They simply man that a plug without a fuse provides effective isolation.
As I said, that's the only interpretation I could think of, but it really makes no sense. As I said/asked, who on earth would plug it back in (to a 'live' socket) after removing the fuse. As we (and Table 53.4) agree unplugging (or otherwise 'disconnecting') something is, in itself, just about the ultimate in 'isolation' - and, as above, anyone in their right mind would unplug equipment (supplied via a plug/socket) before working on it.
Daft it may be, but to be honest I thought it was perfectly normal and sensible to remove a fuse to isolate something that can be plugged in. I usually do it before throwing away a cut off moulded plug and lead for any reason.
So do I, but I wouldn't personally call that 'isolation', would you? "Disabling", perhaps, but I don't really see that 'isolation' is an appropriate word for something not connected to an electrical installation, is it?
'Isolation' and 'taking steps to ensure that the isolation persists' (e.g. by 'labelling' and/or locking an MCB or main switch) are surely two different things? A switch-fuse has recently been mentioned. I would imagine that (even though, surprisingly, such a device does not seem to appear in Table 53.43) switching that off will usually provide adequate isolation. If it can't be locked off, one might then remove the fuse to reduce the risk of anyone re-energising the circuit, but it would still be 'isolated' even if one didn't do that. Just as with the plug (above), if someone were sufficiently daft I suppose thet could switch the switch-fuse back 'on' after removing the fuse (thereby relying totally on the {absence of the} fuse as the sole means of isolation) - but, again, who on earth would do that, and why?
As far as Table 53.4 is concerned, it's perhaps a matter of clarity/words more than anything else. It seems a little odd to include in a list of 'devices for providing isolation', something that only provides isolation by its absence. If they are including fuses in that list, why not also 'cable', since removing/disconnecting cable is another sure method of achieving isolation (by the absence of a connection)?
As regards another recent comment, I'm a little confused by what Table 53.4 says about 'Isolation Switches' (i.e. 'Isolators'). It seems to be saying that, whilst isolators to BS EN 60669-2-4 and BS EN 60947-3 are both suitable for Emergency Switching and Functional Switching, the latter are only suitable for isolation if they bear the specified symbol - which, by implication, means that the former (ones to 60669-2-4) are suitable for isolation even if they do
not bear that symbol. Can you make sense of that?
Kind Regards, John