Boiler

[firebird]

Hi

A question for John (Bogstandard)



In the photos and video section looking at Florin's engines you mentioned the 3bar/litre rule. Later this year I will be needing a small boiler. Could you, briefly for now, explain what it is.

Cheers

 

[Bogstandard]

Hi FB,

The best person to explain this totally accurately would be Sandy.

Basically the ruling states that say if your boiler capacity is 1 litre, you can have it running at 3bar (approx 45PSI) maximum, or 2 litres water capacity running at 1.5 bar, or 0.5 litres running at 6 bar, without needing a valid boiler certicate. But there are recommendations about the safety valves and gauges. But that to me is a bit sketchy.

Here are Sandy's determination of the findings for the 2007 rule.

UK Boiler testing rules changes. Spring 2007.

The following changes to the ‘Examination And Testing of Miniature Steam Boilers’
code of practice (Spring 2007) have now been agreed and accepted by leading
insurers in the UK.

These new rules effect those originally set out in the New Edition 2006 code of
practice, these being the ones I detailed for you in an earlier post.

What follows are extracted clauses (in italics) as they are written, followed by, where
it is felt beneficial, a line or two by me in order to clarify.

Introduction, Page 3, para 4;
Small boilers (i.e boilers with a capacity of not more than 3.0 barlitres) are exempted from the requirements of this code. However, it
is recommended that small boilers be fitted with, at least, a safety
valve and a pressure gauge and that these be tested every 12 months
in order to ensure correct operation at the correct release pressure.
The boiler and the pipework installation should also be checked at least every 12 months.

This is good news for the majority of you, since it doubles the original exemption
figure of 1.5 bar/ litre capacity, and is the biggest change from a model boating point
of view. Basically it now means that at least 85% of our model boat boilers are now
exempt from the requirements of the new code….i.e they DO NOT need to be
Tested.

A telephone call, made to the notifying body/publishers of these new rules, confirmed
that ‘EXEMPT’ also includes the steam test requirements.

Having said this, they then highlighted/emphasised the recommendation made in the
statement above, and I must agree that they should be implemented by everyone, for
your own safety, as well as that of other bystanders….in actual fact I am surprised
that these were not made MANDATORY.

For the remainder of you (those with boilers greater than 3 bar/litre capacity) you will
still be required to get your boilers pressure tested every 4 years and steam tested
every year (Max 14 months) , however, the following changes have been made to the
steam test rules…….

10 Steam Test


10.1 An examination under steam pressure shall be undertaken, a)
before first placing the boiler into service, b) after every
hydraulic test, and c) at intervals not exceeding fourteen months.
10.2 The boiler shall be steamed and further examinations carried out
as pressure is rising and whilst the boiler is at working pressure.
10.3 Correct operation of the following items shall be verified:
-Boiler water feeding arrangements by at least two independent means
(hand pump, injectors, mechanical pump, etc.)
-Pressure gauge
-The water gauge(s) should be blown down and the water should be
seen to recover to its level without delay.
On boilers of less than 10 bar-litre capacity with a total internal
volume not exceeding two (2) litres it is acknowledged that the
provision of two independent means of water feed arrangement may not
be possible. Therefore for the purpose of testing of these boilers:


a) One (1) means of water feed arrangement is acceptable.
b) Water in the gauge glass must recover its level without delay
following movement of the boiler.
c) Water gauges fitted to boats whose boilers fall within this
size category do not have to be capable of being blown down.


The water gauge and pressure gauge should be clearly visible.

10.4 The boiler shall then be steamed at maximum firing rate and with
full blower operation. The test shall be continued for sufficient
time as to allow the Inspector to be satisfied that stable conditions
have been attained. The operation of the safety valves shall be
checked to ensure that they operate at working pressure and that
pressure does not rise by more than 10% of the working
pressure during safety valve operation.

I would think that the paragraph in bold italics will cover the new requirements for
most of you.

