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Padmount Schrader valve size

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    Padmount Schrader valve size

    Has anyone ever come across a pad mount transformer that has a larger than normal Schrader valve size? I came across one a while ago that our chuck wouldn't fit onto.

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    Quote Originally Posted by phasor View Post
    Has anyone ever come across a pad mount transformer that has a larger than normal Schrader valve size? I came across one a while ago that our chuck wouldn't fit onto.
    Yes, I have seen these its like a 3/8 vs a 1/2 or something. What did you end up doing, were you able to make anything work? I'd like to know where to find the proper fitting please post a link if anyone knows I can't find them at the normal hardware stores.

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    Quote Originally Posted by SecondGen View Post
    Yes, I have seen these its like a 3/8 vs a 1/2 or something. What did you end up doing, were you able to make anything work? I'd like to know where to find the proper fitting please post a link if anyone knows I can't find them at the normal hardware stores.
    I can't remember how we dealt with that one it was a while ago but I've been doing some research and I can't really find any info. Everything I've found online basically says all schraders are the same size.

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    I have not found any hardware to fit this schrader valve.

    We have done one of two options, first being just relieve the vacuum to atmosphere (not our preference) which is the recommendation from the manufacturer.
    The second option is to take a poly bag and tape it to the end of the nitrogen output. Tape this bag around the relief valve and fill the bag up with nitrogen. As you pull the relief valve, continue to fill the bag with nitrogen and the relief valve will suck in nitrogen as you remove the vacuum. Unfortunately, neither method will pressurize the transformer, but you won't be taking a sample with a vacuum on the transformer.

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    Quote Originally Posted by phasor View Post
    I can't remember how we dealt with that one it was a while ago but I've been doing some research and I can't really find any info. Everything I've found online basically says all schraders are the same size.
    Schrader Valves are not all the same size, just most are the 1/4" variety.
    Dimensions
    Schrader valves are classified by their material, diameter of intended rim hole, length, and shape.

    TR-4, straight metal stem (8 mm dia.)
    TR-6, straight metal stem (8 mm dia.)
    TR-13, straight rubber stem (11.5 mm dia.)
    TR-15, straight rubber stem (16 mm dia.)
    TR-87, short 90 metal stem (10 mm dia.)
    TR-87C, tall 90 metal stem (10 mm dia.)
    and also:

    TR 413, 0.453 in (11.5 mm) rim hole diam. 1.25 in (32 mm) long
    TR 415, 0.625 in (15.9 mm) rim hole diam. 1.25 in (32 mm) long
    TR 418, 0.453 in (11.5 mm) rim hole diam. 2 in (51 mm) long
    TR 425, 0.625 in (15.9 mm) rim hole diam. 2 in (51 mm) long
    The standard Schrader valve has the following threads:

    External thread
    Metric: 7.7 mm OD, thread root diameter is 6.9 mm 0.794 mm pitch
    Imperial: 0.305 in OD, thread root diameter 0.271 in 32 tpi (threads per inch; thread density)
    Internal thread (to accept the threaded valve core)
    Metric: 5.30 mm OD 0.706 mm pitch
    Imperial: 0.209 in OD 36 tpi

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