Whilst researching answers to other current electrical questions on this n.g. I came across BS4163:2007, pithily entitled "Health and safety for design and technology in schools and similar establishments ? Code of practice".
BS4163 contains some interesting clauses, which include the following:
"For standard nominal 230 V a.c. supply with neutral at, or approximately at, earth potential, the socket-outlets should conform to BS 1363-2. Equipment that requires installation in a particular location or that requires an industrial type plug, should be supplied by socket-outlets conforming to BS EN 60309-2, colour coded blue."
and
"Socket-outlets that supply voltages greater than extra-low voltage and up to 250 V (a.c. or d.c.) and that do not conform to BS 1363-2, BS
7288, BS EN 60309-2 or BS 546 (shuttered) should conform to BS 5733."This represents another example (re: my previous reference to the Regs and the OSG being somewhat out of kilter) where shuttering on socket outlets has clearly been considered, but interlocking has not been prescribed in lieu of shuttering for IEC309 connectors.
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On a second point, I have been trying for a while to get an official view on the use of workshop wide e-stop systems and BS4163 has the following to say:
"Emergency switching systems should be provided in each separate student work area. [...]. The systems should switch off all circuits supplied via the switch-disconnector[1] in an emergency. Critical circuits specifically installed to remove hazards (e.g. fume extractor fans, lighting, alarm circuits) should not be controlled by the emergency system.
"The emergency switching device should be a remotely operated contactor or circuit breaker that opens when the coil is de-energized. The switching device should be controlled[2] by a series of readily accessible push buttons[3] evenly distributed around the work area, at an approximate height of 1.5 m, and clear of benches and machines. It should only be possible to reset the remotely operated contactor or circuit breaker by a single key-operated spring return switch sited within view of the work area it controls. A responsible person should retain the key. (See also BS EN 60204-1, BS 7671 and BS EN ISO 13850.)
"Push buttons should be conspicuous, and coloured red on a yellow mounting surface (see BS EN ISO 13850) and a safe condition sign conforming to BS 5499-5 should be in place adjacent to each switch.
"The emergency stop system installed in a workshop should not negate any other safety systems fitted to machines, e.g. braking systems on hand fed wood cutting machines."
I have seen installations where a latching/key release e-stop button has been installed in lieu of a key-operated start switch but BS4163 does not allow for this alternative (and arguably slightly less safe) arrangement.
Cheers, DaveyOz.
[1] "In each workshop area it should be possible to disconnect and isolate all electrical circuits that supply fixed equipment and socket-outlets by a single switch conforming to BS EN 60669-2-4 or BS EN 60947-3. The switch-disconnector should be readily accessible, clearly labelled ?main switch?, and lockable in the ?off? position. The switching device should not control lighting, space heating and specific socket-outlet circuits for cleaning purposes." [2] I presume that by "controlled" they mean "de-energised" [3] i.e. "mushroom-head emergency stop switches".