the Line Test switchs, 3HIS418 and 3HIS438, and verifies that all of the lines pull down to the segment 2 vacuum level. The switches temporarly define all of the lines to be Sources by saving the Source/Probe switch status and returning the pre Line Test configuration when the switches are turned off. This is the "Drawdown Test", and the pass/fail status is printed on the Thinkjet printer next to the HP terminal.

The HP turns on the Leak Test switches, which close all of the "B" Valves to isolate the lines from the headers. (If any of the solvent extraction switches are on during a leak test, the "C" valves will close and stay closed, even though they indicate open on the TDC screen.) The HP sets the vacuum level alarm limits and moniters the drop in vacuum. The alarms are annunciated on the TDC and printed on the HP terminal printer. When the leak test for header one is turned off by the HP, the PLC will turn off the Segment 2 Switch and return to segment 1 vacuum level.

When the run starts, the vacuum is switched to the segment 3 level and starts a timer with the time limit specified in the cure table. The segment time is usually specified as 960 minutes so that it will remain as long as necessary. If the time is used up before the bags get vented, then the segment 4 vacuum level is loaded into the setpoint and the segment 4 time specification is loaded into the timer. If this segment times out, then the bags get vented and the segment number that is reported to the TDC and the HP goes to zero. The change from segment 3 to segment 4 may be specified as a function of the Part Temperature. The cure point for the change is called 3YT3450.

In a normal cure, the bags are vented to atmospheric pressure when the autoclave pressure reaches the Vent Bag Pressure specification, 3YVB450. The PLC puts on an internal hold on pressure when it reaches this point, which is released when the bag(s) are actually vented. The point 3QI450 indicates that the vacuum level in the header is less than 1 In. Hg. If the bag does not get vented for some reason, the run can not continue. The operator can not over ride this hold. The hold is indicated on the TDC Hold Screen by "Vacuum Holding Pressure".

During a Stop Before Precure, the presure drop is put on hold at the VBP until both headers have at least 5 inches of vacuum. During an AWACS run, the VBP is used to switch to the back pressure segement #5. The AWACS back pressure is vented at a time into a temperature segment. Refer to the sections on AWACS and Stop Before Precure for more information.

2.8 Solvent Extraction System

This system is shown on page 4 of the P & C diagrams. It consists of the solvent extraction tank, 3EV470 which connects it to the vacuum system, and the 32 "C" valves. The system may be operated in either automatic or manual mode. For normal vacuum system operation, all of the C valves are closed. They may be opened individually by setting the switches 3EXT401 -3EXT436 on. The tank vacuum is turned on with 3HIS471. This will draw the solvent from the filter to the extraction tank. The automatic mode is started with 3HIS470. It will open one C valve on each header individually for a specific duration, currently 30 seconds, close them and open the next. If a C valve is opened with the manual switch, it will remain open until it is selected with the automatic feature and will close afterwards.

The switch 3HIS400B will close the Source line B valve during solvent extraction. This will isolate the source line from the vacuum header while the C valve is open. This is the normal operating setting. This switch is used for one method to clean out the filters and vacuum lines after an extraction run. This is done from the Solvent Extraction Screen on the TDC, which is accessed from the Startup Screen. This routine will NOT vent a probe line, even though it indicates that the filter is open on the screen. The probe lockout is done in the logic lines that write to the valve.

The easist method of cleaning out the lines is to turn on the Solvent Extraction vacuum source and all of the 3EXTxxx switches while the high temperature vacuum fittings are being replaced after the run. The other method does not require the caps removed from the lines inside the chamber. Vent the vacuum header, Line Test, and turn on solvent extraction. The first method cleans out the lines from the fittings through to the filter. The second method cleans out the lines from the vacuum racks through the filter. Neither method can clean out all of the lines all of the way. Both methods clean out the filters. The extraction may be either automatic or manual. The volume of air flow may be diminished below useful rates if all of the caps are removed and all of the extraction switches are on at the same time.

The automatic extraction program operates by using indirect addressing for 16 bit words on the 3EXT4xx switches. If the addressed word has the most significant bit off, it is set on by adding 32k to the word. When closing the valve, 32k is subtracted from the word if it is >= 32k. This prevents changing all of the other valves should a switch get changed manually during a solvent extraction by the operator.

2.9 Oxygen Analyzer

2.9.1 Oxygen Analyzer Maintenance and CalibrationO_2;

(Applicable to Autoclaves #6 and #3)
Monthly Calibration and Testing

1. Verify and calibrate to atmospheric oxygen content, which is the "CAL" mark on the panel meter. Open "Calibrate" header valve, close "Sample" valve, suck on tube attached to the exhaust port. (You are breathing this atmosphere anyway, and this avoids moisture in the cell.) Adjust the span control to read 20.9%, the calibration mark.

2. The Zero Oxygen reading must be verified because the Span Control has enough gain to give atmospheric percentage O₂ readings under fault conditions. Provide a low pressure regulated source of freon or N₂. Flow through the Test port and verify and/or calibrate to zero. If the zero control is adjusted, then perform the zero and span calibration several times until both readings are correct.

3. Close "Calibrate" and open "Sample" valves. Verify the reading on the TDC console matches the meter, which will change slightly when the air flow stops. If there is a 1% error, do a 4-20 mA driver board calibration, detailed below.

4. Verify setpoint (on #6 only). Listen for relay while reducing the span control. The relay should de-energises at 19.5% O₂. Adjust the setpoint as necessary, reset calibration to atmosphere, and lock both knobs.

Yearly cell replacement

1. Cell degradation is indicated by monthly calibration requiring several turns of increase of span control.

2. Fuel cell is type "B3", color coded orange. The warranty is for 12 months. These items should be ordered just before they are used. The spare cell should be used first. It is located in the spares cabinet, second floor of the autoclave control building. Autoclave #6 analyzer was put into service 3/2/88. Autoclave #3 analyzer was put into service 4/20/88. #3 and #6 cells have both been replaced since then. The change dates should be recorded on the cover of the Analyzer Manual.

3. Allow 15 to 30 minutes for new cell to stabilize before initial calibration, and recalibrate the following day. There will be several percent of drift over the first day, but very little after that.

4. The 4-20 mA isolated driver board should be checked for zero and 100 % adjustments. Set the meter to zero with the front cover span control. Adjust the zero trim pot on the driver board, R6 for 4 mA. Set span control on the cover to 100 % and adjust trim pot R4 for 20 mA. Repeat until 4 and 20 mA correspond with 0 and 100 %. Reset Span control and verify reading on the TDC console.

5. Note that this circuit is different from all of the other 4-20mA signals in the autoclave. All of the other transmitters are current sinks, this one is a current source. The wiring on the terminal strip in the back of the PLC cabinet is different for this device.

The manufacturer of the instrument is:
Teledyne Analytical Instruments
16830 Chestnut Street City of Industry, Calif. 91748
(213) 783-7181 (818) 961-9221
Analyzer model 326RB, S/N 59339, 5933?

The local vender for the cells is:
O2 cell vender is ???

2.9.2 Oxygen Analyzer Operation

The analyzer operates at low autoclave pressures. The MOV that feeds the gas to the analyzer unit (which is located in the (#3) PLC cabinet) opens at 1 PSI and Closes at 2 PSI. This narrow range of pressure exists while the Purge cycle is operating, after blowdown. The O₂ reading of 19.5 % terminates the purge cycle. The line has a pressure relief valve located downstream from the MOV. It will "bark" momentarily while the autoclave is pressurizing. This is normal since the MOV takes a finite amount of time to close. An additional delay in closing is due to the Low Pressure Switch valve closing at a lower pressure, and these two valves share a common timer. Refer to the section on pressure related MOVs for more information.

