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  1. #1
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    Default Air Compressor Recommendation

    I currently have a 2nd hand ProAir compressor that uses a Swan SVU-202 head. The plate states it has a bore of 65mm and stroke of 51mm providing 15.54cfm or 440lpm. Looking at brochures for this Swan unit it appears that the free-air (actual output) is nearer to 8cfm or 225lpm.

    I have started using an el-cheapo mist cooler when cutting and the existing compressor seems to work at around a 50% duty cycle. It comes on every 30 odd seconds for around 30 odd seconds. This i fund noisey and annoying.

    I am thinking of getting a newer compressor that will not run for a long or with a much noise. In the sub $2000 area what are you using/ your recommendations?? I would prefer an upright unit, around 150 to 200L tank and maybe around 400lpm free air (just guessing at what would be required for it to run less).

    I would buy second hand again and also do not feel I need brand names. My compressor isn't used all day every day by a long shot.

  2. #2
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Mk1_Oz View Post
    I currently have a 2nd hand ProAir compressor that uses a Swan SVU-202 head. The plate states it has a bore of 65mm and stroke of 51mm providing 15.54cfm or 440lpm. Looking at brochures for this Swan unit it appears that the free-air (actual output) is nearer to 8cfm or 225lpm.

    I have started using an el-cheapo mist cooler when cutting and the existing compressor seems to work at around a 50% duty cycle. It comes on every 30 odd seconds for around 30 odd seconds. This i fund noisey and annoying.
    That sounds like a lot of air for a mister, what pressure are you using for the mister?

  3. #3
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    Started at 100psi but then turned it down to 85psi.

    It could be that my compressor is worn and not filling the tank as quick as it should. I would hedge thought a 100L tank filled at 100psi would have lasted a little longer than 30 seconds before turning on the motor.

    As I said before, $20 el-cheapo eBay mister. I find it needs quite an amount of air flow in order to suck up the coolant.

  4. #4
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    Quote Originally Posted by Mk1_Oz View Post
    In the sub $2000 area what are you using/ your recommendations?? I would prefer an upright unit, around 150 to 200L tank and maybe around 400lpm free air
    Not gonna happen unless you have 3-phase.

  5. #5
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    Quote Originally Posted by elanjacobs View Post
    Not gonna happen unless you have 3-phase.
    Should have said that I have 3-phase although would like to keep it under a 5hp motor if poss.

  6. #6
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    I’d say you’ve got enough output from the compressor, but need a larger receiver. I picked up a decent size vertical one and put it outside. If I’m just using the air blower for clearing chips etc I’ll go a few days without having the compressor on.
    I’d also check the pressure switch settings on the compressor.
    I’d increase the cutout to 120psi and drop the cut in to just above what you need for the mister.
    Compressor will run for longer but not as often.

    Steve

  7. #7
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    Quote Originally Posted by Mk1_Oz View Post
    I have started using an el-cheapo mist cooler...
    I think that's your problem, not the compressor. My little 6.5cfm Clisby has no problem running my Noga Mini Cool. From memory I run it at around 30psi. If you need 85psi to get your el-cheapo to work it must be very inefficient. A Noga will be cheaper than a new compressor.
    Chris

  8. #8
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    Quote Originally Posted by BobL View Post
    That sounds like a lot of air for a mister, what pressure are you using for the mister?
    I second Bob's implication here. If you can lower the discharge pressure, the air in the tank will last longer.

    Michael

  9. #9
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    If noise is the main issue with the existing compressor, could it be moved a distance away?

  10. #10
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by jack620 View Post
    I think that's your problem, not the compressor. My little 6.5cfm Clisby has no problem running my Noga Mini Cool. From memory I run it at around 30psi. If you need 85psi to get your el-cheapo to work it must be very inefficient. A Noga will be cheaper than a new compressor.
    I run my ebay cheapie misters at 35 psi and slow flow rate, just enough to wet the cutter and work piece area being machined. If the mister is having trouble aspirating the lube/coolant you might have a leak somewhere or is the lube/coolant too viscous? I use a 3: ATF : Kero mix in a 1L PET washing up liquid container. I should preface the following by saying I have a small mill so can only mill small stuff but so far this year I have only used up about 1/3rd of the bottle.

