SVEA 123R slow, minor issues

Discussion in 'Fettling Forum' started by askvictor, May 21, 2019.

  1. askvictor Australia

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    So while cleaning out the camping cupboard, I came across a svea 123R that I haven't used for a couple of decades. I decided to rebuild it, using BernieDawg's youtube videos. I also replaced the fuel seal. It works, but takes about 12 minutes to boil 1L of water (air temp 15 deg C, almost no wind). It seems to be a bit inconsistent in heat output (judging by the noise - it seems to sometimes sound faster, sometimes slower). Any ideas on what I can do to speed it up?

    There's also a tiny bit of flame leaking out from the adjustment tap - is this just a matter of tightening the nut in a bit more to deform the graphite collar?

    Also, does the pip need replacing (i.e. how important is it to replace it)? I don't have the penta-key to remove it; if the original rubber in the pip has hardened up, will it still function as intended? What's the failure mode of the pip when the rubber has aged?
     
  2. JP2

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    Hi
    Yes tightening the nut will stop the leak but you should do a bunk test to make sure it is the only one. If you stove has never had any maintenance, I will go for it to make sure everything is right. Here a link to show you how it is done.
    Have fun

    SVEA 123R Disassembly
     
  3. itchy

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    A liter of water in 12 min is pretty good for a little stove like this but boil times can also depend on the pot shape. I'd run it a few more times and make sure not to fill the tank too full as that can slow things down quite a bit. It sounds to me like you have done a good job.

    When you tighten the spindle nut, do it very gently and in steps. Too much will make the spindle tight to turn. A little flame at the spindle is irritating but does no harm in the short term.

    Also a leaking pip in the safety valve could result in a small flame when the pressure in the stove gets higher. However, the real danger would be if the stove overheated and there was no pressure release. IMO all the evidence of that ever happening has been hearsay (that will get some responses).
     
  4. snwcmpr

    snwcmpr Subscriber

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    I have only had and only seen a candle flame on the SRV.

    After preheat, slowly open the valve to increase flame. It is not like the kitchen stove .. ready as soon as you want it. It takes a few minutes for the tank to get hot and give the max pressure.

    After rebuild you might need to run a tank or two.
     
  5. Majicwrench

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    Like was said above you need to do a bunk test. Er, dunk test. Stick stove in fridge for a few minutes with cap loose, remove, tighten cap, submerge in bucket of warm water. Pressure will build in font and look for bubble. These need pressure or they are really weak.
     
  6. snwcmpr

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    Bunk (dunk) test .. agreed.
     
  7. askvictor Australia

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    OK; I've tightened the spindle nut which has stopped the leak there, but in a dunk test I'm getting a bubble of air from the SRV every 5 seconds (also, when it's running, it doesn't burn out of the pip, but if I direct a flame in that area it does give off some flame, so it's clearly leaking a little from there); I'd presume this means I need to replace the pip?
     
  8. JP2

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  9. askvictor Australia

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    Yep, flame is nice and blue. Have just replaced the pip (using a very dodgily constructed penta-key ground down from a hex key, which in turn is also replacing one of the lost 'legs' of the stove), but I'm wondering if it's worth putting some loctite/threadlocker on to the thread? Certainly before I heated the SRV up to break the previous threadlocker I wouldn't have had a chance, but once it's gone, is it worth replacing?
     
  10. Tony Press

    Tony Press Australia Subscriber

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    @askvictor

    I always replace with a medium strength threadlock.

    Cheers

    Tony
     
  11. JP2

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    @Tony Press
    Hi, with the medium one, do you still have to heat it when you wanna go back there or a little force suffice?
     
  12. askvictor Australia

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    First up - thanks everyone for the replies!

    After replacing the pip, and trying another bunk test, there was still a bubble pop up from the SRV every few seconds. I tightened the SRV some more (I think to beyond where it started), which stopped the leak (well, a bubble formed inside the SRV, but didn't leave, so it _seems_ to be enough. I can still activate the spring from the inside easily enough, so I'm figuring it will still work as a safety (yes, I've read there are two schools of thought on this matter).

    Regarding the dunk test - does the fact of bubbles leaving the fuel tank mean that some water has gotten in, or should the pressure have been sufficient to prevent this?
     
  13. Tony Press

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    I set the pip up and test it without thread lock; then I carefully count the number of turns to loosen it again (not right off), apply thread lock, and re-tighten to the correct number of turns.

    I then test again to make sure.

    I always use heat to break any threadlock where soft brass is involved.

    Tony
     
  14. JP2

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    Look like you did a good job.
     
  15. askvictor Australia

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    Hmm; after replacing the pip and threadlocking the nut into place, and a dunk test (very, very slow bubble forming from the pip), I tested it out in the real world. Started fine, built up some good heat, but then a flame started coming out of the SRV. Initially small/candle like, it started to get bigger an bolder until it seemed it wasn't going to turn around - I turned off the fuel and doused the thing with water.

    Any suggestions what to next? I wasn't using a windshield or anything that would create undue pressure in the tank, so I suspect the problem would be with the SRV itself, but with a new pip, and it being tightened in quite far (or so I though) I don't know - I guess tightening it further might be a thing if it's releasing at too low a pressure. Or is there something else I'm not considering?
     
  16. JP2

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    Hi, what model of srv do you have? On most models a new spring is 13 mm long. How long is yours?
    Some pictures could be nice.
     
  17. askvictor Australia

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    Not sure of the model of the SRV (or how to identify); I can only presume it came with the stove, which I think was late 70s or 80s vintage; it uses a penta-key for disassembly. Photo of disassembled SRV is attached. The spring is about 9mm; does this mean the spring needs replacing?

    IMG_20190602_132835.jpg
     
  18. JP2

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    Ok yes 13mm long spring for your pantagone srv is good but I can not say that it will be in the pressure norm if you straight you spring to 13mm but it will probably stop the leak.
    To make sure it will be ok, you can still make a test as on the following link.
    For safety reasons, I can't tell you it is ok, it is your responsibility to make sure it is ok.
    Here the link
    Simple way to check an SRV
     
  19. Tony Press

    Tony Press Australia Subscriber

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    The simple answer is that either the pip is not seating properly, or the SRV is set too lightly.

    1. First tighten the penta a quarter of a turn and test (not by running the stove, but by putting a cold stove in warm water with the spindle closed). Repeat if still leaking.

    2. If that doesn’t work, take it apart again and make sure the pip is level in the pip holder, and the mating surface is clean. Stretch the spring about 15%. Put it all back together, and do 1.

    Cheers

    Tony
     
  20. askvictor Australia

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    Thanks for all of the suggestions :)

    Does stretching the spring change anything in the long term? I would have thought this would be lost once it gets compressed again. Are there any specs on the spring if I were to replace it?

    I'll check the pip is sitting properly, though given the fuel release from the pip got higher as the temperature increased, I would not have thought this would be the problem.