2.10 Set Point Limiting for Air Temperature

2.10.1 Setpoint Limiting Rational

The problem with temperature over shoot with large parts in the autoclave is because the heat generated takes longer to reach the part thermocouples on large parts than those on small parts. This additional time lag eventually causes too much heat to be applied to the small parts. A solution is to limit the Air (OIL on AC #2) Temperature Setpoint to a maximum number of degrees above the Part Temperature Setpoint. The point 3TDH540, "Temperature Deviation High 540" , counter, plc addr 5109, is the maximum number of degrees that the air temp setpoint may exceed the part temp setpoint. There is no limit on the how much lower the air temp setpoint may be on cooling. This temperature will be set to limit the excessive temperature on the light parts. It may be left at the nominal 15 degree value. This function may be disabled by putting a large temperature deviation in the register, e.g. over 100 degrees.

2.10.2 Setpoint Limiting operation

A simple clamp on the maximum air temperature setpoint has the serious drawback that the Part loop integral will continue to accumulate. This creates a situation where the part loop will call for a very high air temperature, if it were not for the limit. The slow part loop will then take a very long time to come back into a reasonable range, and then will cause a large undershoot in air temperature. The solution is to limit the offending integral term within the part loop calculations. This is done outside of the Honeywell PID routines. The limiting operation will set the Air Temperature Setpoint to the number of degrees above the Part Temperature, calculate what the Part Temperature Process Demand (3TC500OP) should be, and set the integral term to make it so.

2.11 RTU FUNCTIONS

2.11.1 Resetting the RTU System

1. Observe the lights on the Minicop, RTU, and bottom PLC I/O rack

A. The IN and OUT lights, lower right on the minicop will blink when the Minicop is communicating with the RTU.

B. The 2nd and 3rd RTU lights will blink at the same time.

C. Every 6 IN/OUT light blinks, the minicop will send data to the PLC and the "I/O" light on the left of the Minicop will blink once.

D. The RTU lights will blink in series, top to bottom during its power up tests.

E. If the "Active" light on the right module, bottom rack of the PLC is not on, or if Active light(s) on the analog modules are out, then proceed to step 3. Step 2 may have to be done afterwards.

2. The Minicop reset switch will restart the program that talks to the PLC and the RTU. It gives up trying to talk with the RTU after 5 unsuccessful reads. It will also give up after two wakeup calls to the RTU without a correct response.

A. Press reset switch DOWN.

B. The Fault light will blink twice and the OUT light (lower right) will blink once or twice.

1. If it blinks twice and does not start up, cycle the 5 volt power on the RTU. This is 3UCB8, 8th circuit breaker down on the left bank. The RTU lights should indicate self test mode.

2. Press reset on the Minicop and it should start up.

3. If the PLC rack Active light or the analog active lights are out, then something in the PLC rack has died.
IMPORTANT: DISCONNECT THE DAISY CORD TO THE NEXT RACK UP BEFORE YOU CYCLE POWER, OR THE RUN WILL BE TRASHED, AND MOST OF THE TDC SWITCHES WILL BE TURNED OFF.

A. Disconnect daisy chain cord, be careful of fragile latch and pins.

B. Cycle power on rack 34 with circuit breaker 3UCB5.

1. The autoclave will start to blow down when the power is turned off to the rack, but will refill when the connector is put back on.

2. Do not reconnect cord while rack power is off.

C. The Minicop and RTU should start up at this point, if they don't, then follow procedure 2.

4. If the RTU Health alarm is on but the Minicop, Plc, and RTU are all communicating, then probably one of the smart transmitters has lost its marbles. The indication on the TDC is only that some value does not change. Refer to the troubleshooting procedure in this document for locating the failed transmitter with the PLC loader setup.

The Smart Field Communicator is used to reset the transmitter. The procedure is to reenter the Device Tag Name, LRV and URV values and make the data Non-volatile. (You can get the scale values for each transmitter from the TDC detail.) Be sure that the transmitters on the RTU are in digital mode. (The transmitters connected to the analog input modules are in analog mode and will not give the RTU Health alarm.)

DO NOT USE THE SFC ON AN ANALOG TRANSMITTER THAT IS CONTROLLING SOMETHING. ALWAYS LEAVE THE DISPLAY IN "READY..." BEFORE DISCONNECTING THE SFC.

5. As a last resort, change the Minicop with the spare. If you do so, be sure the rack power is off, AND REMOVE THE DAISY CHAIN CABLE TO THE NEXT RACK UP. HONEYWELL SAYS THAT FAILURE TO DO SO CAN TRASH THE PROGRAM.

2.11.2 RTU System Description

The analog sensors for vacuum and plant air & nitrogen pressure are read through the Novatech "DE-NET" interface unit and the Honeywell Mini-COP. Honeywell Refers to their proprietary communications protocol with the Smart Transmitters as a "DE-NET". Novatech, the manufacture of the interface refers to their unit as either the RTU, for Remote Terminal Unit, or as a FIU, for Field Interface Unit. We will continue to refer to the interface as an RTU. This term will frequently encompass the complete interface unit, including the MiniCop. This overview describes the system operation. For more information, refer to these publications.

2.11.3 RTU Reference Manuals

DE-NET OPERATING MANUAL, Novatech, Inc.

ST 3000 Smart Field Communicator Operating Guide,
Honeywell 34-ST-11-09
This tells you how to use the hand held Field Communicator box to talk directly to the transmitters. It is primarily used to reset an ST that has "Lost its marbles."

ST 3000 Smart Transmitter Installation Guide,
Honeywell 34-ST-09-01
Mechanical, options, and parts lists

IPC 627 MiniCOP User Manual Form No. 627-8991
Describes the PLC to MiniCOP interface. This will describe the somewhat obscure way that the PLC program communicates with the MiniCop.

IPC 627-70 User Manual Form No. 627-8993
This is the Model 70 manual, but is fairly close to the -1002 model. It describes the OS-9 operating system commands. It is of limited use unless you intend to do program development. The minicop is a multi-tasking system, and as such requires a great deal of effort to use. The back has a list of OS9 level error messages.

BASIC09/RUNB User Manual Form No. 627-8994
This is the Basic Interpreter that executes the program to read/write the Novatech box. It has the BASIC09 error messages.

Basic Language applications program.
No documentation, look for it in the MiniCOP. The program has a compiled and source code version. The source code can be put into the interpreter and "PRINT" messages installed for debugging. Expect to spend days of effort if you attempt this.

2.11.4 ST3000 Smart Transmitters

The Honeywell Smart Transmitters communicate either in digital mode or traditional 4-20 mA. analog. When in digital output, the data ones and zeros use 4 and 20 mA for the bit levels. The output can be read with the Smart Field Communicator, "SFC", but a voltmeter reads only pulses. The SFC is used to set the transmitter hi and low limits, tag name, dampening, and mode. It is also used to calibrate and zero the gauge. The details of the set-up are in the SFC manual, and a "Crib sheet" is availiable. The transmitters operating in analog mode are connected to the analog input cards on the PLC rack. They are the autoclave pressure and vacuum headers. The vacuum probes connect digitally through the RTU.

