Boiler testing

In message , Mike H writes

I still can't find it!

But the North Wilts MES website has a summary of the kind of thing that any UK model engineering club is likely to demand concerning PRE-EXISTING boilers

To put the rules into some perspective, a medium sized 5" gauge model is not likely to have a boiler that exceeds 100 bar.litre.

There are additional rules/guidelines concerning supervision of amateur building of new boilers. I would suggest that although some might think them onerous, few could argue that they are unreasonable. Rules/guidelines applicable to commercially built boilers are a different matter.

--Hmm, bar.liter, eh? Is this a way of measuring hoop stress?

Capacity in litres x Pressure in Atmospheres = Bar Litres

AWEM

I would think its a way of estimating the amount of stored energy - and hence the hazard that it presents should it let go.

Hoop stress would require diameter, pressure and wall thickness, though I am too lazy to arrange them in the correct way to work it out.

Steve

Slightly off-thread - but hopefully tapping into the local expertise - does anyone know what should be done about testing air compressor receivers ? Just normal domestic in the garage type of stuff. I drained a lot of rusty water out of mine the other day, and it made me wonder about its internals.

Steve

Ours at work was inspected by someone from the insurers. I remember it being a visual and functional inspection with wall thickness checks using an ultrasonic probe. Can't remember at what size of receiver this became necessary. (The separate environmental inspection got concerned about what happened to oil from the oil catcher.)

--FWIW it's easy to "hydro" one with a hand pump and a gauge; just fill it up with water and see if it will hold, say, half again what it's rated? What would be a safe maximum?

I think the standard at my local live steam club, (Vancouver Island Model Engineers) is an initial test at twice working pressure. All subsequent tests, are at one and one half working pressure. For a new boiler, all parts must be submitted for inspection before the boiler is assembled.

Steve R.

In message , steamer writes

In the UK, to all intents and purposes, you can't steam in public unless you are insured and you can't be insured unless the boiler has a "current certificate". The certification process is regulated by a joint agreement between the clubs and insurers and effectively provides a documented history of the boiler.

It includes a requirement that a new boiler shall be hydraulically tested to twice nominated working pressure. Any subsequent re-tests may be at 150% nominated working pressure.

There are also annual "steam tests" in which it has to be demonstrated that the safety valves will not allow the pressure to increase by more than 10% above the nominated working pressure no matter how hard the fire is driven.