Boiler Testing

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Heath & Safety Commission Issues

As the Society is part of the Southern Federation of Model Engineering Societies, and also meets in an unfenced public park, we are bound the Goverment's Health and Safety rules.  As a result we have carried out a risk assessement on our facilty, and keep the necessary documentation for inspection. There are also an attendance and an incident book at the track office.

In line with normal safety requirements ALL steam locomotives operating on the track, or traction engines being steamed in a public space, must have a currrent valid boiler certificate.  This equally applies to visiting locomotives, and the certificate must be shown before steaming.  The operation is only covered by the club's insurance on recognised steaming days; on other days, members are required to carry their own personal insurance.

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Requirements for Testing Model Boilers

Please Note: From 2006, new boiler regulations have been introduced by the Southern Federation of Model Engineers.  Until the new NADMES policy has been fully revised, the existing NADMES regulations are included for guidance.

1.  Introduction

For members who are unfamiliar with the procedures for testing miniature boilers, (i.e. boilers not exceeding twelve gallons capacity), the following minimum requirements have been approved by the Southern Federation of Model Engineers, if public liability insurance is required when operating live steam models.
In addition to this, the rules of NADMES and most other clubs preclude the steaming of locomotives on club tracks without a current boiler certificate being in force.  This also applies to any other operation of steam models, (e.g. traction engines), in public by club members, if undertaken on behalf of the club.

2.  Testing Procedures - Overview

All boiler tests shall be carried out by two approved boiler testers, or one tester and a witness who must be a current club member, but neither person can be the owner, builder or designer.
It is preferable that these persons are qualified engineers, or persons who have had a good knowledge of manufacturing live steam models.  In either case, they should have experience of model boilers, with sufficient knowledge of how to construct a safe boiler.
A thorough visual inspection shall be made of all new boilers, before commencing a hydraulic test, to ensure that all joints appear satisfactory.
The test gauge used must be a properly calibrated gauge, and on completion of a steam test, the model's gauge should be marked with a red line indicating the maximum permitted working pressure.

3.  Testing of Copper Boilers

When testing NEW copper boilers, a hydraulic test will be carried out using cold water to twice working pressure for a period of twenty minutes.  During this time the boiler will be examined for signs of distortion, or collapse, and any appreciable distortion would of course condemn the boiler.  Slight leakages can be rectified and when corrected, the boiler may be submitted for another test.
On conclusion of a successful hydraulic test, the boiler is to be steam tested for five minutes at it's working pressure, to check for correct operation of the fittings and safety valve[s], and check for any leaks.  The safety valves fitted to the boiler must be able to prevent boiler pressure from rising more than 10% above working pressure, however hard the boiler is worked.

Subsequent boiler tests require the boiler to be hydraulically tested to one and a half times working pressure for a period of twenty minutes.  All other aspects of the hydraulic and steam tests remain the same as the initial test, but is not necessary to remove cladding and lagging, or separate the boiler from the engine [frames].
A successful hydraulic and steam test will result in the issue of a certificate for the boiler concerned, which is valid from the date of the test for a period of two years.

4.  Testing of Steel Boilers

The testing of steel boilers is in many respects similar to that of copper boilers, however there are some differences as noted here:
  • Stainless steel boilers will not be accepted for test.
  • Steel boilers made of certified steel plate, welded by a coded welder and constructed to an approved design, shall be subjected to an initial hydraulic test of one and a half times working pressure, this will also apply to any subsequent test.
  • Steel boilers not conforming to all of these conditions will, on an initial hydraulic test be subjected to a a pressure of two and a half times working pressure.  On any subsequent test, this required pressure will be twice normal working pressure.
  • A successful hydraulic and steam test will result in the issue of a certificate for the boiler concerned, which is valid from the date of the test for a period of one year.
5.  Preparation for Test

When preparing a boiler for test it is the owner's responsibilty to ensure it is fit for the purpose.  That is :
  • To ensure all fittings are tight and secure.
  • The firebox, smokebox and grate have been cleaned out.
  • The tubes have been cleaned.
  • Have a pre-test, by using your own hand pump, or test pump.
  • To ensure that the correct fitting is available to connect your boiler to the club's test pump.
6.  Fittings Required for Test

Illustration of fitting required by members, to connect to the Society's pump and gauge set for boiler testing.

Each model engineering society will have it's own hydraulic test rig, but there is currently no recognised standard for fitting sizes used for connection.
NADMES has adopted the thread size of 5/16" x 32 tpi M.E. (male) for the boiler end of the pressure test rig.
A member's own fitting should be made to attach to it, as illustrated.  (The other end may be attached directly to the boiler, or connected by a pipe/flange etc.).  Whilst it is possible that the boiler tester may have additional fittings, this should not be taken for granted.

7.  And Finally

Please remember that boiler testing is time consuming, even when no problems are experienced.  Boiler testers are volunteers who are willing to undertake the task, often at fairly short notice.  It should normally be arranged to do the test at the new Club Workshop, however there may be a need to do it a a members home; this may involve travelling expenses, and it is therefore requested that members who require this service offer reimbursement.  It is the intention of all club boiler testers to be helpful, but it is unfair to expect them to prepare boilers; their task is merely to test them.  Please remember their time is valuable too.

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