2.11.5 RTU System Details

The RTU, communicates with the transmitters. It puts all of them in "Broadcast" mode whereby the Process Variable, "PV", is sent continually. It can then read all 8 channels on a circuit board simultaneously. The PV and transmitter "Critical Status" information is made available to the MiniCOP. This communications is visible by the blinking lights on each unit. The miniCOP will blink the In and Out lights about every second. The RTU has 4 leds. The top LED should always blink when the FIU is running. The second LED indicates Receiving Data from the MiniCOP, and the third is the RTU Transmitting light. The fourth led is not used for this application. The first three LEDs should blink during normal operation. The power on self test will sequence all four of the LEDs and will continue to do so until the MiniCOP talks to it.

2.11.6 MiniCOP

The MiniCOP is a computer that runs on a 6809 processor. It has its own operating system called OS9, a ram based disk with something like 170K of Non-volatile memory (as long as the battery works), Basic, and three serial ports. The terminal is plugged into the left ASYN connector: 9600 baud, 8 bits, no parity. The FIU plugs into the lower right ASYN connector, its baud and communications protocol are fixed. The PLC communicates with the MiniCOP through I/O rack addresses. Refer to the MiniCOP User Manual for the arduous details. The MiniCOP signals that it has new data by setting a coil, which causes the PLC to read all of the data and status registers in the MiniCop.

2.11.7 Subroutine 102

Subroutine 102 is the ladder logic routine for the analog inputs, (excluding TCs). The first 20 lines collect and average the 4-20 mA analog inputs. ~~These are averaged over 16 scans, about 0.8 seconds, to reduce the noise, jitter, and crosstalk in the analog modules.~~ Each channel is ~~summed to a buffer register, divided by 16, and~~ offset with 4 mA. The channel is then multiplied by 1.25 so that its span is from 0 to 4095 counts. This is the same range that is produced by the smart transmitters in digital mode, and hence eliminates the need to do the offset everywhere a datum is used.

A word on PLC programming. The Honeywell version of a DO ... WHILE loop is a EOS (End of Skip) followed by a NSKR (Not Skip and Retain) instruction. The EOS occurs first, and the numeric identifier is greater than 8K. This instruction is "Compiled" as a jump at the time the PLC is changed from Program Mode to Run Mode. The NSKR instructions with addresses lower than 8K do not jump to a different section, but scan intervening lines of code without executing them. The former type of NSKR saves execution time, but the latter does not. Back to the RTU...

Line 49 is the start of the RTU program. The timer will alarm if the subsystem does not get good data on one pass and another New Data strobe within 33 seconds. The error detection scheme is described below. The initialization section is next, and executes on the first scan following PLC startup. It sets the COP for 6 terminal strips on one RTU. The NSKR block at line 67 sends the "10" instruction which is to read PVs and status continually. This division of functions is to allow a functionality upgrade. A return from subroutine instruction is executed if there is no new data.

2.11.8 Read MiniCOP to PLC

The routine that brings in the data from the COP starts on line 85. It sets three pointers: GETQTY @ 5014 = Quantity of channels, SENDIAR @ 5015 = PLC memory write indirect address register, and COPADDR @ 5016 = MiniCOP database starting address. Subroutine 106 reads the individual MiniCOP values and writes them to the specified PLC addresses. The pointers are then loaded with the COP and PLC addresses for the channel statuses, and 106 is called again.

2.11.9 MiniCOP Software Test

The Terminal Emulator from Honeywell is located in the C:\AC directory, with the program name EMULATOR.EXE. The configuration file for this package is in the same directory. Connect the 9 pin SERIAL port on the Compaq to the left hand 25 pin D connector on the MiniCOP. This is the OS9 terminal port. Pressing return and / or hitting RESET on the MiniCOP should get the OS9 prompt, "OS9:". If it does a "Testing Sector" message, then the MiniCOP operating system is gone and requires a cold boot. The MiniCOP program may get corrupted to the point where some of the functions will work but others will not. Try some of the OS9 commands.

DIR Directory of the root directory. It should return the following display:

   directory of . 09:51:51
CMDS            DATACONTROL     VideoDemo       backup     restore
denet2          prgmb

DIR CMDS Directory of the CMDS executable programs directory should return:

directory of CMDS 09:51:58

Attr        Binex       Build       Clear
Copy        Date        Deldir            Del
Display           Dir         DskBak            Dump
Exbin       Free        Ident       Inkey
Ipc621            Link        List        Load
MakDesc     Makdir            Mdir        Merge
Mfree       Procs       Pd          Rename
Reset       Save        Setime            Setport
Shell       Sleep       Tmode       Unlink
Verify            Xmode       Basic09           RunB
DataControl VideoDemo   TV

MDIR Directory of the compiled and linked program modules in the 6809 memory. This display should result:

module directory at 09:52:08

Boottp            TLoad       RBF         D0          Disk
Firq        TP          T1          T2          T3
SC6551            SCF         IOMan       Clock       Sysgo
OS9p3       OS9p2       Init        OS9p1       DskBak
Shell       Mdir        backup            restore           denet2

The last three files will be listed within alphabetical order.

MFREE Lists the free memory within the processsor work space. This display, or values fairly close should result. If there is no free memory, the application program can not be run.

OS9:MFREE

Address pages
--------- -----
E00-ACFF 159
B800-B9FF 2
Total pages free = 161

If this much of the MiniCOP works, then it is probably in good shape. For a warm fuzzy feeling, "LIST" the source code for the applications programs. PRGMB in the root directory is the batch file that starts up the DENET2 application program when the switch on the MiniCOP is pushed down, or power is restored. DENET2 is the basic language program that talks to the PLC and RTU. Listing it will scroll through several pages of program. PRGMB is very short.

2.11.10 Stand alone Minicop Program Test

At this point, the program should be able to try talking to the RTU once it is run. The applications program may be started by pressing the Reset switch (down) or by typing PRGMB at the OS9 prompt. Move the cable to the lower right connector, also called "/tp" or tape port. Now press reset. A single line should be rewritten on the terminal several times. It begins with a question mark and ends with changing Hex digits. If so, it is ready to go.

If the first method fails, then try the second. Cable to the terminal port and type "PRGMB". If there is a problem with the set up then you should get an error message. Look first in the back of the 627-70 manual for error messages, then look in the Basic09 book for messages. Important note: If there is not enough memory to load and run the applications program, the message you get is "Module Not Found", but it can also mean "Not enough free memory". You can execute the commands in PRGMB by typing them at the terminal, one at a time. The one causing trouble should return the error message.

If PRGMB does nothing, try moving the connector again. If this fails, then check the DATACONTROL command setup in the next section. If everything fails, welcome to the club. Don't give up. Start all over again, take notes, and verify everything before proceeding to the next step. Good Luck.

2.11.11 Cold Boot MiniCOP

The MiniCOP software is reloaded from the files in the Compaq computer. This procedure is necessary for a new MiniCOP, or when the software has been corrupted. The initial setup is the same as for talking to OS9, that is:
1.    Connect Compaq to Left Serial connector of MiniCOP
2.    Change directory in PC to >\AC, execute EMULATOR
3.    Hit RETURN, If "Sector Testing" message, skip item 4
4.    Trash MiniCOP completely. Power off, PLC disconnected
      or off, remove MiniCOP and undo battery. Wait 5 minutes.
      Reinstall MiniCOP and power up, get sector test or retry
5.    At "Connect .... and hit return" message, hit RETURN
6.    Press F3 "SEND", File:MINICOP.BIN, 20 Second delay,
      DO NOT HIT RETURN YET.
7.    Change connector to lower right serial connector on
      MiniCOP. Press Return. Data is transfered
      The lower right IN/OUT lights blink.
8.    When the lights stop, reconnect to left connector
      and hit <CTRL> E. An error message appears.
9.    Do the DATACONTROL set up in the next paragraph and then
      verify MiniCOP program and data.

