GE 90-30 PLC error

noobboy1997

Member
Join Date
Jul 2018
Location
Hong Kong
Posts
4
Hi, I am new to the GE PLC.
Our company hired contractors to build a plc control system for electrical interlock and changeover system around the 90s.
The system worked well until a firmware upgrade done by the maintenance team a long time ago, we have to clear the fault table every 2 weeks.
As a client, I have very limited understanding on how to use the PLC and diagnose the error.
The system is using I have no idea what the fault location it is referring to and what causes error. The system is currently using CMM311 and CPU351 modules.
Any advice or help is highly appreciated.
https://imgur.com/a/rf8LJ4d
https://imgur.com/0SfMJpU
 
Last edited:
The fault entry in the "QIS" PLC is telling you that the PLC stopped running its program because it was told to do so by a "SVC_REQ" instruction in ladder logic. Search the program for that instruction. If there are more than one instance of the SVC_REQ function, the one that shuts down the PLC will have a function code of 13.
The fault entries in the "TIS" PLC point to the module in rack 0, slot 3. Rack 0 is the one with the CPU. They are generated as a result of a "COMMREQ" function in ladder logic. I can't tell you anything more without knowing what module is in that location and without seeing how the COMMREQ instruction is set up. Those faults themselves do not cause the PLC to shut down, but whatever was supposed to happen due to the COMMREQ instruction did not happen.
 
Thanks for your reply.
Rack 0 Slot 3 refers to the CMM311.
From the inpsection report the following is found between the TIS and TIK PLCs.
What are these codes stand for?
[LD Block,'COMM': Rung 00017, Instruction] COMM_REQ COMM.R02241 3 2
[LD Block,'COMM': Rung 00028, Instruction] COMM_REQ COMM.R02256 3 2
[LD Block,'COMM': Rung 00040, Instruction] COMM_REQ COMM.R02271 4 1
[LD Block,'COMM': Rung 00052, Instruction] COMM_REQ COMM.R02286 4 1
[LD Block,'COMM': Rung 00071, Instruction] COMM_REQ COMM.R02301 4 2
[LD Block,'COMM': Rung 00082, Instruction] COMM_REQ COMM.R02316 4 2
[LD Block,'COMM': Rung 00094, Instruction] COMM_REQ COMM.R02331 3 1
[LD Block,'COMM': Rung 00106, Instruction] COMM_REQ COMM.R02346 3 1
------------------ Search Results ------------------
Found 8 instances of "COMM_REQ" on target "TIS"

[LD Block,'COMM': Rung 00017, Instruction] COMM_REQ R02241 4 2
[LD Block,'COMM': Rung 00028, Instruction] COMM_REQ R02256 4 2
[LD Block,'COMM': Rung 00040, Instruction] COMM_REQ R02271 3 1
[LD Block,'COMM': Rung 00051, Instruction] COMM_REQ R02286 3 1
------------------ Search Results ------------------
Found 4 instances of "COMM_REQ" on target "TIK"

------------------ Search Results ------------------
Found 0 instances of "COMM_REQ" on target "QIS"

And there is no SVC_REQ instruction reference is found from all three PLC programs. Can it possibly be in the subroutines?
 
The CMM311 is a serial communications module. The COMMREQ instructions most likely command an exchange of data between two PLCs.
If your company will permit it, make a backup copy of the programs and post them here. I have Logicmaster software and I can take a look at them and perhaps tell you what may be going on.
 
The fault location is showing the rack dot slot.

I am guessing that the CPU is in slot 1 as the stop fault is 0.1

I am guessing that the CMM311 is in slot 3 based on 0.3

Other than that, I suggest you find a programmer to assist.

Edit: Better answers came quicker
 
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I am sure these things are related to the ladder logic, my supervisor told me that there ‘s something possibly be changed in the program during maintenance, but i need some time to convince my company to give me a view on this.
Does the COMMREQ or the SVC_REQ stop the PLC from giving its desired output?
Is it merely related to the comm module?
 
According to the fault table entry in the QIS PLC, it was commanded to stop running due to a SVC_REQ function. So yes, the SVC_REQ will "stop the PLC from giving its desired output".However, the times and dates on that screen shot are confusing. The fault occurred on 7/19, the PLC's internal clock reads 8/06, but the table was last cleared on 7/28???
 

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