Gas jet adjustment

[jamespetts]

I have recently been trying to set up a large ceramic gas burner using Bix equipment (destined for a Stuart 504 boiler) and a commercially available propane/butane mix gas cylinder. I was able to get the equipment connected and working without much difficulty, but I am not sure that I have correctly adjusted the jet position: my difficulty is that the flame seems to be yellow wherever I put the jet in the holder.

I have placed it now to minimise the yellowness, but it always seems particularly yellow when I turn the gas up.

I have been reading Keith Appleton's "Complete Guide to Minature Steam" CD-ROM, which suggested opening up the gas jet a little. I did this before I started, using a very fine drill that was a tiny bit bigger than the existing hole, thereby making the existing hole fractionally larger.

Is it a problem that the flame is partly yellow (with blue fringes) when running? Ought I not have increased the hole size of the jet at all? Would obtaining a new jet without an increased hole size make it work better?

Also, what do people here think to Appleton's suggestion of running the exhaust steam pipe under the gas cylinder to reduce the chilling effect of gas leaving the tank, which can cause low gas pressure and reduced heat at the burner?

[baggo]

Hi James,

It sounds as though you may have upset the gas/air ratio by opening up the jet and you are not getting enough air for the amount of gas passed. A small increase in diameter of the jet means a much bigger increase in the area of the jet. You may be able to compensate by increasing the size of the air holes but I would suggest getting a new jet first and trying it again.

John

[SteveW]

James,

jamespetts said:

Also, what do people here think to Appleton's suggestion of running the exhaust steam pipe under the gas cylinder to reduce the chilling effect of gas leaving the tank, which can cause low gas pressure and reduced heat at the burner?

An eminent chap at my club advocates running on liquid gas rather than the gas type of of gas. He makes his own tanks with two taps, one sources liquid from the bottom while the other from the ulage at the top. His burner has a loop of feed pipe. The flame is started on gas and when its going it's open up the liquid and off on the gas.

There is a down side of home made gas tanks and that's the need for testing regularly but you do get to make them fit the model.

Regards your yellow flame: can you reduce the pressure at bit or introduce more air?

[jamespetts]

stevew said:

An eminent chap at my club advocates running on liquid gas rather than the gas type of of gas. He makes his own tanks with two taps, one sources liquid from the bottom while the other from the ulage at the top. His burner has a loop of feed pipe. The flame is started on gas and when its going it's open up the liquid and off on the gas.

Appleton suggested that as an alternative, but I don't really think that my somewhat basic model engineering skills are up to it.

baggo said:

It sounds as though you may have upset the gas/air ratio by opening up the jet and you are not getting enough air for the amount of gas passed. A small increase in diameter of the jet means a much bigger increase in the area of the jet. You may be able to compensate by increasing the size of the air holes but I would suggest getting a new jet first and trying it again.

Ahh, perhaps. That's rather annoying, since I did it pursuant to instructions! I'll get another jet and see what it's like unmodified.

Thank you for your help, both of you :-)

[SteveW]

James,

It's easier than you think...

jamespetts said:

stevew said:

An eminent chap at my club advocates running on liquid gas rather than the gas type of of gas. He makes his own tanks with two taps, one sources liquid from the bottom while the other from the ulage at the top. His burner has a loop of feed pipe. The flame is started on gas and when its going it's open up the liquid and off on the gas.

Appleton suggested that as an alternative, but I don't really think that my somewhat basic model engineering skills are up to it.

If you use commercial gas canisters get the flame going and invert the canister. You'll need to re-adjust the flow a bit sharpish and there's usually quite a bit of hysteresis but it's do-able.

[jamespetts]

stevew said:

James,

It's easier than you think...

jamespetts said:

Appleton suggested that as an alternative, but I don't really think that my somewhat basic model engineering skills are up to it.

If you use commercial gas canisters get the flame going and invert the canister. You'll need to re-adjust the flow a bit sharpish and there's usually quite a bit of hysteresis but it's do-able.

Ahh, that sounds easier than making my own cannisters :-) The difficulty is, though, that the gas pipe is copper, making turning the cylinder upside-down somewhat difficult.

Is the upside-down cylinder method better than the exhaust steam pipe under the cylinder method, and are there any good ways to do it when it is attached to the burner with a stiff copper pipe?