2.11.12 DATACONTROL Command Setup

This is the program to use to set the configuration into the applications program. It needs to know how many RTUs are on the line, (1), how many terminal boards in each RTU, (6 on #3, 7 on #2), and the command number, (10). At the OS9 prompt, type DATACONTROL. From the menu, select PUTREG to write the following values:

Address     Value Explanation
1           1     # of RTUs on the cable
2           6     (AC #3) # of boards in the first rtu
            7     (AC #2)
12          10    Command to read the smart transmitters.

Use the GETREG menu selection to read back these three values and verify them. Now go back to the MiniCOP software verification procedure above.

2.11.13 GOTCHA

The MiniCOP is not a simple little black box; it is not easy to deal with. Little problems can be very difficult to resolve, so take your time and be patient. The main books you need are the Honeywell Terminal Emulator guide, the fat COP manual--627-70 Model, the MiniCOP manual (DATACONTROL and how to miswire the connectors), and the Basic09 manual. A file was provided by Honeywell about how to load load files from the Emulator. It is called READ.ME.

2.11.14 RTU Error Detection

Errors are tested in the last part of the PLC RTU Subroutine. This can not be accomplished until you have a loaded and working MiniCOP and RTU.

The channel status table is located at PLC address 7950. SEARCH FOR THIS ADDRESS AND YOU WILL FIND A "VIEW PAGE WITH THE STATUS OF EACH TRANSMITTER. 48 OR 56 IS OK. ANYTHING ELSE IS BAD. 32 MEANS IT CAN'T READ THE BOARD. AN ODD NUMBER MEANS THE TRANSMITTER HAS FAILED.

Individual coils are set for each channel reporting obsolete or bad data. This section is a DO ... While loop with the skip identifier of 8197. Each channel status is checked for a value of either 48 or 56. 56 is good data with a negative number. 32 means that the terminal strip was read but the data has not been updated since the last PLC reading. 0 indicates that the RTU is not reading the terminal strip.

The bad channel coil is set or reset by using indirect address read/writes. This is a 16 bit register operation which means that 16 coils are manipulated at one time. The indirect address register points to the highest coil address, and the next fifteen lower coils are included in this operation. To set a coil, the register is tested for a value less than 32,768, which is the decimal value of the most significant bit. If it is not set, then it can be set by adding 32k to the register. If it were not tested for this bit being set, then adding 32k to it would cause register overflow and reset the coil. The reset bit line works the same way, by testing for the coil to be set before subtracting 32k. The pointers are then incremented and the skip instruction tests for the last address in the status table of interest. This limit will have to be changed if additional transmitter interface boards are added. Since all channels are not necessarily used, and individual transmitters may be down for the usual exorbitant MTTR, a means to disregard individual channels has been provided on line 102.

Coil 648 is set if the error status coils match the pattern in three registers. 5102, 5103, 5104 are set with ones in the binary positions for the bad channels. For example, the first terminal strip on AC #3 has two empty channels in the 3rd and 4th locations. These are binary values of 4 and 8 = 12 in decimal. Note that if a transmitter is added or removed, you must change the bit in these registers, otherwise adding a transmitter would cause an RTU health alarm. The channel data reads, status reads, and error detection part of this subroutine operated only when the COP indicates that a complete update is ready from the RTU, which is about every 6 seconds. The "Health" timer is located ahead of this section which will execute every scan, which allows the timer to operate. The RTU Channel OK bit, 648, means good data on the last update. The New Data coil indicates that the next data is ready. The combination of these events will reset the timer and prevent the alarm. Typically, one of the channels will report obsolete data every minute or so. When this happens, the timer starts accumulating time. The next read will not reset the timer, since the last read had an error. If the current read results in all good data, the timer will be reset with 12 seconds on it. If another channel has wimped out for one pass, then the timer can reach 18 seconds before being cleared. Watching the timer can give an indication of degradation, even without an RTU Health alarm. Looking at the coils at 1566, 1582, 1598 as registers in the "Multi" window leads to the offending channel(s).

Troubleshooting the RTU system is done by isolation. The lights on the MiniCOP and the RTU indicate the data communications between these units. Sometimes the two stop communicating, especially if the PLC has been stopped. The MiniCOP switch labeled PRGM / RUN / RESET will restart the COP program, or put the COP into the OS9 operating system. "RESET" will blink the RUN and Fault lights a couple times and then start communicating with the RTU. If the RTU is not responding correctly, the COP will make two attempts and then transgress to never-never land. In this case, verify the communications connections and try again. Cycling 5 volt power on the RTU will put it into self test mode with all 4 leds blinking. A communications from the COP will stop this mode.

Putting the COP into OS9 operating system mode will stop the data aquisition program. It is expecting a terminal to be on the left hand connector. It will prompt for the time and then give the OS9 prompt. If it is functional, then the commands DIR and MDIR will give a listing of the directories and memory resident modules. MDIR CMDS will give a listing of the "disk" based program modules. This software is loaded through the serial port (TP is on the right) from the boot loader tape and the DSKBACK tape. If the programs have been corrupted, then a complete load is indicated. Refer to the COP user manuals for additional commands and operation. Not all of the commands listed in the book are included with this system.

Troubleshooting the PLC portion entails following the error status from the timer to the error detection logic. A View page is provided for the error status registers starting at 7950. Watching the (1566+) coils on the Multi window and the registers on the view screen will illuminate the problem. Putting some other value in a status register should be rewritten within 6 seconds if the RTU -> COP -> PLC system is operating.

The smart transmitters have proven to be very reliable devices. Only one hard failure out of a hundred devices has been proved within the last year. They will occasionally loose their "Marbles", (a technical term). The test is to use the Smart Field Communicator, SFC, on the transmitter. Connect it to the transmitter and press ID. The message "Failed Comm Check" indicates an open loop, try reseating the terminal strip connectors. The message "Invalid Database" indicates that the transmitter configuration is bad. This can happen because of static or garbled communications. Re-enter the low and high range values and make it non-volatile. This should bring it back. Then try the A<->DE function. It will ask you to verify the change, enter yes or no. Be sure that the transmitter is in digital mode for the RTU and in analog mode for the Analog transmitters. AC pressures, vacuum sources and calibration air pressure are all analog.

2.12 Blowers

Circulation and Combustion Motors Controls are around line 246. The two fan motors have several safetys built in between the TDC switch and the Motor Control Center, MCC. The primary safety is a timer that will turn off the operator's switch if the "M" contact in the MCC does not close within a few seconds. The Combustion motor will turn off in 4 seconds and the Circulation Motor will turn off in 8 seconds. This will occur if the power switch is turned off, or if the local control on the MCC is turned off. The local control turned to "HAND" will over ride this feature. Both motors have these contacts to enable the PLC output to the MCC:

Door is closed and locked
Simulation is not on.
The operator motor run switch is turned on.
The Circulation Motor is within temperature limits:
Bearing temperatures are below 180 deg. F.
Air temperature in the Bell Housing is below 170 deg F.

