Anyone buy a high pressure pump

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  • John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,743
    Socialist State of Maryland
    I shoot PCP's and use scuba tanks to refill them. Filling the tanks means a trip to the dive shop, which doesn't open till 1100, and costs $8 per fill. Currently, after a few 3000 LB fills, I have to top off with my hand pump. I'm getting to freaken old for that. :lol:

    I guess my biggest concern is the procedure for filling the bottle. I would assume you have to preload the pump line to a higher pressure than the tank before opening the tank valve but I haven't really researched it in depth.

    The Chinese pump prices are coming down which is the only reason I am considering this.
     

    BigTinBoat

    Active Member
    Jan 12, 2016
    335
    Eastern Baltimore County
    John,
    I've got a Shoebox compressor. Works great. I use a CAT ultra quiet compressor with it. If you watch any of the air gun forums you will find that most all of the Chinese compressors are "disposable", and basically made to fill guns, not scuba or scba tanks.

    I attach my bottle, start up the compressor and let the line pressure get up to about 1000psi and then slowly open the bottle valve to bring the line pressure up to the bottle pressure.
     

    Melnic

    Ultimate Member
    MDS Supporter
    Dec 27, 2012
    15,285
    HoCo
    Is the scuba tank at 3000 psi or 1000? I thought fill was 3000psi? how do you go from 1000 up to 3000?

    For scuba you also have a yearly inspection don't you plus another one every couple years?
     

    BigTinBoat

    Active Member
    Jan 12, 2016
    335
    Eastern Baltimore County
    I already have a 120 volt 125 PSI compressor. Can I use that instead of the CAT?

    Yes, I originally had a small 2 stack compressor but it was quite loud. This CAT is ultra quiet, I run my compressors in a spare bedroom upstairs. This way during the summer it is much drier air coming out.

    I've had my Shoebox (F8 model) for a few years now. Not the fastest, but durable and easily "rebuildable" with o-rings.
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,743
    Socialist State of Maryland
    Is the scuba tank at 3000 psi or 1000? I thought fill was 3000psi? how do you go from 1000 up to 3000?

    For scuba you also have a yearly inspection don't you plus another one every couple years?

    The average scuba tank is 3000 PSI. I never run it below 2000 as it makes for too much pumping to top off the PCP's. They need a visual inspection every year (done at my local dive shop for $17) Every five years it needs a HST NDT Inspection. I take mine to a guy in Frederick and he does the HST and annual for $42. You can have the local dive shops send tanks out but then you have to pay shipping.

    I just take the wife out for a drive to FDK, have lunch and drop off tank. In a couple of weeks, we go back and do it again. :lol:

    The shoebox air compressor is essentially a booster pump. It takes the 125 PSI from a normal compressor and brings it up in two stages up to 4500 psi. Because the shoebox pistons are small, the process takes a while. The pistons are something like 1/4 inch and 1/8th inch. :shocked3:
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,743
    Socialist State of Maryland
    Yes, I originally had a small 2 stack compressor but it was quite loud. This CAT is ultra quiet, I run my compressors in a spare bedroom upstairs. This way during the summer it is much drier air coming out.

    I've had my Shoebox (F8 model) for a few years now. Not the fastest, but durable and easily "rebuildable" with o-rings.

    How long would it take to go from 2000 to 3000 psi?
     

    BigTinBoat

    Active Member
    Jan 12, 2016
    335
    Eastern Baltimore County
    How long would it take to go from 2000 to 3000 psi?

    I have a 45min SCBA bottle and it usually takes approx 10min for each 100psi rise. (3500 to 4500 is about an hr and a half) Depending on the capacity of your scuba tank the time would vary.

    You mention that the Shoebox is a "booster pump". What's the difference between a "compressor" and a "booster pump"?
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,743
    Socialist State of Maryland
    Well a regular compressor takes ambient air and compresses it usually to about 125 -160 PSI. The booster takes that output and compresses it through two more stages in order to get higher pressure. Larger boosters are used with 1500 psi to pump up aircraft shock struts to 3500 PSI. Those are much larger boosters and take a shorter time. The hobby type pumps like the "shoebox" have smaller pistons and take longer to fill a bottle.
     

    BigTinBoat

    Active Member
    Jan 12, 2016
    335
    Eastern Baltimore County
    Well a regular compressor takes ambient air and compresses it usually to about 125 -160 PSI. The booster takes that output and compresses it through two more stages in order to get higher pressure. Larger boosters are used with 1500 psi to pump up aircraft shock struts to 3500 PSI. Those are much larger boosters and take a shorter time. The hobby type pumps like the "shoebox" have smaller pistons and take longer to fill a bottle.

    So basically you're saying a "booster" is a "pump" that compresses air starting at a higher then ambient pressure. Reason I questioned you is that most of the guys who "promote" those Chinese HPA "Compressors" use the term "booster" for the Shoebox somehow trying to indicate the Chinese compressors are somehow better. Didn't want you to get caught up in their hoopla. By their definition their "compressor" then consists of a "compressor" along with a (2nd stage) "booster".
    Believe me I would not trade my shoebox for 10 Chinese "compressors". Sure they might be a bit faster in the beginning, but I have not seen one report of anyone using one of them to fill bottle lasting more then a few hours of use.
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,743
    Socialist State of Maryland
    I used large boosters in my early years as an aviation mechanic that is why I know how they work. I checked out the company that sells the shoebox and selling replacement parts is is a big plus for me. If I'm going to fork out some dough for one of these, I want to be sure to get one that has good support.
     

    Vic

    Ultimate Member
    Jul 2, 2010
    1,454
    Whiteford, MD
    I have one of the chinese compressors that goes up to 4500 psi. It works okay, but keeping it cool is a little bit of a pain. I paid $250 for mine but think if I had to do it again I'd probably save up and get one of the Venturi Air compressors. I think they look pretty solid and should last years. I feel my chinese is starting to die and it is only a year or so old. Guess we'll see. I think some of the smaller VA pumps are only around $500 and some will operate off 110 VAC or off your vehicles 12 VDC. Since PCPs are getting so popular I think the personal compressors are going to become more abundant so keep your eyes open.

    Again, the big thing I dislike with my chinese one is keeping it cool with ice water. If fills my small tank pretty fast, but gets hot pretty fast too, even with ice water running through it.
    V
     

    BigTinBoat

    Active Member
    Jan 12, 2016
    335
    Eastern Baltimore County
    I used large boosters in my early years as an aviation mechanic that is why I know how they work. I checked out the company that sells the shoebox and selling replacement parts is is a big plus for me. If I'm going to fork out some dough for one of these, I want to be sure to get one that has good support.

    From what I've seen Tom Kayne offers fantastic service. And the only spares I have purchased are the hard o-rings. Tom sells those, but you can buy much cheaper from an o-ring supplier.
     

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