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  • Compressor check valve repair

    I have a Harbor Freight air compressor:
    http://manuals.harborfreight.com/man...5999/95498.pdf

    After a few years it would not reach the full 100 PSI pressure and I found that the check valve was leaking. I took it apart and found that it had a soft silicone valve that had become distorted by the spring, and I figured that a replacement from HF would have the same design flaw. So I decided to try and fix it by making a better valve seal. I was going to use brass but I did not have any, so instead I used a piece of Delrin plastic rod. I also used a counterbore to clean up the seat in the valve for a better seal. Here is the piece where I was using a boring bar to create a pocket for the spring:



    Here is the disassembled valve:



    I found that the OD was too large to fit in the brass cap, so I had to turn it down more. The small end was too small to fit in the lathe chuck, so I used a mini-lathe chuck to hold it, and the live center to keep it from wobbling. Here's the setup:



    I used an O-ring in a small groove on the short part, but it didn't seem to seal very well. So I added a larger O-ring and it seems to work reasonably well, testing it by blowing into the threaded connector that goes to the tank. It's still not perfect, but perhaps with higher pressure than I can produce (even though some people have called me a blow-hard ), it might work well enough.

    This was to some extent a practice project, and I might redo it in brass, but I wanted to know if anyone had any experience fixing a valve like this. I might use some soft flat silicone gasket rather than the O-ring.
    http://pauleschoen.com/pix/PM08_P76_P54.png
    Paul , P S Technology, Inc. and MrTibbs
    USA Maryland 21030

  • #2
    Originally posted by PStechPaul View Post
    I have a Harbor Freight air compressor:
    http://manuals.harborfreight.com/man...5999/95498.pdf

    After a few years it would not reach the full 100 PSI pressure and I found that the check valve was leaking. I took it apart and found that it had a soft silicone valve that had become distorted by the spring, and I figured that a replacement from HF would have the same design flaw. So I decided to try and fix it by making a better valve seal. I was going to use brass but I did not have any, so instead I used a piece of Delrin plastic rod. I also used a counterbore to clean up the seat in the valve for a better seal. Here is the piece where I was using a boring bar to create a pocket for the spring:



    Here is the disassembled valve:



    I found that the OD was too large to fit in the brass cap, so I had to turn it down more. The small end was too small to fit in the lathe chuck, so I used a mini-lathe chuck to hold it, and the live center to keep it from wobbling. Here's the setup:



    I used an O-ring in a small groove on the short part, but it didn't seem to seal very well. So I added a larger O-ring and it seems to work reasonably well, testing it by blowing into the threaded connector that goes to the tank. It's still not perfect, but perhaps with higher pressure than I can produce (even though some people have called me a blow-hard ), it might work well enough.

    This was to some extent a practice project, and I might redo it in brass, but I wanted to know if anyone had any experience fixing a valve like this. I might use some soft flat silicone gasket rather than the O-ring.
    I have this same problem and hope to get an answer to my problem. My check valve is leaking on my 100l two horse compressor. I open the check valve and noticed the washer which is spring loaded was worn. I machined a new washer from delrin. It worked beautifully and the compressor stopped its tell tale hissing noise which shows itself by the pressure switch. But after a couple of cycles it started again. To my surprise the delrin washer was melted by the heat of the compressed air going into the tank.Is there a product that is easily machinable that has sealing properties and is heat resistant. Something with a shore hardness that will seal itself against a brass seat.

    Comment


    • #3
      Originally posted by plunger View Post
      .Is there a product that is easily machinable that has sealing properties and is heat resistant. Something with a shore hardness that will seal itself against a brass seat.
      I repaired my compressor non-return with a 90 Shore hardness Polyurethane seal,

      - Nick
      If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

      Comment


      • #4
        Looking at your first picture, it seems that the boring bar should be rotated 90 degrees so that the narrow edge is toward the front of the lathe with the top of the bit on the center line. Like this:



        Do you have a reason for putting it that way?
        Last edited by winchman; 11-04-2016, 02:36 AM.
        Any products mentioned in my posts have been endorsed by their manufacturer.

        Comment


        • #5
          I have machined a brass washer plate to hold a normal tap washer and will see how it stands up. I put a washer in my oven at 284 degree celcius and it seemed to have no effect. Time will tell.

          Comment


          • #6
            Originally posted by winchman View Post
            Looking at your first picture, it seems that the boring bar should be rotated 90 degrees so that the narrow edge is toward the front of the lathe with the top of the bit on the center line. Like this:



            Do you have a reason for putting it that way?

            I'm not sure why I did that. It was in 2013 which was before I took machine shop classes, so I was doing a lot of things that were not quite correct. If you look closely at the picture, you may see that the boring bar was held in a boring head that had an MT2 taper, which I had in the tailstock. I had not thought about holding it in the turret toolholder as pictured above. Here is a picture that shows it better (or worse):

            http://pauleschoen.com/pix/PM08_P76_P54.png
            Paul , P S Technology, Inc. and MrTibbs
            USA Maryland 21030

            Comment


            • #7
              Originally posted by PStechPaul View Post
              I'm not sure why I did that. It was in 2013 which was before I took machine shop classes, so I was doing a lot of things that were not quite correct. If you look closely at the picture, you may see that the boring bar was held in a boring head that had an MT2 taper, which I had in the tailstock. I had not thought about holding it in the turret toolholder as pictured above. Here is a picture that shows it better (or worse):

              Does your compressor work.

              Comment


              • #8
                It still works (last time I checked, several months ago), but it gradually loses pressure. I don't use it often. If I did, I might do more to fix it right. I probably need to do a better job of smoothing the surfaces on which the O-ring seats. A thin coating of grease or silicone may also help.
                http://pauleschoen.com/pix/PM08_P76_P54.png
                Paul , P S Technology, Inc. and MrTibbs
                USA Maryland 21030

                Comment


                • #9
                  How about a piece of some of the silicone kitchen products;are heat resistant to 450 degrees F.

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