J
We have recently had a few incidents where GE 90-30's fault when an online edit is saved. At least two sources at GE have said that it is the nature of the beast... as online edits are made, the PLC memory becomes fragmented. Eventually, memory is exhausted and the processor crashes. Once, we have received a warning message which prevented us from saving the change, but usually we crash without warning. Even the serial and ethernet ports shut down and we must cycle power to the rack to get them back.
We asked GE if we had overlooked this in the documentation. Amazingly, they say it's not in the documentation!
GE's only solution is to occasionally stop the processor and do a "stop mode store," which will load the logic without fragmentation. This is probably acceptable in many applications, but not ours.
We use these PLC's for utilities and HVAC at a rapidly growing hospital campus. Due to the growth, new features or logic changes are required frequently, while keeping the processes online. We can switch most of the systems to manual to do the stop-mode store, but our client strongly objects to doing this very often.
We are already using 364 CPUs, which are the most capable available in terms of memory and horsepower, so we can't just throw more hardware at the problem.
The main solution we are currently considering is to use GE's hot standby redundancy scheme to allow us to stop-mode store one processor while the other is in control. Obviously, this is an expensive and complicated fix, but less so than porting all the logic to a new platform.
I'd be interested in hearing others' experience with GE or other equipment.
Thanks,
John McCoy
We asked GE if we had overlooked this in the documentation. Amazingly, they say it's not in the documentation!
GE's only solution is to occasionally stop the processor and do a "stop mode store," which will load the logic without fragmentation. This is probably acceptable in many applications, but not ours.
We use these PLC's for utilities and HVAC at a rapidly growing hospital campus. Due to the growth, new features or logic changes are required frequently, while keeping the processes online. We can switch most of the systems to manual to do the stop-mode store, but our client strongly objects to doing this very often.
We are already using 364 CPUs, which are the most capable available in terms of memory and horsepower, so we can't just throw more hardware at the problem.
The main solution we are currently considering is to use GE's hot standby redundancy scheme to allow us to stop-mode store one processor while the other is in control. Obviously, this is an expensive and complicated fix, but less so than porting all the logic to a new platform.
I'd be interested in hearing others' experience with GE or other equipment.
Thanks,
John McCoy