Super heater configuration

[nigel jones 5Participant @nigeljones5]

[nigel jones 5Participant @nigeljones5]

If I install super heaters on my 71/4 Invicta it has occurred to me that the steam regulator is the last part in the pressure chain before the cylinders – and that if I were to have a SH failure in the firebox the entire contents of the boiler would rapidly exit via this route! I intended to use copper pipe for down the fire tube, mated to stainless going into the firebox with a stainless return at the fire door end. This was to be silver soldered rated >800 degrees. I don't want to braze it as I don't like brazing! I am now paranoid about the effect of a major failure in the firebox – what do you think the outcome would be?

[OuBallieParticipant @ouballie]

Fizzy,

There was a long descusion about just this in 'Ours' many many moons ago, if memory serves, but do not remember if there was any definitive outcome.

One of the theories/arguments for not having the regulator before the SH elements, was that when closing said regulator, steam already in the system would continue to expand and heat up and the loco would not stop as required.

Anyway, with our locos, the volume of steam is too small to have any effect, and in any case, the full size ones had no such theoretical problem.

All my locos have/had the regulator before the superheater.

As you mentioned, a boiler would empty itself PDQ, and in quite a spectacular fashion.

Saw this happen at the JLS Club one Sunday when a safety valve was tapped to stop it leaking. It cried enough, parted company with the boiler and took off skywards. Made everyone jump at the sound and sight of all that pent up energy being suddenly released.

A spectacular sight it was.

Oh, it was a brass safety valve to boot, never to be found, it having been eaten away at the boiler bush, hence brass being a taboo for such fittings.

Geoff – Still coughing

[nigel jones 5Participant @nigeljones5]

Thanks Geoff

Anyone else??

[julian atkinsParticipant @julianatkins58923]

hi nigel,

due to the very basic boiler, and very basic valve gear etc on Invicta, i dont think there is much point fitting superheaters. it is not as if you are going to be able to run the loco with long travel valves and long lap and expansive working.

i am otherwise a strong adherent of superheaters on miniature locos.

the regulator position on your design is a further very strong reason not to fit superheaters.

the return bends on stainless elements should not be silver soldered anyway and ought to be TIG welded

cheers,

julian

[nigel jones 5Participant @nigeljones5]

thanks Julian and all – I had a rethink and the returns can easily be tig welded. Interested in why you think it will be a very basic boiler as it is the same for any other loco, basic or otherwise. I do intend to run this, and may well upgrade the valve gear to a better design at a later date, and I don't fancy it blurting wet sooty water all over me. With the returns welded there should be less risk?

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