Tilley is pulsing/hunting

Correct - but no-one's suggesting the process goes as far as this.

Yes, I think that's exactly what happens - and the frequency and amplitude of those perturbations is determined by the pressure gradient between the tank and the top of the vapouriser. This, in turn, varies the venturi effect just above the vapouriser jet, varying the amount of air drawn in and thus the mixture. All of these factors work together to produce the pulsing.

This definitely won't help the situation.

Yes, this is the crux of it, whatever the exact causes. My feeling is that low tank pressure is the key - whatever the state of the vapouriser, the problem can usually be ameliorated by increasing tank pressure. Keep the buggers pumped up to normal working pressure!

 

Increasing the pressure does fix it, a bit anyway. It could be partly the gradient issue - or could be that with more pressure, there is more heat to the burner and thus more heat to the vapouriser which helps overcome the issue.

if this is an old/used vapouriser issue, then there is a reason why increased pressure is required to keep a happy lamp. As you say, the short term fix is to pump harder - and when that causes your thumb pain, get a better vapouriser.

 

That's probably true, but some of the earlier comments may lead one to think otherwise.

For example, it was said to be observed that the tank of a pulsing lantern tends to heat up quickly - with the most likely cause being the amount of fuel that is pressed back into the tank every time the pulse occurs is boiling hot.

"boiling hot" may well have been a turn of phrase in this context. The to-ing and fro-ing of liquid fuel could cause heat to travel back to he tank - but the net direction is outward, of course, so I wonder if it would add much

 

There's something that you might or might not have missed, Ian. I might not be 100% right but I believe, within the confines of the vaporizer, the fuel would remain mostly, a liquid, even when the vaporizer is red hot. That's excluding the area at the jet orifice. However, should the internal volume of the vaporizer expand due to the heat, there would be a minute amount of liquid fuel transforming into gaseous phase within the vaporizer, creating higher than normal pressures. This could only be relieved mainly by escaping through the jet orifice and by compression of the air volume above the fuel in the tank. Therefore, the fuel in the vaporizer would tend to expand mainly to both directions. More towards the path of lesser resistance. If the jet has a larger orifice, it would offer less resistance and vice versa.
I have a British Monitor No. 36 blowlamp that pulses, and with each successive pulse, the flame would surge and retract repetitively. At the same time, I could feel bubbles or liquid fuel being forced back into the tank with each pulse, through the opening the of the fuel pickup at the bottom of the tank. Shortly, the tank would become so hot that its untouchable.

 

Yes, as I said above, this is why there's a restriction in the fuel flow path at the bottom of the vapouriser - to prevent too much back pressure towards the tank and help maintain a pressure gradient from the tank to the jet thus overall promoting a fuel flow in that direction...

 

Once I had a 500CP Picostar (designed for kero w/ torch preheater) which did exactly this! You could even hear the vaporizer foot valve clicking and the fuel bubbling when the high pressure (and bright light output) phase happened. And the tank got really hot in almost no time! That lantern was nearly NOS (truly clean) and I tried almost everything to cure it: cleaning the vaporizer & foot valve thoroughly again, new mantle, different kind of fuel and mixtures etc.: nothing really helped, although there were some partial improvements. The solution was finally to put some brass gauze into the upper part of the vaporizer.
So it's probably a combination of various reasons: shape of the mantle and its distance to the vaporizer, kind of fuel, pressure, inside surface of the vaporizer and perhaps some more that I don't know yet.

I don't agree: My assumption is that when pulsing happens a quite large amount of liquid fuel inside the upper part of the vaporizer is evaporated almost at once due to some boiling delay. This in turn increases the pressure in that area very quickly. When the pressure has escaped through the jet and towards the tank it suddenly drops because no more liquid fuel is present in that area. This in turn causes liquid fuel to come in from the tank again. After some short time it starts to boil with delay again, increasing the pressure. Then process starts from the beginning. My observations were so far that the frequency is not only dependent on the pressure, but also on the flow restriction caused by the fuel pickup and the the foot valve, so far present (variation on the mechanical inertia of the liquid fuel inside the lower part of the vaporizer). But surely the vaporizer doesn't heat up and cool down significantly with the pulsing rate because of its thermal inertia.

 

A check valve would have stopped the pulsing altogether but unfotunately, I don't think its practical on such lanterns. It would quickly fail from the heat. Besides, it would be impossible to immediately shut off the lantern when pressure is relieved from the tank as the residual fuel in the vaporizer could no longer return to the fount.

 

You are right in this respect, Martin. There will be a momentary drop in pressure in the vaporizer soon as some of fuel is ejected through the orifice or being pushed back to the tank. What I meant earlier was that most of the liquid in the vaporizer remains a liquid no matter how high the pressure (assuming there's no increase in volume of the vaporizer and no breakdown of the fuel into carbon). Liquid is largely incompressible in that locallized part. Instead, the pressure elevated by heating would create a force towards any directions that would give way. In case, the air volume in the tank and the outlet of the jet. Otherwise, a rupture somewhere along this path...the vaporizer if you're unlucky.
Of course there are other factors chiming in at the same time such as a partially clogged jet or vaporizer that could accentuate the effect.
In actual, I agree that its not completely liquid in the vaporizer when this happens. The fuel within the vaporizer closest to the jet outlet could well have become gaseous for a while. This is where it would surge/ flash off towards the jet orifice. At the same time, this localized volume increase due to the gasified fuel would push some heated liquid fuel in the lower portion of the vaporizer back to the tank.

