brian777999 Posted January 17, 2014 Share Posted January 17, 2014 How do you tell if an older model steam boiler (Wilseco, Mamod etc.) is safe to use.... other than firing it up and standing back a considerable distance while wearing eye protection ? Link to post Share on other sites More sharing options...
corax67 Posted January 17, 2014 Share Posted January 17, 2014 One method is to fit one of these http://www.modelenthusiasts.com/mamod-engine-water-level-foot-pump-adapter.html It allows you to pressurise the System with air - rather than a compressor this can be achieved satisfactorily with a bicycle track pump (the tall standing ones) which are perfectly capable of supplying up to 120psi but your Mamod boiler safety valve should vent at around 20psi if memory serves me correctly. You will need to use ballistic shield of some description - 3/4 inch Perspex is sufficient for this type of application - in case of major failure and ear defenders are strongly recommended too. In the event of catastrophic failure this setup means that hot water & steam are not vented along with boiler bits and the building of pressure can be done gradually & with fine control rather than by merely firing up to let nature take it's course. Link to post Share on other sites More sharing options...
The Bigbee Line Posted January 17, 2014 Share Posted January 17, 2014 A hydraulic test is the safest way. You need to decide on a test pressure, then blank everything off to allow the boiler to be pressurised to the required test pressure. That's what the big boys do. No one ever deliberately does that under steam (or even air) Link to post Share on other sites More sharing options...
brian777999 Posted January 17, 2014 Author Share Posted January 17, 2014 A hydraulic test is the safest way. You need to decide on a test pressure, then blank everything off to allow the boiler to be pressurised to the required test pressure. That's what the big boys do. No one ever deliberately does that under steam (or even air) I have an air compressor with a pressure gauge which I use for airbrushing. Can that be used to test the boiler ? Link to post Share on other sites More sharing options...
The Bigbee Line Posted January 17, 2014 Share Posted January 17, 2014 I have an air compressor with a pressure gauge which I use for airbrushing. Can that be used to test the boiler ? Look at http://en.wikipedia.org/wiki/Hydrostatic_test it has lots of useful info. Safety first. Link to post Share on other sites More sharing options...
RMweb Gold RedgateModels Posted January 17, 2014 RMweb Gold Share Posted January 17, 2014 Hydraulic test every time! there is little stored energy so if you get a failure all you get is a leak, no sudden release of energy etc. Find yourself a local pressure gauge repair shop and ask them to run it up on water Link to post Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted January 17, 2014 RMweb Gold Share Posted January 17, 2014 I have an air compressor with a pressure gauge which I use for airbrushing. Can that be used to test the boiler ? The short answer is "No", not if you value your personal safety. If the boiler does have a fault and the steam (or air) is released under pressure, it will spread into the room with explosive force as it expands. Water on the other hand will not expand. Things will get wet, but no one should be hurt. As the Bigbee line says "Safety first" This video demonstrates the hydraulic testing of a model steam boiler. NB usual disclaimer. I have nothing to do with the video, so I suggest you check other sources as well for advice. There may even be companies that would do the test for you. They certainly exist for full size boilers in industry and are used by the preservation movement. PS eye protection won't protect the rest of your body from bits of flying metal !! Edit to add PS Link to post Share on other sites More sharing options...
RMweb Gold Happy Hippo Posted January 17, 2014 RMweb Gold Share Posted January 17, 2014 The only safe way to test a boiler is by hydraulic test. Because water is in-compressible, it only requires a small amount of extra water to bring the boiler under test to the required pressure. If the boiler should fail, you are left with a puddle of water. Testing a boiler with any form of gas, including air from a compressor, will turn your boiler into a potential bomb! If it 'lets go' there will be a rather violent and explosive end to the boiler with parts of it flying around the test area in a similar way to a hand grenade detonating. the late Jack Wheldon, who wrote extensively in the likes of MRC about smale scale live steam, once hydraulically tested a Mamod boiler to see what it was capable of withstanding.. He gave up at 200psi! The brass boiler which was only of soft soldered construction was visibly bulged but it was still holding. Most model boilers will go on ad infinitum providing they are looked after. As an aside: the killer of small boilers is using de-ionised water in them. (Often sold as 'distilled' from motor factors and which it is not!). The Water leaches the zinc out of brass, causing a white crumbly deposit to form. I have had to replace a number of boilers for customers where the boiler fitting was mounted onto the boiler via a brass threaded bush. The thread of the bush disintegrating then a tap was gently put down the thread to clear it out. Now this doesn't happen over night, but it is something to be aware of especially in older 'toy' boilers. hth Edit: grammar Link to post Share on other sites More sharing options...
