Hi Martin,

In Gauge '3' (2.5" at 1:22.6) I would say that most live steam engines are run at around 80psi even though they are being used in a "scenic" setting (e.g. not passenger hauling). You could most certainly run a steam engine at a lower pressure and there might be reasons to do so in G3, one of which would be the 3 bar/litre boundary.

Essentially the boiler test certificate requirements (required at G3 GTGs and at any MES Rally) are less onerous if the boiler is <3BL. The bar/litre is a combination of the total water capacity of the boiler x the normal operating pressure, so reducing the operating pressure can bring some engines below this 3B/L boundary (at least in G3).

However, assuming you will be running on your own track – formal boiler testing may not be an immediate concern for you, although I would still recommend you familiarise yourself with the general requirements and make your own safety checks. You can find more info at the Southern Fed website.

Overall though, I think Neil probably has the best advice for you.

Get the boiler built as originally specified for the engine design (again assuming they have been built to an existing design – LBSC/Evans etc.) and run it at the recommended pressure. If you have a boiler built for you make sure you get the maker to provide you with a hydraulic shell test certificate too. You are going to either spend quite a lot of time building these boilers/engines yourself – or paying someone else (a lot) to do it for you. So it makes sense to end up with an engine/boiler combination that is saleable for a fair price should the need arise.

Regards,

IanT

Edited By IanT on 11/03/2015 11:26:22