Tilley is pulsing/hunting

Am new at Tilley and since I received it has been pulsing or "hunting" quite noticeable compared to my Vapalux that is not so obvious. Would like to get the wisdom of the Tilley owners on how to minimize or reduce it to where I do not get annoyed - possible reasons for pulsing.

Thanks

Ron

 

Not an expert (sorry Ron! ) but as I have (and use) a Tilley I know a little something from experience. Mine likes a lot of pressure in its tank, else it pulses. There is a leak (since this weekend) so I need to replace the seals. Because the loss of pressure it started pulsing. Maybe yours likes a lot of pressure too. The (real) experts will surelly come with other causes/solutions.

Take care,

Wim

 

Lots of pressure is the answer normally. The basic rule is with a pint and a half of kero in the tank then a total of 100 pump strokes is operating pressure. It is important not to exceed this in lamps without a pressure tit and I have always found it useful to do this with older lamps and then re set the pressure tit by filing it off until the inner and outer are level. Some years ago I fitted a pressure gauge to a Tilley and found that the 100 strokes does give about 30psi or a tad over 2 bar.

I have found a lot of people who are reluctant to use this full pressure and this is a common cause of a hunting burner.

::Neil::

 

Hey Neil/Wim. Last night I had nothing else to do so I disassembled everything. I noted that only weeks ago I remove the black grit on the cleaning needle/wire and lo and behold the black hardened stuff was back clinging to the needle wire which again I sanded down. I had a super fine wire and seems the hole is not clogged. I assembled it again and well, the pulsing was not that obvious and was more like flickers once in a while. The culprit may be in the fuel itself - sulfur which I know does solidify and attach to the wire. I may have to try running it on low sulfur kerosene alternative to see if the problem will be minimized. Am not sure if pure paraffin oil would work (one used for wick lamps).

While I am at it, anyone tried mixing a bit of automotive fuel injector additive to kerosene in their tilley lantern? Have read through some forums and I really did not get definitive answers. Some say its just a form of kerosene type mixture.

I also noticed that the original Tilley Happy Mantles were a bit thick once burned through and all I get on my tilley is perhaps 20~30 watt light output. On my Vapalux, I am using 500 CP (Gasman marketed by Coleman) mantles which when burned through give more than 100 watts of "whiter" blinding light if you look at the mantle directly versus the tilley mantle.

Yes, I normally do only 50~ pumps but when the pulsing starts, I get it up to about 90~ but still pulses. After cleaning, it only flickers once in a while even at lower pressure.

Apologies for the long topic but needless to say, I need to sort things out with my Tilley.

Ron

 

You got to remember that these are not super high quality products. Rolls Royce they ain't. There is always some minor variation in the burners and generators. Also with most makes there is another factor which is the fuel restriction built into the fuel feed system. In Tilley that can be so poor that you get virtually no fuel through those silly alloy control cocks. I have suspected for a while that insufficient fuel restriction may be a factor in this hunting we see in some lamps. Kinda complex but essentially the pressure induced in the vaporiser due to the expansion of a liquid to a gas tries to push fuel back down to the tank. Small reduction in pressure as fuel is vented through the gas tip and fuel flows again only to have the process repeated. A restriction in the fuel feed tends to reduce but never eliminate this effect. That is why they hunt and increasing pressure may help but if the combination of fuel feed and generator want to hunt they will. Fuel quality should not affect this allthough there are of course other problems with poor fuel.

::Neil::

 

Neil, it does make sense as I compared the diameter of the vaporizer on the Tilley vs the Vapalux and the tilliey is slightly thinner in diameter. I would think thought that partial reason for hunting is as you said restriction in fuel flow + evaporation on the generator. There seems to be very little room for the fuel to expand into gaseous form since the Tilley vaporizer is thick walled and only sufficient room for the cleaning needle. Unlike the Colemans vaporizer which is thin walled, there is enough room for fuel to flow freely even with gunk build up. I noticed the black crumbly build up in the upper 1/3 portion of the cleaning needle. Tha build up I suspect restricts the flow and starts to pulse. Since cleaning it with sandpaper did eliminate the pronounced pulsing/hunting and noticeable just a flicker from time to time instead of on a regular interval. Am not sure until I obtain a spare cock and vaporizer to try it out since availability is almost zero this side of the pond. Hence, I will troll Ebay UK for some reasonably priced spare. In the meantime, I will just have to inspect the needle prior to use and make sure to bring some sandpaper along.

