She's Gona Blow! (Boiler pressure testing)

tmuir · She's Gona Blow! (Boiler pressure testing)

An Australian Garden Rail group(Rails in the Garden Inc) has done a series of boiler pressure testing for small scale boilers to set a standard for boiler testing on boilers of 70mm or less diameter so they can get workcover in New South Wales for thier engines.
I haven't quiet got my head around it all but as small boilers are much more simplified than boilers for engines that can pull people they want to allow simplified construction techniques and boiler testing.
Thir website is
http://www.ritginc.org/

and the boiler test paper is
http://sgcox.site.net.au/ritg/boiler-tests.pdf

They built several boilers and tested them to destruction.
The boiler thickness ranged from 1.2 to 1.6mm and end plates from 1.2 to 3mm and they used different construction methods from flanged plates to disks to just soldering a sheet over end of tube.
All were silver soldered.

The lowest pressure that any of them failed was 1000PSI!!
I think the chances of any of our boilers ever going 'POP' with a 15PSI safety valve is pretty remote even though they are soft soldered and made of thinner material.

Have a look at the document its an interesting read. The pictures of the 'inflated like a baloon' boilers makes it worth it alone.

yosa

Shocking photos mate. As you say though, we must be well within the safety limits. Interesting that the soldered joints held up despite massive distortion to the main body. Before reading this, I would have said that the ends woul pop well before the boiler ballooned like that.

Tell you what they remind me of, remember those old cartoons where boilers or containers explode and form the same shape? Life imitating art.

sparky

yeh we have to do that with my uncles 2" scale clayton wagon

SPOKESMAN

Great so we can try some safety valve mods then?

Wallace

Great stuff tmuir. Would have never guessed that happened.

Although it was something I always wanted to try, a blocked boiler tested by heating to destruction, I don't have one I wish to spare, but don't really need to now.

tmuir

I also have another document from the 16mmngm group that says poeple have hydrolic tested the standard Mamod loco boilers to 120PSI at which point the site glass would leak and would reseal again at 60PSI.
So they should be safe up to atleast 30 maybe 40 PSI.

Someone correct me here but besides the steam dome the mamod loco boilers are pretty much the same construction as most of their other boilers of the same age so I would guess they should rate the same.
Certainly would not have a problem fitting my 20PSI safety valve to my other mamod boilers.

sparky

i do think there fairly simular

SPOKESMAN

My Bowman M135 has a modded safety valve - the spring is 'stuck' in the boiler - so tried a slightly stiffer spring, screwed in the reaining collar tighter and it doesn't blow off so much - more one big <sound effect> and then its OK for an entire run . . .

sparky

so it sounds better, does it run for a bit longer being more presure kept inside or is it just it runs with more power