[SteveW]

James,

It occurs to add that heating the main gas canister can be dangerous. A lot depends on the gas used and I can never remember whether Propane (includes mixtures of) or Butane is the problem. The issue is the change of pressure with temperature, one of them can generate excessive pressure at elevated temperatures.

[Noddy]

A job came my way a couple of years ago, after the Zambian guy who was doing it before, used a portable gas cooker on top of his electric hob to cook his dinner during one of zambia's frequent powercuts.

He had forgotten to turn the electric hob off, and when the power came on again, the gas cylinder ruptured, killing him.

I never met him, but avoiding the attentions of one of his girlfriends was a pain (she was ugly as hell, thick and regarded me as his spiritual brother!).
K

[houstonceng]

Steve W wrote "A lot depends on the gas used and I can never remember whether Propane (includes mixtures of) or Butane is the problem"

The pressures generated by Propane at increased temperature are very much greater than Butane. consequently, it is not advised that you build yourself a refillable gas-tank for a model - unless you are going to use Butane only in it.

[Chris Kelland]

Hi,

I think I have the same burner, also for a 504. The instructions say that only butane should be used, not a mix or propane. May well be the problem.

Chris.

[jamespetts]

Thank you everyone for your replies. My instructions (for a Bix 008 burner) do not indicate whether to use butane alone or a propane/butane mix, but I understand that butane alone would not be hot enough for all but a small boiler, and mine is quite large. The equivalent gas burners in the Stuart range advise a 70/30 butane/propane mix, as does Appleton in his Guide (although warns against using pure propane). The information about Bix refillable gas tanks suggests either butane or butane/propane mix.

As to the dangers of heating the tank, that, presumably, would depend on degree. No doubt, putting a gas tank on top of an electrical stove would heat it enough to make it burst, but an exhaust steam pipe a centimetre or two below is a different proposition. It is of note that Appleton suggests the exhaust steam pipe, rather than the live steam pipe. Note also that the tank becomes extremely cold during usage (enough to make it uncomfortable to touch) because of the chilling effect of rapidly vapouirising liquid. How hot would an exhaust steam pipe from a Stuart Score connected to a Stuart 504 get? The idea is just to counteract the chilling, rather than heat the gas cannister to much above ambient temperature.

[steammadman]

turning the gas canister upside down when lit is not only courting disaster but
DICING WITH DEATH
it might work once or twice THEN you can bet your bottom dollear the grim reaper will be eyeing you up

DONT DO IT

[SteveW]

Guys,

I have a camping stove that includes a vaporizer associated with the main burner. This would be pointless on gas. Again it depends on the gas used and it seems from above that Butane is the safer stuff.

When it's cold the liquid gas can freeze as it boils off to gas for the burner. By taking liquid from the canister and vaporizing it somewhere else you won't be stealing heat from the canister and it'll stay liquid. I recall someone here complaining that their blow lamp died every time they got near to silver soldering temperatures. The gas had frozen.

As regards what sort of temperatures to avoid it comes down to that experienced on a nice sunny day. Avoid leaving your canisters in bright direct sun light. This IS potentially dangerous.

[jamespetts]

steammadman said:

turning the gas canister upside down when lit is not only courting disaster but
DICING WITH DEATH
it might work once or twice THEN you can bet your bottom dollear the grim reaper will be eyeing you up

DONT DO IT

What makes turning the cannister upside down dangerous?

[havoc]

I would not dream of turning my propane bottle for the brazing outfit upside down, but neither do I see the danger of turning a small canister like use for gauge 1.

There is some danger and that is that if the gas doesn't vaporise before it reaches the jet, then (a lot) of liquid gas squirts out of it. This can cause large flames and fireballs or engulf your engine in flames. Also if you use some sort of flexible hose and this disconnects. So I would not recommend the use of piping liquid gas to a burner for beginners unless you use a proven design.

[steam4ian]

G'day James et al.
I am not sure we have answered the James' original question regarding the yellow flames.
James enlarged the jet which will pass more gas and thus need more air. Solution enlarge the air openings. Problem, the gas air mixture may exceed the capacity of the ceramic burner and develop back pressure in the gas/air mixing chamber reducing the amount of air drawn in and so yellow flames.

