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  • #31
    Pressure drop

    Originally posted by Dragons_fire
    my old mini 8-gallon compressor used to sit in the corner of the garage on the pallet that my mill/drill came on!!

    i think if i dont mount it to the floor, and i take it off the pallet, it would tip over, so im gonna try leaving it on there. tomorrow morning i might try throwing a rubber mat under the pallet just to reduce a little noise...

    i also need to see if i can take the regulators back tomorrow morning... i picked up 2 for $12 each, but if i use an air ratchet (as an example) that i want to regulate to 90psi, when the tool is running, the gauge says 90, but when i stop it slowly builds up to 150psi, and the when i use the ratchet again, it has a 150psi burst at the beginning and then goes back down to 90psi. they siad they operate up to 160psi, but it alsmost seems like there is a little bypass that eventually pressurizes the hose to 150... i want to use it for some spray guns and other stuff that needs to be regualted a little more accurately...
    Thanks df.

    What you have is a case of "pressure drop" that occurs whenever air (gas), water (fluid) or electricity (??) "flows" from one point to another. Without that "pressure drop" (differential) there will be no "current". In the static state no flow/current will occur. This pressure differential may probably be due - at least in part - to the "draw-down" (usage rate) of the tool being in excess of the compressor, regulator, hose (size and length), fittings, orifices etc. all causing an individual "pressure" (and "flow") "drops/losses" which are additive. It may well be that your compressor capacity (free air delivery) is inadequate. You can do better quite often with a larger receiver. The whole system from compressor to tool/s needs to be assessed. The regulator/s may well be part of the problem but not be all or most of it.

    I'd be careful of that compressor tank pressure at 150 psi as it seems a bit on the high side to me.

    I'd be careful of the probably single-phase motor driving it as well.

    Most "domestic/portable" (small-ish) ones here in OZ are limited to 7 bar (105psi). I have a higher pressure one that is 10 bar (145psi) - as rated and as made, tested and certified.

    Many "cheap" regulators are limited to 7 bar, have high pressure drops and low flow rates.

    Good regulators for my compressor are lots more expensive than the "cheapies".

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    • #32
      Mine had been sitting on the pallet sitting on an old rubber tire for the past 9 years. The rubber absorbs the vibration.

      Comment


      • #33
        Laz,
        So, -- do you have much of a problem with condensation -- I would assume NOT out at the exit points, with that much effort to prevent it! -- but, when you do a drain, do you get much, do need to do a drain often?

        Your part of the world and mine should be pretty similar in the temp/hum ranges and, as I mentioned earlier, and Lane says, we just dont have a problem with it.

        Since you've shown your piping set-up, a curious thought comes to mind.... (pause here to let the flame police not read any further)--- Lane and I (and Henry) have (gasp!) plastic pipe extensively plumbed from the compressor mounted outside on through our shops, with drops and runs going every which way .... could this possibly have an effect on the forming of condensation?

        Anybody heard/know of any thing about this possibly being a factor?

        Tho, even here, there is a disparity.... My shop is the largest at 28x32 with by far the most plumbing (I like an air source everywhere!), then Henrys at 24x24? (not sure) with less plumbing and then Lanes little "closet" shop with the least plumbing. But, even Lanes has probably got over a hundred feet...
        If everything seems to be going well, you have obviously overlooked something........

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        • #34
          Originally posted by oldtiffie
          It may well be that your compressor capacity (free air delivery) is inadequate. You can do better quite often with a larger receiver. The whole system from compressor to tool/s needs to be assessed. The regulator/s may well be part of the problem but not be all or most of it.

          I'd be careful of that compressor tank pressure at 150 psi as it seems a bit on the high side to me.

          I'd be careful of the probably single-phase motor driving it as well.

          Most "domestic/portable" (small-ish) ones here in OZ are limited to 7 bar
          those 2 regulators are on the new 60-gal compressor.

          im not sure if i explained it right before, but whats happening, is if i have a setup that goes from the tank - regulator - 25ft hose with a blow gun on the end, i should be able to regulate it down to 20psi. then i should only get 20 psi at the gun no matter what... right?? if i have a gauge at the gun, it will go up to 150psi (approximately, its probably more like 145) and then when i pull the trigger, i get a burst of 150psi, and then it goes back down to 20psi. if i let go of the trigger, the hose will go back to 150psi in about 30 seconds. then i get a burst when i pull the trigger again.

          mostly i use stuff like air ratchets and an air sander. so a little blast of higher pressure shouldn't affect too much, but im worries that while the tool is not in use, the valve in the tool is holding the higher pressure. i also would like to us it for painting sometime soon, and i think it would need to be more accurate than that for painting. ..

          thanks guys...

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          • #35
            air compressor blow-off

            Hi all: Before you place the compressor in its resting place, consider removing the pet-cock at the bottom of the tank and run a length of air hose to a position suitable for you to bleed off the condensate easily. I've done this at work and at my shop. This means it gets bled a heck of a lot more often than when I had to get down on the floor and do it. Wayne.

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            • #36
              Originally posted by Bill Pace
              So, -- do you have much of a problem with condensation -- when you do a drain, do you get much, do need to do a drain often?
              No problems with condensation Bill -- the system works great. But when I'm painting I still use an air separator, and it still removes water. No matter how much you do passively, you'll only get ~ 75% of the water out of the system. That's fine for air tools, but for painting, and maybe plasma, good plumbing is not enough.

              I didn't do anything clever, I just followed Devilbiss' airline plumbing recommendations:
              • 3/4" pipe for up to 20 CFM
              • Slope the pipe back to the compressor 4" per 50 ft
              • First air drop should be at least 25 feet from the compressor

              http://www.autorefinishdevilbiss.com...c/hosefits.pdf


              My "shop" is tucked into 1/2 of my 2-car garage, so I didn't have the wall space for 25 feet before the first air drop. So I folded-up the 25 feet like an accordion.
              I built that system in 2005, when copper was reasonably priced. It's crazy expensive now -- I wish I had added more drops when I had the chance

              Lane and I (and Henry) have (gasp!) plastic pipe extensively plumbed from the compressor mounted outside on through our shops, with drops and runs going every which way .... could this possibly have an effect on the forming of condensation?
              The only thing that really matters is that you have enough pipe run to give the air time to cool off and condense the water out. Copper will cool the air down faster (in theory), but you've probably got much longer runs than I do.
              Last edited by lazlo; 06-25-2008, 12:36 PM.
              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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              • #37
                Originally posted by wtrueman
                Hi all: Before you place the compressor in its resting place, consider removing the pet-cock at the bottom of the tank and run a length of air hose to a position suitable for you to bleed off the condensate easily.
                Yep, that's basically what I described here:

                Originally posted by Lazlo
                I plumbed a kick lever with a ball valve on the bottom of the tank, and the 2x4's are so I can purge the tank with flick of my toe
                I added a ball valve with a long lever (kick plate) to the bottom of the tank with a section of pipe that directs the water to the door of the garage.
                The only thing I need to add is one of those bronze silencers. 120 PSI is friggin' loud coming directly out of the tank. Scares the Hell out of my kids
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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