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Screw compressor good for a small garage shop?

Discussion in 'QUESTIONS & ANSWERS (Get Help Fast Here!)' started by P-Ritch, Apr 4, 2017.

  1. P-Ritch

    P-Ritch United States Swarf Registered Member

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    Hey All,

    Pretty new here and have a question right off the bat. I'm setting up a small shop in my garage and was about to pull the trigger on quincy 5HP 2 stage piston compressor. Then a great deal showed up on craigslist of a quincy 5HP screw compressor with a built in refrigerated dryer still on the pallet asking about 75% the cost of a new one. I'm going to be using the air for a small blast cabinet mainly and few air tools at first, but within a few years I'd like to get a CNC mill as the finances allow.

    It would be about $1500 more for the setup, but it would include the dryer (right now I'm about to spend $2k for the new piston setup). Would that be a good choice? Right now I'm looking at it as buying a compressor I could eventually grow out of vs buying a compressor that I would eventually grow into.

    What are your thoughts and opinions on the matter.
     
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  2. Strangerthings169b1

    Strangerthings169b1 United States H-M Supporter - Premium Content H-M Supporter-Premium

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    A screw compressor is generally both quieter and more efficient than a piston machine. Can you get me a model number? I might even have a parts breakdown for it on my computer. I work on mostly screw compressors every day.
    5 HP is a nice size too.
    A refrigerated dryer will get you a dewpoint of between 34 and 38 F. Think of it as something like a window AC for compressed air'
     
  3. woochucker

    woochucker United States Active Member Active Member

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    The dryer will allow you to use the blast cabinet all day. And not have the media wet and clumping.
    If you have the funds, and don't find it unreasonable, the screw compressor is the way to go. It produces more air, and is quiter. It can cost more to repair, but if you take care of it, replace the filters, change the oil, you won't need repairing.
     
  4. FOMOGO

    FOMOGO United States Active User H-M Supporter-Premium

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    1. In Tucson you really shouldn't need a dryer. Screw compressors are great, But you should be able to get a good used two stage unit for under 1k on Craigs list, and spend the money saved on other needed shop equipment. JMO. Mike
     
  5. Strangerthings169b1

    Strangerthings169b1 United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Woodchucker is right, I was called out to "repair " a Sullivan 25HP screw machine just this week. That particular machine is over 30 years old and the only thing that was wrong is the owner forgot where the reset lever was from the last time I showed him,,, 4 years ago.
     
  6. P-Ritch

    P-Ritch United States Swarf Registered Member

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    Strangerthings, the model is a 4152002717. That was the other perks I was considering about it as well was the cooler outgoing air and the quieter operation. It's going to be right next to the cabinet in the garage and that would be more than welcome.

    FOMOGO, that is my current dilemma. I don't feel I can really justify for my current situation and location. However, where I hope to see myself in a few years shop-wise I would need more air on demand. But things don't always go the way you plan, so it could be a waste after all.

    I didn't know the maintenance was less involved for a rotary screw compressor. Thanks for all the input so far!
     
  7. P-Ritch

    P-Ritch United States Swarf Registered Member

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    The only issue I'd have to add so far is that the piston is single phase so I'd be able to plug it right in to my current 230V, but the screw is 3-phase so I'd have to get a converter. I'd more than likely go with a VFD.
     
  8. mksj

    mksj Active User H-M Supporter-Premium

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    Recently upgraded my compressor to a Champion HR5-8 Advantage two stage 5Hp, it includes an after cooler, Auto drain, Mag starter and low oil shutoff. I added an hour meter for oil changes, and will switch to synthetic after it is broken in. I believe air flow wise a piston vs. screw will give similar CFMs but depends on the working pressure, so at 150 PSI a screw is rated for around 16-17CFM, the HR5-8 is 17.3 at 175 PSI. At 125 PSI a screw will increase to around 21-22 CFM. The screw will be much quieter, but then it runs all the time when you are using it, so energy wise if you are using it intermittently a two stage I would expect to be cheaper. Durability wise, they both will probably outlast us, the better air pumps units are rated at around 30,000+ hours. I previously had a Curtis industrial CA-5, but the Champion is a bit quieter and has a low speed air pump. So very satisfied with it and it cycles about 25% of the time when using a die grinder, a blast cabinet it would be running more frequently. Quincy also makes good compressors, but they require you to buy their maintenance kits to extend the warranty, and more recently there seems to be more complains about taking care of warranty claims. The dealer that I purchased mine from (Pacific Air Compressor) sold a number of different brands and recommended the Champion. If you need higher airflow for a blast cabinet they sell 4 piston two stage 7.5Hp unit that flows 26 CFMs at very low pump speeds. Either way, both brands at this level should be reliable and last a long time with basic maintenance. I use two air filters, the second is a 1 micron coalescent filter, can't say I have ever had any water in the drains.

    If you want to check out the HR5-8 I am also in Tucson.
    20170126_144922.jpg
     
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  9. Silverbullet

    Silverbullet Active Member Active Member

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    Do your self a favor , get the deal on the screw air compressor. If you don't I bet down the road you will regret it. But it's your choice from my past forty plus working years I've gone cheaper only to pay twice. ThAt machine will last your lifetime if you maintain it . Never know where you may be in ten years the compressor will be.
     