  11. #11
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    Mister problems aside, an answer to your original question around a compressor

    I use one of these
    https://sydneytools.com.au/product/c...air-compressor

    By comparison to a piston compressor it’s very quiet, keeps up with my suction type sand blaster free running.

    If I had 3phase available I’d be looking for a screw compressor, but that will exceed your 2k

  12. #12
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    Thanks all.

    It did occur to be overnight after reading threads regarding mist coolers, that mine seems to be inefficient (what do I expect for $24!!). It uses alot of coolant and alot of air. I will check for leaks as the coolant is just water soluble oil and water.

    I have read that most people are using around 35psi which would help alot if I could get mine to run that low.

    I have decided to buy a Noga mini cool and am in the process of ordering one. The el-cheapo was really just an exploration of whether these things are as good as flood coolant (I am yet to commission the flood coolant of any of my mills or lathe).

    Once the mini cool is in operation I will take another look at compressor requirements as I suspect my needs will change significantly.


    Quote Originally Posted by racingtadpole View Post
    Mister problems aside, an answer to your original question around a compressor...I use one of these...

    Well that looks a funky thing. Plenty of air. I will read up on it.


    I have 3 phase via a 10HP rotary converter. I think the whole 10HP will only be used when taking BIG cuts on the horizontal mills but allocating say 5HP to a compressor might cause issues. Something to ponder.....

  13. #13
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    I’d say a 10hp rotary converter would be flat out starting a 5hp compressor even on its own due to the high startup current.

    I know my 7.5hp converter won’t start the 5hp high speed winding. No dramas if I spin it up first on the low speed setting the change over when it’s running.

    I’ve seen those Sydney Tools compressors before and wondered about longevity and also about how intelligent the multi-head. Haven’t looked into it but are they smart enough to not start all heads at the same time for example. Also can you just run the one head - for the situation where you know that you’re pushing the capabilities of your supply with other gear but still need a bit of air?

    Steve

  14. #14
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    Quote Originally Posted by OxxAndBert View Post
    I’d say a 10hp rotary converter would be flat out starting a 5hp compressor even on its own due to the high startup current.

    I know my 7.5hp converter won’t start the 5hp high speed winding. No dramas if I spin it up first on the low speed setting the change over when it’s running.

    I’ve seen those Sydney Tools compressors before and wondered about longevity and also about how intelligent the multi-head. Haven’t looked into it but are they smart enough to not start all heads at the same time for example. Also can you just run the one head - for the situation where you know that you’re pushing the capabilities of your supply with other gear but still need a bit of air?

    Steve
    If the compressor has an unloaded soft start the in rush on start up is a non issue, as evidenced to some degree by you changing over from low to high during operation.

    My compressor is nearly 9 years old, at this point it appears the tank will be the mode of failure over the compressor heads, every time I drain it, the water is getting rustier.. (having said that Im not doing myself any favours by not emptying it as often as I should because its a pain where I have it positioned) The switch gear on them has no level of intelligence to it, same as any other compressor, if the pressure switch drops in everything gets turned on. You could put contactors or just manual switches in line if you wanted that level of control (personally I'd upgrade the electricity in the shed before I considered attacking the compressor wiring if I was in that position). They do have high temperature cut outs on each head unit, in standard trim that is the only condition under which not all the heads will run simultaneously.

  15. #15
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    Thanks RT.
    Just looking at a couple of reviews online and seems the current models do actually have individual motor switches.

    Also realised I left a couple of key words out of my previous post. The reference to low-high switching was on my lathe...not on a compressor.
    As you say though, if the compressor is soft start it shouldn't be an issue anyway.

    Steve

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