Cheers

Ron

 

Both Tilly and Vapalux vaporisers are empty steel tubes but both have a restriction where the needle enters at the bottom and about an inch down from the top. The rod is only 1mm dia so there is actually a lot of space inside the tubes. I am not sure how carbon build up affects the burn but it may just be that the reduction in volume is the cause of the hunting although the carbon does tend to build in the upper chamber and does restrict gas flow. I have seen maybe three or four vaporisers that have burst at the top end due to carbon accretion in the upper chamber. That can only be a fuel quality problem. We don't see this in the UK. I think if I remember right this bursting mostly happens in Germany. Means there is some quality of German kero that deposits more crap in the tubes. So it might be worth trying a few different types of fuel to see if any are better in use. One thing though. Do not use gasoline or naphtha as these lanterns are not designed for it and it is dangerous. ::Neil::

 

Thanks Neil. The Vapalux and Tilley Bowlfire seem to be behaving well but the Tilley Lamp seems not to. As you said, each lamp has some sort of problem either in the vaporizer or somewhere else. I will try to work it out so I do not need to have special fuel just for the Tilley. It may just need a change.

Ron

 

Pulsating or 'hunting' only affects one of my Tilley lamps but I have several paraffin blowlamps in my collection, and pulsating affects about one-third of them. I now suspect that it is caused by a combination of (a) restricted liquid fuel flow into the vapouriser, and (b) reduced volume of the vapour space within the vapouriser. Both are caused, of course, by carbon build-up. It's easy to change a Tilley vapouriser, but less easy to get the carbon out of a blowlamp vapouriser!

Phil

 

As an experiment I ran some Tilley lamps on white spirit for a while and whilst they ran they also proved more prone to hunting, so "wrong" fuel may certainly cause it...

The main causes though are low pressure, a leak, or just before the fuel runs out.

I have one lamp were the fuel pickup is at a slightly different angle and it always pulses for a while before running out. It also "runs out" while there is still quite a lot of fuel in the tank.

 

Thanks for those thoughts, Gneiss. However I have eliminated leaks, low pressure and wrong fuel as causes for pulsating.

The most significant piece of evidence for my theory is that on the blowlamps that pulsate, the fuel tank gets hot. Very hot, and very quickly. The pulsating effect is much more marked in blowlamps than on the one Tilley in my collection that shows this effect, but I think the cause is essentially the same. Here is my thinking:

In a normal running pressure lamp, blowlamp or stove with a clean vapouriser, liquid fuel enters the hot vapouriser where it begins to absorb heat and its temperature rises. Once boiling point is reached at the system pressure, further along the vapouriser, the liquid fuel boils off into a vapour which fills the space between the top of the liquid and the orifice. Equilibrium is reached when the rate of flow of cold fuel entering the vapouriser matches the rate of vapour emission from the orifice. Flow of fuel is in the forward direction only. With a vertical vapouriser such as in a Tilley lamp, there is a temperature gradient along the length of the vapouriser which ensures that the liquid fuel is heated and boiled at a steady rate.

In the pulsating appliance, where carbon has been deposited inside the vapouriser, the temperature gradient along the vaporiser becomes more marked because the rate of heat transfer through the layer of carbon is less than that through clean metal. Vapourisation therefore occurs suddenly, and further towards the end of the vapouriser, causing the liquid fuel to flash into vapour and expand rapidly. In the choked vapouriser there is reduced volume into which this vapour can expand, so the pressure rises rapidly, and this pressure surge can be sufficient to push fuel and vapour back into the tank. On contact with cool fuel, the vapour condenses and contracts rapidly, releasing its latent heat into the fuel tank, and the pressure in the vapouriser drops rapidly to where it is below the tank pressure. Fuel surges back towards the vapouriser, where it flashes off into vapour, and the cycle repeats.

To cure a pulsating Tilley lamp, fit a replacement vapouriser. For a blowlamp, sadly this isn't possible.

