Rack no 2 is continuously going in fault mode due to AI cards or Bus connector failures

Hello Siemens PLC users,

We are facing one genuine issue in our S7300 PLC system panel. 

We have connected S7300 PLC with 4 local racks via Ethernet switch. 

Our Rack no 2 is continuously going in fault mode due to AI cards or Bus connector failures.

card number is : 6ES7-331-1KF02-0AB0

in last 6 months 7 AI cards became faulty. Fault is solved by replacement of faulty cards

with new one. Our panel earthling is proper and we are not able to find actual root cause for this problem.

Kindly suggest exact method or solution to solve this issue on permanent basis. 

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Split from How to troubleshoot BUS FAULT?.

Hello,

Have you troubleshoot the failuer cause of previous AI module?

How & which types of sensors are connected?

Is any specific channel failing everytime? 

Please check above points.

Hello 

We have connected 3 wire RTD sensors, Wika make 2 wire Pressure transmitters and

Flow meters with all i/o cards.

We have not found any actual root cause of problem yet. but this particular card failure happens when our UPS power fails. At the time of power failures we found these failure of cards.