Boiler hydraulic test 4 hours

[endckr111Participant @endckr111]

Hi,
I have the opportunity to purchase a scotch boiler for a steam plant I’m building, boiler looks ok, fairly old but un-steamed,  but I notice on paperwork, the hydraulic test was four hours in duration at 2x working pressure, which does sound excessive,, and putting a lot of strain on boiler which does concern me, although it did pass
I was hoping someone could put my mind at rest and advise me to go ahead with purchasing, or should I steer clear!

look forward to your replies

mark

[bernard towersParticipant @bernardtowers37738]

If its withstood the pressure what difference does the time make other than the time to inspect for deformed plates/tubes etc and obviously leaks.

[endckr111Participant @endckr111]

From what I’ve read, allowing boiler to undergo 2x pressure, for that amount of time can strain the seams/ boiler tube joints, even though they don’t leak, under steam pressure things can go wrong. I guess a boiler inspectors opinion would be the best way

[Speedy Builder5Participant @speedybuilder5]

If it would make a difference, why doesn’t time enter into the calculations of boiler design ?

Bob

[Nigel Graham 2Participant @nigelgraham2]

Twice EP for four hours? No.

 

This summarises the MELG scheme applicable to miniature boilers of working pressure in Bar X fluid capacity in Litres, above 3 Bar.Litres, in the UK:

Only the initial shell test is 2X WP – obviously assuming the boiler is designed for that. That is when newly-built, before first use. Though a club boiler inspector might want that for boiler of unknown provenance (usually one bought without test certificates).

Repeat test: 1.5 x WP repeated at 2 years for steel, 4 years for copper.

The required test time is only 20 minutes, not 4 hours. If it’s going to leak, or fail, it will in that time.

Steam accumulation test: maximum pressure reached when deliberately steamed hard. WP + 10% allowance. This ensure the pressure-gauge works, the safety valve(s) open at the marked pressure on the gauge, and the water-gauge and boiler feed arrangements all work. Annual, for all types of boilers, provided it has passed the hydraulic test.

 

It looks as if the certificate might be for the initial shell test.

 

The requirements for small boilers, such as those on 16mm-scale locomotives, small steam-boats and the like are a bit lighter.

 

[endckr111Participant @endckr111]

I can confirm this 4 hour hydraulic test was 4 hours @120 lbs after initial build. Maybe It was for shell test, but can’t confirm that, back in 1990!
Your thoughts much appreciated, but do I buy it?

[Paul LousickParticipant @paullousick59116]

Our Australian (AMBSC) code for boilers requires an initial test at 2 x maximum working pressure for not less than 20 minutes and 1.25 x working pressure for subsequent, re-testing.

[Charles LamontParticipant @charleslamont71117]

The point is that the duration of the test is irrelevant. During a boiler pressure test, the test pressure needs to be applied for long enough to satisfy the inspector that the boiler will hold pressure. The initial application of the pressure applies loads on the stucture of the boiler, creating stresses that it has been designed to withstand. Maintaining the test pressure for a longer period will not make the slightest difference to those stresses. It does not matter.

Buying or not is your own decision – nobody here can make it for you. We don’t know where in the world you are. If you have a model engineering society local to you, they will have a boiler inspector who may be able to examine the boiler and advise.

 

[endckr111Participant @endckr111]

Thanks guy’ for your replies, now I have some better understanding of procedure. There is also some asbestos lining the firebox, with refractory cement covering the walls, obviously the asbestos will have to be removed and replaced with a safer material. I shall endeavour to find a boiler inspector, to give it the once over, that’s if I decide to go ahead with purchase.

[Martin ConnellyParticipant @martinconnelly55370]

The time being held at pressure in a hydrostatic pressure test is usually to allow temperatures to stabilise so you only check if the pressure is falling after the designated test time. For the stainless steel pipes where I worked we had a 30 minutes soak time that was not put on the manufacturing time, the pressure tester had a few minutes to set up the test, dry off the outside if wet and was then expected to go and do something else for that 30 minutes. At the end of 30 minutes the pressure gauge was looked at to see if the pressure was falling and if it was find where the leak was (usually a plug or blank was leaking). Typical pressure test time had a set up time that was based on things like the number of bosses to plug and the number of flanges to blank off. The actual time booked for the test was under 5 minutes. The reason for doing hydrostatic testing is because as well as being low energy, if you have removed all the air in the part under test, even a very small leak will produce a rapid drop in pressure.

