converting from town gas to propane

[optima21]

Hi guys,

I've tried to find this on the internet but think the internet might be too modern to give me an answer. Ive got a friend who has a small muffle furnace that hasnt been used for a while.... and last time it was it would have been used on town gas, so we are looking 50+ years ago. I know that previously things that burnt town gas were converted in the late 1960's/ early 1970's to burn natural gas so thats fine, also you can convert natural gas burners to run on propane. both of these could be done by changing the size of the gas jets. so are there any gas engineers here who would know what difference the gas jet should be to work properly. I cant even find what pressure town gas was used at. or can you just plumb it into a low presssure 37mBar propane regulator and see how it goes. he'll be using it outside so carbon monoxide wont be an issue if its not perfect combustion.

 

[brightspark]

give it a go using an adjustable propane regulator .at worst it will blow the flame out if the pressures to high and then you can turn it down

 

[gordon stephenson]

I converted a large overhead gas heater from town gas, experimented with jet sizes made from mig tips, drilled through in small increments in conjunction with as brightspark said an adjustable regulator,

 

[Kayos]

Town gas has a very, very low flame speed do I would suggest starting with a tiny jet and find someone with a flue gas analyser to check how it is burning

 

[Tom O]

This might help

 

[timgunn1962]

Do you have any details of the burner and/or the jet(s)? Ideally pics? Is there a movable choke to allow adjustment of the air:fuel ratio (and therefore the flame temperature)?

If the jets are something fairly standard (a somewhat relative term) like the 1BA-threaded Amal 187-series, there should be no problem sorting out suitable replacements. The difficult bit is working out the sizes. Town Gas had a low Calorific Value and the jets for the "new" Natural Gas tended to be smaller when things were converted from Town Gas to NG. Rejetting from NG to Propane is relatively well-documented and it is usually possible to get pretty close. Going from Town Gas might be a lot less clear-cut.

Most of the things that got converted during the changeover to NG were relatively simple rejetting jobs for the gas fitters involved, with the correct jets for NG having been sorted out by the manufacturers of the equipment. As I understand it, the clever guys were the ones who converted the "odd" industrial stuff that was either effectively one-off, or was tuned to give a particular combination of temperature and reducing atmosphere for a specific industrial process (like a muffle furnace, perhaps?). I gather they often rocked up with a new burner, or just a new gas mixer, and a box of assorted jets, took a stab at an initial jetting based on experience, then tested, changed jets and tested again until they had a working setup.

As far as I can tell, the Amal Atmospheric Injectors were the mixers they'd fit: developed by Amal and British Gas to provide a wide range of adjustment between the interchangeable jets and the adjustable choke. These are still made by Burlen, though stocks are thin on the ground at present.

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I use them in Propane forges and Heat-Treat "forges" and find that the Butane jetting gives slightly higher maximum temperatures on Propane than the Propane jetting, which is why I've linked the Butane injectors. The choke then allows lower temperatures to be readily achieved.

Best advice is get lots of pics: Lets have a look at what you've got and try to work out what your options are. If you can get a close look at the installed jet to see whether it is stamped with a size, that would give us a starting point and might make things much easier.

 

[gaz1]

@Keith 66

Flame fast DS 320 Brazing hearth / Forge

I just acquired a Flamefast DS 320 combined brazing hearth & Chip forge from a school clearance, its in good nick but has no ceramic chips. Flamefast inform me that its an obsolete model that was intended as a brazing hearth with forging capability and that i would be better of converting it to...

www.mig-welding.co.uk

you can use wood gas instead

 

[Agroshield]

This might help

You will have to tell us if the pressures in that document are in Freedom Units, Kanukistani Kopeks per square moose or whatever.

That is useful info. for natural gas (methane) and LPG (propane). The original article burnt town gas (also called coal gas). See https://en.wikipedia.org/wiki/Coal_gas for its calorific value.

This gives an overview of its development: https://www.claire.co.uk/component/...f-gasworks-manufactured-gas-plants-in-britain

If you want to know the typical supply pressure of town gas, these people will surely know: http://www.nationalgasmuseum.org.uk/gas-industry-chronology/