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Thread: Filling station air leak

  1. #1
    Marksman

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    Default Filling station air leak

    Good day to all

    I have a secondhand filling station that leaks air at the red arrows.




    I have tried the following:


    • Using white plumbers thread tape (PTFE), from winding a few layers to a thick layer. It seems to disintegrate as I cannot see any tape on the threaded parts when I unscrew the connections.
    • Using nothing at all after cleaning the threads.


    I have tightened the fittings as far as I feel comfortable and near the end of my strength. I have noticed that the thread of the rifle's filling adapter does not completely screw across all the thread and not sure whether they are compatible?

    I have searched this forum and found mention of PTFE tape only. Other resources on the web mentions Loctite 545, Vibra-TITE 444 and 446, and Permatex 592.

    I have no previous experience with high pressure fittings and would appreciate all assistance from the vast experience on the forum.

    Thanks
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  2. #2
    Sharp Shooter

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    I had a problem with one of my, what I did was, put a o-ring in it and screw in the parts, just have to find the right diameter o-rings, otherwise it will "squash it and will damage the seal and leak again.
    Hope that helps, it worked for me.
    Marcos.
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  3. #3
    SAFTAA FT Colours '15
    BOSS 2017

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    Try a bonded washer
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  4. #4
    Marksman

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    Thanks gfighter

    So, this is a process of hit and miss until you find the right size (after judging approximately)?

    Quote Originally Posted by Mark_F View Post
    Try a bonded washer
    Thanks Mark F.

    Any specific washer? Supplier? Google says it is a rubber washer bonded to metal. And I assume the rubber side goes in first with metal against male thread?
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  5. #5
    Sharp Shooter

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    Quote Originally Posted by Lood View Post
    Thanks gfighter

    So, this is a process of hit and miss until you find the right size (after judging approximately)?
    Normally a "fat" o-ring with the same ID of the female connector as the thread only goes so far, find one more/less the same 'space' where the thread ends and you're good to go.
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  6. #6
    Marksman

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    Thanks. I will need about 5mm at the probe end. Could I use two o-rings? Not sure if I would cover 5mm.

    The thread at the clamp goes all the way.
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  7. #7
    Sharp Shooter

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    Quote Originally Posted by Lood View Post
    Thanks. I will need about 5mm at the probe end. Could I use two o-rings? Not sure if I would cover 5mm.

    The thread at the clamp goes all the way.
    Not sure what you mean about 5mm, I was talking to put inside the connectors, if the thread goes all the way, put a thinner o-ring, and remember doesn't have to be overly tight, Also if it's the case šll the way in, maybe a bonded washer at the outside as Mark suggested. The 5mm that you're talking about is the outside "gap", not the inside, the thread normally don't go all the way in, it leaves a small space between the male and female "end wall" where should have a seal.
    You put the o-ring inside the one that don't have the thread in the outside but the inside, that's the female, the male has thread outside.
    Is that clear?
    Last edited by gfighter; 18-09-17 at 16:45.
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  8. #8
    Marksman

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    I estimate that there should be about 5mm of space left in front of the male thread towards the female "end wall" inside the female thread. That is judging by the white PTFE still protruding. I grasp your instructions. Will see if I can fix it that way.

    Thanks
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  9. #9
    Sharp Shooter

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    Put an o-ring inside, it will seal, don't worry about the outside gaps.
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  10. #10
    Marksman
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    Your problem most likely stem from not identifying the types of connections you are using. As a general rule high pressure air (or hydraulic) fittings / connections do not seal by using the thread of the fittings / parts. The threads are used to hold the parts together, thus providing mechanical force to apply pressure on the real sealing surfaces. The sealing surfaces can be coned shape or flat surfaces.

    Coned shaped surfaces
    The coned shaped surfaces are visible on the front inside of the connecting parts, one part will have a female cone shape and the mating half of course a male cone.


    Above an example of cone faced fittings. The coned shaped surface must be of the same standard e.g BSP, JIC, etc.

    Flat faced surfaces
    For flat faced sealing surfaces you will have to use a bonded washer.
    Below a picture of a bonded washer.


    Maybe you should visit a good hydraulics company in your area so that the people there can assist you with identifying those fittings.
    Last edited by Marius in Afrika; 18-09-17 at 18:12.
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  11. #11
    SAFTAA FT Colours '15
    BOSS 2017

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    Quote Originally Posted by Lood View Post
    Any specific washer? Supplier? Google says it is a rubber washer bonded to metal. And I assume the rubber side goes in first with metal against male thread?
    Like these :
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  12. #12
    Marksman

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    I bought the setup (my first) as is, but have a feeling it is not supposed to be sealed or modified to obtain a proper seal.

    The rifle's filling adapter (female) looks cone shaped inside while the male is flat. Gfighter's o-ring might temporarily remedy this.

    On the connection to the clamp I notice that the only surface is located way in the back past the entry point of the pressure gauge. Thus, too far to act as a sealing surface. This might require a bonded washer as per Mark-F.

    Have obtained o-rings. Will keep you updated. Thanks
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  13. #13
    Marksman

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    Some feedback...

    O-ring seem to have sorted out leak at the quick fill adapter. I believe the problem there is a flat male against cone shaped female.

    Tried some Pratley Pratlock on the connection to the filling station clamp - out of desperation. Did not work. Have not had a chance to get hold of a caliper but I suspect the male thread is tapered.

    Will keep you updated
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  14. #14
    Sharp Shooter

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    "have you tried the bond washer on that connection?
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  15. #15
    Marksman

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    Could not get hold of one yet. My workshop manager colleague supplied me with a treasure trove of o-rings but returned a blank stare when I asked him if he has bonded washers...

    We are in the semi sticks. Not sure who can supply them? We have plenty agricultural related businesses in the area
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