  10. ewkearns

    ewkearns United States Active Member Active Member

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    Screw compressors don't do well in unheated areas. Given your particular situation, you might need to heat the cabinet.
     
  11. Silverbullet

    Silverbullet Active Member Active Member

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    EwKearns, that funny most all two behind compressors use screw drive in all kinds of weather. They just don't breakdown when there maintained. I've worked on them at a rental company . They are the best ones for quick pressure and cfms . So I think he would have no problems . One time in twenty years we had a customer bring his own in with a problem , no oil and wiped out the bearings in the pump.
     
  12. BigMo

    BigMo United States Iron Registered Member

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    Can u use a vfd to start a compressor? Didnt know that

    Sent from my SM-G900V using Tapatalk
     
  13. mksj

    mksj Active User H-M Supporter-Premium

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    Yes, but most VFD manufactures do not make a single phase 5 Hp VFD, you need to buy a 10Hp and derate it to run on single phase. So you are looking at an expensive proposition, and then you also have the refrigeration drier load on a scroll. A few people have posted using the Chinese HY VFD 7.5 or 10Hp to run a 3 phase 5Hp compressor, but not sure of the long term reliability of those VFDs.
     
  14. terrywerm

    terrywerm New Member Liaison Staff Member H-M Supporter-Premium

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    I would go for the screw compressor if it is within your means. As for running with a VFD, most screw compressors start at no load and the load comes on shortly after startup. Additionally, screw compressors don't start and stop, instead they load and unload, some even modulate to meet the demand for air. Many of them have timers set up so that once the compressor has been running unloaded for a certain period of time, it will then shut down.

    I used to manage and maintain a bank of four Sullair 20 HP rotary screw compressors that provided all of the air for an entire manufacturing facility. The plant would run most of the time on just two, sometimes required three to meet demand, but we always had a fourth to stand in if we had to take one off line for maintenance. Cut in pressures were staggered so that one compressor would be the 'lead' followed by lag 1, lag 2, and lag 3. Every so often I would change them around so that they would all gain hours evenly, or at least as close as possible. Long story short, it was a fantastic setup. We also ducted the exhaust from the units so that during the summer outdoor air would be drawn in to the compressor room for cooling and the hot air would be exhausted outside. During the winter we used indoor air for cooling and the hot air was ducted out into the warehouse.
     
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  15. ewkearns

    ewkearns United States Active Member Active Member

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    I don't have a lot of experience with them, but I know we had 4 Kaeser 50 hp compressors and they were very sensitive to the cold. If the oil got too cold, it would throw an error code and that would be the end of that, until we took steps to heat the cabinet. We finally put thermostatic heaters inside the cabinet. When they work, they are great. The old Ingersol-Rand 11" X 11" I cut my teeth on, never gave this sort of problem....

    Personally, I don't see a lot of benefit in one in a home shop, but if you have the money, they are quiet. But how much CFM does the average HSM really need? I don't think they make anything much smaller than 25hp.... I know the new ones don't have a huge inrush current, but how much free amperage is available in the average home shop 3-ph panel?
     
  16. 12bolts

    12bolts Global Moderator Staff Member Active Member

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    Get the screw compressor. Like you said, its something to grow into, and media blast cabinets consume ridiculous amounts of air. Its a real pain blasting something for 30 seconds, and then waiting 3 minutes for the compressor to catch up.....

    Cheers Phil
     
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  17. bobshobby

    bobshobby Australia H-M Supporter - Premium Content H-M Supporter-Premium

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    Screw compressors generally are set up to run continuously, just loading up and unloading as required, however you can set up a control that will shut it down if its going to idling for long periods of time. Screw compressors also have very specific requirements for oil quality, use the right oil and you shouldn't have any problems. treated right it should last you a lifetime.
     
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  18. Tony Wells

    Tony Wells United States Vice President Staff Member Administrator

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    If you call the compressor shops, they will probably tell you no. They generally, as already pointed out, are continuous run, cycling an intake valve to unload them. The need for a constant circulation of oil, and the subsequent separation and recovery gets a little impractical on a frequently started and stopped machine. They are seen where there is a constant, non fluctuating demand, like a blowmolding plant, or a plant that manufactures plastic bags, which start off as small tubes that are blown larger as they exit the extruder. I have seen them in shops where there are enough machines and operators to keep them running loaded enough of the time. There is a start/stop ratio and time formula for this, but it escapes me at the moment. For a small home shop, it would not be my first choice at all.
     
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  19. coolidge

    coolidge United States Active User Active Member

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    Piston compressors are LOUD as hell WHAAAAAAAAAAAAAA!!!
     
  20. bobshobby

    bobshobby Australia H-M Supporter - Premium Content H-M Supporter-Premium

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    Some years ago I worked in a shop where the demand for air varied quite a bit, some times the screw compressor ran unloaded for maybe 20 minute and others it was flat out for maybe an hour or more. The plant electrician made up a smart switch so that if it was unloaded for more than say five minutes and the reserve pressure was still quite high it would shut down, but if the pressure was below a set point it would keep running. This worked quite well.
     

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