cardosocea
Member
Hello,
I have an application where I need to implement an override of a temperature trip. Essentially, this is a distillation column, but when running a boil-out cycle, the temperature has to be raised past the trip for normal operation.
Now, I've thought about wiring a key switch that when moved would increase the trip limit for a given time (2 hours) and once reset would require a 24 hour interval to allow the operation again. At the same time, if the override was active, the feed valves to the column would be closed shut.
The problem is that the nearest Safety IO is at a fair distance from the location where the switch would be installed and I was wondering if it would be possible to connect the switch to the nearest PLC which would transmit the status to the Safety PLC along with a watchdog bit and so on.
I have to run a risk assessment and get someone else to verify the design before changing anything, but would like your opinion on whether the network communication on this would be feasible or to disregard it straight off the bat and bite the bullet with a cable run?
Thanks in advance.
Edit: Forgot to say that this is running on a safety plc, not hardwired trip.
I have an application where I need to implement an override of a temperature trip. Essentially, this is a distillation column, but when running a boil-out cycle, the temperature has to be raised past the trip for normal operation.
Now, I've thought about wiring a key switch that when moved would increase the trip limit for a given time (2 hours) and once reset would require a 24 hour interval to allow the operation again. At the same time, if the override was active, the feed valves to the column would be closed shut.
The problem is that the nearest Safety IO is at a fair distance from the location where the switch would be installed and I was wondering if it would be possible to connect the switch to the nearest PLC which would transmit the status to the Safety PLC along with a watchdog bit and so on.
I have to run a risk assessment and get someone else to verify the design before changing anything, but would like your opinion on whether the network communication on this would be feasible or to disregard it straight off the bat and bite the bullet with a cable run?
Thanks in advance.
Edit: Forgot to say that this is running on a safety plc, not hardwired trip.
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