PLC Program problem - Siemens S5 115U

[hubertooru]

Hi All,

I am a Plant Engineer of a Cement grinding and packing factory here in Lae, Papua New Guinea. I have a MEchanical Engineering background and am not very deep into PLC. I have only gone throgh bascis programming and Wiring Diagrams as every Engineer know.

2 days ago, my plant have experienced a pattern fault and the PLC Program turns to be faulty.

It is a SIEMENS S5 115U CPU943B..........

Can anyone of you help me with Clues to tackle the problem.

thank you

 

[mohamedzobaa]

You can specify the cause of problem if you have the software with cable and read ISTACK

 

[parky]

You need to go on-line & check the ISTAK, here it will give you the info on what & where the plc faulted (assuming it has Stop light on & no run light).
The chances are that if no one has touched the program then it will be one of the following:
1. Battery fail & plc lost power in this case it will need to be re-loaded.
2. Hardware failure this could be any of the modules or rack, istak will give you the address of i/o it failed on.
If it has stopped on program then the most likely causes are a call to a non existant i/o or a databloc is smaller than the address the program is trying to access in this case the likely problem would be in some indirect addressing i.e. a loop that scans through datawords & the pointer has incremented > than the length of the block, you will need to understand the program & what it's trying to do.

 

[curlyandshemp]

Hi All,

I am a Plant Engineer of a Cement grinding and packing factory here in Lae, Papua New Guinea. I have a MEchanical Engineering background and am not very deep into PLC. I have only gone throgh bascis programming and Wiring Diagrams as every Engineer know.

2 days ago, my plant have experienced a pattern fault and the PLC Program turns to be faulty.

It is a SIEMENS S5 115U CPU943B..........

Can anyone of you help me with Clues to tackle the problem.

thank you

Assuming that the S5 has been running for years, that would eliminate a program issue for a crash. Faulty cards such as analogs and communication cards could cause a crash if these hards have a failure.

If that is the case, you need the Step5 software and 20ma Current Loop cable to go online with the PLC, check the ISTACK as to which card caused the crash

Without a Step5 computer to go online, you have really no chance of finding the problem