Tim Ganz
Member
We have an oven with 32 zones and a Controllogix L7 controls the oven and all the steam valves, plate heaters and T/C's come in over different Point IO racks on Ethernet.
Today we lost the adaptor on one of the Point I/O racks and on the HMI the temperature never changed but when we found out we had a problem some of the plate heater zones had started melting down and when we took a temp reading were around 900 degrees and the steel of the heater was melting in some places.
The HMI showed a setpoint of 400 degrees on all those zones and a PV of 310-330 so the PIDE was giving 100% heat output and we normally have heat an cool but the zones in question are heat only.
PV comes from the point IO rack and gets multiplied by 0.1 so the scaling is right and it reads right on the HMI then the destination value goes straight into the PIDE.
I have almost no experience with the PID setups but it looks like when we lost the point io rack with the T/C's the last value that was written when we lost the rack is what stayed and what the PIDE controlled with and it was below setpoint so it kept giving 100% heat output. Am I on the right track here?
I need to prevent this from happening again so I am thinking of polling the point io racks the see if they are active and if not disable the whole heater circuit or all zones that the failed rack is involved with? is there an easy way to do this?
Also is there anything in the PIDE instruction that can help? looks like its loaded with features but I don't understand most of them and I have to put something into place this weekend while the line is down.
Does the PIDE do rate of change in some way meaning if it has 100% heat for x amount of time and temp has not increase x amount then fault/alarm/shutdown?
If not in the PIDE is there a simple way to do this in ladder logic. Everyway I am considering seems like a boat load of programming.
Any tips are appreciated.
Today we lost the adaptor on one of the Point I/O racks and on the HMI the temperature never changed but when we found out we had a problem some of the plate heater zones had started melting down and when we took a temp reading were around 900 degrees and the steel of the heater was melting in some places.
The HMI showed a setpoint of 400 degrees on all those zones and a PV of 310-330 so the PIDE was giving 100% heat output and we normally have heat an cool but the zones in question are heat only.
PV comes from the point IO rack and gets multiplied by 0.1 so the scaling is right and it reads right on the HMI then the destination value goes straight into the PIDE.
I have almost no experience with the PID setups but it looks like when we lost the point io rack with the T/C's the last value that was written when we lost the rack is what stayed and what the PIDE controlled with and it was below setpoint so it kept giving 100% heat output. Am I on the right track here?
I need to prevent this from happening again so I am thinking of polling the point io racks the see if they are active and if not disable the whole heater circuit or all zones that the failed rack is involved with? is there an easy way to do this?
Also is there anything in the PIDE instruction that can help? looks like its loaded with features but I don't understand most of them and I have to put something into place this weekend while the line is down.
Does the PIDE do rate of change in some way meaning if it has 100% heat for x amount of time and temp has not increase x amount then fault/alarm/shutdown?
If not in the PIDE is there a simple way to do this in ladder logic. Everyway I am considering seems like a boat load of programming.
Any tips are appreciated.