model boiler hydraulic pressure testing

[phil burman]

Yes but you should test at a pressure that is significantly higher than the maximum operating pressure. In pressure testing pipelines it is not uncommon to test to "yield". This technique actually removes defects.

Phil

<font face="Verdana, Arial" size="2">Originally posted by gmatov:
You know, if you put whatever pressure you test at, and the vessel stays at that size, you just might be setting up a burst in the future.

If you test and the vessel doesn't come back to near zero, with indicators all around it, it has stretched, and it will stretch the next time you get to that pressure, and more the next time, till you get a burst.

You are talking minis, so a "little" bomb, but still.

Have to go look at my big train book to see what working pressures were, but they were not very high in the early engines, large pistons, yes, area was good enough for the metals they had.

Pressures were relatively low. When they went too high, big bomb.

Make the vessel of the best metal that is realistic.

Cheers,

George

Get a hydraulic Porta_power jack, clean it out of the jack oil, put water in it, put a guage on it, and if you need, a pressure regulator. It will make all, or as little, pressure as you need. 20 bucks or so.</font>

[billyboy]

has anyone any ideas/drawings of how to make a water pump to deliver around 100-150 psi of water into a model boiler, ive made the boiler and fixings and the boiler at the moment is in an un-soldered condition, i just need a way of delivering the water upto this pressure. any ideas please?

thanks bill

[SGW]

This has probably been disucssed in back issues of Live Steam magazine, since there have been numerous locomotive construction articles over the years and this problem would have (or should have) come up for every one of them.

An e-mail to Neil might yield some results.

[railfancwb]

Any hand operated boiler feed pump with check valves on the water and boiler sides should do the trick. Doesn't take much water volume from the pump to bump the pressure up once the boiler is full of water if there are no leaks. I use the hand pump in my loco's tender...

Charles

[hitnmiss]

I built a simple pump with o-ring for piston rings and one-way check valves with stainless balls. Worked well, much easier than I thought. In fact my boiler has a 60psi safety valve and I was testing to 120... On the 1st hard pump on the handle the pressure shot to about 200psi

hmm, 100psi isn't that much. Maybe fill a rubber air line with water, fit to the full boiler and squeeze the line in a vise?

[Al Messer]

You can do it without a pump IF you're VERY careful. Fill it completely full of water--no empty spaces at all. Plug all openings except for the pressure gauge connection. Then, with a Propane torch, very gently heat the boiler shell. It does not take very much increase in temperature to send the pressure zooming upwards. This is NOT a Steam test so don't keep the heat on it too long. After it has successfully passed this test, you can give it a proper Steam test.

[Al Messer]

P.S. Bill, haven't you found a local model engineering or live steam club yet?

[TECHSHOP]

At my old work when a single wall tank got "sucked in" (think the can on the stove science trick, scaled up to 1500+ gal). We filled it with water, sealed all the openings, and added some "plant air". When the dents popped (mostly), depressurize. This was with automated pneumatic valves, and a safety valve, with nobody close if the damn thing went "BOOM".

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Today I will gladly share my experience and advice, for there no sweeter words than "I told you so."

[charlie coghill]

For my pump I used two check valves with flow going the same direction. The check valves were screw to a 1/2 pipe "T".

From the intersecting connection on the "T" a 1/2 pipe nipple was screwed in. A packing gland was welded on the end of the nipple. A piece of stainless steel is used for the ram and a lever connected to the ram.

The end of the lever is connected to linkage and the linkage is connected to some sort of base.

You conld also add a pressure gage down line some where.

[barts]

Do it like Charlie described... I've used 5/8" stainless rod
running in 1/2" brass pipe for years on "Otter", our 19'
steamboat. Works like a charm, all you need is an
O-ring groove in the end and a tee and two checks.

- Bart