Parasene double burner fettle - advice needed

Discussion in 'Fettling Forum' started by Twoberth, Dec 4, 2021.

  1. Twoberth

    Twoberth United Kingdom Subscriber

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    I got this double burner from Alan @G1gop at the Northern England meet, (thanks Alan), and just got round to fettling it.

    I started with the right burner, and after rinsing the tank and cleaning the burner pipes and jet I filled it with clean paraffin and fired it up. It fired up fine, but then within a few seconds it started to pulse heavily (about one pulse per second) and it became so bad it blew itself out. This happened several times, so I suspected loose debris causing an intermittent blockage.

    After cleaning out the pipes with a pipe cleaner, and re-rinsing the tank, I found what I thought was the culprit.

    2021-12-04 001 012.JPG

    However, another test fire showed the same pulsing problem. Also, the left burner suffered from the same phenomenon (and no spiders).

    Pulsing problems have been solved in larger burners (e.g. Primus No.3) by using an inlet jet and/or a gauze plug at the base of the burner, so I decided to put a gauze plug in the base of each Parasene burner.

    2021-12-04 001 015.JPG

    2021-12-04 001 018.JPG

    This reduced the pulsing enormously. but not completely. Both burners run fine now as shown...

    2021-12-04 001 022.JPG

    ...but chug loudly like a steam train under load.

    While I am happy to live with the chugging, I would love to understand properly why it happens. I suspect it is related to the fairly long, narrow bore pipes that connect the tanks to the burner.

    Has anyone else come across this chugging 'problem', or does anyone have any cures or explanations?
     
  2. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  3. Twoberth

    Twoberth United Kingdom Subscriber

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  4. Twoberth

    Twoberth United Kingdom Subscriber

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    I replaced the feeder tubes on the right-hand burner with larger bore tubing to try to eliminate the pulsing,

    2021-12-11 001 001.JPG
    2021-12-11 001 002.JPG
    but even though it gives a nice strong flame, it still pulses away!

    2021-12-11 002 004.JPG

    I notice that @ally reported his double burner pulsing in this post here. Ally, did you manage to stop the pulsing after ultrasonic cleaning and other fettling jobs?
     
  5. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @Twoberth .
    You say you were able to reduce the pulsing but not the chugging... what is the difference between pulsing and chugging? Is it the frequency of the effect or the magnitude, or something else?

    I would have said that what you need is a flow restrictor placed in the base of the silent burner. Brass gauze such as shown in this link is ideal:

    Vaporisation Gauze for No.96 and No.100 stoves.

    However you say that you tried that but still have “Chugging”

    Best Regards,
    Kerophile.
     
    Last edited: Dec 11, 2021
  6. Twoberth

    Twoberth United Kingdom Subscriber

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    Hi George,
    I use chugging and pulsing to mean the same thing.
    Initially the pulsing was so severe it frequently blew the flame out.
    Then the rolled gauze reduced it significantly, but not completely.

    Then I put my scientists hat on. In your post here Prabhat #2 resonance problem you mentioned..

    '3. On an operating stove you effectively have a "bubble" of paraffin vapour sandwiched between the nipple and a column of liquid paraffin. You need to ensure this is bubble is stable. If not, you get pulsing of the flame, or in the extreme case,liquid paraffin coming out the jet, causing "flaring".'

    ...so I thought that if the vapour bubble was unstable, then a larger pipe supplying the column of liquid paraffin may reduce the distance and frequency with which the liquid meniscus in contact with the bubble oscillated, and so reduced the resonance.

    The gauze plug I have in place in these Parasene burners (below) is exactly the same as I use in lipstick burners. However I may try a finer mesh.

    [​IMG]

    I may also try one of the burners on a normal two pint stove, which should tell me if the pulsing is caused by the burner or the liquid supply pipes.
     
  7. ally

    ally Subscriber

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    I've had a similar problem recently, the left side worked fine and the right had significant pump resistance, I managed to break the pipe unscrewing from the stove frame for (hopefully) future repairs

    :)
     
  8. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Twoberth Commendable you’ve got down to working on that Parasene, Duncan. I’m surprised it’s misbehaving, since it’s what I’d class as an ‘uncomplicated’ stove.

    You refer to (some) large burner’s use of that gauze plug restrictor but a Primus 85 I have has as a restrictor a plug with a pinhole in it, fractionally larger than the jet orifice. Gauze offers less of a restriction than that and I wonder whether you’ve gone in the wrong direction with the wider bore feed tube when a jet orifice-sized restrictor in the fuel line might work better.

    Either way, for a Parasene to throw up a problem is peculiar indeed.

    John
     
  9. Twoberth

    Twoberth United Kingdom Subscriber

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    Well, I think I am making progress - but more to do with solving the problem rather than understanding the cause. This is the progress...

    I tool the burner off the right hand Parasene tank and tubing and removed the gauze plug so that it is 'as received'. I then fitted it to a regular 2 pint stove tank and it worked PERFECTLY (below), so now I have proof that it is not the burner that is causing the pulsing.

    2021-12-12 001 003.JPG

    I then fitted back on it's original tubing without the gauze, and it pulses like crazy.

    2021-12-12 001 005.JPG
    2021-12-12 001 008.JPG
    2021-12-12 001 011.JPG

    There are no blockages in the Parasene tank/tubes and the fuel is clean, so now I know it is the tank/tubing configuration that is the root cause of the pulsing.

    I decided to take John's advice (@presscall ), and put in an orifice plate as well as a gauze plug.

