cardosocea
Member
Hello Guys,
I've inherited a system that manages the bulk material loading onto 4 reactors. The system is built on an SLC PLC and the majority of the valves are on a DeviceNet network where we can issue commands and receive their position feedback.
Apparently this has been unreliable from the start and although we are looking at the entire replacement of it, with the Covid-19 now appearing we're trying one last push to get it working properly and potentially extend its life a bit longer.
The problem we have is that the additions every now and then either go completely wrong (wrong material added) or to the wrong location or the quantities are off (like double charging).
The logic in the PLC essentially waits to see all the quantities to change from -32767 to something different and if all of them are different and a start bit is made, it copies the addition data onto a buffer and then another part of the program deals with the requests in the buffer and routes the addition through.
I've followed the logic and can't quite see what could cause this sort of problem there as it's not consistent, so gut feeling told me perhaps the problem is in the SCADA (FactoryTalk View SE).
In there it essentially takes the values for each addition and writes to the tags in the PLC. This however is done with the Set command and, according to the manual, to speed it up they used the & to execute these in parallel fashion. This is one thing I wasn't sure would be the cause of the problems, but since the logic waits to see all the variables changing (by checking for bit 15 to go to zero), I assumed it would be ok.
I know the description is quite vague, but would you guys have seen any similar system before or potentially problems that would explain these woes? Or places to look for what could cause this too.
Likewise, the pop up from where the additions can be controlled is available in several nodes. Is there a known issue when using reusable pop ups across different clients for the same application? Meaning that we have 4 reactors to load and the system looks at all 4 so potentially two additions may be asked to be performed at the same time. Would there be a way to limit this?
I've inherited a system that manages the bulk material loading onto 4 reactors. The system is built on an SLC PLC and the majority of the valves are on a DeviceNet network where we can issue commands and receive their position feedback.
Apparently this has been unreliable from the start and although we are looking at the entire replacement of it, with the Covid-19 now appearing we're trying one last push to get it working properly and potentially extend its life a bit longer.
The problem we have is that the additions every now and then either go completely wrong (wrong material added) or to the wrong location or the quantities are off (like double charging).
The logic in the PLC essentially waits to see all the quantities to change from -32767 to something different and if all of them are different and a start bit is made, it copies the addition data onto a buffer and then another part of the program deals with the requests in the buffer and routes the addition through.
I've followed the logic and can't quite see what could cause this sort of problem there as it's not consistent, so gut feeling told me perhaps the problem is in the SCADA (FactoryTalk View SE).
In there it essentially takes the values for each addition and writes to the tags in the PLC. This however is done with the Set command and, according to the manual, to speed it up they used the & to execute these in parallel fashion. This is one thing I wasn't sure would be the cause of the problems, but since the logic waits to see all the variables changing (by checking for bit 15 to go to zero), I assumed it would be ok.
I know the description is quite vague, but would you guys have seen any similar system before or potentially problems that would explain these woes? Or places to look for what could cause this too.
Likewise, the pop up from where the additions can be controlled is available in several nodes. Is there a known issue when using reusable pop ups across different clients for the same application? Meaning that we have 4 reactors to load and the system looks at all 4 so potentially two additions may be asked to be performed at the same time. Would there be a way to limit this?