AB Safety PLC I/O Sudden communications lost without alarm

[AlQattan14]

Hi guys,
This my first time posting hope I get help in my issue..

I have Allen bradley control logix safety PLC (1756-L61S) connected with several remote I/O via ethernet card 1734-AENT, these I/O mainly emergency switch and limite switchs. But time to time (daily once or twice) some input or output card get disconnected randomly each time in different I/O rack for 2 seconds and get connected back again but it causing emergency switch active and interrupting machine processes.
When its occurred no minor/major alarm is registered and the cards get disconnected charging from rack every times it happens.

We replace the ethernet card(1756-EN2T) in local rack still same.

Hope I get support as the problem get appeared more frequently.

 

[drforsythe]

We had the same problem here. I found that there was a product issue and was able to get new modules under warranty within a certain date range. The lead times are awful if you place an order, but my distributor had stock reserved just for this recall. I was able to get replacements in a few days, but had to wait weeks to months to get ones I had ordered.

I cannot find the original technical bulletin on the Allen Bradley Knowledgebase, but I did find an update. Search IN34116 on the Knowledgebase.

Good luck.

 

[AlQattan14]

Thanks drforsythe,

The issue appears randomly every time different remote rack and different cards, if it's specific to one or two card yes I will go for replacement but the issue it keeps jumping to differents cards.

 

[joseph_e2]

Based on that KB article, I wouldn't be surprised to find that it's affecting all of your racks randomly. It's very likely that all of the modules you have are from a similar date range so it wouldn't surprise me if you have more than one bad unit. I would check the date codes on all of the modules the next time the system trips and compare them to what's shown in the KB article.

 

[AlQattan14]

Based on that KB article, I wouldn't be surprised to find that it's affecting all of your racks randomly. It's very likely that all of the modules you have are from a similar date range so it wouldn't surprise me if you have more than one bad unit. I would check the date codes on all of the modules the next time the system trips and compare them to what's shown in the KB article.

thanks joseph,

KB article is mainly on output card while my case most of the time input is disconnected. like attached trend it was three input cards out of 8 in the same rack.

 

[MikeyN]

What is the firmware version of your 1734-AENT? We are currently going through the exact same thing. The cards we are using were manufactured about a year prior to the dates in the posting. We were told to upgrade the firmware on our 1734-AENT to see if that alleviates the issue any. Since I need to replace the controller for capacity issues, we are waiting until production stops to do everything at one time. For reference, our AENT is V4.001 and they are suggesting we flash it to V5.019 (or whatever the latest is when we manage to get it done). If it helps you more, we are using this in conjunction with a 5069-L306ERS2, soon to be a 5069-L310ERS2, so it isn't unique to the 1756 platform.

 

[AlQattan14]

What is the firmware version of your 1734-AENT? We are currently going through the exact same thing. The cards we are using were manufactured about a year prior to the dates in the posting. We were told to upgrade the firmware on our 1734-AENT to see if that alleviates the issue any. Since I need to replace the controller for capacity issues, we are waiting until production stops to do everything at one time. For reference, our AENT is V4.001 and they are suggesting we flash it to V5.019 (or whatever the latest is when we manage to get it done). If it helps you more, we are using this in conjunction with a 5069-L306ERS2, soon to be a 5069-L310ERS2, so it isn't unique to the 1756 platform.

Our current 1734-AENT firmware version is V3.005, did you receive recommendation from AB regarding upgrading to V5.019 (or whatever the latest is when we manage to get it done)?

Yes look like not related to 1756

 

[MikeyN]

Yes, the recommendation came from Rockwell via our distributor.

 

[Steve Etter]

Check the RPI settings for each of your safety modules and other ethernet devices. You could be up against a communications threshold.

Start with non-critical devices and increase their RPI settings.

 

[JeffKiper]

I've had several of them just randomly drop the connection. I found that there was a date range just like the above posters have said. We also did a firmware upgrade of several of them and the problem went away.

 

[AlQattan14]

Check the RPI settings for each of your safety modules and other ethernet devices. You could be up against a communications threshold.

Start with non-critical devices and increase their RPI settings.

I've had several of them just randomly drop the connection. I found that there was a date range just like the above posters have said. We also did a firmware upgrade of several of them and the problem went away.

My RPI in AENT card was 20ms and we change to 100ms one month back but still same, and in IB8S is 10ms, from your experience what should be the RPI in each?

 

[Steve Etter]

I would only adjust the RPI for non-safety related devices, especially to start. 100ms for non-critical equipment has worked well for me. I have never modified the RPI for a safety module. Also remember to look at the RPI for any Produced and Consumed tags.