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Well-Known Member
Sep 12, 2008
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Hi Guys,

Have Copied Sandy C's info on UK model boilers.

Boiler testing in the UK

Prior to January 2006, the many national and local organisations, which administered the affairs of the many branches of the hobby, had in place their own requirements for the examination and testing of model steam boilers. However, there were many differences in each party’s requirements, which led to inevitable confusion.

To overcome these discrepancies, the main party’s involved, got together and came up with a common set of rules which have now been accepted by the Health and Safety executive, all the major providers of insurance for the modelling hobby and the various model engineering organisations.
The basic requirements of the Pressure Systems Safety Regulations 2000 (PSSR) and the Pressure Equipment Regulations 1999 SI NO.1999/2001 (PER) P.E.D 97/23/EC. were used as a the basis for the new regulations.

These new rules came in to operation/effect on 1st January of 2006.

Those involved were as follows: -

Ground Level 5” Gauge Mainline Association.
Health and Safety Executive.
Midlands Federation of Model Engineering Societies.
Model Steam Road Vehicle Society.
Northern Association of Model Engineers.
7 ¼” Gauge Society.
Society of Model Experimental Engineers.
Southern Federation of Model Engineering Societies.
Members of the Trade, Manufacturers and the Model Engineering Press.
Royal Sun Alliance Engineering.

It should be noted that, whilst these rules have been adopted by the leading providers of insurance for the model engineering hobby, individuals, or organisations seeking insurance from other insurers will need to check that these rules are acceptable to the insurer.
Most model clubs (especially those affiliated to one or more of the above) have adopted these rules, however, some may still have additional requirements and/or recommendations concerning recording and reporting of boilers and boiler tests etc, and any such requirements may be contained within publications produced by them.
Such publications/requirements shall be used in conjunction with these new rules and shall not be considered stand alone instructions and shall not amend, or overrule any part of the new rules.

From a model steam boating point of view the following are the main rules: -

Small boilers, (i.e. boilers having a capacity of not more than 1.5 Bar-Litres) are exempt from the testing regulations, however, they should have their Safety valves tested at least every 12 months in order to ensure correct operation at the correct release pressure.

The Bar-Litre capacity is found by multiplying the total internal volume of the boiler (in litres) by the working pressure in Bars.

1 Bar = 14.5038psi.

1 litre = 0.22 (UK) gallons/1.76 pints

1 (UK) pint = 0.568 Litre.

For all other boilers, up to 500 Bar/Litre capacity the following shall apply: -

New boilers: in either Copper or Steel will be subject to a hydraulic test pressure of 2 x (Twice) maximum working pressure with subsequent tests being to 1½ times working pressure. The applied test pressure shall be sustained for a minimum period of 10minutes.

Previously tested boilers: In either Copper or Steel shall be subject to a hydraulic test of 1½ times working pressure. Again held for a minimum 10 minutes period.

Steam Test: An examination, under full working steam pressure, shall be undertaken,
a. Before first placing the boiler into service.
b. After every hydraulic test.
c. At intervals not exceeding 14 months.

This basically means a steam test is required every 12 months, however 14 months is stated to allow for clubs etc, organising suitable test dates/facilities.

Commercially built boilers and their certificates.
In respect of new boilers, inspectors SHALL accept test certificates issued by recognised commercial boilermakers, provided that the certificates are in accordance with the Pressure Equipment Regulations 1999 (PER) and, where appropriate, carries the CE mark and the documentation has been endorsed by the manufacturers Notified Body.

Certification periods:

The certificate of hydraulic test shall be valid for a period not exceeding: -

Copper boilers: Four (4) years from the date of the test.

Steel boilers: Four (4) years from the initial test date of a new boiler, with subsequent test at intervals of TWO (2) years.

Steel boilers in service prior to 1st January 2006 shall be subject to being tested every TWO (2) years.

Steam test: (all boilers) Valid for period not exceeding 14 Months.

So there you have it, I hope that clears up any queries, at least for the UK.

Countries such as Australia, New Zealand and the majority of Mainland Europe have, for the main part, adopted the (PSSR) and (PER) regulations as mandatory, and as such they have (to the best of my knowledge) now also endorsed these new rules, however, local clubs/societies may also adopt their own additions. (Not amendments).

From a manufacturing viewpoint, ACS Engineering complies with all of the above regulations.

A full text of these new regulations is available from: -

Walker Midgley insurance brokers Ltd.
Yorkshire Bank Chambers,
S1 2HD

Telephone number 0114 250 2770

I believe there is a small fee.

Sandy Campbell (proprietor ACS Engineering)

Can some body please clarify this bar/litre rule .If my boiler is under 1litre and operates at 1bar is it exempt.I always build with a safety factore of 8 ,hydraulic test twice working pressure and makes sure that there is no pressure rise when safety valve is open and the burners are flat out.Most but not all of my marine boilers are of the smithies type with meths burners .As a lone modeller i don't wish to join a club just to use the boiler test facilities as its not fair to the club is there anyway i can get an independent test certificate . I have public indemnity insurance that covers for working on machine with small commercial steam boilers and they are willing to cover my model boilers but i require a test cert .Thanks in advance

I think you will now find that the regs have been amended slightly, and the new ruling is for exemption on boilers under the 3 bar/litre rule. Which should cover almost all boilers used in model boats, and small garden rail locos.

