Simplex superheater

[steam4ian]

G'day experts.

I don't have a copy of the boiler plans for Simplex except for the one drawn by Baggo for his Simply Longer. B's plan has there 3/4 inch flues.

My question is about the size and number of flues in the standard Simplex boiler.

On DrJ's web site his photos show only one flue and superheater for his unsuccessful boiler (simmer down DrJ). DrJ does your second boiler have only one flue and superheater? BTW I like the concentric tube idea.

Is one flue standard for Simplex? What diameter is it? What is the "normal" superheater element form?

All advice will be used.

Regards
Ian

[alanstepney]

The standard Simplex boiler has:
13 tubes of 7/16" outside diam
1 superheater tube of 1 1/8" dia.

The superheater is 2 x 7/16" x 20swg tubes (stainless steel).

The "single tube" actually concentric tubes, type of superheater has been shown to be far less effective than the twin tube types.

[Shawki Shlemon]

HI Ian
Simplex is a free lance and therefore you can do what you like , secondly in my opinion what you don't see again is what you like too .
Is your boiler barrel around 5" dia ? I use 2 x 1" super heater tubes and use concentric type . I agree with Alan that the two tube type is more efficient , matter of choice . I use 5/8 "dia for the outside and 5/16" dia for the inside . I hope the photo helps .

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[steam4ian]

G'day Shawki

Thanks for the reply and picture. I can see the boiler is for a C32 judging by the designation on the header.

My barrel is 4" but the wrapper is 5" overall. The tube length is only 8+ inches. 3/8" tubes will just work whilst 1/2 are a bit on the big size but will do.

The existing boiler jambed in two 1" flues and 11 1/2" tubes so finishes up with the fire box too high. According to all the formulae it has too many tubes. I haven't played around with the 1" and 1/2" combination yet to see what I can fit.

I like the concentric superheater idea as I think I can manage that; it could even extend into the firebox and be a radiant type

Thanks again

Regards
Ian

[davidm]

This is my Simplex, with the boiler by Western Steam to the original drawings by Martin Evans. The radiant superheater is 3/8 stainless with a welded 'dart' at the firebox end (from Polly Engineering, and I notice that they now advertise one specifically for the Simplex).

But as Shawki says, you can do what you like. If I were starting again I would have two flues and therefore, presumably, more superheat.

By the way, scans of the original ME articles are available on the Model Engineer web site.

David

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[drjohn]

Hi Ian

The only thing I would add is that with two superheater flues, you have less proper flues, and with the difficulty of cleaning the superheater flues, you end up after a while with considerably less heat exchange area for the boiler water.

What a super smart, clean and tidy smokebox assembly David!

DJ

The "single tube" actually concentric tubes, type of superheater has been shown to be far less effective than the twin tube types.

It has been stated on this forum by much more knowledgeable people than me, that superheating in our scale (5") is more just steam drying rather than true superheating, and with my concentric one glowing red hot above the fire, it seems to work just fine with hardly a trace of wet steam from the chimney when running. (that was also the case in my first simplex running in UK weather.)

[steam4ian]

Thank you DrJ, David, Shawki and Alan.

You have provided just what I wanted to know plus a little more besides. This is a great site

I agree with DrJ about the flues getting dirty. I managed to keep my tubes (those in the boiler) quite clean but the flues have about a 1/32" layer of baked on soot in them.

Regards
Ian

[nigelh]

Hi folks,
a "simple" question, I hope, concerning connecting my 7/16" od stainless super heater tube to the vertical steam pipe that goes down to the "T" block and cylinders.
I'm ready to cut the 5/8" x 26 tpi thread on the steam pipe and went looking for a suitable nut, to check my thread against but it seems that 7/16" od pipe compression fittings aren't available, at least out here in Cyprus!
Does anyone know where they can be had from, in the UK or have I to make one and, presumably, the compression olives to go with it.

Maybe someone has found an easier solution ??
Any comments/thoughts would be appreciated!
Thanks
Nigel

[jma1009]

nigel,
you mustnt use compression fittings on any part of a boiler or its pipework. they should all have proper nipples silver soldered to the pipe.
cheers,
julian

[nigelh]

Hi Julian,
thanks very much for that - I hadn't realised what is obviously a very important point!
cheers
Nigel