Barrie The problem is that the model engineer's boiler testing regime is as much an insurance issue as it is to do with boiler test codes. The majority (nearly all) of model engineering clubs, and their boiler inspectors, are covered by insurance schemes arranged by the Southern Federation of Model Engineering Societies or the Northern Association of Model Engineers. These policies limit models to no more than six inch scale (half size) so a model is in a smaller representation of a larger prototype (yup, I know about non- prototypical designs, ie Simplex). There are some small steam plants that were commercially built and marketed for trade/practical use, other than as representation of a model of a larger machine. Their use could be construed as other than a modeling activity. Now if you were to build a boiler that was the same size as was sold to originally power such a machine it might not be seen as being a model. However, if the boiler could be shown to be a less than six inch scale representation of the original design then no problem. Hope that all makes sense!!!!! The boat issue was covered by permitting steam powered plants in model boats providing they are a scale model of a full size boat and does not carry anyone. (Someone has yet to challenge the scale issue by building a half size QE11!!!!) ChrisC originally wrote........ "Looking for something in the 80-100 psi range under the assumption that this would be a sensible value for a double-expansion engine..." Unless he is building something at an extremely large scale I don't think he will need a boiler that will fall outside the code. Phill wrote: > Hmmm That doesn't make sense.... > > How can a 1/12 beam engine not be a model ?????? It is still an > industrial > engine, technically....... But So is a 3.5" gauge loco, still > technically a > locomotive, and therefore not a model......... > So a scale boiler for a 1/12 beam engine is not a problem, providing it meets the bar-litre criteria. Want to go bigger than the code/insurance limitations permit, you still don't have a problem, you will just need to get your boiler commercially tested. Regards Mike Leahy MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.