Boiler ?’s

[jeveristParticipant @jeverist]

1. Complete beginner here. Bought this boiler off eBay hoping to make it work and learn a bit about making steam before I take the plunge into model steam engine building. 

[jeveristParticipant @jeverist]

Sorry, tried to imbed a photo and ended up posting. Advertised as a Stuart/MACC. All the threads are 1/4 x 32 except the bronze fitting top right which is 5/16 x 26. Crazy threading on these beasts. Planning on replacing the fittings. I think the empty “ports” are 1) “superheated” steam outlet, upper left 2) safety valve, upper right 3) blow off valve, lower right (can’t see in pic). The valve to the right of the pressure gauge is the wet steam outlet, and the valve at the lower left is the check valve for water inlet. I plan on replacing all the valves and the pressure gauge. Will pressure test boiler before putting any fire in the box. Am I on the right track, and does anyone recognize this boiler. TIA for any help

[Harry WilkesParticipant @harrywilkes58467]

Sorry cant help with ID of boiler however the threads 1/4 x 32 and 5/16 x 26 could have been used by Stuart over the years Stuart used both ME threads and some Witworth.

Looks a nice boiler hope it works OK for you

H

[bernard towersParticipant @bernardtowers37738]

Take all the fittings off and fit blanks on all but two and do a had test to at least 1.5 times WP and if thats successful try 1.75 times and if ok I would say you’re good to go.

[jeveristParticipant @jeverist]

Thanks, Harry

[jeveristParticipant @jeverist]

Thank you, Bernard. I am confused now. I was under the impression that in order to hydrostatically test the boiler, after filling the boiler with water, I would ultimately need to blank off all the orifices except the one connected to the water pump and hydraulic pressure gauge. I don’t understand your direction of leaving 2 orifices open, unless you mean as an intermediate step to filling the boiler with water before pressurizing. Please forgive my ignorance

[noel shelleyParticipant @noelshelley55608]

One to fill by and one as a vent ?  The vent to be plugged once ALL the air is out. IF the fittings are serviceable re use them, to replace them will be costly. The top right, wet steam may be for a blower though there doesn’t seem to be one, for coal firing you may need one. In the world of model steam 40, 32 and 26TPI are common, referred to as ME threads. Good luck.  Noel.

[jeveristParticipant @jeverist]

Thanks for clarifying, Noel. That’s what I was trying to say

[Nigel Graham 2Participant @nigelgraham2]

26TPI Whitworth form is standard Brass Thread for all diameters in its range, not ME, though neither scales are “crazy”.

You need replace the fittings only if they are damaged or worn, and the replacements will need threads to match their mounting-bushes threads. That should not be a problem for the ME-threaded one (32 & 40tpi), perhaps more awkward for the brass-threaded one, though you could always make an adaptor for whatever goes on it. Or make a new fitting with that same thread.

Brass Threads are not very common in smaller-scale model-engineering but can be found on larger-scale models, usually steam road vehicles; and fittings for them are more likely to be sold by the traders catering more for that aspect of the hobby.

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This boiler looks as if it has never been used, or has been used only a few times with gas firing, so I would think there is nothing wrong with the fittings. So why replace them? Leave ’em be! Unless testing reveals a fault, don’t disturb them other than if absolutely necessary for the hydraulic test.

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However, do calibrate the pressure-gauge, and you can do that with the boiler-test set (provided you can trust its own gauge of course). The boiler’s own gauge should read to at least one-and-a-half times working-pressure, preferably twice; and the working-pressure (at which the safety-valves open) should be marked indelibly on it.

It’s best marked by a thin red line on the dial itself but pressure-gauges are delicate and some can be very hard to dismantle safely, so the bezel can be marked instead.

Do you know what its w.p. is? If not already marked on the gauge but not clear in the photograph, or stated in any literature supplied with the boiler, it may be – well, ought to be – stamped on some part of the boiler that can be letter-stamped, or on a permanently-affixed plate. One place to look is around the foundation-ring or on this pattern, perhaps the ash-pan wall.

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I would also like to see a protector on that exposed gauge-glass.

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Regarding a blower, this boiler might not need one, especially if the chimney is extended higher. If it had one I would expect it to be fitted to the wall of that conical smoke-box, with the jet pointing up the centre of the chimney. There will also be an opening for its steam-pipe, via a bulkhead-union to seal it, through the wall.

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