Not enough steam

[circlip]

Tel, If you look at the photo showing the end of the Stuart boiler on the images link, there probably isn't enough room to put the boiler in from the water gauge end due to the "Pressed in" details. However, this doesn't mean that the burner flame pan should be biased to the chimney end. IMHO I have to agree with Tel, that the fire SHOULD be biased towards the "Working " end. How many loco's have the chimney above the firebox? Can we have a photo of the official meths burner in its relative position OUTSIDE the boiler casing?

[Tel]

There's no doubt that's the reason for it, right enough, but it still doesn't make it right. Wouldn't be a great deal of trouble, I image, to cut that section out, and make a nice looking clip-in dummy for when it's not in use. OR make a real fire door there.

Why am I getting this urge to fit a platform to the front bumper bar of my truck, mount the steering wheel there and hire a tillerman every time I want to drive somewhere. I could even fit a speaking tube so he can hear me over the engine

[steam4ian]

G'day James, Tel, Sir Ian et al

The fact that the metho tank is at the chimney end implies this is the cooler end.
JAMES, for pity's sake put your gas burner at the non chimney end even if it is only to humour us old f@rts. Block off air openings at the chimney end so that the gas path is from the front (business end) to the back (chimney end). Maximise the length of the hot gas path.

BTW make sure the gas jet is clear.

Regards,
Ian (another one)

[ron]

Please read my last post, the gas burner fits fine at the opposite end from the chimney without cutting or modification. The meths burner only fits from the chimney end but if it did fit in the other end it probably wouldn't matter as unlike the gas burner the burner tubes of the meths burner are almost the full length of the underside of the boiler whereas the biggest ceramic gas burner I could get was a bit over half the length, but as I've posted already I haven't found the position of it critical.
Ron

[mutley]

just to add my two pennys worth, the flame looks very lazy and is popping back. Most gas burners I've seen have a more defined flame pattern. The poping /blowing back may imply a lack of air/ incorrect combustion.

Andy

[circlip]

James, it also looks like you've taken the lagging down to the baseboard covering the bottom of the boiler casing sides? Popping of flame also suggests not enough airflow. Ron's' comment about the lubricator being a long way from the engine? Regard all pipes and fittings between the boiler and the engine as radiators, so ALL help to cool the steam. Ian.

[steam4ian]

G'day James

I've just looked at your video. At 2:52 after the oil fire has died down you can still see the gas flames coming up the chimney. The burner must be at the opposite end to the chimney.
BTW, then the oil will not catch fire.

The flame is popping back because it is not getting enough secondary air; I surprised you have not had a blow back at the gas jet. You haven't got enough combustion space around the burner, take out some of the lagging.

Summary, again: Put the burner at the end remote from the chimney. Make sure it can get plenty of air from the non chimney end. Open up the combustion space so as not to cramp the flame.

Regards
Ian (Honorary BOF)

[paul]

tel said:

Why am I getting this urge to fit a platform to the front bumper bar of my truck, mount the steering wheel there and hire a tillerman every time I want to drive somewhere. I could even fit a speaking tube so he can hear me over the engine

ROFL. You crack me up Tel.

Can't you show it a real flame for just a few seconds James so you'll know if it's your heat source or something else?

Looking forward to seeing this one really chugging

[jamespetts]

Thank you everyone for your many and detailed responses to my steaming problem - they are most helpful!

There seem to be two distinct categories of issues: (1) problems with the firing of the burner itself; and (2) problems with the positioning of the burner in the firebox. I hope that you will all think my approach sensible in attempting to address the problems separately, and attempting to address no. 1 before I try to address no. 2. The plan is to try to get the burner working properly outside the firebox, then try to get it working properly inside.

Somebody on another forum kindly uploaded this video about how brightly that the burner should glow when it is working properly: my burner does not glow anything like that brightly (I thought that I was looking more for blue flames than a bright glow - those flames seem orange, rather than blue or yellow - is that a good colour?), even when the burner is entirely outside the firebox, which makes me think that the main problem is something other than lack of secondary air. Another thing that I notice is that the very far end of the burner (away from the jet) often is not in flame when the gas is turned fairly low, and the rest of the burner is alight - I am not sure what sort of problem that this indicates.

Ian, your comment about gas flames in the chimney was of particular interest to me: that suggested that the burner was not combusting all of the gas for some reason, which was then burning when it touched the surfaces in the chimney that had been made extra hot by the oil fire.