Martin C

[SillyOldDufferModerator @sillyoldduffer]

That a boiler held test pressure for 4 hours won’t damage it.   Why the test was that long is lost in the mists of time: possibly it failed an earlier test, and the embarrassed builder had to convince others it was properly fixed.   Wouldn’t put me off, more important it passes a pressure test today.

Will the boiler be steamed in public at a club or in private?   Clubs inspect boilers for insurance reasons.   If a boiler failure injures a bystander the claim might run into millions. Accidentally blinding a child is expensive!  Risks that might not apply at home.

Steaming a boiler in private does not require inspection or tests.   You can pretty much do whatever you like provided only you and your property are at risk.   Really must be private though; if the worst happens you are personally liable.

Small boilers aren’t particularly dangerous.  Though they might cause serious injury, it’s almost unknown.  So, a small boiler can be rendered adequately safe in private by steaming inside a closed garage (to keep passers-by out) with the operator behind a simple screen.   Safety glasses and ear-defenders recommended!

Asbestos is more worrying. Some types are much unhealthier than others, and no-one knows what’s in Mark’s boiler!   Might not be asbestos at all.   Asbestos is most dangerous when disturbed, so due diligence before removing it.  Keeping it in perspective, asbestosis is far more likely to strike folk persistently exposed to it in quantity.  But there are plenty of historic cases where exposure was minimal, one likely cause being playing just once with an old WW2 gas-mask.  Low risk, high impact.

At home, Mark could wear a suitable face-mask.  Or, if he’s my age, he could tolerate the risk.  As asbestos illnesses take decades to develop, pensioners are likely to die of something else first!

I’ve no idea how a club inspector would react to asbestos in a boiler?

Dave

[endckr111Participant @endckr111]

Thanks Dave for your reply, I intend to use boiler purely for home use, no intention to go public with it, and I will give it another hydraulic test at 1.5 just to make sure it hasn’t developed any leaks since it’s fairly old.Regarding asbestos, I will take all precautions that are available to me, which shouldn’t be a problem, plus as Dave mentions I’m old, so not to worried about it!

[duncan webster 1Participant @duncanwebster1]

If I were faced with the asbestos I’d immerse it in a big bucket of water and keep it under. Then the fibres can’t become airborne

[endckr111Participant @endckr111]

Good point Duncan! Definitely wet it down, before anything, be interesting once I receive boiler, what exactly will be involved!

[SillyOldDuffer]

On SillyOldDuffer Said:

I’ve no idea how a club inspector would react to asbestos in a boiler?

Maybe with a sharp intake of breath.

Perhaps the test was just carried out very early in the morning (0400) and the numbers are being misinterpreted.

[endckr111Participant @endckr111]

Hi Guys,
<p style=”text-align: center;”>         Thank you for all your comments and suggestions, all taken onboard board. I have now taken ownership of said boiler, and to see what I’m up against, I removed one top side panel, and that has exposed two sheets of suspiciously looking asbestos, the firebox back head inside firebox itself is lined with same sheet, so material  that can standup up to direct heat in firebox required, the rest of firebox has a lining of refractory cement,so and that’s as far as I’m going, till I can remove it, and replace it with some other material, ceramic board ect,any suggestions on that? The pipe work and fittings need replacing, new manifold for starters, so any suggestions on what I should remove and replace ect please to hear your thoughts.some photos of current state! I might start anew thread,on fittings &pipework suggestions, as this thread was more testing/asbestos related. Here’s afew photos of boiler which might help!</p>

[bernard towersParticipant @bernardtowers37738]

If you damp down the asbestos first then remove you can replace with vermiculite sheet

[noel shelleyParticipant @noelshelley55608]

There is no indication of size. Do you have the drawings, what is it’s design pressure. It may have withstood a 4 hour test but looking at the staying on the end plates I would question if it was sufficient for anything but a low pressure. I would seek the advice of a boiler inspector before you spend any money or time on this boiler. There are insulating materials we have used that look like asbestos but have no fibres in them and are NOT asbestos, We had all the paperwork for it as it was being used on a ship. Good Luck. Noel.

[endckr111Participant @endckr111]

<p style=”text-align: left;”>Hi, regarding boiler size, it’s 5”x 12”, the test pressure was 120lbs, and its working pressure is 60lbs. I have no drawings for said boiler, only a copy of test, and that’s all. I have no intention of using it at high pressure, maybe around 40lbs 50lbs</p>
I guess it is, vermiculite sheet ok to use directly in firebox, as it will be in direct contact with fire.