Phil

 

I'm really not convinced that carbon buildup will have any significant affect on the temeperature gradient along a vapouriser... Carbon is a pretty good conductor of heat and we aren't talking about a very thick layer.

 

Sorry, Gneiss, but carbon isn't a good conductor of heat - the thermal conductivity of carbon is 1.7W/mK, compared with brass at 109W/mK. Even a relatively thin layer of carbon on the inside surface of a vapouriser will act as a thermal insulator, a bit like scale on a kettle element.

I agree that the pulsating effect is not particularly severe in my experience on a pressure lamp, but on a paraffin blowlamp it is much more dramatic. I have seen blowlamp vapourisers completely choked with carbon, and I have also seen vapourisers glowing cherry-red on the outside due to the build up of carbon on the inside.

 

Graphite is a form of carbon and it is an excellent conductor of heat at up to 470W/m.K, carbon nanotubes are even better, so clearly it is highly dependant on the precise form the carbon takes...

I very much suspect the the figure of 1.7W/m.K applies to non compacted "soft" carbon, but the form isn't specified.

A vapouriser is steel at

 

I confess I don't know all the answers; I'm just speculating based on my own experience. However I'm beginning to doubt my own theory, as I have been using a 500 series Tilley today which pulsates, yet that lamp has got a brand new 500 series vapouriser in it...

Exploding vapouriser syndrome probably occurs due to the steel tube overheating and softening. The cause could well be internal carbonisation, or a hotter flame due to a weak mixture. As the carburation in a Tilley burner is fixed, I'm at a loss to explain the latter, other than fuel quality.

The more I learn about lamps, the less I know!

 

One of the ways manufacturers reduce this hunting is to restrict the fuel flow. This restriction limits the effect of back flow. In a Tilley the lower end of the vaporiser is restricted where the brass end of the rod passes the fitter. However there is also a degree of restriction in the valve and I wonder if it is the quality of the valve machining that affects the hunting. Try fitting another valve to see if this changes or eliminates the beat. ::Neil::

 

Good suggestion, Neil. This is an X246B 500 series which is otherwise as-new. I've got a spare control cock so I'll try replacing it and see what happens.

 

Those lanterns worry me some. In the instructions Tilley state that for full pressure you give 150 pump strokes. That is well in excess of the 100 strokes for the 300 series which I know generates around 30 psi. I am guessing but I think 150 strokes will give around 40psi or perhaps more. These post 1957 tanks are rather prone to failing with a dished down tank and shoving 40 psi in there has to be a bad idea. ::Neil::

 

I couldn't agree more! In practice, the lamp gives perfectly adequate light at 80-90 pumps, so I don't go any further.

Update on the pulsing. I filled the tank last night, lit the lamp - and the pulsing has disappeared. I'm still trying to work out why this happens; clearly, with a full tank the air space is smaller and more resistant to compression, but what factors cause the pulsing to start in the first place? Perhaps there is a chance combination of vapouriser condition, fuel cock condition, dip pipe diameter, fuel quality and tank pressure that creates and maintains an oscillatory pressure variation under certain conditions.

I have had to conclude that the cause of pulsing in pressure lamps is quite different from that in blowlamps.

Phil

 

Phil

There are quite a lot of lamp gremlins lurking in various parts of the planet. That are extremely cryptic and rarely seen, but their presence is manifest by phenomena such as you describe above whereby a lamp develops an seemingly incurable affliction, then inexplicably rights itself.

A related species of gremlin creates black mantle disease, but that is often incurable...

Tony

 

You're quite right. Intermittent faults obey Sod's Law, more politely known as The Law Of Maximum Cussedness, which states: "If a thing can happen, it probably will. The higher the inconvenience potential, the greater the probability".

Life is governed by Sod's Law. I don't mind, because being a devout pessimist, I am either always being proved right, or pleasantly surprised. And don't forget the definition of an optimist: "Someone who is not in possession of the full facts".

We'll probably never know all the facts when it comes to pressure lamps.

 

That reminded me of a saying my father came out with once. Not the sort of thing he would usually say.

"A pessimist is a man who thinks all women are bad. An optimist is a man who hopes they are."