As a result of that comment, and also Mutley's comment about the "lazy" flame (it only popped back near the begining: after I changed to a fresh gas tank, the popping stopped), I wondered whether there might be any leaks in my burner, so I tested it by immersing it in water. A video of some of the testing is here. What can be seen on that video is that, not only does air escape from the top of the burner, through the air holes, as it should, but a substantial amount of it also escapes around the sides, where the ceramic is joined to the metal base. I also found a leak (not shown on the video) between the jet holder and jet ring. Blowing into the pipe when the burner was immersed in water (before the Blu-tak was added) showed a steady stream of bubbles coming from the jet - that would suggest to me that it is not blocked, although I could be wrong. However, what militates against the jet being blocked is that the burner's behaviour has been consistent from the start when I first installed that no. 8 jet from new, having replaced the previous no. 16 jet that I had there.

I suspect that these leaks (especially the first) might well substantially reduce the performance of the gas burner. The odd thing is, I cannot see any visible leaks when the unit is not immersed in water: the cement stuff seems to be in tact. How would one go about fixing a burner like this? Somebody earlier suggested "fine cement" - might I ask what sort of fine cement?

John, as to a larger burner, the burner that I have is the largest one that I could find anywhere (if anyone knows of where to find a larger one, I should be very interested). One thought that had occurred to me was that it might be worthwhile having two burners (the second one smaller than this one), one at each end, so that the entire underside of the boiler is covered with active heating, substantially increasing the total heat going to the boiler. I do not want to do that, however, until I have made my existing burner work properly. Can anyone foresee any problems with using two burners, however?

Thank you again for all the attention that you have given my problem: I am determined to try to fix it if only I can find out how! I am somewhat hampered by not knowing a great deal about how the ceramic burners work (in detail: I understand the basics), and a Google search does not help much, either. Any information would be much appreciated :-)

[mutley]

jamespetts said:

Thank you everyone for your many and detailed responses to my steaming problem - they are most helpful! ....



Somebody on another forum kindly uploaded this video about how brightly that the burner should glow when it is working properly:

that is how I would expect the burner to behave. It seems to me your problem is with the burner.

[circlip]

Only took a few minutes of search James, try www.mainsteam.co.uk they have info on burners. Fine cement may be a typo error for Fire clay cement. A long time ago there was a product called Pymura that used to be advertised in ME round about the 50's which was a fire clay cement, was used at times to make "Brick arch" in loco boilers cos it was a radiant, bit like ceramic burner really. Ian.
Having said that and checking this site, they seem intent on selling a CD relating to ceramic burners. Just to give another clue to correct operation, look at a Calor Gas portable heater, the radiants on these are usually the same type of ceramic material.

[jamespetts]

Circlip and Mutley, thank you for your replies. I know about the Mainsteam website - indeed, I have a copy of the CD (not just about ceramic burners, but about model steam engines generally), but there is nothing in there that helps with this particular problem or gives detail about exactly how burners should work or precisely how the flame should look.

I have made a short video of me testing the ceramic burner outside the boiler, to see whether this helps with diagnosis of the problem at all: it can be found here. Does this provide any clues?

I have also found some very useful information on a website of a UK company called "Maccsteam", about how big a boiler that one needs to run a steam engine of any given size at a given pressure. Using that, I have calculated that the Stuart Score displaces about 1.33 cubic inches of steam per revolution. That would mean that, to run the engine at 900rpm constantly, the boiler would need to have an output of 1,193 cubic inches of steam per minute.

They sell a number of boilers themselves, as well as ceramic burners (which can be made to order - I am now considering ordering one of theirs, as this Bix burner does not seem to be behaving itself). The largest of their standard boilers is their 4" horizontal boiler, a return-flue, cross-tube type powered by a single ceramic burner (notably, a far smaller one than I use, and one sealed into the firetube, without any secondary air supply at all, which strongly suggests that ceramic burners need no secondary air for operation). That 4" boiler has a steam production rate of 710 cubic inches of steam per minute at 50psi (without lagging), and a boiler capacity of 900ml. I am therefore hoping that my ~2l, lagged boiler should be able to generate at least 1,193 cubic inches of steam per minute at 50psi with the correct heat source configuration, especially since their slightly smaller boilers produce significantly less steam (the 3.5", 750ml boiler having a capacity of only 385 cubic inches of steam at 50psi), unless, for some reason, the Stuart 504 is many orders of magnitude less efficient than the Maccsteam boilers (I cannot see any immediate reason why it should be if properly fired).