    2021-12-12 001 012.JPG

    2021-12-12 001 013.JPG

    The result is that it still pulses, but the flame is acceptable.



    So what did I learn?

    First, the power of collective thinking promoted by posts on this site. Thanks to @kerophile I now understand what was happening (unstable vapour bubble causing resonance and therefore pulsing). I suspected the small diameter tank feeder tube was the cause (I still do), and first wanted to solve the problem 'at source' (i.e. below the burner) by using bigger feeder tubes, but then @presscall suggested more lateral thinking, in using an orifice plate.

    An important lesson is that you don't have to cure the root cause of the problem, or even know where it is. The solution can be produced remote from the cause - especially where fluid is flowing.
     
  10. hikerduane

    hikerduane Subscriber

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    Something similar in my Coleman AA lamp. Asbestos wick, fine mesh for a filter, a conical disc with three small holes last.
    Duane
     
  11. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Twoberth Well done that man! I know, not altogether resolved though. Maybe I’m flogging a suggestion to ridiculous extremes, but what if you insert a restrictor plate with a much smaller hole, or none at all and let the fuel percolate through the rim, which I assume is not a gas-tight fit with the burner inlet?
     
  12. Twoberth

    Twoberth United Kingdom Subscriber

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    @presscall John, that is exactly what i intend to do. In fact, while fiddling around with my small drills I though about putting in a blank restrictor plate, and just letting the fuel pass round the rim.

    I may do that, but now I have moved on to the frame. Does anyone have a Parasene decal image I can use please?
     
  13. ally

    ally Subscriber

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    @Twoberth

    sorry, I missed your alert

    no, sadly I broke the right hand burner pipework, it's in the pile while I calm down :lol:

    :)
     
  14. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    That creased me up laughing - been there, done that Ally.

    John
     
  15. Twoberth

    Twoberth United Kingdom Subscriber

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  16. Twoberth

    Twoberth United Kingdom Subscriber

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    Well, I still have not solved the pulsing problem.
    Following on from the discussion above, I tried;
    1. Gauze. (reported above)
    2. Gauze and orifice plate with .35 mm hole (reported above)
    3, Gauze and fiberglass wool (no improvement)
    4. Gauze and blank orifice plate (suggested above, no improvement)

    This is the blank brass orifice plate on top of the gauze (it was brazed to a steel washer so it can be removed with a magnet and picker)

    2022-01-03 001 011.JPG

    So what is the root cause of the pulsing, and what do I know so far.... ?

    1. It isn't the burners (they work perfectly on a normal stove tank)
    2. It is not easily solved by gauze and/or orifice plate.

    Whatever it is, it affects both burners, so..

    3. It may be the connecting pipe/fitting configuration.
    4. It may be the tank internal feed pipes.

    So the next experiment was to separate 3 and 4, and I did this by connecting one of the the Parasene tanks and one of the burners together using a short length of 10mm pipe.

    This produced no improvement, with pulsing regardless of the fuel level in the tank, and regardless of the burner/tank position. Below is the video of the tank on it's side, but there was the same effect with the tank in it's normal position and the burner sideways (with wired on cap).
    .

    So, I suspect it is the tank's internal pipe configuration that is causing the pulsing.

    Next step it to change the Parasene tank for a Optimus 111 tank, and use the Parasene pipework and burner. But before that I have to make the tank fittings....

    to be continued..
     
  17. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Curiouser and curiouser …
     
  18. Twoberth

    Twoberth United Kingdom Subscriber

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    Well, it's not the tank!

    I replaced the tank with a home-made nickel plated one shown here, mainly because it has the same thread fitting as the Parasene tank. However it still pulses,



    so the only other culprit could be the connectors that fix onto the base plate,

    2022-01-03 002 003.JPG
    2022-01-03 002 004.JPG
    2022-01-03 002 005.JPG

    I rigged up a connection that eliminated this component, and it got rid of the pulsing



    The question now is how do I eliminate or modify this component. Drilling a much larger hole through the connector, and countersinking the inlet pipe made no difference to the pulsing, so now I am back to square one.

    Any suggestions would be greatly appreciated.
     
  19. Aleks-S

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    IMHO. Puffing (pulsating) occurs when a cold portion of fuel enters a heated area and rapidly evaporates, taking away the calorie supply and (same time) pushing the liquid part of the fuel towards the tank. (like water dripping on a hot iron).
    I.e. the same "vapour bubble", but periodically appearing and disappearing. Or rather, changing in volume with a simultaneous change in pressure.

    This effect would be especially inherent on stovers with a horizontal feed tube, such as the Optimus-8r. That is why the wick is installed there - to moderate the puffing (helicopter sound).
    (See also the illustration to my "Engine theory of stoves puffing-gurgling" Prim Compact gasoline stove )

    I would try insert a large diameter wire (or a bunch) into (along) the tube to reduce it volume as much as possible. It will also provide a more smooth temperature distribution along the tube, especially if it partially will be placed inside the burner also.

    Or stuffing the feeding tube (betwen tank and burner) with fiberglass cord. But there is a menace that it will be pushed inside the tank by pulsiting. It is necessary somehow to immobilize it against of such pushing out.
     
  20. Twoberth

    Twoberth United Kingdom Subscriber

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    @Aleks-S Many thanks for your suggestions. I did experiment with the burner supply tube both vertical and horizontal and it made little difference, but I also note that in the last video where the pulsing was eliminated the burner was much higher than previously. I will try using a wick in the coming days and report the results.