 

Tony

Perhaps the reason they suddenly stop pulsing is the gradual build up of carbon in the vaporiser that reduces the fuel flow to the ideal rate.
Perhaps after years of use the original manufacturing tolerances have long gone. Replaced by a chance level of carbon.
?

Richard.

 

got similar with my TL136 unless the pressure is high it does this but is fine as the pressure drops my x249 doesn't do this, I was blaming the length of feed tube for his behaviour

 

@Tulyard

My experience is that a long used (and not cleaned) vapouriser will be more prone to erratic behaviour than a new, or thoroughly cleaned one.

Sometimes the problem is wth the burner or the fuel flow.

Cheers

Tony

 

About the issue of a pulsating lantern, blowlamp or a stove, I have quite a firm belief that it usually starts if there is sufficient pressure gradient between the vaporizer and the air-pressurized fuel tank. When the fuel is 'superheated' at the upper part of the vaporizer, it would exert extra pressure in all directions. A flow would be created if there's room for expansion. The jet orifice could only permit a limited flowrate throught it. Now if there is a sufficiently large volume of air in the fuel tank, the extra pressure from the vaporizer would tend to exert and force some of the heated fuel back towards the tank, since the air volume above the fuel would be the only thing that could be compressed. This would then equalize the pressure from the tank to the vaporizer again. All this will repeat again.
If you pump more air into the tank, this would reduce the pressure gradient between the heated vaporizer and the tank and thus reduce the likelihood of a noticeable pulsing.
I have tested this theory on a roarer type burner with a hollow wire lead. The hollow wire was formed into a coil around the flame ring to create a longer path for the fuel to be heated up more than normal before it reaches the jet. The resultant flame was pulsing like a steam piston engine.
I then fitted a hydraulic check valve on the hollow wire between the tank and the burner. The pulsing was eliminated completely. I realized that all the superheated fuel after the check valve would have no other way to expand except through the jet orifice.
Note: The liquid fuel in the hollow wire/tube between the check valve and the burner is not compressible and could not vaporize into gas before leaving the jet orifice. If the hollow wire is not sufficiently strong, it would rupture.

 

Yes, I agree with your reasoning above (I've thought this for years) and this is why there is a restrictor in the fuel line somewhere - to reduce back pressure into the tank. I would further suggest that all lamps and lanterns pulse all of the time. As you increase the tank pressure, the pulses become quicker (the frequency increases) and shallower (the amplitude decreases) until a point is reached when the Mark I human eyeball can no longer notice the pulsing. That makes perfect sense to me, anyway...

 

@MYN , full ack to your reasoning.
My own observation was also that the tank of a pulsing lantern tends to heat up quickly. This most likely because the amount of fuel that is pressed back into the tank every time the pulse occurs is boiling hot.
And I also observed exactly what @David Shouksmith described at lanterns that were poorly pressurized (e.g. when they ran for a longer amount of time unattendedly, because the beer was more important ).

 

The beer. That's it. Indeed a very valid reason for almost everything.

 

My theory is that a build-up of carbon in a vapouriser acts as an insulator and the liquid fuel is then turned to gas in a hot-and-miss manner

The pulsing is likely (surely) to be a result of changes in gas pressure in the burner - and therefore probably in the vapoursier. If a dollop of fuel is heated in a closed vessel it will increase in pressure. The vaporioser is not a closed vessel - but with a small jet at one end and a queue of fuel and the other, there is limited room for expansion in the short term. I don't see the gas as forcing its way down the fuel type and rising in the tank. You would expect to hear the bubbles. And whilst the vapour would condense in the short term, the fuel tank would heat up with potentially catastrophic results, which have been seen where external heat has been applied to a tank.

But the level of the liquid/gas interface in the vapouriser could bob up-and-down a bit. If the vapouriser is clogged, when the fuel is "down" it might be in a more insulated position, and thus not vapourising well, until the pressure at the jet end drops when the liquid fuel rises to create a burst of pressure.

My completely untested theory does offer some explanation why this is mainly a function of an well-used vapouriser. Among its weakness is that the frequency of pulsing means that the difference between up and down is likely to be very small which makes it a bit odd. But I still think it all points to the vapouriser not performing its duty at a steady rate.