air compressor that doesn't need oil separator for condensate

[anchorman]

I need an air compressor, about 7.5hp max. 15 - 25CFM at 110psi (leaning towards more to have margin for future needs). Having never purchased and installed one previously, I never considered the need for an oil separator for the condensate coming out of the tank.
What are the best options? this won't get used constantly, but might get used a lot at times.

power available is 208V single and three phase, 480V three phase, and 120V single phase.

Some people say that rotary screw compressors don't like to sit idle - how true is this, and on what is this based?
I'd like something quiet <70db when running...

Reciprocating compressor is an option, but oil separation gets expensive, they are noisy, and I'd have to build some sort of enclosure and get the enclosure approved. oilless reciprocating/rocking piston type could work, but most affordable ones are not rated for 208V phase, I've considered running three or four of the california air tools compressors in parallel, but their 230V models specifically say not to run on 208V.

Who make the best affordable screw compressor? Do these need an oil separator? Other options I should look at?

 

[Matt@RFR]

For limited use, I would go with a Quincy QT-7.5. Mine is a 208V model and it's the quietest piston compressor I've ever been around.

There are numerous condensate water/oil separators on the market. Just grab a cheap one for your use and be done with it.

 

[eKretz]

Powerex makes a good oilless compressor. They aren't cheap though. I've got a 47 CFM Powerex compressor head (OPT150 I think it is) that I run at more like 20 CFM with a pulley change. Nice because it's quiet.

You might want to look into one of those Eastwood scroll compressors. I've heard good things.

 

[Bill D]

I would guess a scuba air compressor passes no oil into the air. super expensive, I bet.
Bill D

 

[Scruffy887]

I would guess a scuba air compressor passes no oil into the air. super expensive, I bet.
Bill D

Very low CFM but 4000+PSI if you want to make something explode violently.

 

[Scruffy887]

OP is asking how to remove oil from the water that condenses in the tank. Most people I know just toss the water outside out back. I made my own separator from a few 5 gal plastic buckets. The "filter" bucket drains into a collector bucket and the collected water is pretty darn clean. True that I have never emptied that bucket and the water evaporates enough that I don't need to. Kaiser 10hp air center running in an air conditioned shop. It will run all day when it runs, but that could be a day with a week or 2 between.

 

[anchorman]

OP is asking how to remove oil from the water that condenses in the tank. Most people I know just toss the water outside out back. I made my own separator from a few 5 gal plastic buckets. The "filter" bucket drains into a collector bucket and the collected water is pretty darn clean. True that I have never emptied that bucket and the water evaporates enough that I don't need to. Kaiser 10hp air center running in an air conditioned shop. It will run all day when it runs, but that could be a day with a week or 2 between.

pretty darn clean doesn't pass an EPA inspection, so I don't have that kind of option. And now that I know that it's not allowed, the penalties would be double. I can probably work out getting a compliant filter system, but looking to reduce the number of maintenance jobs in my life.

 

[Strostkovy]

California Air makes oilless compressors that are very quiet. I think they have an 8HP model which isn't super cheap but isn't terrible. In my experience oilless compressors are less energy efficiency.

Regarding oil lubricated compressors, they can all handle intermittent duty as long as they occasionally get hot enough to remove the moisture that accumulates in the oil.

That being said, our future endeavors will use oilless compressors as much as possible. Adding and removing oil is a huge pain.

 

[anchorman]

Powerex makes a good oilless compressor. They aren't cheap though. I've got a 47 CFM Powerex compressor head (OPT150 I think it is) that I run at more like 20 CFM with a pulley change. Nice because it's quiet.

You might want to look into one of those Eastwood scroll compressors. I've heard good things.

Thanks. The smaller eastwood scroll might work, the big one needs more power than I have without running a new circuit. need to check if it has a proper tank (i.e. ASME certified). I thought about tying 3 of the harbor freight or california air tools 10 gallon compressors together, but not sure how the3 safety people will like those tanks.

 

[anchorman]

California Air makes oilless compressors that are very quiet. I think they have an 8HP model which isn't super cheap but isn't terrible. In my experience oilless compressors are less energy efficiency.

Regarding oil lubricated compressors, they can all handle intermittent duty as long as they occasionally get hot enough to remove the moisture that accumulates in the oil.

That being said, our future endeavors will use oilless compressors as much as possible. Adding and removing oil is a huge pain.

they tell me the 220V models shouldn't be used on 208V power. I wish they would offer their compressors with a three phase 208V option, or even a single phase 208V model. The heads are relatively cheap, and definitely nice and quiet, even without an enclosure. I have use the harbor freight knockoff version, and it's very unobtrusive.

 

[Strostkovy]

they tell me the 220V models shouldn't be used on 208V power. I wish they would offer their compressors with a three phase 208V option, or even a single phase 208V model. The heads are relatively cheap, and definitely nice and quiet, even without an enclosure. I have use the harbor freight knockoff version, and it's very unobtrusive.

I have two heads on a compressor that I'm going to be running on 208V at slightly reduced pressure. But a 12V buck boost transformer isn't that expensive.
I got mine used for $100 each from a university. I'll post some pictures of the final setup later.

 

[Strostkovy]

Oh, and I really enjoy having a digital pressure switch. I can set the compressor range at what I normally need and on occasion bump it up if the need arises.

 

[anchorman]

Powerex makes a good oilless compressor. They aren't cheap though. I've got a 47 CFM Powerex compressor head (OPT150 I think it is) that I run at more like 20 CFM with a pulley change. Nice because it's quiet.

You might want to look into one of those Eastwood scroll compressors. I've heard good things.

Do powerex make the oil-less scroll compressors that everyone else sells? looking at the pictures, quincy sells one that looks identical.

 

[john.k]

Typically ,instrument air compressors from big boiler systems are a source of oil less compressors ......they are ultra expensive new ,but sell quite cheap used ,due to bulky dimensions ..........friend uses a 40cfm Compair /Maxam oil less for bead blasting as a business.

 

[eKretz]

Do powerex make the oil-less scroll compressors that everyone else sells? looking at the pictures, quincy sells one that looks identical.

Dunno, but I wouldn't put it past 'em.

 

[john.k]

You can buy major brand screw compressors that are oil less .....normally the screws are oil flooded ,but by using high precision timing gears and rotors ,the screws can run without lubrication ..........I can just imagine the cost ,when a set of precision bearings for a oil flooded screw are around $10k.

 

[DDoug]

Oil less screw compressor