Safe ?

You have to remember it is gas you are using here, if the flame goes out and the gas keeps going ……….

what happens next depends on how far away you are.

Under or in the firebox? Internally, one would definitely need a flame failure device, I would suggest.

I have seen the effects of igniting fuel mixtures in confined spaces. The uncle of a friend was killed about 40 years ago while relighting a furnace after the Christmas break.

An idiot, who should have been watching a gas/oil flame in a kiln left the job and the flame went out. Luckily there was no explosion on that occasion. The kiln had just been completely relined with refractory bricks at huge expense. The electrostatic precipitators were hurredly de-energised and the kiln was well ventilated before attempting to relight the flame! It probably cost us two hours, or more, at a time of tight production reserves, but could have been a disaster.

Another instance was that of an auxiliary firing fan casing, that exploded because there was a fire in the coal store and burning embers were entrained in the air flow. Before the incident, some workers congregated around that particular fan on cold days or nights…

Be very careful, is my advice.

A gas stove won't give a very good heat output you would be better off with purpose made burners. Also unless the boiler is designed from the start for gas firing it may not be that efficient as the tube sizes should be altered and you don't get as much radiant heat through the sides of the firebox into the water legs, it all tends to go along teh tubes.

Properly designed it should not harm the boiler running on propane.

This is the type of burner that is often used made up onto a manifold to hold as many as you need, each gives about 5400btu

Edited By JasonB on 29/05/2018 07:41:43

So a form of hot bulb/glow plug system would help make things safer, in theory

My best guess, absolutely fine in that application BUT do not expect it to make steam at anything more

than a rate to maintain a running tick-over, maybe less.

Does beg the question, is it a functional test of the engine or is it a functional test of the boiler's ability to generate steam?

If of the engine only, then you could use air to pressurise the boiler.

Using gas to heat the boiler, from the heat intensity and corrosive products of combustion point of view, it should be less bad than coal firing the boiler.

Regards,

Richard.

Kevin

As has been said above, without seriously big burners, and a large bottle of propane, you will struggle to get enough heat into the boiler to produce useful steam.

A "Steam Test" for official purposes requires a full coal fire, with full blower, to check that the safety valves can release all the steam produced.

If you want to test your boiler for minor leaks and is the pipework ok, etc. then make up a water hand pump, valves and gauge and then hydraulically test at the boiler's normal working pressure.

If you want to test the cylinders and running motion then get a compressor that can shift at least 4 cufm.

Norm

Jason's video shows why it is not easy to get a gas fire to burn inside a firebox. If that very tall flame gets into the tubes it will go out, leading to incomplete combustion and sooty tubes. However it obviously can be done as our USA friends have shown. The model gas turbine guys burn a vast amount of paraffin in a small space, but they are under pressure which I think makes it easier. I'd be very interested in an authoritative article on the subject.

As most carbon based fuels burn in air at roughly the same temperature (about 2000C) , I doubt propane would get much hotter than a coal fire. From my armchair I don't think gas heating a model boiler would be unsafe unless you did something silly like letting the room fill with gas before striking a match or attacking it at a point with oxy-acetylene.

For a test, OK. Trickier to get the best out of gas or oil in a model loco boiler I suspect, a different firebox design would be needed. With gas there's no mass heating the firebox – it's all flame. In a conventional model locomotive I'd guess quite a lot of steam is generated by the mass of hot coal in contact with the firebox not just that made by hot gas playing on the tubes and boiler skin.

A full size firebox includes a few hundred kilograms of white hot firebrick arranged in an arch. Mainly to improve combustion it also retains heat rather than blowing it out the chimney. Never noticed an arch in a model locomotive firebox; on a small scale are hot coals alone sufficient to do a decent job?

LBSC famously proved that spirit burning boilers weren't the last word in model boiler design. Did he finish the job though? I can't help feeling that a modern analysis would provide better design guidance and improved boiler performance.

Dave

It might be easy when you know how, but when I had a play I found it very easy to screw up, flames going out, yellow flames, mini explosions. Gave up eventually, but would still like to know how to do it. By it I mean burn enough gas in a small space to run a 5"g loco. Full size men managed to burn oil, and gas must be easier than oil surely.

hi , if american use propane in 5' models , why we cannot make it ? for me its interesting but I need drawing of the boiler and the burner …. who have ?