Expanding boiler tubes in the firebox

[nigel jones 5Participant @nigeljones5]

I am building a steel boiler in 5" which will need copper tubes expanding into it – fine at smokebox end but how do i do it from inside the firebox?

[nigel jones 5Participant @nigeljones5]

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Nigel ,

The easiest way is to make a rubber bung expander arranged at right angles to end of pliers type handles . Then just operate up through the bottom of firebox .

MikeW

[nigel jones 5Participant @nigeljones5]

Thanks – can you please elaborate on this, it is not something I have heard of?

[Romeo R.LParticipant @romeor-l]

Hello,

From recent club experiances you don't want to mix copper and steel, it causes a metal reaction in the boiler itself resulting in wearing the boiler out alot quicker, this was in 7 1/4" so i believe that in smaller conditions it might happen quicker,

I know its not much help but hopefully some advice,

Romeo

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Nigel ,

Basically a piece of thick walled synthetic rubber tubing is put on a rod between two collars . If the collars are now forced together so as to squeeze the rubber tube endwise then the rubber tube will expand in diameter . If the rubber tube and the two collars are made just a slight amount smaller diameter than bore of your boiler tubes then applying the end wise force will efectively swell the rubber tube into the bore of boiler tube and expand it into tube plate .

The general idea is extensively used in industry to expand tubes into dies so as to make (eg) deep grooves for O rings in pipework . You should have no trouble expanding annealed copper tubes this way .

Full size boiler tubes on steam locomotives are usually (not quite always) made from a special brass alloy .

MikeW

[nigel jones 5Participant @nigeljones5]

is it worth soft soldering them after expanding them to ensure a good seal – comsol etc?

[Author]

Posts