Recommissioning a small vertical boiler

[Mark Salzedo 1Participant @marksalzedo1]

I bought a small 3″ diameter silver-soldered copper coal-fired vertical boiler a few months ago. I am in the process of recommissioning it. Whilst cleaning the boiler, I noticed two bulges on the inner underside. I have made a short video here

Do you think it is worth spending the time (and money) making up blanking plugs to pressure test the boiler. It certainly has been steamed in the past, it is coated with soot deposits. Does it look like it has been over-stressed at some point? I bought it to steam a small Stuart 10V steam engine, so a working pressure of about 40 psi (max. 60 psi) should be adequate. It would be used ‘privately’ and not in a public setting. But it still needs to be safe to use.

It is obviously a non-commercial boiler and it didn’t come with a certificate. Most of the fittings are serviceable but need a good clean. It has an old ‘Bonds’ pressure gauge, which probably dates it. I bought it quite cheaply, around £80 I think. It would be a shame to just throw it away. I suppose I should press ahead make the blanking plugs and pressure test it. Anyway, any suggestions and advice from those who are more experienced with boilers will be appreciated.

Happy Christmas and New Year.

Many thanks.

[Clive Brown 1Participant @clivebrown1]

I would pressure test, perhaps to a lowish value, with a view to using it. Difficult to be certain from video, but it seems to me that the lower tube-plate was formed that way. The general scantlings, as far as can be seen, look reasonable

40psi is masses to run a little Stuart off-load. 20psi WP would be plenty.

[noel shelleyParticipant @noelshelley55608]

Hi Mark, for the bulge to have occurred on the inside of a curved surface is likely to have been from one of two reasons:- One SERIOUS over pressurisation or two the boiler ran dry and the copper became soft. The former does NOT have to have been steam pressure, it could have been caused by over enthusiastic  pumping for a hydraulic pressure test but now distorted it’s strength is much reduced. If you are a member of a club then talk to the boiler inspector. If you have the knowledge and understanding of what you are doing examine the boiler VERY carefully ! It may be possible to by VERY careful work force the inner firebox back into a circular shape, by pressing a round object into the firebox, greased to lubricate. If all still looks OK then conduct a hydraulic test to 1.5 X working pressure, in this case 60PSI. If there are ANY leaks then it is not fit for service or REPAIR.

For private use the above could be considered OK but I would urge you to get a proper boiler test at a club.

By all means make the bungs and try.  Good luck. Noel.

PS If you can get your hands on a domestic pressure cooker, replace the rubber mounted T valve with a brass fitting and pipe to your engine, or just drill a hole for the fitting – it works, gives 15 PSI, I tested a Stuart No 1 this way.

[Mark Salzedo 1Participant @marksalzedo1]

Thanks Noel and Clive for the advice and suggestions. The bulges in the first video aren’t all that clear, so I have uploaded another here They appear where the copper shows through, the dirt and grime have been removed. The largest bulge is on the right-hand side and the smaller one to the left.

I don’t belong to a club (at the moment) nor am I conversant with the intricate construction of boilers but the bulges did raise flags. It will be a shame if it has to be binned but I am reluctant to spend too much money on it at this stage if it is all in vain. It may be that 20 – 30 psi would be quite sufficient for the Stuart 10V. So, it is a difficult call. Thanks again.

[noel shelleyParticipant @noelshelley55608]

Hi Mark, looking at the pictures again, there appears to be some slight distortion on the firebox tube plate that makes me think it has been caused by hydraulic pressure – far to much of it. This is very easy to do by accident, and in industry it’s called hydroforming.

Some would think that 300PSI is a high pressure. A small hydraulic car jack may well go up to 10,000PSI.

Good luck. Noel.

[Clive Brown 1Participant @clivebrown1]

The 2nd. video does show up the bulges more. I’d definitely keep any pressure on the low side but I still think that it could run a small engine for demo. purposes.From your post it seems that you might not have facilities for making blanking plugs so perhaps that reduces your wish to test the boiler.

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