Hi Glenn

I have a 3” Marshall with a steel boiler built in 1997 by Bell Boilers and have just checked back through my paperwork. If you are going to get a test certificate and insurance the boiler materials must be supplied with a certificate of conformity as being approved for boiler use. My tube was certified to 50 bar. The welding has also to be done by a coded welder with a current certificate. Masteel of Lichfield would seem to be suppliers of suitable materials. A talk to your club boiler inspector would seem to be a good idea.

Regards John

Contrary to popular belief there is no one grade for making a model boiler. Long ago there was a product classed as Boiler Plate but that was a long time ago. Whilst some of the grades are more preferable to others mostly in relation to their oxidation propertied (rusting) a certified low carbon steel will pass all the tests for models. The steel has to have its Mill Certs when purchased, these will tell you and your boiler inspecter only that the material originated from a trusted supplier and was tested and offers no indication as to accepted uses. The steel supplied to you will have no marking to tie it to the cert! There is no pass, fail or for that matter anything you can determine from Mill Certs, but if there were ever to be a problem you have traceability back to the supplier. You can weld the boiler without being coded, the UK regs state that samples be made availible for testing but dont say which test…and there are lots!. One way to prove suitability is to have your completed boiler fully Non Destructive Tested and certified by an authorised NDT Weld test house. After you have jumped through these and other hoops let me add a word of caution…unless you are a very, very experienced welder (Im talking professional level for many years) your efforts will be a waste of time and your boiler will leak. Its one thing to weld two pieces of metal together but welding a water tight pressure vessel is a million miles away….in the opposite direction. I have welded many boilers (alas not certified any more) and used to weld for BNFL, and on accasion some of my welds failed test, requiring many hours of corrective action until the man with the scope say yes. I now only make copper boilers! Good luck with your build. The last time I tried to obtain suitable tube for a steel boiler I was unable to. If you want to buy a 3m length I can point you in the right direction but other than that I know of no one who is willing to sell any.