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Thread: SCUBA Tank Vented - grrrrrrrrrr....

  1. #1
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    SCUBA Tank Vented - grrrrrrrrrr....

    I was topping up my 80 CF SCUBA tank yesterday with my ShoeBox compressor and went in the house for dinner with the tank at about 2800 psi.... It takes an hour to do 150 psi, and I was back outside 45 minutes later.... Looked at the gauge on the fill yoke and it was at ZERO.... The outside of the tank was covered in condensation so I suspected it blew the yoke O-ring.... Took off the fill clamp and it looked fine.... Then I noticed a puddle on the floor beside the tank....

    My fill line from the ShoeBox to the SCUBA tank has a 5000 psi glycerine filled gauge on it.... YUP!.... the puddle was glycerine and the safety plug in the back of the gauge was long gone and the gauge was empty and the needle was stuck at 1000 psi.... Goodbye gauge and goodbye a full tank of air....

    If I had been in the shop at the time the gauge blew it would have scared the heck out of me.... but I probably would have been able to shut the tank valve before I lost all the air.... It wasn't a violent event, as the gylcerine was just lying in a puddle below the gauge....

    Anyway, now my poor ShoeBox has to fill my SCUBA tank from empty.... 20 hours and counting....

    Bob

  2. #2
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    And as a sequel to what happened yesterday, today my small oil-less shop compressor quit.... I salvaged the parts from it and I'm using the tank as a holding tank between my big shop compressor and the ShoeBox.... I'm running a filter/oil trap between my shop compressor and the small tank, and then a dessicant filter between that and the ShoeBox.... The new setup should be better than the old one.... and the big compressor won't run nearly as often....

    Bob

  3. #3
    ShoeBox Designer TomKaye's Avatar
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    Well for once its not MY stuff busting!! Sorry you had trouble Bob but it sounds like your on top of it.

    Tom

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    And nowwwwwwwwwwww.... my ShoeBox won't build pressure past 2600 psi without shutting off.... I turned off the valve in the SCUBA tank but left the line and ShoeBox pressurized (shut off) overnight to check for leaks and it was fine.... so I figured that was pretty good since I have about 70-75 hours on it with no rebuild so far.... There are no external leaks anywhere but even with the collar full right it shuts off at 2600....

    Where do I look?....

    Bob

  5. #5
    ShoeBox Designer TomKaye's Avatar
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    You have a partial leak in the lower cylinder. Replace the orings in that one first.

    TK

  6. #6
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    Thanks for the quick reply, Tom... I pulled the bottom cylinder apart, and the first thing I noticed was that the retaining nut on the piston end was very loose.... I thought about just tightening that and trying it but didn't.... I followed your video and on disassembly I couldn't find the second O-ring.... nowhere to be seen or hooked out.... Then I pulled apart the check valve and the O-ring was in there!.... I guess somehow it became dislodged and the piston drove it down there!.... I couldn't believe it either!.... I examined both O-rings, and the one that was driven out of place was a bit distorted (oval) but otherwise looked OK, and the outer O-ring (closest to the crankshaft) was perfect.... I tried both O-rings on the piston, and the outer one was nice and snug but the inner one (that had been dislodged) was just a sliding fit (snug, but not as tight as the outer one)....

    There was a fair amount of grease in everything.... nowhere near packed full, but a reasonable amount in all the nooks and crannies.... I removed all the O-rings and cleaned the check valve, spring, and cylinder with varsol, blew it dry, and reassembled it using Dow 55 O-ring lube.... I swapped the two cylinder O-rings, putting the snugger, outer one on the high pressure side, nearest the check valve.... Upon reassembly, I tested for leaks with soapy water at 90 psi, found none, so fired it up.... It worked fine, so I readjusted the spring collar to just clear the Oilite bushing (ie minimum setting).... I pressurized just the fill hose and it was just starting to tick the side of the switch at 3300 psi.... I don't know how much adjustment there is (pressure wise) on the spring.... but I now have the full adjustment remaining to increase the shutoff pressure....

    I nearly always just fill my SCUBA tank, only rarely using it to fill a 4500 psi bottle I have (and it's full right now).... so I don't yet know if it can be adjusted up to 4500 psi or not.... but I'm back in business for filling my SCUBA.... In case you were concerned, I have a 4.5K burst disc inline between the ShoeBox and my SCUBA tank for safety.... I'm sure impressed by this little compressor.... and by how easy it is to rebuild.... Thanks for a great product, and even better customer service....

    Bob

  7. #7
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    See Below....
    Last edited by rsterne; 09-07-2011 at 11:45 PM.

  8. #8
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    Well after a partial clean and rebuild of my ShoeBox my SCUBA tank is once again full.... The first maintenance was after 70-75 hours of use....

    Bob

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    Hi.. just wanted to know if you are using your scuba tank for actual diving?

    Thx

  10. #10
    ShoeBox Designer TomKaye's Avatar
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    No he uses it for air rifles. The Shoebox is not certified for breathing air and has no filters.

    Tom