I have no objection to the concept of preventative maintenance, especially if pressurised systems are at play, but folks do seem to like to bang on about legal requirements which seem to be figments of their imagination.
It strikes me, that if one has an unvented cylinder, then the occasional test of the pressure release valve, and checking the dump pipe and tundish etc are free of obstruction would be sensible. With an indirectly heated cylinder, you are going to have to be monumentally unlucky to arrive at a set of circumstances where it is in steam production mode!
In reality I expect most people who have them rarely if ever have them inspected - they probably came with the house they bought and are just "there". It does not seem to be a problem in real life either, since one is not routinely reading about steam explosions. In fact gas ones seem far more common - and those are exceedingly rare.
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