Roddy Angus Posted January 17, 2014 Share Posted January 17, 2014 If you have a local model engineering or model boat club they may be able to help. Depending on size, steam boilers have to be tested at various intervals and any boat or engineering club whose members use steam models will be able to advise on the availability of an experienced tester. Roddy Link to post Share on other sites More sharing options...
brian777999 Posted January 17, 2014 Author Share Posted January 17, 2014 Most model boilers will go on ad infinitum providing they are looked after. As an aside: the killer of small boilers is using de-ionised water in them. (Often sold as 'distilled' from motor factors and which it is not!). The Water leaches the zinc out of brass, causing a white crumbly deposit to form. I have had to replace a number of boilers for customers where the boiler fitting was mounted onto the boiler via a brass threaded bush. What should be used ? Link to post Share on other sites More sharing options...
PatB Posted January 18, 2014 Share Posted January 18, 2014 What should be used ? Bronze is the stuff. No zinc in it, just copper and tin. Typically, for model boilers, a variety of bronze called gunmetal is used. If you don't have access to a pump, a small, low pressure boiler of the Mamod type can be safely tested to working pressure by filling it (and I mean filling, with no air/steam space) and then heating it until the safety valve (which you did check wasn't stuck beforehand, didn't you?) lifts and expels water. For a toy type boiler for my own, personal use (ie, no public display or giving to kiddies for example) I would regard this as adequate and it's a lot less mucking about than the sort of test that is appropriate for higher pressure units as used on proper live steamers working at more than the 15 psi or so that Mamod oscillators see. For a bit more margin of safety it isn't hard to modify a spare safety valve with a stronger spring. Indeed, the simplest way of going to double the working pressure (normal for a "proper" hydraulic test) is to remove half the turns of a standard spring and fit it with a spacer (of half the installed length of the standard spring) to take up the length. This doubles the spring rate and so will roughly double the pressure at which the valve lifts. WARNING: On no account must such a modified valve be used under steam on a standard boiler. Such a valve needs to be obviously and indelibly marked to prevent it from being used by mistake. I would favour wiring a big metal label to it, painted red. Link to post Share on other sites More sharing options...
brian777999 Posted January 18, 2014 Author Share Posted January 18, 2014 So anybody intending to build their own boiler should also be buying a water pump and a pressure gauge for testing purposes ? I live in Cairns, Australia and as far as I know there are no Model Engineering clubs near here. There is not much of anything near here ! Link to post Share on other sites More sharing options...
RMweb Gold Happy Hippo Posted January 18, 2014 RMweb Gold Share Posted January 18, 2014 The UK is lucky in that boiler testing for model steam loco boilers and their like has been devolved to the various Model engineering federations and other associated Associations within the UK. There used to be an exemption to testing for boilers under 3 bar litres, which covered Mamods, Wilesco and most of the locos produced for the G scale/16mm brigade. However, this was supersceded on 1 Jan 2013 by a blanket rule for testing of all boilers and also, where applicable. gas tanks. Allegedly, this was brought about by new regulations formulated by the bunch in Brussels There are guidelines set down for the testing of model boilers, although I cannot find any formal qualifications for boiler testers of such. Most clubs use words such as 'should be/preferably/experienced' and these are the guys that get authorised by the club to test boilers. Not only do the boilers require a hydraulic test, but also a steam test as well: the steam test is to ensure the safety valve(s) can do their job effectively. But it should be noted that these regulations apply to boilers which are in being used publicly at shows or being used to give rides at exhibitions etc and are for 3rd party liability insurance. I'd even be as bold to say the test is only good for the day of the test, a bit like an VOSA test on a car, or a gas free test on an empty fuel tank (only valid for 24 hours) But such a test does indicate that the owner has made every effort to ensure that the boiler is safe for operation. (Although it may not be operated in a safe manner due to incorrect technique) What you do in the privacy of your own home etc is a different matter. There must be thousands of Mamods and their ilk in peoples homes, and these folk have no inkling about the regulations that are now in place. I suspect that many are run and have run for many years without any safety issues, and I cannot see the Government bringing in a boiler amnesty as they do every so often with firearms. It would be interesting to open the likes of a new Wilesco and find out what guidance the manufacturer gives to boiler certification and retesting! Link to post Share on other sites More sharing options...
