Locating kerosene leak on burner

Discussion in 'Fettling Forum' started by HaakonJ, Nov 15, 2019.

  1. HaakonJ

    HaakonJ Subscriber

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    Hi

    I recently bought an Optimus 155 quite cheaply ($25), and need a bit of help locating a leak. After some basic fettling I got it running quite nicely. One side works perfectly, with a steady, strong blue flame. The other side also burns nicely, but there is an obvious leak of kerosene vapor from the burner unit. Usually when I have leaks at a jet, graphite nut or burner base of comparable burners (Optimus 111, Phoebus 625 , etc) they are quite simple to locate. Either visually or by using a torch. Usually the leaking spot lights up or gives a flash of ignition if I hold a butane torch to the particular spot. This time, there is no luck with that method. I suspect the burner itself could have some stress cracks, and leaks where the flame of the quick heater hits the burner.

    Are there any good ways to test for cracks in a burner, and possibly locate it?

    Håkon
     
  2. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Optimus 111T burner fault - A mystery solved!

    Read through this thread, in particular see the technique for leak-finding, described by threedots:

    “I played a small pencil blow torch on the affected side when the burner was running and discovered the leak when the fine blow torch flame turned from blue to yellow in the area.
    It had a very fine leak that seemed to open up only when the burner was very hot.”

    Best Regards,
    Kerophile.
     
  3. presscall

    presscall United Kingdom SotM Winner Subscriber

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    As it did with the leak on one of my 155 burners. Good tip from Threedots/Kerophile. Good luck Håkon!

    30103931-38FA-4990-9EA6-4FDD5E94248C.jpeg

    John
     
  4. HaakonJ

    HaakonJ Subscriber

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    @kerophile @presscall
    Thanks, your input gave a lot of good information. I made a little video showing some of the problems. As you can see, the torch lights a few small flames on the underside, on the side of the pre heater. Not the case on the opposite side. I did more thorough testing than shown in the video.

    @presscall did your leak cause a lot of fumes as well, or just the little flame shown in your image?



    I also took the burner off and installed it on a classic brassie tank, to get a better view of the underside while running the burner. At lower pressure, the asymmetrical flame pattern is clearly visible, where I get rich, yellow flames on the (suspected) leaking side. The small flame on the underside is also visible.

    IMG_20191115_230005.jpg

    This points quite clearly towards a leaking burner, right? Even though I know which area of the burner is leaking, I am still not sure how to pinpoint the exact location of the crack/cracks. The flame(s) on the underside is appearing at the vent holes(?) that go around the burner edge.

    Well, I guess I have to buy some silver rods and read up on silbrazing now ](*,)

    Håkon
     
  5. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  6. presscall

    presscall United Kingdom SotM Winner Subscriber

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    The escaping gases immediately ignited on the lit burner but if I’d have blown the flame out there would have been fumes.

    The sort of vapour leak seen in the video is something I’ve seen when the spindle packing nut needs tightening up a little, Håkon.

    The photo appears to show an outer cap not properly seated and the flamelet underneath would be the vapourised gas spilling out of the cap-to-burner mis-mating through one of the air inlet holes in the burner skirt.

    John
     
  7. HaakonJ

    HaakonJ Subscriber

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    @kerophile
    Thanks for the link! Will be reading more thoroughly when I have the time.

    @presscall
    The cap is seated with the edge underneath the small lips that holds the cap in place. Not sure why it looks to be out of position. I agree it looks similar to a packing nut leak, but I am quite certain it is not leaking. It has been tightened, which didnt improve the leak, and there is no ignition of any vapor if I try to put the torch flame to the nut. I have never had a graphite nut leaking where I couldn't light the fumes.

    I took some photos in good light of the underside. It shows cracks in various places, which may be the cause of the leak. I left it pressurized over night, but there was no kerosene on the burner today. Might be a case of leaking only while hot?

    IMG_20191116_111305-01.jpeg IMG_20191116_111205-01.jpeg IMG_20191116_111347-01.jpeg

    Håkon
     
  8. presscall

    presscall United Kingdom SotM Winner Subscriber

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    Sometimes not if it’s a very ‘lean’ mixture. A crack in a graphite packing could make that happen.
    Well, just a thought.
    If that wasn’t it and if it were my burner I’d apply a bead of silbraze wherever I detected what I thought might be a crack. Your close-up photos are helpful. I’ve used close-ups like that to detect pinholes in burners that the naked eye (well, mine!) couldn’t spot even with a magnifying glass.

    John
     
  9. HaakonJ

    HaakonJ Subscriber

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    Thanks for your thoughts. I'm sorry for asking silly questions, but could you elaborate on what you mean by a "lean" mixture? Isn't the fumes coming out of a leaking graphite seal always 100 % kerosene vapor? There is no mixture of air before the kerosene leaves the graphite nut? If you by "lean" means it's a small flow of kerosene vapor from the leaking point, so that the flow of air around the packing nut diffuses the vapor too quickly for it to light up, then I'm not sure this is the case with my burner. This leak seems quite vigorous, and I've had what seems like much less vigorous leaks at the nut light up easily with a torch. Hmm, I realize I'm confusing myself :? :lol:

    Anyway, so you would try a new graphite packing before brazing those small cracks? I'm thinking I might as well have a go at brazing the cracks while I already have the burner disassembled to install a new graphite packing. Or do you consider it a case of "if it ain't broken, don't fix it"?

