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Steam Regulations and YOU.

Steam regulations were introduced in the last century after much lobbying by the insurance companies of the day to control any improper usage and construction of pressure vessels, ie steam boilers, to make them safer around the public at large and to cut down on excessive payouts.

In those early days boilers were mainly for commercial use and tended to be much larger than any boiler a modern steam enthusiast would be dealing with, despite the fact that modern boilers are made of much better materials.

This legislation was introduced and a standard of 1000 bar/lbs was set up as a minimum for boiler pressure/capacity. Anything above that had to be independently and meticulously checked, both in the build and testing of the pressure vessel.

As a guide, 1000 bar/lbs is the same as 100 bar/gallons, so if you had a boiler of 25 gallon capacity (which is very small in the commercial category) then you were allowed a pressure of only 4 bar (56.8 lbs/sq inch) unless you were certified to ministry standards, and as many commercial boilers far exceeded this size this meant extremely low boiler pressures being used unless the boilers were tested first.

And so the minimum level was set, standards were improved and the insurance companies had something to work to and knew where the blame lay if things went wrong...

And along came people wanting to make a smaller model of the real thing, usually locomotives and traction engines, trying to build their model with easier materials, and at the same time at a much smaller scale than the 1000 bar/lbs.

To bring you up to present day, this measurement is converted to 500 bar/litres and to give you an example of your boiler size, if you have a boiler with a barrel length of one foot (30cm) and a diameter of 4 inches (10cm), then the capacity is 150.8 cu inches (2.356 litres), you can see that with a 50lbs/sq inch pressure (3.5 bar), your figure would be 2.356 x 3.5 = 8.245 bar/litres which falls well below the government minimum standard.

There have been boiler failures in the past with these smaller versions owing to poor material standards and construction methods, and this is where boiler testing comes in.

For yourself, as a model boiler builder, if you want to operate your boiler in a public place then you need your model insuring and the insurance companies still use those same antiquated standards, meaning you will need your boiler testing and certifying by a competent person who can be found at your local model steam club or society.

If in the other hand you do not wish to use it in a public place, then there are no legal requirements, but for your own safety it is better to get your boiler tested properly.

Happy steaming,


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