Do my calculations seem correct, or have I made an error somewhere? Am I right in concluding that the 504 should produce plenty of steam if only I can fire it properly? To recap, any tips on getting it to fire properly? Thanks to everyone who has helped me so far :-)

[jgb7573]

Hi James,

A general point about the amount of steam produced by a boiler of given size. Generally speaking, the quantity of steam produced is a function of the heating surface area. The larger that area is, the more steam will be produced. So your 2l boiler will not necessarily produce any more steam than the MaccSteam 900ml boiler. It depends on what the area of the return tube plus cross tubes of the MaccSteam boiler are, compared with the bottom half of your (externally fired) boiler plus its circulation tubes.
This is obviously a generalisation, because the amount of heat generated by the burner affects things significantly. So you need to get your burner working right too!

Best wishes,

John

[mutley]

Hi James
You say you changed the jet in the burner. Did you put a larger jet in or a smaller jet? Why did you change the jet size? Changing the jet size may require more or less air for combustion. Do these burners take the combustion air in at the back by the jet or up around the ceramic material?
Out of intrest what is the capacity of the boiler in litres and whats the operating pressure?

Andy

[jamespetts]

Thank you again for your replies :-) John, I take the point about the heating surface. Part of the problem so far might be that the ceramic burner is a lot shorter than the firebox, so the potential heating surface area is not being fully realised, which is why I am considering either adding a second burner, or getting the Maccsteam people to make a larger one for me (dependant on cost), although I should like to try to get my burner working properly first, if I can.

Mutley, I changed the jet from a no. 16 (larger) to a no. 8 (smaller) after advice on another forum that the no. 16 jet was probably too big. I found that, after I changed the jet, I had a more blue and less yellow flame. The burner in question is listed by the manufacturer as requiring either a no. 16, no. 12 or no. 8 jet. I cannot find where to buy a no. 12. I (or rather, my father) did drill out an extra air hole at the bottom of the burner, but, as can be seen on the video, blocking that hole with my finger had little effect on combustion (blocking the side holes made the flame yellower, and blocking all four holes almost put the fire out).

The burner gains its air by holes located around the jet area, in the same way as a blowtorch: the gas-air mix is then, presumably, passed into the block beneath the ceramic,where further pressure from incoming air/gas forces the mixture out through the holes at the top where it can be lit.It is supposed to be sealed around the edges, I think, but on my immersion test (link to video in earlier post), I found some leaks.

[mutley]

Hi James
I had a chat with a guy at Guildford small engines group today about ceramics burmers. The jet is mounted in a "holder" which is secured in place by a screw! The idea behiond this is so you can fine tune your air/fuel mixture to suite your particular application. How far in have you set the jet holder? trymoving it in and out to see if you can get the flame to burn better. Hope that makes sense.

Andy

[jamespetts]

Apr 13, 2008 16:39:16 GMT mutley said:

Hi James
I had a chat with a guy at Guildford small engines group today about ceramics burmers. The jet is mounted in a "holder" which is secured in place by a screw! The idea behiond this is so you can fine tune your air/fuel mixture to suite your particular application. How far in have you set the jet holder? trymoving it in and out to see if you can get the flame to burn better. Hope that makes sense.

Andy

Ahh, I knew this all along - I have spent a long time trying to adjust it, but it does not get any better than seen on the video posted above. Indeed, you can see me on the video adjusting it in the way that you describe :-)

[jamespetts]

I think that I have found - with some assistance - the solution to the problem with the burner. I wrote yesterday evening both to Forrest Classics, who supplied the burner, and to Maccsteam, who make custom burners, enquiring about the problem, and linking them to the Youtube video (and, in the case of Maccsteam, asking for a quote for a possible replacement burner).

