Whilst using a Petromax 829B this evening an unusual thing happened. The lamp had been lit for about half an hour and was at a pressure of 2.5 Bar. It was running well. Suddenly and without warning the light dimmed and the lamp started to gurgle and roar. The flame had drawn back into the mixing tube and the mixing tube was glowing red hot. I quickly turned the valve wheel back and forth a few times thinking that there must be some dirt at the jet but it did not help so I released the pressure and put the lamp out. After the lamp had cooled down I lit it again and it behaved completely normally. Does anyone have an idea what might have caused this? It was quite alarming and I wonder what could have happened if the lamp had been allowed to burn in this condition for a while? I suspect it would have been badly damaged.
You could have ended up like this. Or worse! : Once the flame find it's way into the mixing tube, it acts like a small torch just above the jet, and eventually melt the first bend of the u-tube. (This was the tube of a Standard flood light I left unattended. I silbrazed the hole afterwards, and it worked again after that.) This can happen for various reasons. Your mantleholder might be damaged. I've seen ceramic mantleholders that misses a part between two or more holes, giving the flame a large and easy way back into the mixing tube. But it also happens sometimes for no seen reason, and some lanterns are more prone to it than others. Make sure you have a good jet and everything is tight and well screwed together. And on some types it might be a good idea to check that the adjustable height of the mixing tube vs. the jet is fairly accurate. The important thing is to react, just as you did, when you hear this "gurgle and roar". This was, as I understood it, what Ari was trying to explain on his Optimus 930 when he talked about a new sound, apart from the normal hiss, that apparently reminded of a hornet (seen here.). Always look out for underburn (is this the correct words for lamps, or is it just for stoves? Perhaps one should call it backfire?) when you hear this sound.
Thank you Christer. I had the lamp in the garden and I was only a short distance away but by the time I had realised what was going on the j-tube was glowing a fierce red. I have had the hood off and there appears to be no damage. I think this happened for 2 reasons. Firstly, the jet was dirty with carbon and secondly, the J-tube adjusting screw was loose so that the air gap was too narrow. Presumably the jet suddenly became partially obstructed which reduced the flow so much that the flame retreated back into the tube. I'm not sure if the incorrect setting of the air gap made this more likely to happen or not.
Lets hope for the best. But I wager this is a lantern you will keep an extra eye on whenever you run it hereafter. I have a Primus 1094 that generally works perfect, but sometimes it acts like yours for no reason. Oh, well... of course there is a reason. I just haven't found out what (yet ). I hear it at once, since that deep gurgling roar starts.
I had that same problem with an Optimus 930 and a Veritas Superb and I never did find the cause! Jeff.
You are absolutely right. I was quite scared! It has never happened before but I won't trust this lamp. I think I will rinse out the tank tomorrow just in case a fine particle in the fuel caused a block at the jet.
I get the same fault now and again on an Anchor 950. I have tried changing the jet, resetting height of the J tube, new needle tip, cleaning air tube and vapouriser tube, and it still happens now and again. Turn it of, cool and relight and it's OK again. Very baffling and frustrating as you cannot trust the lamp thereafter. Steve.
Yes. Obviously one shouldn't leave lamps unattended for long periods but this happens so quickly that it means I feel uneasy walking away from the lamp for even a minute or two. As Christer said, this is the same "underburn" that can happen with pressure stoves. As others have said they have checked everything out and have found no obvious fault or have changed jets etc and it still happens it seems dirt might be the culprit. Something causes a sudden pressure drop which starts the underburn but perhaps even if the jet is cleared quickly the underburn continues and the lamp will not go back to normal operation so the only solution is to extinguish the lamp and start again. In this respect, there appears to be a "flip-flop" state whereby once underburn has started it is stable and is very difficult to flip back into normal burn. I read a German page that suggested that blowing hard into the hood at the jet whilst moving the valve wheel back and forth can restore normal burn (sometimes) but I haven't tried that!
I'd guess the underburn will continue as long as the temperature of the J-tube is above the flash-point of the fuel. I'd also guess that blowing hard into the jet area will cool down the J-tube to below the flash-point and the lantern will burn as normal. I once saw the results of what I presumed to be underburn in a military BiaVap lantern - the very top of the mixing dome had a ~8mm hole melted through it...
The same is happening to me with a Vapalux 300x. When it gets hot the mixtures withih the burner to ignites and the light dimms. I don't know how to fix this. Any advice? Juan
I would check that the burner is clean. You can unscrew the air buttons to get the whole burner/mixing dome assembly out and clean it. When you have the assembly out make sure there are no cracks or holes where there shouldn't be. Then check the vaporiser. Remove the vaporiser from the lamp and check for carbon build up inside. Clean the vapouriser if you need to but if these are worn out they need to be replaced. Check the cleaning needle is still there. There may also be a worn jet and that means a new vapouriser as well. Make sure you are pre-heating properly and to be thorough rinse out the tank to check there is no dirt in the fuel.
Do not know if this is of any significance or not, but looking back over the times when my Anchor 950 showed this phenomena, it is always when the tanks is low, perhaps below one third full. Even though the pressure is high it does not seem to like running on a low tank level. Any ideas? Steve.
Interesting Steve. My tank was also low when this happened. I suspect grot in the fuel. This could be especially problematic with an Anchor because they have steel tanks that rust. Regards, Stephen
