PX 828 300HK fire ball

Discussion in 'Fettling Forum' started by Piotrek, Dec 4, 2023.

  1. Piotrek

    Piotrek Czech Republic Subscriber

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    Dears,

    I would appreciate some advice regarding my PX 828 300 HK from approx. 1940. Dismantled, cleaned, washers replaced, old rapid functioning (so cool ) but mantle gives quite a lot of fire instead of light. I can get much bigger fire ball then visible on attached pics, but problem is visible even on these pics below.

    Brand new 350CP nozzle installed. 500 CP cheap mantle. Gap between nozzle and tube set as for 500CP – using Petromax tool. That micro-regulating screw inside the mixing pipe does not change situation. I cannot disassemble the mixing chamber, so regulation of the gap is limited - I can try to reduce the gap, but not make it larger.

    Manometer was not working so I installed one from other PX lantern. I am not sure if the pressure is right, but at approx. 1 atm rapid works, and after that I pumped more. At lower pressure and playing with needle I can limit the fire, but the light is not as bright as it should be.

    Help please… IMG_20231201_205548075.jpg IMG_20231201_205551235.jpg IMG_20231201_212658039.jpg IMG_20231201_212839088.jpg IMG_20231201_213027597.jpg

    Piotrek
     
  2. MYN

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    You're almost there.
    Looks like it is burning a little to rich or having too high a 'fuel-to-air ratio'. Or not drawing in enough air. Check that the J-tube isn't glowing red during operation and there should be no loud 'growling' noise.
    A Petromax 828 from 1940 should still feature the older design of two-flat nuts holding the J-tube mixing chamber within the inner hood. By using the Petromax tool, I suppose you're having a 14,2mm gap between the jet(nozzle) and J-tube inlet? Check again with a vernier caliper(if you have one) that it remains at that distance after tightening the flat nuts holding the J-tube. Sometimes the gap distance gets somewhat reduced after tightening. Normally there should be no problems adjusting the gap larger up to 17 or 18mm, unless the J-tube's threads are worn or missing. Are there any obstructions within the inner hood preventing you from doing so?
    In any case, check again that you're using a 300HK or at most, 350CP jet and it is not worn. The jet orifice should be around 0.20mm in diameter accompanied with a 0.19mm diam cleaning needle. If it is worn, the burn will certainly be too rich. Sometimes, a slightly loosened jet(nozzle) would give you a similar problem. Check that it is tight and without leakage.
    When the fount is pressurized with fuel, the jet orifice should also be ejecting a straight, very thin stream of liquid fuel(when cold) vertically(upwards). The fuel stream should, preferably be strainght, unskewed and not dripping or spraying sideways.
    If it is, check the height of the cleaning needle when at the 'down or opened position'. Otherwise, the jet might be also defective or partially blocked by dirt if the fuel stream isn't straight and perfectly vertical.
    There could also be other issues causing these kind of problem but you need to get a few basics secured and verified first.
     
    Last edited: Dec 5, 2023
  3. Piotrek

    Piotrek Czech Republic Subscriber

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    @MYN - Thank you very much for instruction.
    I have another 828 300HK as a parts donor. I can replace some parts, but definitely will start simply with enlarging the gap, because indeed It was set for 250CP distance as I measured again using Petromax tool. 350CP jet is new, bought from Petromax shop, so I will check other potential issues and hopefully show it properly glowing this week.
    Piotrek
     
  4. Piotrek

    Piotrek Czech Republic Subscriber

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    Dears,

    I enlarged the gap to 16mm and this is almost max that I can achieve here. To change the gap I had to take an inner hood from another 828 (I am not able to separate mixing chamber from the mixing tube in the “main” 828 ). Mixing chamber and ceramic nozzle are from Primus 1082 (here in Primus parts I can not separate nozzle from mixing chamber :) – but that should be ok, because Primus is 300-500 lantern.

    Anyway, after these changes lantern lights great at the beginning. After several minutes fire around the mantle is visible and growing, mixing tube is red hot. No 'growling' noise noted.

    I can replace any part to verify what is wrong, but I do not know where to start – vaporiser upper part?

    At the attached pics it is visible that lantern runs OK at the beginning and getting worse after a while. Red hot mixing tube is visible as well.