The lines that detect the bearing temperature have some deadband built into them to minimize the quantity of transient alarms generated. It is usually about 5-10 degrees. This logic is used throughout the program and looks like this:

3TI600           491             480                   1095 °
Ö‑[B2]‑‑‑‑]>[‑‑‑‑[K2]‑‑Ú‑‑]>[‑‑‑‑[K2]‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑( )‑‑‑À
°                      °                                      °
° 1095                 °                                      °
Û‑] [‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑ì

It works like this: Bring in the temperature and compare with the constant 491. If it is more than 491 counts (160 deg), then test if it is greater than 480 counts, (157 deg.). Which it is, so set coil 1095. On the next scan, 1095 contact will be set, so the first comparison can fail and the coil will remain set until the temperature drops below the value of the second comparison. The deadband will keep the coil turned on as the input varies over a few counts due to noise. The TDC operator is spared multiple alarm as the signal varies above and below the threshold.

Circulation Blower Bell and Bearings cooling control.

Warning alarms are given when the bearing temperatures or the Bell Air temperature is within 10 degrees of shutdown. The cooling for the housing is provided by finned coils connected to the two inch cooling water line. The cooling water is turned on when the circulation motor is running. The most probable causes of loss of coolant will occur when the hand valves are turned off, the strainer is plugged, the cooling tower isn't, or the flow sensor breaks.

The flow sensor will detect a gradual loss of coolant. The alarm point is only in the TDC, and will not shut down the motor. The motor will shut down on high temperatures only. The strainer can be bypassed and cleaned while the motor is running, but a loss of coolant may or may not allow the run to complete. The powers that be may decide that the heat problem is not as serious as the load in the autoclave. In which case, turning the hand switch on the MCC to "HAND" will defeat all of the PLC alarms and safetys. The MCC overload protection will continue to function.

2.13 Door Stuff

Two extra features are provided at the door for the convenience of the users. The circulation and combustion motors may be turned off at the door by setting the ping pong valve halfway between closed and open, and then pressing the Open Door pushbutton. The valve must be all the way open to actuate the door hydraulics. The interior lights may be turned off while the door is open by closing the ping pong valve. This is recommended for extensive periods with the door open.

Two related but not identical indicators are "Safe to Open Door" Indicator light, 3QI300B, and "Ready to Open Door" status on the TDC, 3QI300A. Ready to Open means that the autoclave is blown down and that the 4 inch vent valve is all the way open. Safe to open is the permissive to run the door controls. It requires, in addition, that the N2 blocking valve is closed, the Ping Pong Valve is open. The blowers do not necessarily need to be shut down to open the door, but will sometimes make Safe To Open cycle on and off. Note that Ready to Open will come on at the end of a run, after the purge cycle is complete. (Purge cycle does not show up in these lines of logic because it will keep some pressure in the autoclave.) The circulation blower may cause these indicators to come on and go off. This is due to the air circulation causing slight pressure and rarification relative to the atmosphere. A gusty wind, which will blow down the stack, has also been known to cause this situation.

A redundant note: The fastest way to get the door open is to hit the ESTOP switch, open the PP Valve and hold door open button. The ESTOP will blow down and terminate the purge cycle. READ AND PAY ATTENTION TO THE MAN IN AUTOCLAVE PROCEDURES, BLOWING DOWN FROM NITROGEN PRESSURES ABOVE 14 PSI CAN CAUSE HYPOXIA, BRAIN DAMAGE, AND DEATH. Refer to the Oxygen analyzer section for more details of the purge cycle operation.

2.14 AWACS 4/26/9

2.14.1 Configured points

Cure Specification points for header 1 (counters):

3YP459      4300 Header 1 AWACS Back Pressure, PSI
3YK459      4301 Header 1 Minutes to wait after Back Pressure
3YG459      4302 Temp Segment to Vent Bag
3YKV459     4303 Time Into T. Segment to Vent Bag

Discrete points:
3QIL459 1089 Flag, Ready to Start Leak Test Header 1
3YQI459 1092 Header 1 AWACS Flag (cure spec)

Cure Specification points for header 2 (counters):
3YP469      4304 Header 2 AWACS Back Pressure, PSI
3YK469      4305 Header 2 Minutes to wait after Back Pressure
3YG469      4306 Temp Segment to Vent Bag
3YKV469     4307 Time Into T. Segment to Vent Bag

Discrete points:
3QIL469 1090 Flag, Ready to Start Leak Test
3YQI469 1093 Header 2 AWACS Flag (cure spec)

Pressures (X1) for Post Pressurization Leak Tests:
3YLT300A 4215 PPLT Header 1
3YLT300B 4224 PPLT Header 2

Note that the register addresses are in the cure table that is down loaded by the HP (and indicated on the TDC). The addresses used within the PLC logic are from the table at plus 500.

Operation:
The cure specification points are down loaded from the HP during initialization. When the Down-load flag, 3QI151 is deasserted, the PLC executes its initialization routine. The cure table registers are copied to addresses 500 higher than the points configured on the Highway. If the AWACS Flag is set for header 1, the back pressure level, 3YP459 is loaded into the Back Pressure Setpoint, 3PC440S. This pressure level is configured on the Highway and may be changed by the Operator. If the AWACS Flag for header 2 is set, the value in 3YP469 is loaded into the pressure setpoint. This value will over write the level specified by header 1 back pressure.

After initialization, the vacuum operation will follow a regular run procedure. The segment 1 vacuum level for each header is applied at initialization. The vacuum leak test segment (Change to Segment 2 Flags) are operational. The vacuum will return to segment 1 when Leak Test is finished. When the Cycle Run starts, segment 3 vacuum is applied to each header and the soak timers start. The specifications in the cure table to change to segment 4 at temperature, or change to 4 at the time-out of the segment 3 vacuum timer will continue to operate. (Segment 4 vacuum will probably never be used on AWACS)

Once the Cycle starts, the Pressure-Holds-Temperature specification puts a hold on the temperature ramp (if it is so configured). The pressure will increase to the Vent-Bag-Pressure. At this point, the AWACS Cure will differ from a standard cure. The pressure will be put on hold by the Vent Bag Pressure(s). The Vent Bag Hold is normally released when the bag vacuum approaches zero. The difference with a standard cure is that the vacuum is terminated on a standard cure, but the AWACS cure will continue to the AWACS back pressure level, which is Vacuum Segment #5.

Either or both of the headers may be vented and / or changed to back pressure at the same or at different specified autoclave pressure. The normal cure will release the pressure hold once the bags are vented. The AWACS cure will not release the AC pressure hold until the Back Pressure Control Loop, 3PIC440, remains at a level that is not less than one PSI below the Back Pressure Setpoint for 15 seconds. Once the back pressure has been applied and stablized to a header, a timer will start counting towards the "Back pressure to Leak Test" delay specifications: 3YK459 and 3YK469. These timers will not be put into hold.

The pressure increases to the lower PPLT pressure and the PLC issues a general hold, 3HIS157. The PLC will not release this hold. Once the Hold is released by the HP or the operator, after the PPLT, the autoclave pressure will increase to the second PPLT pressure, or the first soak level and start the soak timer for the first soak pressure. The temperature hold will be normally released at this point, which can be specified by either pressure or time into a pressure segment.

The back pressure will be vented and the vacuum soak terminated during an AWACS run by the AWACS specifications 3YG459 (&469) Temperature Segment to Vent Bags, and 3YKV459 (&469) Minutes into Temperature Segment to Vent Bags. The back pressure will also be terminated by the segment 4 vacuum soak timer.

Stop Before Precure: AC pressure drops to the VBP level and the pressure hold is put on. Vacuum is reapplied at this point and the hold is released when both headers have at least 5 inches of vacuum.