PatB Posted January 18, 2014 Share Posted January 18, 2014 Unless you have a local club or a friendly local enthusiast, yes, you need to be set up to test any boilers you intend to build to an appropriate standard. What constitutes an "appropriate standard" will vary depending on the nature of the boiler, what use it may be put to, local legal requirements etc. What is appropriate for the boiler of a 10.25" gauge UP Big Boy (which will flatten several suburbs if it goes bang) is rather different from what's needed for a little copper pot that runs a 0.25" bore oscillator in the privacy of your own workshop. I've just had another look in the well respected Tubal Cain's Building Simple Model Steam Engines to make sure I'm not offering incorrect or dangerous advice and I note that, for at least one weeny oscillator, he doesn't mention testing the boiler at all before steaming it. Even given my own somewhat cavalier attitude to personal safety, I'd not consider this wise. However, for another example he mentions the possibility of using mains water pressure as your test pressure source, which hadn't occurred to me. For a toy boiler working at 15 psi, a test to 30 psi is more than enough. That's about 20 m of head of water. It might be worth enquiring with your local water supply company to find out what your mains pressure is, or should be. It could be enough. For more serious boilers, in Australia you are constrained by the Australian Model Boiler Safety Committee Codes. There are three: one for copper boilers, one for steel boilers and one for "sub-miniature" boilers (the sort of thing used for 16 mm scale live steamers and such like). These Codes lay down structural standards, operating parameters and testing procedures and must be followed if your engine ever goes out in public, such as to your local club or exhibition. Equipment such as pumps and gauges may be prescribed in the Codes but I don't know for sure because I haven't read the big boiler documents and it's years since I looked in the sub-miniature one. That said, for your own use you have some latitude in the equipment needed. The fill with water (no spaces), seal and heat method is an entirely valid and (sensibly applied) safe means of applying pressure for hydraulic testing as long as the water temperature does not exceed 100C. However, if you have the skills and facilities to build any boiler more complex than a small pot, you shouldn't find knocking up a small force pump beyond you. A gauge is harder to avoid. You need some reliable means of determining the pressure in the boiler. I wouldn't want to try making a conventional bourdon tube type pressure gauge, but it wouldn't be hard to make something with a piston sliding in a cylinder, lifting a lever of known length against a scale or spring balance of some kind. It probably wouldn't satisfy a club working to the AMBSC Codes but, again for purely personal use, I would be happy with such an arrangement. I would add the disclaimer, though, that I'm a professional mechanical engineer so I'm confident of my maths and material science and good enough at risk management that I can probably do this stuff, nine times out of ten, without blowing myself up . YMMV. BTW, if you need a gauge for boiler testing, I've got one somewhere around that you can have for the cost of postage (although it may be a while before I can dig it out as I'm about to start a job in Canberra and will be away from home for long periods as of this week). IIRC it reads to ~200 psi (enough for a 2xworking pressure test on most modern live steamers now that the terrifying pressures favoured by Curly Lawrence (LBSC) have fallen from favour). I don't know if it works though, and it will certainly need calibration. Edit: Happy Hippo makes a very good point, which has been niggling at me. The toy steam engine (low pressure pot boiler coupled to oscillating or simple piston valve engine) has been produced in the hundreds of thousands over the last 110 years or so. Examples have been run and run, boiled dry, stamped on, rattled around in toy boxes, stored wet in damp sheds for decades before being rediscovered and steamed again, had their safety valves held down and every other form of abuse and neglect that could be inflicted on a piece of machinery, whilst no more than a vanishingly small percentage has ever been subjected to any form of pressure test, even by the manufacturer. In spite of this huge service record, in the hands of non-technical users, I can't think of hearing a single, substantiated or first-hand account of a boiler going pop. Taking the french polish off the dining room table with spilt meths, yes. Setting the carpet on fire, yes, cutting fingers on sharp tinplate edges, yes. Dangerous boiler failure, no. Again, I would emphasise that I'm not talking about "superpots" or proper, internally fired locomotive type boilers here. Just the low pressure toys. Link to post Share on other sites More sharing options...
RMweb Gold Happy Hippo Posted January 18, 2014 RMweb Gold Share Posted January 18, 2014 Again, I would emphasise that I'm not talking about "superpots" or proper, internally fired locomotive type boilers here. Just the low pressure toys. Pat, I've already liked you post so am just coming to agree with you with your point about lp toy boilers. Link to post Share on other sites More sharing options...
brian777999 Posted January 18, 2014 Author Share Posted January 18, 2014 That said, for your own use you have some latitude in the equipment needed. The fill with water (no spaces), seal and heat method is an entirely valid and (sensibly applied) safe means of applying pressure for hydraulic testing as long as the water temperature does not exceed 100C. However, if you have the skills and facilities to build any boiler more complex than a small pot, you shouldn't find knocking up a small force pump beyond you. A gauge is harder to avoid. You need some reliable means of determining the pressure in the boiler. Yes, I definitely intend to buy some sort of water pump and gauge. I would like to have a boiler with a gauge permanently installed on the top so I can see what is going on ! Who supplies these items (and other model engineering needs) in the UK ? Postage from the UK is usually much cheaper than from the US. Link to post Share on other sites More sharing options...
PatB Posted January 18, 2014 Share Posted January 18, 2014 Reeves and Blackgates Engineering are the two main model engineering suppliers I can think of. There's a third big player too, whose name has slipped my mind at the moment. They all have comprehensive websites, or did a few years ago. A search on "model engineering supplies" should turn them up. I suspect that all miniature pressure gauges come from the same manufacturer anyway. Someone like Roundhouse Engineering will probably also be able to supply something as a spare for their locos. A Mamod type boiler will, however, barely get any proprietary gauge I've seen off the bottom stop as they're really oriented towards boilers working at 2 or 3 times what a Mamod will ever see. Link to post Share on other sites More sharing options...
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