If your going to make a 6" boiler then why not make the burner ? Using the ceramic burner material used in the old super Ser roon heaters and some fire cement you can make a burner to suit your job and save about £50. Noel

This is opportune as sometime I intend to embark on a gas burner or my 5" vertical boiler. I've been collecting ideas off the interweb, and this looks worth a punt plate/pan. Clearly needs altering from rectangular to round, but the principle holds good

You might also try robRoy, a chap from New Zealand has made a successful burner for a Rob Roy which has secondary air inlets through the ceramic. I did have Doubletop's email but change of computer lost a load.

There appears to be some dispute over whether secondary air is needed. The Doubletop link and Fizzy's suggestion of several smaller burners suggest it is. I've also seen reference to a sort of doughnut shaped ceramic burner, a big hole in the middle lets the secondary air in. Suffice to say all the central heating boilers I've ever seen have lots of small slits for the flames, and secondary air.

Hopefully the OP will solve the problem for me and let us know!

I've got quite a bit more info, if you want it send e your email via pm

Edited By duncan webster on 18/11/2021 18:51:15

I have a 6" verticle boiler of similar design ! One thought was a series of concentric rings of tube (copper) drilled with small holes (jets) and all mounted on a square radial pipe, fed by the main jet and a venturi. The venturi and main jet would be made so as to be changed or adjusted and the gaps between the rings would give well distributed secondary air. This secondary air would also be controlled by a damper below the burner/firebox. Thanks for your input Nigel, and write your book I will buy a copy ! So Nigel are you saying it is not possible generate enough heat to power a 6" boiler with gas or is it the case that no one has made a burner to do it ? Keep in touch Duncan and Chincoa, may be it can be done. Noel.

PS if the ring desgn in copper worked but was found to get to hot then rings of steel would be plan B !

There are many instances of loco boilers with multiple fire tubes being successfully fired by gas, over in the USA they seem to use it a lot especially in areas prone to forest fires. I gave two references above, here's another USA, and there was an article in SMEE journal some years ago. Also google for Marty burners, ME 3169 and Engineering in Miniature May 2011. ME 4188 had an article on using a modification of a Sievert cyclone burner in a 5"g metro and a 3.5" Rob Roy. Even LBSC showed drawings of a primus stove burner in a model loco firebox, no idea if it worked but his stuff tended to.

Where I will agree wholeheartedly with Fizzy is that you are unlikely to have success in a muti-tube boiler without forced draught, too much pressure drop in the tubes. What you also need to ensure is that the gas has completely burned before it gets into the tubes, once inside it is cooled faster than the burning can heat it, the flame is extinguished and you get unburnt or partially burnt gas coming out of the chimney. (This is a bit of a simplification, but I believe basically correct)

I have a suspicion (no more) that you won't get the same output from gas as you will with coal. My vertical boiler has a 4" grate, so allowing 25 lb/sqft/hr grate loading (actual burning) gives 2 lb/hr, 28362 BUT/hr or 8 kW, the same as a Sievert 2941 burner, but you won't get that to fully burn in a firebox only 4" or so high

Finally there is a suggestion, and I can't put it higher than that, that a vapourised paraffin flame is more compact than an equivalent LPG flame. I have no hard data on that, just something someone told me. All we need now is for someone to take all this info and make a successful burner for a vertical boiler instead of my pontifications