2.15 STOP BEFORE PRECURE

Subroutine 144 provides a means of gracefully backing out of a run that has already started but has not reached the precure temperature limit. It is called by the last lines of the cycle control routine, and is physically located just before the initialize routine. It sets up a pressure ramp down of 0.6 seconds / 0.1 psi, a pressure soak level of zero, and a temperature setpoint of 50.0 degrees. This will put full cooling on in an attempt to immediately reduce the air temperature. If the temperature should continue to rise above the precure temperature, it will not have any effect, since the function is latched in. The Air/Gas function will switch to air. This will in turn start a Purge To Air cycle. The pressure drops until it reaches the lowest Vent Bag Pressure, where it will hold until all the bags reach at least 5 inches of vacuum. It will continue to depressureize until the autoclave pressure drops below 0.4 PSI. This is the pressure Setpoint where the pressure control gets put into manual with a zero process demand. The purge to air cycle will add air to the autoclave, read the oxygen content and continue until the atmosphere reaches a safe level. At this point, Cycle Run Request and Cycle Running are unlatched, and INITCUR coil is turned on. This in turn will call the initialize routine which will use the previously downloaded cure specifications to get ready for the new run. The Air/Gas switch will return to GAS for the new run.

2.16 Initialize Run

Subroutine 134 initializes the cure specification tables. It is called from subroutine 114, which is the cycle run startup routine. This saves PLC processing time, since it is called very infrequently. (Autoclave #2 functions are organized somewhat differently.) The HP sets a flag, 3QI151 (1798) during the time that it is down loading the specifications to a table starting at address 4200. On the trailing edge of this signal, sub 134 is called, provided that a run is not in progress. This initialize routine moves the cure table from 4200 to 4700, so that any changes made to the specifications will not affect a run in progress.

Two down loads occur in a run, one at initialization time, and the Standby Cure after the end of the run when the door is opened, (actually when the ring starts to unlock). The standby cure is indicated by 99.9 deg / minute for the first temperature and pressure ramp rates. The first four lines of this subroutine, (starting about page 246), handle the vacuum source / probe lines differently. The real cure will open all of the vacuum source valves, which will be selectively closed by the HP after the integrity check. Standby cure, at the end of the run, will close all of the source valves. Stop Before Precure will call this routine after depressurization, but for this exception, the state of the vacuum valves are unchanged. In all cases, the Air / Nitrogen selection switch is set back to nitrogen. Initialize will then set the temperature and pressure segments to segment one, and put the current pressure into the pressure demand register. The table is moved by 11 lines of Pulls and Pushes of 8 registers per line. Segments 1 and 2, the first ramp and soak values are scaled and loaded into pressure and temperature counters and timers. The vacuum headers controls are set to segment 1 which is the "holding" levels, and the vent bag switches are turned off. The integrity test and leak tests can be controlled by the HP, or the operator. The actual startup of the cycle is done in subroutine 114.

2.17 Startupcycle Run Request;

2.17.1 Deviation alarm limits

3PC300DV    10 PSI
3TC500DV    30 DEG
3TC540DV    30 DEG
3FC600DV    600 FPM
3PC455DV    60 In Hg
3PC465DV    100 In Hg
3PC440DV    30 PSI

2.17.2 3QI126, OPERATOR CONTROLD NOT BACKUP (1137)

These controls need to be off in order to start a run.

3HIS501     OPERATOR SELECT AIR TEMP
3HIS510     OPERATOR SELECT PART TEMP
3HIS450     OPERATOR SELECT H1 VACUUM
3HIS460     OPERATOR SELECT H2 VACUUM
3HIS465     OPERATOR SELECT AUTOCLAVE PRESSURE

2.17.3 3QI124, OPERATOR CONTROLS READY (1150)

These controls need to be off in order to start a run.

3HIS400     CALIBRATION
3HIS417     LEAK TEST HEADER 1
3HIS437     LEAK TEST HEADER 2
3HIS418     LINE TEST HEADER 1
3HIS438     LINE TEST HEADER 2
3HIS302     BLOWDOWN VALVE LOCKED OPEN
3HIS500     FEEDBACK, PART LOOP, AIR
      This is bypassed by computer shedded                        (1000):

2.17.4 3QIRDY, EQUIPMENT READY TO RUN (1125)

These points must be valid to start a cycle.

3QI200      DOOR IS CLOSED AND LOCKED
3NESTOP     NOT EMERGENCY STOP
3QIRTUOK    RTU HEALTH OK
3BLR600     CIRCULATION BLOWER IS NOT OFF
3BLR601     COMBUSTION BLOWER IS ON

This point is bypassed with 3HIS155, "Equipment Bypass", also known as "Cycle Run Bypass".
3QA110      ALARM LIGHT

The following are bypassed with EQIPMENT BYPASS and CYCLE RUNNING:
3HIS450V    HEADER 1 BAG VENT CONTROL
3HIS460V    HEADER 2 BAG VENT CONTROL
CSHEDDED    COMPUTER SHEDDED

2.17.5 3QI155B, CYCLE RUNNING

This is a sealed in contact. If it is not latched in after CYCLE RUN REQUEST is received, then the request is turned off.

These items may go false after the run starts:
3HIS155A    CYCLE RUN REQUEST
3HIS123     COMPUTER READY
3QIRDY      EQUIPMENT READY
3QI126      OPERATOR CONTROLS NOT IN BACKUP
3QI124      OPERATOR CONTROLS READY
3INITOK     CURE INITIALIZATION IS COMPLETE

These three items must be asserted to start and will immediately terminate a run when going false:

3QI200      DOOR IS CLOSED AND LOCKED
3NESTOP     NOT EMERGENCY STOP
3CR100      MAN IN AUTOCLAVE

STOP BEFORE PRECURE will turn off CYCLE RUN REQUEST and CYCLE RUNNING after the autoclave is blown down.

2.17.6 3QI152 CURE IS INITIALIZED

This point is latched on the training edge of 3QI151, COMPUTER DOWN-LOADING. It is unlatched on the first scan after powerup, on Emergency Stop, end of a cycle, or if a standby cure has been downloaded.

2.17.7 3QA110, ALARM LIGHT

The alarm light is blue to indicate that a fault exists in the hardware that needs to be delt with. The following items which are disabled during simulation:

3FAT304     Open Current Loop on O₂ Analyzer
3FPT304     Open Current Loop on Back Pressure Header
3FPT450     Open Current Loop on Header 1 Vacuum
3FPT460     Open Current Loop on Header 2 Vacuum
3FFT600     Open Current Loop on Circulation Flow Sensor
3FPT301     Open Current Loop on AC Pressure Gauge #1
3FPT302     Open Current Loop on AC Pressure Gauge #2
3FfT575     Open Current Loop on Natural Gas Flow Sensor

Thermoflux Alarms:
3QA600      Flame Failure (Can't light pilot)
3QA601      Local Shutdown or Power Fail
3QA602      Loss of Combustion Air
3QA603      High Chamber Temperature
3QA604      High Tube Wall Temperature
3QA605      High Fuel Gas Pressure
3QA606      Low Fuel Gas Pressure
3QA607      Low Circulation Air Flow
3QA608      Low LN₂ Exchanger Exhaust Temperature
      This needs to be changed to 3QA608L, 1445,
      -120 degrees. It is no longer a Tflux Alarm.;

3HIMALV     HIM Module is alive. This is not a tested feature.

