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  • Air compressor controls

    The thread on PVC air lines brought up several questions about compressor controls. I have a single stage five hp compressor. It has a magnetic starter relay that is controlled by the pressure switch set aprox 90/130. Airing tires and running the bead blaster are the only things that I do that that uses near this capacity. I have been considering installing a second pressure switch set 40/60 and a valve to select which controls the compressor. Both these functions occur near the compressor so a manual selector valve would not be a problem.Any suggestions would be appreciated.
    Byron Boucher
    Burnet, TX

  • #2
    I have a similar situation, a 120 gallon 10hp two stage 34 cfm @ 175 compressor and unless I am bead blasting I am not using close to its capacity. I have considered plumbing an entire new compressor into the same tank, say a 5hp two stage setup to run 120lbs, not 175. Then I could have the little compressor kick in at 100 and run to 120 and have the big compressor kick in at 90 and run all the way out. That way only a demand larger than could be satisfied by the smaller unit would actually kick on the big compressor.
    James Kilroy

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    • #3
      James, Interesting thread as I'm contemplating doing similar.

      I have a Hydrovane rotary compressor identical to this one.

      http://cgi.ebay.co.uk/Hydrovane-15-c...mZ110366609806

      Nice compressor, very, very quiet but after 10 years it's starting to pass a bit of oil thru the system, don't bother me as I don't spray and everything I use needs oil but it needs a service kit fitting.

      Recently as I posted in another post I bought another Hydrovane 15, tripod mounted, off Mad Arthur for £30 thinking it would be good for spares if nothing else, anyway a good service and it's OK to run but :-

      The tripod mounted ones, because they have no tank have a safety device so at a certain pressure they mechanically unload. The idea is so if someone just pipes it into a tank with no cut off switch they won't blow the tank up.

      Internally they are quite different to the normal tank mounted one.
      I don't want this system as at 110 pounds it will unload but the motor keeps running until pressure drops and it builds up again.
      Seems silly to me having a 4 hp motor running all day doing nothing.

      So I am going to remove the old incredibly noisy direct drive compressor that sits on a tank at the side of the original Hydrovane in the hay loft and fit this one onto the tank, both tanks 35 gallon and 45 gallon are already linked.

      I'll wire this in to the cut off switch on the direct drive compressor and drop it to 100 so the unloader valve doesn't cut in.

      Down stairs I'll fit a 3 position switch above the starter box and run a fresh control cable up. Low pressure, both, high pressure.

      That way I can send the original one in for service and still have air and then I have a choice whether I need air fast, 100 # or 150#

      For most things I can get away with about 90 pounds the only things that tax the system are the air tapper and the odd time I use an impact wrench.

      .
      .

      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



      Comment


      • #4
        Those hydrovanes are slick looking units. Don't recall seeing them over this side of the pond much.

        I am intrigued by the idea of having some kind of 3 position switch to give "off", "lo", and "hi" pressure air. I just wonder whether it will really lead to less motor running in the "lo" setting.

        Seems like the tank will buffer the actual pressure used, so changing that pressure switch is only going to reduce that buffer and make the motor run more often?

        Cheers,

        BW
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        • #5
          One consideration is that although you rarely need the higher pressure it does make for a larger "amount" of air in the tank. If you run the pressure switch at say half the present value then the compressor will cycle on/off twice as often.

          Comment


          • #6
            Originally posted by jkilroy
            I have a similar situation, a 120 gallon 10hp two stage 34 cfm @ 175 compressor and unless I am bead blasting I am not using close to its capacity. I have considered plumbing an entire new compressor into the same tank, say a 5hp two stage setup to run 120lbs, not 175. Then I could have the little compressor kick in at 100 and run to 120 and have the big compressor kick in at 90 and run all the way out. That way only a demand larger than could be satisfied by the smaller unit would actually kick on the big compressor.
            OK, but if you are using let's say, the bead blast cabinet......
            The pressure is at 175 psi in the tank and starts to fall as you use the cabinet.
            Pressure reaches 120 psi and the small compressor kicks on and runs.
            The use of the cabinet outruns the capacity of the small compressor and the psi falls to 90.
            The big compressor kicks in at this point.
            Now you have both compressors running at the same time until the psi is at 120, then the small compressor shuts off.
            The large one runs on until 175 psi is reached. Then shuts off.

            Sorry, I see no advantage in that set up at all.
            Maybe you can explain what the advantage is for us?
            pg

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            • #7
              99% of the time I am not using the bead blast booth so the small compressor will fulfill the vast majority of my need, the larger compressor will hardly ever run, I could probably leave it switched off unless I wanted to bead blast. If I get ready to bead blast I can just turn the smaller unit off or take advantage of another 12 or so CFM.

              Another reason to use a common tank is I don't want to take up space with another tank and I don't have to futz with my air plumbing.
              James Kilroy

              Comment


              • #8
                Originally posted by BobWarfield
                Those hydrovanes are slick looking units. Don't recall seeing them over this side of the pond much.

                I am intrigued by the idea of having some kind of 3 position switch to give "off", "lo", and "hi" pressure air. I just wonder whether it will really lead to less motor running in the "lo" setting.

                Seems like the tank will buffer the actual pressure used, so changing that pressure switch is only going to reduce that buffer and make the motor run more often?

                Cheers,

                BW
                Bob, They are nice, really quiet you can be working alongside one when it strikes up and still hold a conversation.

                I had to move to one when I got the CNC as it often runs late at night and my workshop is closer to my neighbour that to my house.
                the old direct drive unit is mega noisy and I didn't want to upset the guy next door, he's a good neighbour as are all of them round here but no point in pushing things when you can easily overcome a problem.

                I agree it will run more often but I found that from 0 to 80 took about 5 minutes, 80 to 100 took about 3 and 100 to 125 took about 4 as it has to work harder to overcome tank pressure.
                so I reckon that running at a lower pressure will reduce pump up time as opposed to unit of power used ?
                .
                .

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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