Coleman fuel valve design

Yesterday I had an interesting experience with a Coleman 220J that I had converted to run on paraffin.

While it was running I discovered that fuel was leaking from the fuel valve spindle. I closed the valve, intending to tighten up the jamb nut after the lantern had cooled down. The leak did not stop after I closed the valve.

After some head-scratching I realised that the spindle and packing was on the pressure (fount) side of the needle valve! I can't for the life of me understand why Coleman made it like that.

Can anyone shed some light on this seemingly arse-backwards valve design? Am I missing something here?

 

Not sure I'm following you... I've had experience with leaking valves before but usually once you close the valve tightly it stops and then you can adjust the packing nut so the leak stops. I had one Air-O-Lantern that would not shut off completely but continued to dribble after the valve was closed tightly. Later found out the very pointed end of the valve had a very slight burr on it but after very carefully filing the end it cleared up the leak.

 

@george , that's what I thought too.

The needle valve cuts off fuel to the generator, but the spindle and graphite seal are still under pressure from the fount.


First image from oldcolemanparts.com, 2nd pic imged.com.

 

Maybe I'm wrong, but if you close the valve tightly you should close both the flow to the generator as well as the spindle and graphite seal. I have to say if this is not the case then you don't truly have a "positive" shut off. That's one of the reasons why the valve shaft is pointed. There are very few lanterns Coleman made that did not have a positive shut off valve and they designed them with that type of tapered point to shut off the entire flow, not just the flow to the generator. Someone will correct me if I'm wrong but there should be no pressure to any part of the lantern once that valve is tightly turned off.

 

@phaedrus42

That looks a pretty stock standard way that valves are used. I think you may have a double problem. The packing needs replacing and you need to look at the needle end of the valve stem. It might be worn or have a bur and it is allowing full to continue flowing despite the fact you have shut it off.

Of course another answer is, you simply didn't shut the valve off correctly/firm enough.

I guess it could have been the dregs of fuel, that was in the valve space, after you closed the valve that was leaking?

 

G'day Phil,
I don't have a 220J but looking at a 242 valve I am pretty sure you are right, the tapered seats do not shut off the fuel from the spindle packing.
But it does push a needle within the pickup tube into the opening at the end of the pick up tube. It relies on the needle being a snug fit in the hole. Vapour from above the fuel level will still reach the packing.

 

A picture is worth a thousand words





Photos posted by nfadude on CCF

 

I understand exactly what you have found @phaedrus42
I have puzzled over this for some time. Coleman put the steel ring between the packing and the wire clip on the valve shaft to prevent the valve shaft from being completely unscrewed when the lamp is operating. If the shaft was completely unscrewed, raw volatile fuel would be expelled at pressure from the valve shaft opening.
As to the why?
Looking at the cut away of the valve body, I guess it’s easier and cheaper to configure the closing with the pressure as it is currently than configureing the valve and it’s chambers to shut off the pressure such as to prevent the shaft chamber from containing pressurised fuel, a commercial decision driven by complexity and of course the cost. Just a thought.
Cheers
Pete

 

The coloured diagram doesn't accurately depict exactly what is happening as the cutaway does.

What a weird way of doing things for a pressure appliance.

 

I'm sure you are correct, @AussiePete . The clincher in the design decision must have been the necessity of having a vertical passage from the fount to the bottom side of the spindle to accomodate the fuel-air valve action.

 

So the moral of the story is, if you have a fuel leak at the spindle, do not close the valve, but open it fully to compress the seal. Talk about counter-intuitive!

 

@Matty , Indeed. But as we can see now, there was a valid reason. I can't think of a safer way without adding complexity and cost.

 

Seems to me the best procedure would be to crack the filler cap open slightly after shutting down.

 

That type of valve can cause another problem. A very few Coleman fanatics have reported that a slight leak of that gland can affect the air/fuel mix and lead to a lean burn and a poor light. It seems that the fuel flow can drag air through the gland. Not experienced this myself but possible perhaps? ::Neil::

 

Well, I suppose if it is sucking air, at least it won't leak fuel

 

Not something I would like to rely on besides it might suck air when fuel is flowing but probaby also leak fuel when the flow is shut off. As I said not something I have experienced. Just something mentioned some years ago that stuck in my brain to look for with a poor performing Instant-Lite burner. ::Neil::

 

The rod in the fuel/air assembly does not play a role in shutting off fuel to the valve, except possibly collaterally. The rod must always be smaller than the hole in the end of the tube, it has to allow some fuel in to function. When the valve is open 1/4 turn the rod is still in the hole and a small amount of fuel flows into the inner tube of the F/A set. Air from the top of the fount is drawn into the large hole in the outer tube shown at the left side of the tube in Robbo55's picture above. The air-fuel mixture then passes through the valve into the generator. As the valve is opened fully the rod is retracted opening the hole for full fuel flow and air flow into to the upper part of the F/A tube stops. In a Coleman kerosene burner there is no F/A assembly, just a straight pickup tube. The rest of the valve is the same. That would mean that the F/A tube was never designed to prevent fuel to the valve or there would be a similar part in the kero lanterns. The packing and gland nut are the fuel control. The packing doesn't fail catastrophically, it starts to leak a little at a time giving ample warning that maintenance is required. Even a worn out packing that can't be sealed by tightening the nut only drips fuel, it doesn't spray a stream of pressurized fuel out. The leak should be noticeable before the lantern is lit and there is time for corrective action. I've had them leak when I pumped up the tank and cracked the valve, I haven't had one start to leak after it was lit and running. Since there have not been a string of fiery accidents or legal actions in the 100 or so years Coleman has been producing these types of valves I think the engineers did a reasonable design job.