A single means of adding water, whilst under pressure, can take the form of…a hand
operated pump via a non-return valve….an external pump (steam or electric) via a
non-return valve…( in the case of a steam pump then it may be necessary to have this
driven from a separate boiler (certified if required)….a simple alternative would be to
replace the normal filler cap with a ‘Goodal’ valve….these allow the addition of water
from a suitably modified squeezy bottle (both available commercially)…and often
used on Garden Railway Loco’s.

On the surface of it, these new rules are great news for you as users…and, in theory,
good for me, as a manufacturer, however, I am required, by law, under the sale of
goods act, amongst others, to ensure that my products are safe for public use, and
therefore I will continue to fully test all ACS boilers, regardless of size, and issue a
valid test certificate (4 yr) as normal.

Happy sailing.

Sandy Campbell (Proprietor ACS Engineering)

Sorry for jumping in Sandy, but didn't know when you would appear again.

I don't think these rules are yet accepted by the MPBA affiliated clubs.

I hope I have explained it well enough.

John

 

[zeusrekning]

Not to highjack, but are you guys saying the gov't regulates the boilers even if they are for hobby use unless they are under 3.0 barlitres?
Tim

 

[Bogstandard]

Not really the government, the insurance companies.

 

[Florian]

As long as you use your boiler inside of your house and if its just you watching it, you can do whatever you want. But if someone else is watching your boiler and lets suppose something happens, you will have a problem.
Even worse, if you present your boiler officialy; there you need to sfollow the rules. If you do not follow the rules or if you do not have a boiler test certificate(for boilers above the 3 barlitres), they can confiscate your boiler. And this is the last thing you want... right?

 

[alan2525]

Regarding boiler pressure testing on small boilers, I can see the problem if you have a large high pressure vessel such as one fitted to an industrial compressor or a small steam locomotive. What is the issue with very small boilers, i.e. Mamod size, 16mm loco etc. I would have thought the main concern was a working safety valve so it just pops off prior to anything going bang, with a pressure test don't they just test the boiler itself to about double working pressure without any ancillaries fitted anyhow? With the very small boilers they seem to be built massively over engineered too. I.e. flanged boiler ends, and thick wall copper tube etc.

 

[firebird]

Hi

Thanks john, That'll do for now. I'd like to bring the subject up again if I may when the time comes and materials etc have been sourced

Cheers

 

[Mcgyver]

Alan, they're not over engineered, or well at least they are engineered - whats the engineers credo? - "build it twice as strong as it needs to be and it'll only fall down half the time" or something. The resulting design; material thickness joints, stays, size etc etc are a funciton of the working pressure * a safety factor.

there is way more you need to consider than a safety valve and hydraulic test. A boiler needs to be engineered with safety factors magnitudes beyond what is pressure tested to and materials have to be right for the job (aren't those little Mamod ones brass ) an it needs the proper assortment of valves, water make up, safety glass, etc. It has to be safe not just for the hydrostatic test, but for all operating conditions and over time. Even a little one is a potential stick of dynamite and needs just as much care as a larger one.

Traditionally in model engineering, people are encouraged to build to "published" designs, meaning the design has been by an experienced practitioner, enough so to have been published in one of the venerable journals. Added to this is that the design gets review by many many eyes and usually several are actually built. I think this is a good idea until/unless one has enough knowledge and confidence to do the engineering on a design - improperly designed or constructed they can be dangerous.

 

[SandyC]

;D ;D

Hi Guys,

John (bogstd),

No problem John I fully appreciate the reason, and thanks for including the text from my original update.

For those that may like some more info, I attach the preceeding document (the one that is updated by the version John posted), this might help put things in better context.

One thing I will add..... the test specifications presented are for COPPER and/or STEEL boilers only.... there is no provision for BRASS boilers under these regulations, it is not an acceptable material in the UK.
They are wholly applicable in the UK and, with few exceptions, for the EU.

Other countries will have their own rules and may even be state dependent (as in the USA), however, they will be broadly similar, so for anyone outside UK/Europe, you will need to get hold of your local regulations.


