Small Rotary Screw Compressors

[Brian Holcombe]

Looking into Kaeser SX3 or 4 and wondering if anyone else makes a similar small rotary screw type compressor? Most seem to be huge.

[Bill Dufour]

I have to ask if you really use enough air to make it worthwhile. It needs to run long enough to warm up and heat up the moisture in it pretty much every time. This means it should run no less then one hour? at a time. Will you save over $100 a year in electrical costs just to break even on oil and filter changes required by warranty?
I could well be wrong but I did not think you used that much air in your shop. If you do sandblasting or spray painting all day long it is a wise investment. For sanding it is cheaper to switch to quality electric machines. I think the break even point is about a 5-10 horsepower reciprocating compressor running most of the time.
Bill D.

list "borrowed" from Practical Machinist site: IR, Quincy, Atlas-Copco, Belaire, and Polar Air (Eaton)

[Peter Kuhlman]

Rotary air compressors as Bill said MUST run for extended times as the compressed air is run through the lubricating oil and it has to be hot enough to prevent moisture build up which will destroy the rubber seals and damage the rotors. Very expensive repairs. I used about 50 of them for oil field well sites - mostly 20 HP. I had to leave valves cracked open to get long enough run times to prevent damage. I can not imagine anything less than a professional, multiperson shop having enough air usage to warrant a rotary compressor. The worst usage is when it stops and starts repeatedly.

[Brian Holcombe]

Ah, thanks fellas. I'm glad I asked here.

Basically I want something small and quiet, it doesn't need to produce much output as I only really need it to run the Maka. It will be short run times.

[jim mills]

If quiet is your main concern. Those refrigerator compressor units are really nice. I had one for years. Panther I believe was the brand. Silent air is another. Not tons of volume, but really quiet. I currently have one of the roll air vacuum pump units to run Brad nailers. Reasonably quiet.

[David Kumm]

Brian, look for a used dental compressor, Jun Air or Silent Air. They are quiet and well made. They go for 500-1000 used but are worth it. I use it for pneumatic gates and clamps and have it piped into my large compressor lines with a valve. Run the Quincy QR when I need lots of air and the Jun Air when I don't. Dave

[Brian Holcombe]

Much appreciated! I think that is the direction I will head.

[Bill Dufour]

I would suggest a piston unit but reduce the rpm so the pump is running around 900 rpm. This is fast enough for lubrication but the lower speed reduces noise. Also reduce the cut in and cut out pressure to reduce noise but keep producing air. You need no more then 125psi or even 100PSI for most folks.. I understand much of the noise is on the intake. I put an oil bath air filter on mine to help lube the cylinders and for quietness.
Bill

[Mark e Kessler]

look for California Air, super quiet I have this one https://www.amazon.com/California-Ai...gateway&sr=8-3

Mark

[Matt Mattingley]

A few summers ago, I built two compressors from scratch. My goal was quiet quiet quiet. I did a fair amount of research. California air and Rolair had the top ratings for small air compressors. But, they are all oilless.

Rotary screw are amazing little machines. They're design to run and keep running....

I built a big three piston 5 hp 80 gallon on a VFD. This is a splash oil. I put a few pressure sensors on to signal the VFD to trip the VFD to a higher RPM if pressure was continuously lowering. My air compressor has about 17 CFM at 90 psi. For low requirements, I run the pump at about one third the maximum RPM.

The other one I built was just the Freon compressor out of a old fridge. It's good for a pneumatic Brad nailer for about 16 shots, but she is quiet!

[Bill Dufour]

Note that a compressor has a minimum rpm so there is enough splash to lube things. This is even true if it has a oil pump.
Bill D

[Matt Mattingley]

Note that a compressor has a minimum rpm so there is enough splash to lube things. This is even true if it has a oil pump.
Bill D

Yes Bill, that is very important in a splash lube piston. Some higher end compressors have pressurized lubricators. Keep in mind not all air compressors are equal.

If your modifying a compressors rpm below manufacture specs,Understand the workings and ability... or you could learn the hard way.

[Tony Zaffuto]

Looking into Kaeser SX3 or 4 and wondering if anyone else makes a similar small rotary screw type compressor? Most seem to be huge.

I have a Kaiser compressor and refrigerated dryer at my plant, probably much larger than your needs. Kaiser are very much top shelf quality, as my nearly 20 years of ownership proves. One issue with Kaiser is the lack of availability of after market preventative maintenance items (key to life in a screw type compressor, is regular maintenance). I have a back up screw type compressor (can't remember the name), but though it ran when purchased, some issues were uncovered, and in the end, I ended up with total cash outlay of nearly 80% the cost of new.

If Kaiser is all you can locate in the size you want, by all means go for it, you won't be disappointed. If you are considering and type of screw compressor, then I would look at a cyclinder style. Again, I can't remember the name, but I was around a piston style, that had a dryer built into the unit, and the compressor was surprisingly quiet. Remember, though, even with an air dryer, take extra precautions to rid the air of moisture: right out of the dryer, an auto moisture valve, take all air taps straight up off the air lines, and dirt/moisture traps at point of use.

[David Kumm]

Splash lube have a minimum rpm. The widest range compressors were the old Quincy QR series. They are a fun project to rebuild and kits are available. A slow running Quincy has a pleasant sound, much different from other compressors. I rebuilt a 325 and a 5125. Dave

[Greg R Bradley]

I don't think you should assume that a Kaeser small unit needs to run continuously and for at least an hour at a time just because other screw compressors do.

I know several people that use them for short periods on mobile shops. That doesn't necessarily make it right. I would just check first. I also know that Kaeser makes oil free compressors.

Every Kaeser I've seen was very impressive.