 

@Reese Williams very well explained. Coleman's are very simple to work on them, a graphite packing will last decades before it gets brittle and start to leak. I'll attach and image I've saved months ago and with better parts explanation. That cutaway is amazing and will go to my saved files too. Cheers Francisco

 

@Pancholoco1911 Great diagram. What is the source? I'd like to post that on the CCF.

 

I know its a bit off topic but what amazes me is how on earth does someone engineer the fuel valve in the first place... its incredible how the internal pathways for the fuel are (Drilled? Cast? however) in the first place in a solid bit of brass. Can't be just drilled because of the angles can it?

Would it be the lost wax method as they do in jewellery making? Even so the fuel channel "elbow" is incredible. I love @phaedrus42 cut down lamp photographs.

Quite incredible!

 

@Reese Williams i borrowed this image from a member on Facebook not to long ago, he was sharing it so I thing he stole it from someone/somewhere. Would be interesting who made that diagram, maybe a google image reverse search.

 

@phaedrus42 , @Reese Williams , @Pancholoco1911

Thanks, this has been a very informative post.

 

@plantpot It doesn't show in the diagram but there is a small plug at the back of the valve. The angled passage is drilled from the outside and the hole plugged afterwards.

 

@ROBBO55 I am with you on this being extremely informative, thanks to all involved, I've learnt much from this.

 

@Reese Williams
Thanks for the explanation.
Now i understand, the graphite packing holds the pressure from fount, even if the fuel valve is shut.
This looks to be a constructional weak point. though you claim no issues since 100 years. But i admit also not having an instant better idea, as the control rod shaft must have connection to the valve axis.
Though......yes, could be managed by tip pushing f/a rod axial instead of tangential....

 

@bp4willi The packing, when in good shape is more than adequate to contain the 30 psi or so that a lantern uses. The fact that it does work is sufficient evidence that it does work. Coleman made something like two million 220 series lanterns plus the thousands if not millions of other models that also used a graphite packing to seal the valve stem. Since they did not abandon that system until they completely redesigned the valve system with the 275 lanterns I am willing to believe that the engineers W.C. Coleman hired knew something about what they were doing. Just because I, who am not a mechanical engineer, can't understand some of the details of why the system works doesn't mean it is a flawed system. Coleman outlasted several other competitors who used very different systems. One interesting thing though, all the other big makers, Prentiss Wabers, AGM, Turner and many of the European stoves use a gland nut and packing arrangement to seal the valve stem. It must not be all that bad a system.

 

In my opinion, the designer of the Coleman shut off valve would have a specific and valid reasoning.
The one I could imagine would be due to the intention to include a fuel-air assembly for quick lighting of white gas/gasoline.
The following is a cross sectional view of a high pressure industrial needle valve that shuts off the pressurized side of the fluid path:-

While it does what should, this does not allow the operation of the fuel-air assembly's plunger rod by the valve's stem spindle end since there's no way for both of them to intersect.
I'd reckon that the original design of the Coleman valve in this topic came at about the time when the intention was for an instant/quick lighting of white gas lamps without the need for preheating by the usual spirit cup.
While there'd be a slight compromise in that it'll not shut off the pressure within the valve's chamber, I think that had been deemed tolerable for the intended application. So long as the intergrity of the graphite packing is not compromised and well expanded around the valve stem and chamber. Any leaks are usually small enough to be remedied by tightening down the gland nut without a spectacular fireball even during lantern operation.

 

Exactly. The packing cannot fail catastrophically because it is contained within the gland nut. The only way it can fail is by wear. When it is worn it will leak only drops of fuel not a stream even under the most pressure the fount will hold. I'm really having trouble understanding why some folks are having so much anxiety over a design that obviously worked, and worked well for so many years.

 

This is a very clever design. Without going into too much detail, which would require a few drawings, the functionality lies in the 1/4 turn of the control knob on lighting. At 1/4 turn fuel AND air enter the vapouriser, not dissimilar to a rapid start on Petromax style lanterns, allowing for easy ignition of atomised fuel/air mixture. Once alight the control knob is rotated further which allows the fuel control rod to be withdrawn from the fuel control orifice. Now that the orifice is fully open pressure qualises in the font and the air is not passing through the inner and outer air/fuel tube, rather fuel alone is going to the vaporiser. I hope this explains things enough. Merry Christmas

 

@Jones the lamp
That has been discussed and drawn above.
And despite no 'known' case of catastrophic fail,
the design is not perfect,
because its not metal on metal shutoff.
Such design is feasible as pic of @MYN suggests. Imagine, the pickup tube rod would be pushed by the valve stem 'nose extension' at the fount side of the metal-metal valve seat.
Such would be a perfect secure design.

And coleman did some other non genius designs. E.g. the stove which had the generator on pressurized side of circuit.
Or the rubber seals at valve stem or shutoff valve in 226 or 325 and other lanterns. (newer designs less clever and less secure, surprisingly)

Those complaining about insecurity of PX design should avoid similar insecure Coleman products with rubber seals.

Keeping in mind Coleman gear usually operates with dangerous gasoline, while PX was meant to use less volatile kero/paraffine.