But even so, insurance should still be obtained to cover you for public liability, even if on or in your own property.


The bar litre rule is fairly easy to understand.

If your boiler has a capacity of 1 litre (about 2 pints), then it's maximum working pressure should be limited to 3 bar (approx 45psi).

As an example, if your boiler has a capacity of 1/2 litre (approx 1 pint), then divide the 3 rule by 1/2, you end up with 6. This means that you can have a max working pressure of 6 x 1bar, or 6 bar (90 psi).

To go the other way, if you have a 2 litre capacity boiler (4 pints), divide 3 by 2 and you end up with 1.5, so you can only have a max working pressure of 1.5 bar (approx 22 psi).

I hope that makes it easy enough to understand.

It is important to note that the rule is not in terms of bar/litre (bars per litre, pressure divided by the capacity), but is in bar-litres (i.e. pressure multiplied by the capacity) as correctly stated in the original. So for the same number of bar-litres, as the boiler capacity reduces, its working pressure can increase.
Hi Guys,

There has been some major changes to the UK boiler regulations and there is now NO EXCLUSION for boilers of 3 Bar-Litre or under.

I attach a copy of the latest UK rules which became effective on 1st January 2013.

Unfortunately it now means ALL boilers used in public must now have a valid test certificate... which can only be issued via a club or a recognised commercial manufacturer.

Some insurance companies do have a recognised tester on their books so that may be of some use.

Sorry to post bad news.

Best regards.


EDIT: These new rules are freely available for download on the internet so there is no copyright issue here.

View attachment 2012_Test_Code_V12a.pdf
if it needs to be hydroed every 13 months you could hydro it twice just in the time it takes to build a steam tractor:)
Hi all,

Chrsbrbnk, and anyone else confused by the new UK regulations document: -
Here is a brief synopsis giving the important points...

For copper boilers the hydro test is always valid for 4 years .

For steel boilers the first hydro test is valid for 4 years and thereafter all subsequent tests are to be at 2 year intervals.

All boilers will require a steam accumulation test every 12 months (there is a lee way of 2 months allowed for the repeating of this test, making it 14month MAX to allow for more convenience with club testers) but only if the Hydro test certificate is still valid.

When the boiler is first tested (from new) it undergoes a primary (with no accessories fitted)HYDRO test at 2 x working pressure. It then has all it's fittings added (water gauge, pressure gauge etc) and is subjected to a further hydro test of 1 1/2 x working pressure.
If it passes this test then the boiler is issued with a Hydro certificate which remains valid for 4 YEARS.
Before the boiler can be used in public the boiler will have to pass the steam test (also known as the steam accumulation test) which is performed at normal working pressure and with the firing (gas, coal, whatever) at maximum output.
The safety valve is tested to ensure that it opens correctly at the normal, set, working pressure and that it can release ALL excess steam without the pressure rising more than 10% above the ,set, working pressure.
The Pressure gauge is also checked to ensure it shows the correct working pressure.
Checks are also made to ensure that the water gauge shows correct level and that any water make up facilities (injector, axle pump, hand pump etc) are working correctly.
If the boiler passes this test then it is issued with a steam test certificate which is valid for 12 MONTHS. (but an additional 2 months is allowed, as stated above, but this only applies whilst the HDRO test certificate remains valid.)

So, this gives you 4 years from first testing (hydro and steam) to build a model before it requires a further hydro test. You would only need to have the STEAM TEST done again if you wanted to use your boiler/model in public at any point after the 1st year.
If you took 3 years to build the model then the 1st Hydro test would remain valid and you would only need to repeat the STEAM TEST... the intermediate year steam tests need not be performed in this case if the boiler/model was not used in public.

After the 4 years are up you would then need to get both Hydro(1 1/2 x wkg pressure) and Steam tests done.
If the boiler is copper then the new Hydro certificate would be again valid for 4 years.
If the boiler is steel, then the new hydro certificate would be valid for 2 years only (this is becouse steel boilers are subject to shell corrosion issues not present in copper boilers).

In all cases, the STEAM TEST certificate is valid for 1 year (with a 2 month leeway on retest, with the above mentioned contraint regarding a valid hydro certificate).

The 2 x working pressure Hydro test is only ever carried out ONCE and remains valid for the life of the boiler.

All other hydro testing is done at 1 1/2 x working pressure.

The only exception to this would be if you modified or added something to your boiler (a new bush for a further fitting or some such) or changed the safety valve setting to a higher value or made any other structural change, or had to make a repair for some reason... In which case all current certificates would become VOID and the boiler would be treated as a new build and would again be subject to the full 2 x working pressure + 1 1/2 times working pressure hydro test sequence again... and, of course, the steam test.

NOTE... in the case of a safety valve setting change... if it is set higher thenthe inspector would need to re-assess the MAX pressure capability of the boiler shell and if he felt it would be close too, or over limit he could refuse to re test.
In the case of a lower pressure setting, then there should be no problem and the retest would then be done using the lower setting as the working pressure.
Changing the safety valve setting, from that stated on the test certificates, would make all documents VOID (including any insurance) and all such changes MUST be notified to the inspector.

I hope this helps with understanding how it all works... the full document can be a little confusing in some areas.

Best regards and happy steaming.


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