On Tue, 02 Dec 2008 17:26:25 +0000, John Rumm wrote:

Rod wrote:
John Rumm wrote:
Tim Downie wrote:

If you buy a good quality cylinder (I'm going to get an Oso) and
have the appropriate safety ancillaries installed I can't see the
point in wasting time and money on an annual inspection by someone
who has gone on a 0.5 day "course".

It's still a pressure vessel with explosive potential (more so than a
vented cylinder). Safety ancillaries can and do fail. May not be
hard to check yourself if you know what you're doing but I'm not sure
I'd want to live on the other side of a party wall to one that hadn't
been inspected for years. For most non-DIYers, annual inspection
probably makes sense.

I think there is another misconception here as well. The only time a
pressurised water cylinder is at explosion risk is going to be when it
has the possibility of being heated to over the boiling point of the
water content. Then there is the risk of the explosive production of
steam should it rupture.

For a cylinder heated via a water flow from a boiler, the chances of
super heating it seem minimal. (after all, pressure testing of steam
or compressed air systems is often done with water because of its
significantly lower risk - its lack of compressibility making it very
difficult to store mechanical energy in it)

But if it has an immersion element, then that would change the risks.

Yes it does - as would possibly a gravity circulated solid fuel stove.

Which are explicitly forbidden as a means of heating unvented HWCs.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html