[Nigel Graham 2Participant @nigelgraham2]

We do have an indication of size one of the photographs shows it is of about one hand diameter by four long! So 4 – 5 inches diameter by 12 long, approximately.

…

Asbestos is recogniseable partly by tiny, sharp, needle-like fibres and it is those that cause the problems if breathed in. So is glass-fibre but the needles are uniform cylinders.

Left alone, and covered, it is unlikely to be a problem but if removed it should be done wet, then carefully wrapped to seal it.

 

The boiler looks like a sort of hybrid between locomotive and Scotch marine types. In the latter, an internal combustion-chamber acts as return-bend on the end of the fire-box (called a “furnace” on these forms of boiler) with a flue or tubes back to the smokebox and flue above the fire-hole.

On this, the combustion-chamber appears to be external: the large black box on the end of the shell. This also seems to hold a superheater.

“The paperwork”. By whom? Is the boiler commercially or privately built? Either way the 2X wp hydraulic test would be right for the initial shell-test; but not repeat tests. (Use 1.5X w.p. for typically 20 minutes, for those, and at every 4 years for a copper boiler.).

Has the boiler been steamed since then? The one, dark image of the firebox interior suggests not, or only lightly, but it may have used oil or gas rather than coal, despite the grate and ashpan.

 

Commercial builders might be able to test their own products but must do so in the proper way and traceably. A private builder intending to steam the boiler in public would need it to be in current test – depending where you are that can be done by a model-engineering society but you would need be a member.

If you want to operate it purely privately (and exhibit it only statically) you do not need have it tested and certified as safe; but in that case for your own peace of mind test it yourself to the normal MELG scheme I have quoted from, above.

I should add, also an annual “steam accumulation test” to ensure the correct working of the pressure-gauge, safety-valves and water-feeds.

Much of the silver-brazing visible looks good, but a boiler-inspector may well want all the superstructure removing to inspect it properly on first investigation.

One aspect of the design that worries me a bit is that apart from the superheater necessarily enclosed, some of the boiler fittings are hidden by casings that do not look very readily removeable. That is not itself a boiler-testing matter but is not good practice as the joints can develop leaks so would need attention.

Connections leaking in a hydraulic test prevent maintaining a steady pressure; and you need be able to identify what is happening to be able to account for the pressure-drop. Those side superstructures would hinder such inspection.

…..

In the end, buying a second-hand boiler of poorly-known provenance is always a gamble – though that is true of any second-hand machine.

[endckr111Participant @endckr111]

Hi Graham,

many thanks for the very informative reply. The boiler was built privately, and test by a civil engineer when first tested, and its only written down in type, explaining pressure and time of test ect.yes the combustion chamber is external right under barrel, travelling along bottom of boiler to rear then up to rear tubes and back through boiler to chimney, which means the insulation on side of boiler has to fairly airtight, as otherwise smoke /gas will be emitted along boiler side tops. The boiler has never been steamed since built, so once all corrective work completed and 1.5 hydraulic test carried out by me, I intend to steam it. But first it needs stripping down and check on thoses hidden fittings that are impossible to get to as it stands

[endckr111Participant @endckr111]

Rear boiler tubes

[SillyOldDufferModerator @sillyoldduffer]

Any markings?  Looks manufactured rather than home-made to me, and representative, not a model.   My guess is it’s educational,  used to demonstrate steam engines in a technical school or college when coal and steam were still big on the curriculum.

The boxy style, black paint, and likely Asbestos suggests post-war rather than pre-war, and made before Asbestos was accepted by vested interests as dangerous.  Apart from being much bigger, oil-fired and painted green my school’s central heating boiler had the same look, and it was installed in the early sixties.

Dave

[JasonBModerator @jasonb]

To me it is just a stationary type horizontal return flue boiler that would likely be found providing steam for a model steam plant, possibly commercially made but certainly aimed at model use.

Plenty of similar designs about, Harris has one in his book so may well have been built by a hobbiest based on his or other designs. The last two photos are the pipe that connects to the superheater that is loose below.

[endckr111Participant @endckr111]

Hi, it was made pre 89, and definitely made by a model engineer, no markings on boiler maybe when I remove the casing something might show up, which will make it slit lighter, currently weighing in at 14 kilos my intensional is to coal fire it, and to power one or two engines, setup as a steam plant.so is  Vermiculite sheet an alternative for inside firebox and boiler sides? Your comments and advise much appreciated

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