A very helpful gentleman called Mike Abbot from Maccsteam sent me an e-mail back this morning saying this:

From your videos it is clear that the burner is not getting enough air mixed with the gas. This could be for a number of reasons but the most common are either a partially blocked gas jet, the wrong size jet fitted, or a leak around where the jet screws into its holder. When working properly the burner should operate with a blue flame, the top of the ceramic material should glow white hot (or at least a very bright orange) and you should be able to open the gas valve on the butane bottle fully without getting the yellow flame that you have. The amount of air being drawn into the mixer tube is directly proportional to the velocity of the gas coming out of the jet. The smaller the jet, the faster the gas and the more air is drawn in, giving a leaner mixture. The bigger the jet, the slower the gas and hence the richer the mixture.



Try cleaning the jet. The holes in these jets are extremely small and you should take great care that you don’t open it up when cleaning it. Special jet prickers are available from John Prescott Engineering 01785 712452. Don’t use anything with a diameter greater than 0.005” (five thousandths of an inch). If this doesn’t work, try using a smaller jet and seal the thread on the jet with a thread sealer, I use Loctite 222.



A few of final tips.



A large proportion of the heat from a ceramic burner is radiant heat from the glowing ceramic material. Unless this is glowing white hot, or very nearly so, then you will be missing out on over 60% of the available heat.



Burners will always burn leaner in free air than in the confines of a firebox.



There should be a slight roar from the burner when it is burning properly. I can’t detect this on either of your videos.



With butane, the burner should operate quite happily with the gas valve fully open.



The burner you have should be more than big enough for that boiler.



Move the burner further away from the gas bottle before you blow yourself up J



I can make you a “Maccsteam” burner 5” x 2” for £40.00 including jet, jet holder and gas pipe, plus £3.00 postage. Delivery would be in about 1 week.

I had previously noticed a small flame emanating from around the ring of the burner when the main flame had blown back in the wind, and wondered whether the problem was a leak in the brass threaded joint between the jet holder and the jet, so I removed the jet, wrapped some PTFE tape around the thread, and reinserted the jet, tightened with a spanner.

After reassembling the unit, taking it outside, connecting it to the gas and lighting it, I immediately noticed that the flame was behaving very differently. There was a distinctive hissing sound, and, within a few seconds, the ceramic started to glow bright orange. Even at maximum gas, there were no large yellow flames.

That, then, seems to be the first of the two issues (the burner itself) addressed. The second is the positioning of the burner: a number of people have suggested that it should be positioned at the other end to improve air flow, and that the hole beneath the chimney should be blocked to prevent cold air from entering the firebox.

As others have pointed out, however, the Stuart 504 is not designed to be fired from that end, so I shall have to look carefully into how to do that (any suggestions, especially for addressing the fact that the hole at the front end is much smaller, on how to do that would be much appreciated).

I shall, however, first run the engine again with the burner in the same position as last time, but with the PTFE tape in place, to assess what difference that that factor alone makes before attempting to adjust the position of the burner: proper scientific testing involves, after all, adjusting just one parameter at a time.

There is one thing about which I remain curious, however, and that is the suggestion that the burner that is significantly shorter than the firebox is "more than long enough": is that right? To my mind, a longer burner would increase the heating area, and thus improve steam production. Perhaps it is difficult to make ceramic burners any longer than 5"? If so, does anybody think that I'd be better off with two ceramic burners, one at each end?

Thank you again to all of those who have been of help - it is, as always, very much appreciated.

[steam4ian]

G'day James

Good detective work. I hope your parents don't object to you becoming an engineer.
Regarding the burner length, follow your own advice, adjust only one thing at a time.
The boiler was designed for spirit firing which is less intense than gas, particularly with a ceramic burner. The old spirit burner would have needed the whole length to get the heat in.

I still contend that having the burner at the "business" end increases the hot gas path and will leave less sensible heat going up the stack. As you say, do one thing at a time.

Regards,
Ian

[circlip]

Haven't seen the boiler on a one to one James but it looks like the "business end", the one with the water gauge, is lower than the chimney end? This should determine that you will get a heat circulation up to the chimney if you put the burner towards the business end. The only problem I have with this is that the gas feed tube has a longer run inside the hot space. T'other Ian.

And another tip, PTFE tape is NOT burn proof and the black sticky residue it forms when having been burnt is called FLOURIC ACID, this has the nasty habit of being able to burn through skin/flesh and just about owt else in't way, BE WARNED!

Oh no it doesn't, thats silicon and viton "O" rings and such like, what it does produce when burnt is a gas which is more potent than PHOSGENE, another not to be messed with nasty, ask any WW1 survivor. My greys getting scrambled again.