geniusintraining
Lifetime Supporting Member + Moderator
Damper control: air to air heat exchanger, pre-heater
We call this a block and bypass dampers, I have process air coming into this preheater at 200f leaving @ a set point of 500f, the means of heating this air is the same air has to be incinerated @ 1400f, so we take a portion of this hot gas and recover the heat to preheat the incoming air
I have a few PID controllers that I’m having issues with at best I can only get +/- 40deg variance, so I am going to “roll my own”
They are controlled by a forward and reverse motor starter, so just cycling/pulsing the contact to get the proper damper position, they both have (now) a 0-5vdc position feed back to the plc
They also need to be in the same mirrored position, due to creating back pressure, if one is open 20 % then the other needs to be closed 80% +/- 5%
Here’s what I plan on doing,
Set up a PID to control a timer preset, depending on how far out of span the PV is compared to the SP, we will increase or decrease the timer preset, but I also need to put a max rate of rise 25 deg per/min
Then slave the other damper with a PID loop, looking a actual position for the other PID control
So what do you think? is there a better way? the controllers that I am using now are no longer made and there is no info on them, I have tried for several days to tune these, but no luck so keeping them is not going to happen.
Damper 116 and 117 are first then if it works I'll go back to the oil heating damper
We call this a block and bypass dampers, I have process air coming into this preheater at 200f leaving @ a set point of 500f, the means of heating this air is the same air has to be incinerated @ 1400f, so we take a portion of this hot gas and recover the heat to preheat the incoming air
I have a few PID controllers that I’m having issues with at best I can only get +/- 40deg variance, so I am going to “roll my own”
They are controlled by a forward and reverse motor starter, so just cycling/pulsing the contact to get the proper damper position, they both have (now) a 0-5vdc position feed back to the plc
They also need to be in the same mirrored position, due to creating back pressure, if one is open 20 % then the other needs to be closed 80% +/- 5%
Here’s what I plan on doing,
Set up a PID to control a timer preset, depending on how far out of span the PV is compared to the SP, we will increase or decrease the timer preset, but I also need to put a max rate of rise 25 deg per/min
Then slave the other damper with a PID loop, looking a actual position for the other PID control
So what do you think? is there a better way? the controllers that I am using now are no longer made and there is no info on them, I have tried for several days to tune these, but no luck so keeping them is not going to happen.
Damper 116 and 117 are first then if it works I'll go back to the oil heating damper