SIMATIC S7-300 / S7-300F

Trouble with FM350 going into SF

Thread Starter: tubeman   Started: 7/18/2012 9:41 PM   Replies: 1

  7/18/2012, 9:41 PM

tubeman Joined 7/18/2012 Last visit: 7/25/2012 Posts: 2 Rating:  (0)

(0)  Need help with our PLC!!! We have been fighting an issue with our PLC going into system fault. We have to date completly replaced our PLC, including power supplies, mmc, profibus cables, backplane connectors, checked grounding and made further grounding as directed by Siemens technical support and three visits from Siemens PLC Tech's. Fault log continuously points to FM350 as the culprit. We have replaced the card as we have (4) to pick and choose from all the same. It is the 6ES7 350-1AH03-0AE0. This equipment has been in service for 7 years. We didn't even have access to the program until about a month ago and we have had this issue for over 2 months and it has been getting worse. So no one has had the ability to change any of the program to create this problem. The only thing that has been noticed is that the hardware configuration for the FM350 is set to 5 volts and we are giving the card a 24 volt pulse, the plug on the side is also set for 24 volts. This has been this way since the machine was commisioned 7 years ago. When the hardware config is changed to 24 volts as the plug is set on FM350 we lose our profibus communications. This was proved out by Siemens techs, They have no explanation either. So the hardware configuration is left in the 5 volt configuration and FM350 set as described with plug in the "D" position and being supplied with 24 volt pulses. When the Fm350 goes into SF, the processor goes into stop mode and then goes into SF also. Due to the way equipment is designed when the processor goes into SF we lose output power, which we should, then lose our DC bus which powers down the drives and then go into a profibus BF2 fault because we have no comms on profibus, which is normal. What is even stranger is the way the faults seem to go into a crazy fault loop and it is very difficult to get processor to reset back into run. Once we have the FM350 reset and not showing SF we can most of the time get everything to reset. Sometimes we can run for a couple days without problems and some days we can never get it to reset. I am willing to upload any information that is requested.I have included the program which should give all the details of our setup and configuration. Attachment: Cuttoff.zip  (9 Downloads) === Edited by tubeman @ 7/18/2012 10:30 PM [GMT ] ===

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  7/19/2012, 6:06 PM

tubeman Joined 7/18/2012 Last visit: 7/25/2012 Posts: 2 Rating:  (0)

(0)  I would like to add to my post that we have been running for a shift and a half with out any SF errors or stopping of the PLC. We placed a dehumidifier into the PLC cabinet and are keeping the humidity below 50% in the cabinet???? This was just by chance that we came across this as we had thought that we were experiencing a heat issue and had noticed that as the humidity raised in cabinet we had more trouble with PLC SF errors. We had started by trying to cool area with a AC unit and when AC would cycle off at temperature setpoint the humidity would raise above 50% and put us into SF fault. So we turned AC off and just are trying to control humidity and so far are having success in staying alive. According to documentation the temperature limitations and humidity are well within the specifications of hardware even without the dehumidifier. Has anyone else experienced this or seen a post similiar to this?? I have searched the forum and have seen many other similiar issues to ours, however I have yet to see any threads to show the problem has been resolved.

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