2.18 Fischer Valve manuals

Manual description Form

Design EZ Valve Body          5118
Type 667 Actuator       1203
Type 67Af and 67AFR Regulators            5144
Type 546 and 546S I/P Transducers         1783
3582 and 3583 Positioner and Transmitter 5054
Model B21 Butterfly Valve (AC #5)         B1200
Type 1066 On/Off Actuator (AC #5)         5231
Design V100 V Ball Valve            5061
1051 and 1052 Actuator Size 33 (for V Ball)     5620
3610J, 3610JP and 3611JP Positioners
      (for V Ball)      5208

Fischer Flow Sensors:
DV3000 Signal Conditioner and DV2000 Vortex Flowmeters 5198

3.0 PLC Program

This section describes the structure, some of the highlights, and more obscure details of the Autoclave #3 PLC program. It assumes that you are familiar with the autoclave and have access to the documentation listed below. This is not intended as a tutorial as much as it is here as a road map through the massive amount of information that has been generated by the equipment vendors and the modernization project team. Much of the experience obtained by operating and observing autoclave operation has been codified in the PLC. These may be searched for by the Loader package.

3.1 Honeywell PLC

Lines of obscure code may function only under fault or extreme conditions. Other times, the obfuscation is due to the Honeywell idiosyncrasies of the Honeywell PLC. A common example of the latter is where what seems should be one line has been divided into multiple lines of code. This is due to the processors internal "Argument Stack" manipulation. The PLC is easy to modify and tolerant of most programming faults, but caution is advised when modifying the software. There is generally a good reason(s) for doing it the way it is. The following PLC and Ladder Logic documents should be consulted for details. A word of warning on the Honeywell information: What they don't tell you is frequently more important than what they do tell you.

3.2 Referenced documentsHoneywell Reference documents

IPC 623 LOADER/TERMINAL FORM # 623-8999
This manual gives the ladder logic programming language description, it does not give "definitions".

IPC 623 MS-DOS LOADER USER MANUAL FORM # 623-8993
This little manual describes the Personal Computer based loader / terminal software package. Its description of the programming language is limited and sometimes inaccurate. It assumes that you have read the previous manual.

IPC 620 SPECIFICATIONS FORM # 620-8995
This manual describes the input / output modules. Jumper settings, wiring, programming, and module configuration is found here.

IPC 620 PROGRAMMABLE CONTROLLER USER MANUAL FORM # 620-8984
This manual describes the system configuration switches. Do not use the PI/OM configuration from this book, it is a different model.

Boeing Process and Control drawings
900-8408 for Autoclave #2
900-8410 for Autoclave #3
These drawings show all of the valves, gauges, and instrumentation. The major tags on the TDC are shown. The minor points and functions are omitted for brevity. These are AUTOCAD generated drawings.

Boeing Control Diagrams
900-8409 for Autoclave #2
900-8411 for Autoclave #3

Control Logic Diagrams (No Boeing document numbers)

These drawings show a schematic representation of the PLC control logic. The normal program flow is left to right and top to bottom. The interface to the TDC network is shown by vertical lines extending to the top of the page. The TDC tags are accessible only by tagname; the PLC tags are accessible only by numerical address. These drawings show the numerical addresses that are used to search for the major functions in the PLC.

TDC and PLC cross reference (No Boeing document numbers)

This listing is dBASE III generated. It can be printed in various formats and sorts. It lists the PLC address, tag name, labels and the TDC tagname. The TDC allows 8 characters for the tag name, and the PLC allows only 7. The TDC tags may have 2 separate PLC addresses for input and output.

PLC complete tag listing.
This list includes additional information beyond that provided by the Honeywell Loader package documentation listing. It is maintained in dBASE.

PLC program listing and cross reference.
This is generated by the Loader software. AC #2 runs over 500 pages, while AC #3 is a mere 325 pages. This description uses line numbers, which should be considered only approximate, since additions and deletions change every subsequent line number.

3.3 Using the PLC Loader software

Both of the Loader books are necessary to understand the PLC programming language and the operation of the terminal. The MS-DOS Loader has gone through several versions in the last year, each time fixing a few bugs and adding some new ones. Some of the bugs are irritating, such as not finding subroutines that are located in the middle of the program. Other bugs are catastrophic, such as trashing the program while modifying logic with the "Duplicate output check" turned on. (This may or may not have been fixed, but i am not particularly interested in testing it.)

This software is very intolerant to keystroke errors. You have been warned. The upcomming software upgrade is proclaimed to be bigger and better than ever. Probably it will be up to the usual high Honeywell standards. The Control Logic diagrams are a fast means of finding the ladder logic responsible for the desired function. The Loader's search function allows searching by address and by address for a general or specific element type. For example, searching for the number 100 will find all of the contacts and coils with address 100, (and, in the older versions of Loader, constants and line comments).. Pressing a contact or coil function key after entering the search address will restrict the search to that type of element. The display will then show the types of contacts or coils available. Selecting the specific element will restrict the search to only that item. Searching takes place from the current line to the end of the program. Pressing Y for yes will start the search over from the beginning of the program.

Counters and Push/Pull instructions are somewhat more difficult to search for. The loader does not recognize their "Implied addresses". The accumulator on a timer or counter may be searched. The preset register is invisible, unless some other line deals with it. The Pushes and Pulls may specify 1 to 8 addresses. In order to search for for these instructions, you need to know the address and How Many words are being read / written. HERE IS THE BIG RULE: ALL OF THE PUSH OUTPUT INSTRUCTIONS TO REAL ANALOG OUTPUTS ARE A PUSH OF ONE WORD. This means that you may find the real analog output address in one of the listings and search for a push of one word. The push and pull instructions are used for all of the analog real I/O operations, including the RTU. The inputs from the TC and analog input modules Pull the entire module at once. The analog modules have 8 channels, so the Pull address is 7 greater than the module address listed on the PLC Control System Block Diagram, 900-8408 sheets 3 & 4.

3.4 PLC Program outline

Program structure MAIN
        Emergency Stop
        Call RTU and Analog inputs          Sub #102
        Call Supervisory                    Sub #103
        Call TC inputs                      Sub #104
        Call Door control                   Sub #109
        Call Cure initialize                Sub #114
        Call Pressure                       Sub #30
        Call Temperature                    Sub #50
        Call Vacuum                         Sub #60
        PID Auto Manual control
        Call PID                            Sub #255
        Call Simulate                       Sub #125
        Read only PID variables by TDC
        Call View Screens                   Sub #126
        Call Startup                        Sub #127
        Call PID Loop Tuner                 Sub #128
             Techmation interface
        TC strobe
        HIM Alive bit
        First scan coil
    Return to beginning of program

      Sub 102 Analog inputs and RTU
        4-20 mA view
        4-20 mA summation registers
        Pull analog modules
        initialize pointers to summation
        Do loop, sum channel readings
        If samples = 16
          Do loop, average analog channels
        RTU error timer; RTU health coil
        If first scan, initialize COP; NSKR 99
        If first scan, Send command to COP, read PV
          (Other command to be determined)

        If Not New data from RTU via COP, then return
        New data:
          Initialize pointers, COP addr, PLC data regs, Quantity
          Call 106, Read Cop Database of PVs
          Initialize pointers, COP addr, PLC status regs, Quantity
          Call 106, Read Cop Database of Status
          Do loop, Test for new and good data
            If bad channel, set coil at 1500 + channel number
            If good channel, reset coil at 1500 + channel number
          Compare 48 coils with 48 bits at 5102,3,4
            Set 648 if bad channel coils match error bits
          Return

    Subroutine 106 Read COP database
        Write starting address and Pull Quantity (1) to COP
      and delay
       Do until Quantity to be read = 0
          Pull one channel, send to PLC table, and delay
          Increment PLC table addr, decrement Quantity
          Test and skip
        View RTU data
      Return

