Gas burner for steam plant

I’ve been slowly putting together a steam plant over the years consisting of a Stuart 10h, 504 boiler and a dynamo from PM Research. I’ve steam tested the set and found the spirit burner for the boiler was a bit of a faff, so I’m currently switching over to a gas fired set-up.

I’ve purchased a bix 008 burner from Forest Classics (great service and good quality product!) which needs a no. 16 jet according to the FC website.

My question- does the no. 16 refer to the hole size/drill size (no. 16 drill = 0.177”/4.5mm)? This sounds way too big for a gas jet to me!? Or am I missing something obvious?

Equally I’d like to learn more about this so any pointers to literature about figuring out what size holes etc. would be gratefully received.

Cheers, Dan

Found this on the web which seems more likely:

Number 3 which has a 0.15mm dia jet bore

Number 5 which has a 0.2mm dia jet bore

Number 8 which has a 0.25mm dia jet bore

Number 12 which has a 0.3mm dia jet bore

Number 16 which has a 0.35mm dia jet bore

Also the No16 jets being sold on ebay claim to be 0.35mm

Forrest also sell the jets

I run my Stuart 10H and other small engines using a "Tubal Cain" 3 inch vertical boiler as described in ME some time back.

I made the burner from bits of material in the workshop. The jet is drilled no. 80, ( 0.35mm) being the smallest drill I had and it runs directly off a Camping Gaz butane cylinder. The air admission is on the underside, not visible in the photo. Works fine, controllable and produces plenty of steam.

The main body is 45mm dia.

Edited By Clive Brown 1 on 18/09/2022 19:26:56

Thanks for the responses chaps, sound like 0.35mm is the size to use.

Cheers, Dan

There appears to be a lot of confusion in the case of burner jets, I'm confused.

I'm building a similar steam plant using a Stuart 504 boiler intended to drive a Stuart beam engine. and eventually a 10V and 10H (not at the same time).

I see that above is recommended a # 16 which is said to be drilled to 0.35mm However looking at eBay again I see a lot of listings where the number is directly related to the hole diameter, e.g. a #20 is 0.2mm dia, a #15 is 0.15 mm dia and a #73 (at random) is 0.73mm dia. Here is an example.

Are there a number of standards? is the latter I mentioned perhaps a European standard?

As I said, I'm confused.

TerryD

Edited By Terryd on 27/09/2022 13:08:08

Yours are metric ones hence the M6 x 0.75 thread, the ones from Forrest etc are the older imperial, though some will say BA is metric

So you are saying that there are a number of standards, is there a different ANSI one? Is there a data chart on the Imperial ones, I seem to get some conflicting results when searching. I tried HMEM but any links I could find are now defunct and most charts are concerned with gas consumption rather than size and I'm no gas engineer, when designing blast furnace equipment our blast valve orifices were measured in feet not mm.

Regards

TerryD

Edited By Terryd on 27/09/2022 16:48:37

I've not found them but if an ANSI one also exists I expect that will be different again and have UNF or similar threads

.

That ebay link that you posted, Terryd, usefully describes the jet quite explicitly

and perhaps even better … the Seller invites correspondence.

If anyone can clarify the muddle, I suspect it will be him.

MichaelG.

Hi Michael, Thanks for the posting, I did some more digging and decided to go metric, I only use imperial when necessary such as working on Stuart models, even then as my machines are metric I have to translate which is not a problem as i had to do a lot of that in my early engineering career when the uK was entering the modern world . I found an 0.35mm jet which he produces and according to information I can glean from the mysterious world of gas jets it equates to a #16 which seems to be recommended size for the ceramic burner I'm constructing. They're not too bad a price either especially as delivery costs are included. I can afford to experiment somewhat with different jets, I know I could look and learn more about them but life's too short, I'd raather be making than learning too much theory these days.

I'm not really sure that the jet size matters that much as long as they are not too small as the gas flow can be controlled by the regulator valve surely? I don't really understand being a tyro in this part of the hobby, I've generally used spirit (meths) burners or gas poker burners in the past.

Regards

TerryD

As well as saying I'm staying with metric I really should have given a reason. It seems to me that a number which is related to the actual size seems more logical. But who am I to say?

TerryD

Welcome to the wonderful world of Gauge Size numbers. They're deeply confusing. They were conceived in the first half of the Industrial Revolution before the need for full standardisation was accepted. Almost every trade and many individual companies created their own system of gauge measure and there isn't much consistency between them. Old engineering reference books are full of different Gauge tables: back in the day it was a huge mess, and despite much tidying up Gauges still have to be approached with caution today. Electric motors can be rewound with a choice of American Wire Gauge, Standard Wire Gauge or Metric magnet wire. Metric is simpler because it's the actual wire diameter in millimeters, but AWG and SWG are less rational. Gas jets suffer the same problem - they're an old technology, identified using ye olde gauge numbers, or metric.

The jet size does matter, usually. The ratio of air to gas is important so the size of the jet depends on the type of gas being burnt, the size of the combustion chamber, and the size of the air-input. If too much gas is in the mix, the flame either won't ignite at all, or burns smokey yellow, producing low heat and poisonous Carbon Monoxide. If too much air is in the mix, either the flame won't ignite, or a large proportion of it's energy is wasted heating excess air which then disappears up the chimney. To get reasonable efficiency the mix, combustion chamber and heating surface have to be balanced, and the mix is also a balance.