    There seems to be a few options in choosing brazing rods for brass at a local store. Either phosphorous-copper rods (melting point 660 C, price 19 USD) vs flux covered silver rods (melting point 640 C, price 55 USD). Could the cheaper ones be used for this application? $55 for a 5-pack of 3mm/250mm silver rods seems very expensive(?). There is also a silver-phosphorus-copper rod marked "2 %, for gas welding of copper and brass", but there is no melting temperature specified. Do I need higher % silver to get good capillary action of the molten braze material?

    Håkon
     
  10. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi Hakon, you only need a small amount of silver brazing material and suitable flux. Have a look on Ebay for Easyflo silver braze:

    Easyflo braze | eBay

    If you have any friends who make silver jewellery, they likely use the correct silver braze.

    A little goes a long way if used correctly, and the fluidity of molten silver braze is that it readily flows into narrow cracks.

    Best Regards,
    Kerophile.
     
  11. presscall

    presscall United Kingdom SotM Winner Subscriber

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    I’m sorry Håkon, I wasn’t sure whether the term ‘lean’ in describing the fuel/air ratio would be understood outside the UK. But you got what I meant.
    The vapour you see, whether from the graphite packing or burner crack (or cracks) can only be kerosene vapour and if it doesn’t readily light when you poke a flame at it it’s because the fuel/air ratio isn’t right for combustion (I suggested ‘lean’ as having too big a proportion of air - more likely).
    The silver content silbraze rod is what I use but unless the ones you’ve seen are much longer, or a thicker gauge, than those I get they do seem expensive ... about eight times the price!

    I probably would replace the graphite to see if that gets rid of the ‘vapours’, but then I don’t rate removing/replacing the burner spindle as a particularly lengthy or difficult task. Both burners were running very well in your video clip.

    John
     
  12. Twoberth

    Twoberth United Kingdom Subscriber

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    I nearly always use Easy-Flo flux and Silver-Flo 55 braze.

    Occasionally, if I need to make two braze joints/repairs on the same piece I use the higher melting Silver-Flo 20 first. As @kerophile says a ‘little goes a long way’. I usually cut chips off the rod with utility pliers and ‘stick’ them over the repair area with flux to avoid melting too much.

    I have used phos-copper rods but I don’t think it flows as well into cracks and thin joints as silver-flo, but it should be good for bridging gaps and filling holes.
     
  13. HaakonJ

    HaakonJ Subscriber

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    I always get amazed by the level of knowledge and helpfulness from members of this forum. Thanks for providing all this information, I now feel much more confident about the task at hand. I have ordered some Silver-flo 55 rods + flux from eBay. I'll do some practicing on a scrap burner I have.

    @presscall I agree it's not a big task, and it probably is the right thing to do first. However, just knowing about those cracks makes me not trust that burner, and I'll be brazing it anyway, if only for the peace of mind :) Thanks for providing much help on the topic.

    Great tip, @Twoberth. I'll use that method. Considering the width of the rod/chip, how much does it spread out on a flat surface? How close does the crack need to be to the chip you put down, so that you're sure the braze flows out to cover the crack? I'm fumbling with my phrasing, but hopefully you understand what I mean.

    Håkon
     
  14. ROBBO55

    ROBBO55 Subscriber

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  15. Twoberth

    Twoberth United Kingdom Subscriber

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    @HaakonJ

    This is a quick mock up of brazing a 'crack'. Its a bit rough, but you should get the general idea.

    The Sil-Flo 55 is 1mm diameter rod

    DSC09033.JPG

    so I flatten the end with the pein of a straight pein hammer

    DSC09034.JPG

    and cut off square chips.

    Next clean and paste the joint with flux. I normally heat the flux first until it stops bubbling and while it is still hot, molten and sticky I stick the chip over the crack. This helps stop the chip from blowing away when you put the flame back onto the workpiece.

    DSC09036.JPG DSC09037.JPG

    The braze chip must be over the crack or it will not flow into the crack and form a seam.

    That small chip is enough to fill this 2 cm long 'crack' with plenty left over.

    DSC09040.JPG DSC09042.JPG

    Mixing the flux with filings as @ROBBO55 suggests is also an excellent way to do small repairs.
     
  16. presscall

    presscall United Kingdom SotM Winner Subscriber

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    @Twoberth @ROBBO55 @HaakonJ
    Good for you for providing the demo Twoberth and good to see that Primus 41 burner repair, which I somehow missed first time round.

    John
     
  17. Simes

    Simes Subscriber

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    I'll second the thanks for the quick 'how to'.

    Some advice I am aware of to consider, but may not.be relevant given the size of a burner, is to pre heat the work piece. Probably more relevant with larger items, it shoukd save some time when actually heating the area to be worked on. There is less of a heat sink effect.

    Sometbing to consider if using a smaller torch.
     
  18. presscall

    presscall United Kingdom SotM Winner Subscriber

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    Very good point Simon. I’ve often resorted to a paraffin blowlamp to do that and arrange the workpiece/blowtorch to be in the torch flame while directing the MAPP torch flame at the sot to be silbrazed.

    John
     
  19. ArchMc

    ArchMc Subscriber

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    This site is amazing. Thank you all for the tutorial and comments.

    ....Arch
     
  20. PriMads

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    @HaakonJ
    One thing I have noticed (and probably not alone) is that even a tiny, tiny leak can cause a stove that smells "exhaust". I was able to leak proof my Radius No. 21 to the point were I can stand over the stove and have absolutely no smell hitting my nostrils at all. Just warm air! This is with charcoal lighter fluid as fuel. I don't know how regular kerosene will do.
    A gas canister stove actually smells more than my Radius.
    Just mentioning this because your stove is meant for indoor use. Better the keep wife happy, you know, and not having comments like "It reeks - it must be dangerous - get it out immediately!" thrown at you. :)