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Non Programmable PID Controller
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Andy,
What do you mean by non-progarmmable PID controller? Can you clarify and be a bit more precise. Most safety systems usually do not use a lot of PID controllers. Controller control, and is usually found in the DCS or control system.
JL,
A pneumatic controller, like the 43AP is still "programmable", you just open the lid, and move the knobs. You may make an arguement that is is not remotely progarmmable, but it is programmable none the less in my opinion.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
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What do you mean by non-progarmmable PID controller? Can you clarify and be a bit more precise. Most safety systems usually do not use a lot of PID controllers. Controller control, and is usually found in the DCS or control system.
JL,
A pneumatic controller, like the 43AP is still "programmable", you just open the lid, and move the knobs. You may make an arguement that is is not remotely progarmmable, but it is programmable none the less in my opinion.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
A firmware chip with a canned PID algorithm or some "C++" logic in a PLC program is programmable, just not easy to change. Vacuum tube circuits are not programmable. Discrete component circuits are on the fringe. What criteria defines programmable? Perhaps volitile, adjustable, ...
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Thanks for all your help
The application of the PID is for the control of pressure in a nuclear system. The controller must be SIL 2 compliant and needs to have an analogue input and digital outputs. When I specified non programmable, I was referring to the controller not being adjustable.
The application of the PID is for the control of pressure in a nuclear system. The controller must be SIL 2 compliant and needs to have an analogue input and digital outputs. When I specified non programmable, I was referring to the controller not being adjustable.
Again, I am not familiar with PID control being in a safety system.
Any DCS PID control function block may be "locked" out via password protection from the operator, engineer, etc - anyone who doesn't have the password.
I would suggest you contact your safety system vendor and see what they offer. I has been at least 4 years since I last programmed a safety system (Honeywell FSC), so things may have changed since.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
Any DCS PID control function block may be "locked" out via password protection from the operator, engineer, etc - anyone who doesn't have the password.
I would suggest you contact your safety system vendor and see what they offer. I has been at least 4 years since I last programmed a safety system (Honeywell FSC), so things may have changed since.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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This company is owned by a member of this forum (member itsmoked ), and he makes custom PID controllers.
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Petrotech sells surge controllers written in C++ blocks that are imbeded in PLC programs such as A/B and GE. The GE PLC is sometimes packaged in a triplicated arangement by Silvertech. Perhaps any of the IEC compliant SIL 2 or SIL 3 PLC's could use PID in the logic solver. However, typically a SIL 1 system performs regulatory control and an independent system trips the individual process equipment areas when the regulatory control system fails to maintain the process within the specified limits.
Andy345,
.... but tuning the PID gains to respond to the system pressure based on your performance objective is what defines them. The dynamics of each process is different so controller gains will be different. Also, you will have different controller gains for the same process if you have different performance objectives.
I do not think that you can get one out of the box and simply plug-and-play. Besides, wouldn't you want to re-tune this thing down the road when some other component in your reactor start to give?
Now, if you want self-tuning controllers, that is a different story.
Fulfilling the requirement for an anolog and numerous digital inputs is easy.
.... but tuning the PID gains to respond to the system pressure based on your performance objective is what defines them. The dynamics of each process is different so controller gains will be different. Also, you will have different controller gains for the same process if you have different performance objectives.
I do not think that you can get one out of the box and simply plug-and-play. Besides, wouldn't you want to re-tune this thing down the road when some other component in your reactor start to give?
Now, if you want self-tuning controllers, that is a different story.
Fulfilling the requirement for an anolog and numerous digital inputs is easy.
How many people here have used a PID control function in a safety system?
PID is for control, and usually in the "control system".
I think andy345 you may want to revisit what you have set up in your control system vs. safety system.
The safety system is a separate system. I have not seen PID control function in a safety system.
If anyone else has, would they like to share?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
PID is for control, and usually in the "control system".
I think andy345 you may want to revisit what you have set up in your control system vs. safety system.
The safety system is a separate system. I have not seen PID control function in a safety system.
If anyone else has, would they like to share?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
Some use TMR or quad safety systems to implement burner management in complex heater firing schemes. Consider a burner management scheme for balanced draft (forced and induced draft) pressure control. This requires three furnace draft transmitters in an auctioneered median-select system, each on a separate pressuresensing tap and suitably monitored to minimize the possibility of operating with a faulty furnace pressure measurement ...