One trick you could try was that I saw years ago when stoves were converted to natural gas. They enlarged the jets for the natural gas and the down the burner tube in the mixing part they tapped a hole and inserted a screw and lock nut. When first lit the gas ring burnt with a yellow flame, the tech then wound in the screw until the flame burned blue and nipped up the locknut. Worth a try and if it doesn't work you can solder over the hole.

The other alternative is a smaller jet.

I agree with Havoc and others, DO NOT turn the cylinder upside down. Consider the volume difference between gas and its liquid for the same kilojoules/BTUs. if you gas cylinder is freezing up then by all means apply Appelton's idea.

Regards,
Ian

[SteveW]

Guys,

As I outlined originally, the gas tank described had two taps, one for gas taken from the top of the tank the other for liquid taken from the bottom. Independent settings for each. Boot up on gas then change over to liquid. A tried and test application

When I outlined using my camping gas canister inverted I included re-adjusting the flow. Whether on gas or liquid my camping stove is very stable and I haven't been killed once or, indeed, had any cause for concern.

At no point did I suggest inverting a Propane cylinder. We ain't talking about acetalene here.

[fredgraham]

Good afternoon,

It is interesting that there is such a reluctance to invert gas cylinders when in use. There is an article in Model Engineeer (11th October 1962)written by messrs Fardon and Brocklehurst who describe doing just that very suucessfully and running a 5" locomotive with it.

The fuel is carried in two 1 3/4 LB bottles inverted in the engine tender each one having its own stop valve so that when one is exhausted the other can be turned on. The burner unit has a vaporising chamber wrapped round the entry to the firebox to warm the gas as it is fed to the burner jet. It is started slowly by cracking open the gas and lighting it at a low setting so that it heats up the burner body and when the vaporising chamber is warm the gas valve is opened to a setting needed to fire the boiler. At the time of writing the article (1962), the authors had spent two years developing their system and did not report having had any life threatening problems.

I have no personal experience of this system but the article is describing gas containers which are considerably bigger than those used in small marine boiler work.

Given that the problem of 'cooling cans' and threats of sudden death resulting if one tries something different, perhaps it would be useful if the LPG can suppliers were asked formally for a solution which was not likely to cause injury and we would all benefit from the exercise.

There are a great many of us who use these cans of fuel and it would seem to be significant marketing opportunity if this convenient form of heating were able to fire bigger boilers for thirsty and bigger engines without the cooling problems we experience.

I have for a long time made petrol or parafin (or a combination) lamps, and have found the performance of LP gas burners comparitively poor and unreliable except for very small engines with limited performance.

[havoc]

It is interesting that there is such a reluctance to invert gas cylinders when in use.

Don't think there is much reluctance. But it should only be done with a proper setup. You need a vaporiser for it to work or even try it. Giving this as a general advise when there are problems with a gas setup isn't right.

[fredgraham]

Hi Havoc,

I think if you read my comments you will find that I gave no advice whatever to the chap with the gas burning problem plenty of others had already done that and I have little experience on which to draw. My comments were drawing attention the fact that inversion of gas tanks has actually been done and the article and source were quoted.

I was not aware that my comment was given as general advice, merely drawing attention to the existence of others who have actually achieved a solution using bottled gas in the inverted attitude and I have not heard or seen a report about their demise. The only actual accidents I have heard about are due to filling tanks with them still in the boat and the gas being heavier than air has collected in the hull and caused some burns to the owner. Most writers I have read, make it very clear that tank filling should be done in open air and out of the boat because of this danger, Keith Appleton and Peter Arnott included.

My remarks were more centred on suggesting that attempts to get manufacturers who have research facilities to provide solutions given that there is a big market for such a solution. If there was a ground swell of requests from model boat enthusiasts through model Mags then maybe the technical editors would have some lobby support to request a solution from the manufacturers who have the resouces and expertise to do so.

If it has actually been done by amateurs in the distant past (1962) then a safe proprietary solution would surely be in all our interests.

Although these two, Fardon and Brockleshaw, have developed their solution, it clearly requires expertise in the use of liquid gas to contemplate home made designs especially
recognising that gas can be very dangerous.

It can be very frightening to users to say that anything involving gas is 'dicing with death' and you say in your last post that you 'dont think there is much reluctance'. Surely if it is 'dicing with death' there ought to be considerable reluctance.

It would be considerably more constructive to have a solution, endorsed by manufacturers, and published by the well known model making jounals so that we can all avoid your 'grim reaper' for as long as possible.