    1.jpg 2.jpg 3.jpg
    and after that I changed the inner casing and installed one from 829B with attached Primus mixing chamber, ceramic nozzle and the same mantle – lantern worked perfectly, no red hot mixing pipe and flames…

    And after that I attached 828 inner casing with Primus mixing chamber, nozzle and mantle but without the top hood (maybe red hot mixing tube was caused by lack of ventilation) – perfect again!

    So finally I added the 828 hood and lantern just runs perfect, no red hot mixing tube and flames! Why, if two hours before it was too hot and in flames after just several minutes of lighting? Definitely bigger gap was a game changer before, but what else after that?

    Is it possible that during several first trials the mantle was also a problem? The mantle had several black areas and was not lighting there, flames outside going higher making everything hot. After burning for half an hour in several parts/hood/inner casing configurations the mantle is all white and bright, no black areas.

    Honestly I have no idea why the mixing tube was red hot and what was the problem except for the air gap. If anybody can give some explanations then I would be very grateful.

    @MYN – thanks a lot for help. After fettling gasoline and spirit lantern this is my first kerosene lantern, so sorry guys for all stupid questions and mistakes.
    Hope this post will be helpfull for someone else in the future.

    Piotrek
     
  5. WimVe

    WimVe Subscriber

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    It is better first to use the right combination of items.
    A 350cp jet , needs a 350cp mantle and 350cp adjustments.
    Just swapping parts and changing adjustments is not the way to go (my idea).
     
  6. Piotrek

    Piotrek Czech Republic Subscriber

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    Good point @WimVe - thanks. I do not even know what needle is there, 500-600cp mantle is combined with 350cp jet and everything works great somehow...
    I brought this lantern from trip in Norway. Cost was approx. 40 EUR and I did not want to spend too much money for new parts and shipping from Germany.
    One day I plan to install 250cp needle/jet/mantle set and try the second inner casing (the defective one with limited air gap), but some parts are not available in Poland and require shipping from abroad.
    Piotrek
     
  7. MYN

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    A glowing J-tube can be due a 'backburn' with the flame from the hot burner progressing back into the tube. This can be caused by a low overall fuel-air velocity. There can be several reasons for low fuel-air velocities within the mixing chamber. Low fount pressure, too wide an air gap between the jet and J-tube(relative to and depending on the parts combinations used). Some J-tubes are longer or fatter than others. Some don't have the 'venturi' at the inlet, etc. All these affects the mixing and resultant velocities, i.e., the dynamics. You need to use the right parts for easier problem identification. Sometimes the occasional dirt particle can partially block and skew the fuel path, leading to slightly lower air-draw, low overall fuel-air velocity and rather poor mixing. This can sometimes induce the burn to take place at a shorter distance from the J-tube inlet, rather than outside the ceramic burner. If you remove the outer hood, chances of tube overheating is also reduced as well as the likelihood of autoignition of the mixture. Autoignition can happen if low fuel-air velocities cause the mixture's residence time in the hot tube to be overly long.
    Although the Primus 1082 is very similar to that of the Petromax, there are some differences that might lead to unexpected results which in turn might lead to confusing scenarios:).
    Usually, the mantle would not have so much impact for this particular problem unless it is not providing sufficient radiant heat to the vaporizer for sustained gassification of the fuel or, way too small to contain the flame.
    It would be convenient to have a vernier caliper at hand. You can measure the needle's diameter with it and compare it's 'snugness' when gauging a jet.
    A 300cp needle won't be greater than 0.2mm in diameter.
    A 500cp piece would similarly fit into a 0.23~0.24mm orifice.
     
  8. Piotrek

    Piotrek Czech Republic Subscriber

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    Thank you @MYN.
    I was wondering about that glowing mixing tube. Right now it is OK. I do not know how I fixed it, but I do not complain:) Most likely mixing tube inlet was a bit askew above the jet and combined with big air gap that affected velocity etc. Brushing mixing tube could have helped as well. I do not want to buy new Px mixing chamber, because these are different from that 80 years old (better old Primus then). Some day I will buy another old, scrap PX for parts.
    These lanterns are so easily fixed on youtube :) I will pay more attention to configuration and details in the future. I have more lanterns to fettle, so any and all advices are much appreciated guys.
    Piotrek
     
  9. MYN

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