JL,
Is this a case where a "safety system equipment" is used in a "control system" application - the burner managment?
BMS typically have their owne "control system". An external safety systems sends an output to the BMS to "shut it down".
This is more typical of what I have seen.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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Is this a case where a "safety system equipment" is used in a "control system" application - the burner managment?
BMS typically have their owne "control system". An external safety systems sends an output to the BMS to "shut it down".
This is more typical of what I have seen.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
Ashereng's premise is correct. A BMS is likely dedicated per heater. Equipment packages sometimes require "autonomous" controls separate from the plant DCS or "ESD" system.
Autonomous control systems might have features that match the safety system design but seperate than a plant shutdown system. These equipment systems likely include PID control. This is true of other specialized equipment control systems such as gas turbine driven compressors or generators. A plant could have a heater or compressor control system that controls the all equipment stuff including the process and fuel inlet shutdown valves. However, (my perfect world) plant would still have process and fuel shutdown valves outside the heater controls. A plant ESD hazard such as a fire would trip the safety system valves regardless of the equipment control system logic. Depending upon the process hazard analysis and SIL study results I might or might not require the process safety shutdown system to include separate instruments within the "equipment" boundry limits. If it is a package heater using waste heat to preheat a hydrocarbon stream I would expect more safety system instruments within the equipment package than if it were a boiler for an institutional building.
Autonomous control systems might have features that match the safety system design but seperate than a plant shutdown system. These equipment systems likely include PID control. This is true of other specialized equipment control systems such as gas turbine driven compressors or generators. A plant could have a heater or compressor control system that controls the all equipment stuff including the process and fuel inlet shutdown valves. However, (my perfect world) plant would still have process and fuel shutdown valves outside the heater controls. A plant ESD hazard such as a fire would trip the safety system valves regardless of the equipment control system logic. Depending upon the process hazard analysis and SIL study results I might or might not require the process safety shutdown system to include separate instruments within the "equipment" boundry limits. If it is a package heater using waste heat to preheat a hydrocarbon stream I would expect more safety system instruments within the equipment package than if it were a boiler for an institutional building.
While this is an interesting discussion I have learned something from, I think the OP was really meaning to say he needed a PID for use in a SIL rated nuke control system. Not actually in a "safety system" per se.
Keith Cress
Flamin Systems, Inc.-
Keith Cress
Flamin Systems, Inc.-
Andy:
Are you sure that the controller needs to be SIL 2? An easier way would be to install a separate pressure SIF independent of the PID controller and implement that within your logic solver.
I agree with Ashereng... any PID is somewhat programmable and even changing the tuning parameters can severely change the operation of the loop and even disable it. To answer Ashereng's question... I have never used a PID loop in a safety system. I do believe that HIMA includes it in their system (H41 and H51) and perhaps Triconex. Others could have the ability but they would not be considered safety rated as part of their TUV certificate. I also think that Yokagowa Centum DCS is TUV certified to SIL 1.
In all of my experience with safety, I have only come across one SIF that was classified as continuous but it was still an on/off valve (the reason was that the operating pressure was very close to the trip set point and trips were expected frequently... don't ask, not my design).
A little late, but hope it helps.
sdl
Are you sure that the controller needs to be SIL 2? An easier way would be to install a separate pressure SIF independent of the PID controller and implement that within your logic solver.
I agree with Ashereng... any PID is somewhat programmable and even changing the tuning parameters can severely change the operation of the loop and even disable it. To answer Ashereng's question... I have never used a PID loop in a safety system. I do believe that HIMA includes it in their system (H41 and H51) and perhaps Triconex. Others could have the ability but they would not be considered safety rated as part of their TUV certificate. I also think that Yokagowa Centum DCS is TUV certified to SIL 1.
In all of my experience with safety, I have only come across one SIF that was classified as continuous but it was still an on/off valve (the reason was that the operating pressure was very close to the trip set point and trips were expected frequently... don't ask, not my design).
A little late, but hope it helps.
sdl
sdl,
Thanks for your response.
My point was that I too have NEVER seen a PID control loop in a safety system.
If it is controlling something, it is part of the control system.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
Thanks for your response.
My point was that I too have NEVER seen a PID control loop in a safety system.
If it is controlling something, it is part of the control system.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
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