However, a poor design that would be completely unacceptable on a central heating boiler, might well be 'good enough' for a small model steam boiler. If inefficiently burnt gas heats faster than meths the owner will probably be happy!

One thing to watch is that gas flames are considerably hotter than spirit burners and if a concentrated gas flame is played on a small part of the boiler, it might put more heat into the metal than the water is able to to remove by boiling. This could cause the boiler to fail by softening the metal, or maybe melting a nearby soldered joint. (Spirit fired boilers don't expect gas flames and might use soldered joints. Gas and coal boilers are stayed, brazed and dimensioned to take the heat.)

I would guess a small combustion chamber would need a small jet, or several small jets, rather than one big one - for mixing.

Dave

Edited By SillyOldDuffer on 28/09/2022 09:54:58

You could always make your own, this is 0.3mm for a hot tube engines main gas supply, the one that heats the tube is even smaller at 0.07mm but I did not atemp that as I can't even see it on the Sivert jet.

Hi Dave,

Thanks for that explanation it starts to reduce the fog to a mist. I can see the simplified theory of gas to air ratio but if you have a gas jet that is a bit oversize surely you can regulate that by varying the gas flow and the Bunsen style air control on a burner?

At the moment I'm considering a ceramic style burner using the standard gas fire radiant which should with the right distribution of gas create a less focussed heat source. As for the boiler construction the Stuart 504 it is intended for seems to be well constructed and there are many types of gas burner on sale including Stuart ones to replace the original meths burners so it should not be a problem. My own boilers which I have constructed so far are basically pot boilers with no external boiler tubes (although I might get a bit more adventurous) silver soldered with Easy Flo or equivalent so I think that they should be ok.

I also thought that perhaps gas jet sizes were related to an older standard such as number drills or wire gauges but wire gauges get smaller as the number increases while the opposite is true of gas jets i.e. from memory in SWG 10g is 1/8th " while 16g is 1/16th" and 21g is 1/32nd". not sure about AWG or BWG but I think that they approximate having used AWG electrical wire in the past.   In the case of number drills they do not seem to relate to older jet sizes, again diameter is inverse to number. I find it all quite confusing hence my decision to stick to metric where there is direct correlation between size and number - my simple mind can understand that much at least

Regards

TerryD

Edited By Terryd on 28/09/2022 13:52:54

Hi Jason,

I've made similar nozzles before for my 3d printer I constructed a long time ago. Those nozzles were in aluminium. As I have no sensitive feed device on my tailstock, to hold the drill I used a small pin vice which was in turn carried with a sliding fit in the tailstock chuck ( hope that makes sense) and was able to feed sensitively by manually feeding the drill with vice held loosely held in my fingers and drill guided by the shaft in the chuck.

Talking about that gives me an idea. I have a couple of miniature chucks somewhere, very nice they are, which I could attach to a spindle of say silver steel in order to do the same job. Hmmm I'll think that one through and perhaps put something together to act as a sensitive, hand held drilling device for very small holes - although not down to 0.07mm

Regards

TerryD

Edited By Terryd on 28/09/2022 14:36:53

The jet size and gas pressure not only govern the volume of gas ! Another criteria is the speed of the gas and it's abillity to entrain/mix with air and burn. This is an interesting balancing act ! A book on the subject is "gas burners for forges,furnaces and kilns" Though for much larger burners than you have in mind it gives and insight into the design. Also Chris Chastain s book on gas fired smelting furnaces. Noel.

gas flames are considerably hotter than spirit burners and if a concentrated gas flame is played on a small part of the boiler, it might put more heat into the metal than the water is able to to remove by boiling.

?

Maybe more heat into the metal than that part of the shell can conduct away into the water space maybe?

regards Martin

Well whilst the metal under the flame does cool through the edge, I think the effect is small compared with cooling by water. Say a flame heats a circle of metal 25mm in diameter, and the metal is 1mm thick. Then the edge area of metal available to conduct heat away into boiler's metal work is about 78 sq mm compared with the 490 sq mm surface covered by water. Also, water absorbs a great deal of extra heat (latent heat) when it changes state from a liquid to a gas. The cooling effect of water is much greater than the cooling effect of the boiler's metalwork, which is why radiators are often water filled.

Examples of concentrated heat causing the temperature of a small area of a metal sheet to rise well above that of adjacent metal include gas-axe cutting, spot welding and laser beams. Severe damage is likely whenever a boiler runs dry, but it will also occur if a flame puts energy into the metal of a boiler faster than the energy can be removed by cooling. This graph shows the yield strength of copper falling dramatically with rising temperature:

So quite safe to operate a copper boiler between 100 and 150°C, but it's lost about half it's normal strength at 300°C, and falls to zero at about 700°C. As that's much less than gas flame temperature, close to 2000°C, it's important the metal of the boiler be kept cool. Absorbing heat by having it boil water is a good way of doing it.

Dave

Hi Noel,

Thanks for adding more information , I'm beginning to see through the fog, but it hasn't cleared completely

The only book I can find related to the second one you mention is by Steve and Stephen D Chastain, - 'Small Tilting Oil Fired Furnaces'. Do you have a link to the one you referred to?

The first one you mention is availble on Amazon pre-owned for £93 so I intend to forego that one, I might see if my local library can access a copy or pop into the British Library next time I'm down there.

Regards

TerryD