      Subroutine 104 Pull module of Thermocouples
        Module counter
        Return on odd scans
        If first scan or module counter = limit, reset counter
      and pointers
        If counter = module n, then Pull module and write to
      buffer (14 lines)
        Read buffer, write to channel addr, increment pointers,
      four times
        Write TC module milivolt value to mV table
        Write TC error code to table
      Return

      Supervisory, alarms, computer shed Subroutine 103
        HP Computer shed timer
          Reset by contact 1700
          (Changes feedback from Computer to Air)
        Simulate request switch
        Total simulation switch
        Reset After Simulate:
          Pressure setpoints
          Circ and Combustion run switches off
        Door and equipment status logic
          Door is closed and locked status
          Door pump operating
        High pressure alarm
        Ping pong valve
        Estop status
        PLC Card Faults exist
        Outputs to Thermoflux
          Circulation Blower Motor Run timer (up to speed)
          Combustion Blower Motor Run timer (enable heating)
          Thermoflux alarm reset button timer, minimum on time
        Open current loop detection ( < 3.75 ma and with deadband)
          One each analog module channel, 10 places
        Setpoint to PV deviation alarms
          Sample deviation for one channel once every 27 seconds
            Initialize channel pointers
            SP - PV greater than limit then Set alarm latch

      \215
        Pressure gauges deviation alarm
        Low LN2 Heat Exchanger Temperature < -100 deg
        Alarm light
          Group 1, open 4-20 loop
          Group 2, ditto
          Group 3, Thermoflux alarms
          Group 4, ditto
          Alarm light output coil 75
      \224
        Man In Autoclave status
        PLC holding status
      Return

      \229
      Subroutine 109 Door Control logic
        Safe to open door indicator
        AC is blown down status
        Door Pump operate
          Open button and safe to open
          Close button and Not Man in AC
        Open Ring output
        Ring midpoint delay timer
        Open door output
        Close door output
        Close ring output
        Door panel lights
        Autoclave Lights output
          Blink timer for close
          Door closing horn
        Bearing temperature hi
        Bearing temperature very hi, (shutdown)
        Circulation Blower Motor Control
          Motor permissives
          M contactor timeout
          Turn off motor switch
        Combustion Blower Motor Control
          Motor permissives
          M contactor timeout
          Turn off motor switch
        AC Low pressure switch MOV control
        O2 Analyzer MOV control
          Low pressure and O2 MOV timer, minimum on time
        N2 blocking valve
          Open permissives
          Vent Valve open and close
          Block valve output
          Block and Vent valves timer
        Low and high Pressure LN2 valves
          LN2 MOVs timer

      \272
        Vacuum MOVs control
          Save port valve selection on Line Test
          Restore port valve selection after Line Test
          Operate MOVs for minimum timer
          Vacuum Valves Arbitration logic
            Leak Test
            Calibrate
            Port source / probe change detect
            Change in switch arbitration
            Close Source valve on solvent extraction coil
            Reset valves to normal operation
          Status of Probe valves
          SKIP unless start and end of MOV Timer
            Current Source valves status update
            One line for each output wire, 2/valve, 3 X 32 lines
            EOS 8300

      \485
        Calibration Air to Vacuum Headers MOV timer
          Open / Close Air to Header 1
          Open / Close Air to Header 2
        Open / Close Vacuum MOV to Solvent Extraction Tank
          Tank MOV timer
        Automatic Solvent Extraction
          Initialize pointers on Auto Switch turningd on
          C valve open timer
          Set / Reset valve switch using indirect address register
          Increment IAR
          Test for last valve
          Turn off all C valves with Auto Switch turning off
      Return

      \507
      Subroutine 30 Pressure control
        Initialize demand register to PV at cycle run
        Reset Equipment Bypass at end of cycle run
        (Cure initialize has already set segments 1 and 2 values)
        Detect change to segment 3
          Set pressure ramp rate, soak level and soak time
        Detect change to segment 5 and set limits
        Current segment is ramp or soak status
        Test for end of pressure cycle
          Reset pressure demand to 0
        Pressure X 1 and Temperature X 1 for hold and releases
        Test for switch to air on cooldown, latch when permitted
          Set Air switch to air on cooldown or on Man in Autoclave
        Set operator control of pressure on Man in AC true
        Set operator pressure setpoint to PV on Man in AC true
      transition
        Test for Temp hold Press release time 1
        Test for Temp hold Press release time 2
        Test for Temp hold Press release by temperature
        Test for Temp hold Press time 1
        Test for Temp hold Press time 2
        Combine releases

      \534
        Temperature holding pressure latch
       Pressure SP X 1 for Vacuum and PPLT hold
          Hold pressure by vacuum until vented
        Temperature is holding pressure status
        Enable pressure ramp counter
        Pressure ramp rate timer
        Press up / down
        Pressure demand counter
        Pressure is at soak point
        Soak timer enable
        Soak timer
        Pressure ramp / soak time remaining
        Try to increment pressure segment
        Segment increment enable
        Pressure segment counter
        Pressure segment status
        Operator pressure setpoint
        Ramp / soak generator pressure setpoint
        Pressure Auto / Manual switch
          Manual PD = 0%
        Operator Pressure setpoint on ESTOP = 0
        Ramp / soak pressure setpoint on ESTOP = 0

        Integral term zeroed on Auto so PD starts at 50%
        Select pressure gauge for PV
        Reset Automatic Purge on ESTOP, door open and high pressure
        Purge cycle operating latch
        Oxygen Analyzer is valid timer
        Purge cycle complete status
        Purging at low pressure, add air to AC
        View pressure stuff

      \567
        Outputs to real world
        Fill air or gas demand from PD
        If adding air on purge, demand = 3FC302 rate
          Clamp at 0 and 4k
        1 inch vent demand and purge rate addition
          Open on ESTOP, blowdown, high pressure, and clamp at 4k
          Clamp to zero on negative numbers (during filling)
        4 inch vent demand from PD
          Restrict valve when adding air on low pressure purge
          Open on ESTOP, blowdown, high pressure, and clamp at 4k
          Clamp to zero on negative numbers

      \578
        Outputs to valves with Emergency condition override control
      loop
        Push Nitrogen control valve
        Push Air valve
        Push 1 inch vent valve
        Push 4 inch vent valve
      Return
      \587

      Temperature control Subroutine 50
        Temp system standby coil
        Set demand to PV on standby going false
        Set demand to PV on cycle run going true
        Detect odd (ramp) or even segment
          Set Soaking or off status
        Detect segment change to 3, set ramp rate, soak temp, and
      soak time
        Detect segment change to 5, set ramp rate, soak temp,
      and soak time
        Detect segment change to 7, set ramp rate, soak temp,
      and soak time
        Detect segment change to 9, set ramp rate, soak temp,
      and soak time
        Detect segment change to 11, set ramp rate, soak temp,
      and soak time
        Detect Cooldown segment change delay timer

          Reset demand SP to present PV on cooldown
        PV X 1 for hold and restarts
        Precure temperature reached delay timer
        Set temp cycle to run
        Temp cycle is running status
        Reset temp cycle running
        Minutes into Pressure Segment for Press hold Temp
        Set press hold temp latch
        Pressure X 1 for release
        Set press release temp
        Press is holding temp status
        Enable temp ramp
        Enable temp soak
        Try to increment segment
        Increment segment enable
        Reset segment counter at end of temp cycle
        Temp segment counter
        Temp segment number status
        Temp ramp rate timer
        Temp demand counter
        Temp is at soak level
        Temp soak timer
        Temp Soak t