Maintenance of RLY outputs

I have had several relay outputs fail.  The solenoid valves wired to those relay outputs had connectors that were supposed to have internal surge suppression - but they did not.

The relay outputs failed after ~50-100k valve cycles.

I was fortunate because I used a relay output module, so a replacement module is all that's required to get them back running again - plus connectors with actual surge suppression built in.

I've had relay outputs running for 10+ years where the valves had proper surge suppression (either in the connectors, or added using discrete components) at IO terminals.

Induction loads when turned off will arc across the opening relay contacts and burn them.  Enough arcs and the contacts start to operate intermittently and eventually fail completely.

adamlahadi

Hi

one of the cons of RLY outputs in s7 CPUs is that they can be damaged over time , how likely this can happen 

what are the factor that can acceleration the damaging 

can they be repaired

kind regards

Oh no.  I recommend adding a relay output module and moving the outputs to those devices, and upgrading the solenoid valve power connectors to have surge suppression built-in.

Once the relay contacts start going bad, you can contact Siemens repair facility to see if they offer repair of your PLC.  If they do, they can <possibly> ship you a certified repaired PLC.  Once received, you put your bad one in the box they shipped, and return it to Siemens.

If they say "no" to any repair / replace option (meaning no warranty), you are welcome to open up the PLC and locate the relays.  If you can find replacement relays, you can attempt surface-mount PCB repair for the bad relays.  Or, you can contact a regional electronics repair facility to see if they will attempt to locate and replace the bad relays.

To be honest, if your job or company reputation depend on the results, add a relay output module, or purchase a new PLC and a relay output module and replace the solenoid valve connectors with ones including surge suppression.

The last recommendation really is the best (right) answer.

adamlahadi

0_Einstein

I have had several relay outputs fail.  The solenoid valves wired to those relay outputs had connectors that were supposed to have internal surge suppression - but they did not.

The relay outputs failed after ~50-100k valve cycles.

I was fortunate because I used a relay output module, so a replacement module is all that's required to get them back running again - plus connectors with actual surge suppression built in.

I've had relay outputs running for 10+ years where the valves had proper surge suppression (either in the connectors, or added using discrete components) at IO terminals.

Induction loads when turned off will arc across the opening relay contacts and burn them.  Enough arcs and the contacts start to operate intermittently and eventually fail completely.

adamlahadi

Hi

one of the cons of RLY outputs in s7 CPUs is that they can be damaged over time , how likely this can happen 

what are the factor that can acceleration the damaging 

can they be repaired

kind regards

 but, what about in case of onboard outputs