 

This is my Coleman (gasoline) 236 on the left. If it’s not pumped until you can’t pump any more, it pulses. At low pressure it pulses badly. Pumping it immediately smooths out the pulsing and, under high pressure, it stops pulsing (to the eye) altogether.





Cheers

Tony

 

That's what the user manual would suggest if it pulses.
Probably to increase the resistance to a backflow or to top up a fuel-starved generator or both.
The exact explanation for all that might be more complex than what we have discussed thus far.

 

That might well be the case and possibly factors other than the ones we've so far described are involved. For instance, ambient temperature and air pressure my also be involved to some extent. Notwithstanding that, I think we've identified the main causes and the remainder are peripheral to those.

Essentially: if a lantern pulses, pumping it up to working pressure is the first step. If that doesn't cure the pulsing, then the lantern will need servicing - a thorough cleaning, possibly new seals and maybe even replacement parts e.g. a new vapouriser/generator...

 

Newly purchased, all seals renewed, 1960 Guardsman pulsing. Fitting a new vaporiser cures the problem. Decided to clean out the inside of the old vaporiser using a copper wire and carb cleaner. Pictures show what I got out.
The old vaporiser now provides a steady ring of stable blue triangles.

 

I have three Tilley Guardsman lanterns all manufactred in the 50,s and in good order.. I have serviced them ,,, swirled out the crap from the font with nuts etc , replaced seals with the modern " viton " synthetic rubbers and cleaned filters... pipe and all etc, the vapourisers seemed all ok and were heated and quenched to remove carbon , pricker wire cleaned and carbon sanded off ... but
recently as an experiment I used a few drops of upper cylinder lubricant " Lucas oil " in the paraffin C1 I have ...surprisingly after a few illuminations.... I really get a difference and a smooth bright light ,a sound hiss and constant running ... they all seem to use less fuel... I only use three drops in a pint of fuel .. it makes a big difference ... Lucas oil UCL can be used in petrol or diesel engines... I use it in my Peugeot .. I suppose any diesel injector UCL would suffice but its worth a try in a difficult lamp maybe.
Alb

 

@Alby, sounds very interesting, I’m going to give it a try.

 

That is interesting @Alby .
Definitely some truth to it. I have never tried any fuel or lubricating additives on the fuels for these lanterns but I've had some experience (an indirect version) which might leads to similar reasoning as yours.
In my case, it was not on a Tilley but a Petromax. There was a very noticeable pulsing on my lantern when it was burning pure kerosene. The pulsing could not be brought down to tolerable levels no matter how much I pumped it up. I did not clean it further. I did not attempt the usual brass gauze trick to counteract that.
What I did was to replace the kerosene entirely with 'highway' diesel. And I restarted the light-up but of course, with more preheating. The result was amazing (as what's in your case with the Lucas oil). Steady white light, zero pulsing and flicker-free. The thing is not about diesel but reasoning. Of course, diesel contains additives to alter its burning characteristics but that has nothing to do with pulsing within the vaporizer/fount. I'm suspecting that the presence of some oilier components with higher boiling points in the fuel is somehow altering the overall flashpoint as well as the rate of vaporization. This somewhat reduced or smoothed out the 'Leidenfrost effect' and resulted in whatever surprises we've experience on those.

 

I haven’t visited the Forum for a while, so it was very interesting to read the discussion on the subject of pulsing or surging, which has exercised my mind for some time.

Since first noticing the problem (in blowlamps) I have encountered it a couple of Tilley lamps, and in each case, replacing the vapouriser has cured the problem at a stroke.

I suspect it’s the profile of the carbon build-up within the tube which pre-disposes a vapouriser to cause pulsing.

Thanks for some very interesting points raised in the discussion.

Phil

 

Usually pulsating on a Tilley is the control cock gland washer. The tiny one under the knurled gland nut. Base-camp recommend fitting 2 washers. I concur but I fitted a gland washer and a very small O ring.
Any other leak will cause kerosene to come out whereas this washer allows air in when the lamp is running.

 

Wow mind blowing, that's for sure.
Very interesting what members have come up with.
Thanks.

 

Re the liquid fuel in the vaporiser. It does only vapour at the top near the jet as it gets hot. I have generally cured some pulsing by adding 2 washers in the control cock gland. Until today.
I have an unlit 1990 (new improved) 246b. Everything is factory new but I have heard that some factory new vaporiser tubes are duff. The seals are obviously 30 years old so have been replaced. Lamp was filled and lit.
It pulses.
I've done everything from more fuel, less fuel, different vaporiser, different burners, more pressure, less pressure. More new seals and washers and nothing cures it.
I did just watch a YouTube video were a guy has a Coleman, different thing altogether but I watched. It also pulses. He narrowed it down to fuel rising and dropping up and back to the tank. This was caused by a little cardboard tube in the Energizer breaking up. Once replaced the lantern works fine. He just keeps replacing them as they don't last long..
I am now beginning to think the pulsing in the Tilley comes from a problem in the riser from the tank or the control valve as everything else has been changed/ replaced/swapped and fiddled with. Fuel rising and dropping.
My next step is to replace, fiddle and swap about the spring and washer in the check valve in the bottom of the control cock and also check there is no problem with the riser tube. The check valve is either sticking, the spring too weak, spring to strong, dodgy washer, dodgy washer seat. Never have an issue with my pre 61 guardsman, it behaves.
I will report back later this week