Florian..... what you say is not quite correct for the UK, here the rule is...if you are the sole user/operator and on PRIVATE land (owned by you) you can use any boiler you like without the need for tast certificates etc, providing no one else is present....if members of the public can also have access then you have an entirely different problem (and this also applies in your own home) in that, in the eyes of the law, the private land is now seen as a PUBLIC place.... and for this you need both A VALID TEST CERTIFICATE, and INSURANCE ..... inside your own home, other members of your family are considered to be THE PUBLIC as far as any claim made on an insurance policy, should an accident occur, INSURANCE would almost cetainly not uphold the claim, and you could actually be prosecuted in law.

If you use, or plan to use your boiler, in a PUBLIC place, then for boilers above the 3 bar/litre capacity, you must hold a valid HYDRAULIC PRESSURE test certificate, and valid STEAM TEST CERTIFICATE.... the latter cannot be obtained without the prior.
Failure to hold both, will exclude you from obtaining VALID insurance, and/or will invalidate any existing insurance until they have been re-obtained....... BE WARNED.

ALAN 2525,

In the extract (posted by Bogs) you will see my comment regarding the STEAM test also being EXEMPT.

Personally, I was surprised they did not make this mandatory for one very good reason...... even a small boiler can become a hazard if it is not operated within it's designed envelope.

Believe me Alan, you would not want to be on the receiving end of even the humble 'MAMOD' small boiler, operating at 15psi- 20psi, let alone a similar size boiler operating at 45psi, should it decide to fail.

Even at 15psi, the contents of the boiler are at 121deg C (249.8deg F) and these would travel a considerable distance (easily 15ft) should a rupture occur..... at 30 psi the temperature would be 134.5deg C (274deg F).... at 45psi temperature would be 144.6deg C (292.4deg F)...... and at 60 psi it would be 153deg C (307.4deg F).... at these higher pressures a small rupture could easily send the contents aver 70ft..... result....if someone is in the line of fire.....DON'T EVEN CONSIDER IT.


Yes, I agree, a SUITABLE safety valve, in conjunction with a small (accurate) pressure gauge should be satisfactory...... the problem is....without undergoing a VALID steam test....how would you, or others around you, KNOW that the safety valve is operating at the correct pressure.

For that matter, how would you know that the safety valve was SUITABLE, or not faulty in some way.

SUITABLE means...... it can safely pass all excess steam generated by the boiler, running at FULL BURNER power, without the pressure in the boiler rising more than 10% over it's normal maximum working pressure.

For a 'MAMOD' running with the normal (supplied) spirit burner, or the solid fuel tablets alternative, then this should not be a problem, providing that the SUPPLIED SAFETY valve is in good working order.

Where a big problem can occur, is when users change over to 'CERAMIC' gas burners (as can be purchased for 'MAMOD' models)........these are far more powerfull than the standard spirit burner, and therefore, it is highly unlikely that the standard SAFETY valve would be able to cope......a more suitable one would need to be installed......this would almost certainly require a modification to be made to the boiler (generally a larger bush would be required)...so now you have a potential problem with safety.

UNLESS you subject the boiler to both HYDRAULIC and STEAM tests.

Finally, some of the early 'MAMOD' boilers were constructed of pretty thin BRASS, (of dubious specification) and were also SOFT soldered.... (later ones are silver soldered, under EU directives)..... this is not suitable for steam temperatures (even at 15psi)..... soft solder becomes malable and loses around 50% - 60% of it's strength at 15psi steam temperature.... failure is not far off.

OK guy's I think that is enough of my drivel for now.


BTW ALAN..... I was BORN in SCOTLAND but raised in WANSTEAD and after I married I moved to HARLOW, where I lived for some 30 years, before escaping back to my HOMELAND..... BRIAN and I go back a long, long way, but that is another long story.

Keep steaming you guys. ;D

Best regards.

SandyC



View attachment Boiler testing in the UK.doc