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E Stops used in Lab areas

Andy

Hello All,

              I'm looking for a cost effective way of introducing E Stops to Lab and Clean room power circuits. Some of these are rows of single phase sockets on benches in test and evaluation areas and others are complete power shut offs for 3 phase power to production equipment. These circuits would literally be Emergency use only as the name suggests. I don't really want to use contactors on the socket circuits mainly to reduce the the possibility of added noise on the lines.

Question is

a) Has anyone had experience with shunt trips or bolt on modules to existing RCDs for the socket circuits these could be fitted locally with the reset under lock and key in the plant room. Is there a best practice for this type circuit?

b) Most three phase equipment in these areas have E Stops built in but the requirement is to isolate the complete room. So the more I think about it the more I'm considering a main contactor or shunt trip device on  the output of the   equipment UPS. It is possible the UPS may have a facility for this but it's not obvious.

If anyone has experience in this field please advise.

Much appreciated

Andy

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  • 0

    What would be the reasons for activating the e-stop - i.e. what sort of hazard are you trying to mitigate? I suspect a lot of the systems out there are regarded as safety critical so need to fail safe - hence the usual arrangement of NC stop buttons and a relay/contactor(*) - so if anything goes wrong with the button circuit, the current stops and the springs open the main contacts. Shunt trips normally need power to trip, so a failure of the button circuit would typically result in the main contacts remaining in whatever position they were in - usually closed.

    * Often a safety relay, with all kinds of extra monitoring and duplicated contacts to try and detect welded contacts or other defects and still shut the system down safely.

    So it depends on the application really.

       - Andy.

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  • 0

    What would be the reasons for activating the e-stop - i.e. what sort of hazard are you trying to mitigate? I suspect a lot of the systems out there are regarded as safety critical so need to fail safe - hence the usual arrangement of NC stop buttons and a relay/contactor(*) - so if anything goes wrong with the button circuit, the current stops and the springs open the main contacts. Shunt trips normally need power to trip, so a failure of the button circuit would typically result in the main contacts remaining in whatever position they were in - usually closed.

    * Often a safety relay, with all kinds of extra monitoring and duplicated contacts to try and detect welded contacts or other defects and still shut the system down safely.

    So it depends on the application really.

       - Andy.

Children
  • 0 in reply to AJJewsbury

    Hello AJJewsbury,

                                 Thanks for your reply.

    These circuits are RCD protected however there is a lot of test equipment on racking in bays for use by no technical operators who would not necessarily know what to disconnect should anything go wrong. So the E stops are a for their one go to point to be sure of isolation.

    I take your point about welded contacts and have even seen two contactors in series on some semiconductor wafer deposition tools but these were all 100A plus 3 phase. I suppose to combat the risk of welded contacts I'll need to do RAMS for their operation. However These circuits would be maintained by site facilities and tested regularly along with the RCDs. 

    I have had an idea about Pilz relays but these seem to figure more for equipment but again would still require a contactor.

    Thank you comments and interest

    Andy

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