Emergency stop button

[alan2525]

I work in a Design and Technology Workshop, we have a key switch for turning the power on and three mushroom headed E-stop buttons around the workshop for cutting off power to fixed machines and 240v sockets (some sockets are isolated by the keyswitch and some are on an uncontrolled circuit)

Current system doesn't conform to BS 4163

Insert Key in Key switch, turn power on and leave key in keyswitch (power is turned off if key is removed)

When emergency stop button is pressed, power is switched off, but E-stop buttons can be turned to reset which returns power. Seems odd using a button marked "EMERGENCY STOP" to switch the power on!

Does BS 4163 just relate to new builds? I would have thought health and Safety was a priority and all D&T workshops should meet those regulations.

 

[mattylad]

Sounds like its wired wrong.

IMO the ES buttons should stop it without being able to turn it back on.

 

[stillp]

The power should not be restored just by resetting the e-stop.
Operating the e-stop should drop out a contactor, which can only be re-energised by a deliberate manual action. See BS EN ISO 13850.

There is a BS on the subject of D & T workshops, but I'm away from my office for a few days and can't find the number. Try a keyword search on http://shop.bsigroup.com/

 

[big-all]

why not remove the feed that permits the kill switch to re-energise the machine
and insert a sperate key switch to re-energise

 

[Spark123]

Sounds like the key switch and push buttons are just wired in series on the control circuit to power the coil of a contactor.
Should be wired as a retaining contactor with the key switch operating momentarily to pull the contactor in.

 

[alan2525]

Does BS 4163 just relates to new builds, or should existing D&T workshops conform to those regulations too?

 

[alan2525]

Sounds like the key switch and push buttons are just wired in series on the control circuit to power the coil of a contactor.
Should be wired as a retaining contactor with the key switch operating momentarily to pull the contactor in.

The Key switch isn't of the momentary type, it's just turned to the on position to switch on and turned off to remove the key and turn off the power.

 

[holmslaw]

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