OT: Rotary vane vs. rotary screw compressors

For a small shop / 1 man garage , is it better to go with rotary screw or rotary vane? Are there any drawbacks in going with a vane compressor?

I rarely see rotary vane compressors being used at manufacturing plants and cabinet shops. I did a little reading and learned rotary vane is older technology but some companies still make them, like Mattei.

Assuming price is not an issue, which one is the better choice?

Mattei I saw one in HGR....came from a wood working shop.

I could tell this, as I lifted up the hinged cover and found about 2"
of sawdust stuck everywhere, soaked with oil.

Thing had 25k hours on the clock, I rang up Mattei USA and they sort of laughed
it off. Not really a problem with those machines, and the time was
good, and plenty of time left before rebuild.

There is also Compair hydrovane from GB.

Vane compressors are less efficient,but a lot cheaper to buy.......In big sizes ,a screw compressor is just about mandatory for energy savings.....The screw assy is not fixable if a bearing collapses ,or something falls into the rotors......When I last worked ,a 200 hp screw air end was $50,000 exchange from any of the recognized makers.A vane can be rebuilt just about indefinitely,and we used to cut the grooves for the vanes oversize,and cutout thicker vanes.....A vane rebuilt for micarta and bearing/seal costs.....Screws also use high precision bearings ,that often cost $6000-$10,000 a matched set.

john.k said:

Vane compressors are less efficient,but a lot cheaper to buy.......In big sizes ,a screw compressor is just about mandatory for energy savings.....The screw assy is not fixable if a bearing collapses ,or something falls into the rotors......When I last worked ,a 200 hp screw air end was $50,000 exchange from any of the recognized makers.A vane can be rebuilt just about indefinitely,and we used to cut the grooves for the vanes oversize,and cutout thicker vanes.....A vane rebuilt for micarta and bearing/seal costs.....Screws also use high precision bearings ,that often cost $6000-$10,000 a matched set.

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So I am guessing in the 7.5 hp to 15 hp range, the efficiency of a screw compressor vs. vane is not a factor worth considering? If so, why are Vane compressors not more common than Screw compressors , in the aforementioned HP range?

I dont know exactly.....depends on energy cost ......but one thing I have noticed is the cheaper screw compressors run at massive gearups.....like 5 to 6 x motor revs.You cant speed up a vane,due to friction heating of the sliding surfaces.....But screws are basically just funny shaped gears meshing together in a flood of oil,so can be run a very high revs.......however the old high quality ones that went 20,000hrs hours between rebearings were direct driven at 1400-1500 revs.

john.k said:

I dont know exactly.....depends on energy cost ......but one thing I have noticed is the cheaper screw compressors run at massive gearups.....like 5 to 6 x motor revs.You cant speed up a vane,due to friction heating of the sliding surfaces.....But screws are basically just funny shaped gears meshing together in a flood of oil,so can be run a very high revs.......however the old high quality ones that went 20,000hrs hours between rebearings were direct driven at 1400-1500 revs.

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I'm thinking in the size the Op is asking about (under 15 hp or so)
The sliding vane power loss would be about the same as the screw's
gear up losses.

But a perusal of the brochures should give full load amperage/efficiency
numbers pretty plainly.

I know a vane is running at constant power/pressure as there is a by pass valve that opens at the set pressure
Do not know for sure on a screw but probbably the same

Peter

And you are ruling piston compressors out because? Screws are spendy, vane can be subject to wear, and pistons just clunk along. If it were my small shop with relatively minimal air use it would (is) be piston.

2¢

WHHJR said:

And you are ruling piston compressors out because? Screws are spendy, vane can be subject to wear, and pistons just clunk along. If it were my small shop with relatively minimal air use it would (is) be piston.

2¢

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Noise and compactness of package is why I am not interested in piston compressors. The Air center by Kaeser or the equivalent model by Atlas Copco are very compact.

Kaeser screw or Quincy piston. Both efficient, quiet, and reliable.

Take your pick...

Spud said:

Noise and compactness of package is why I am not interested in piston compressors. The Air center by Kaeser or the equivalent model by Atlas Copco are very compact.

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One of our British members should be along shortly to help you with choosing a compair hydrovane in the smaller sized ones.

Atlas Copco is a top brand,we had several big ones electric and diesel........In fact the only real trouble we ever had with compressors was heat related degradation of the oil..........flakes of "shellac" form and block filters and oil coolers.....you must keep the oil coolers clean........The two big cost maintenance items are oil separators and special oil if its required......We had another issue........if you change the brand of oil in the compressors ...everyone gets sick and goes home.........one for Thermite to ponder.

This is also a comparison that I'm making at the moment. I like the simplicity of a rotary vane compressor. Not many moving parts, easy to pull one apart and service it when need be, and seems like service intervals are very far apart. All the critical tolerances come fairly easily from the 'wear in' period where the vanes bed to the housing... I run a very small low pressure one (1/4HP) for the air blast on my VMC and it's been great, running long hours in dirty conditions with no problems at all, dead quiet as well.

Rotary screws seem very complicated, with very particular maintenance requirements: up to and including sending oil samples to the manufacturer at regular intervals to maintain warranty coverage!. Also in some videos I've seen of the smaller ones (< 10HP) running the noise they make can be quite high pitched. I have also been around a few larger ones (10-15HP) installed next to printing lines and they couldn't be heard at all over the other activity in the room.

Piston compressors are also dead simple, but I have yet to hear one that is actually quiet and nice to be around. My current one is a low RPM model (~600 rpm at the pump) with an inlet silencer and I still built a cabinet around it to quiet it further. Sometimes other machines are noisier, but few run as regularly as the compressor, so I think for my next machine pistons are out.

The main issue with rotary vane compressors that I've experienced so far is that very few people want to sell me one! I talked to a local distributor of various piston/screw compressors to see if they stocked any vane compressors and he asked if I had "been transported from the 70s?"...

There are a number of large Hydrovane units for sale second hand around me at the moment (15-25HP) but no smaller ones. I think the main issue you're going to face is simple availability...

The quietest compressor I have ever seen was a big Belliss and Morecombe piston compressor driven by a 2500hp synchronous motor .It ran about 250rpm direct coupled,and the only sound was the clicking of the lubricator ratchet drive.....but you could feel it working through the floor...Our 200-500hp screw units were very noisy,and required earmuffs near them.........just the big fans on the oil coolers made a deafening noise,and generated massive amounts of waste heat.........in fact if I got wet,a few minutes standing in the compressor room,and i was dry.....good on a cold day too.

Hydrovane are common and have a seriously good rep here in the uk, problem is cost, in the lower to mid single digit hp range there far more costly than a piston pump. They are very common over here in the uk and kinda get speced to fill the gap between cheap piston and double digit screw compressors. Life span 100,000 hrs is common but you have to stay on top of the servicing, abused and repairs will cost a fortune equally they have to be ran hard to stay dry, intermittent use as in just topping a small tank off once a day and you will have issues, inversely they will happily run there full 2k hours between oil changes non stop and do it year after year.

Worth adding i have a 2kw HVO2, its only rated for 8CFM but reality is it will give any of the supposed 3hp piston pumps i have ever encountered that seam to get rated at 12 or 14CFM a real run for there money. Bought new it cost me close to £2K a few years back, but it should see me out life wise. Properly serviced they just continue to bed in, whilst most screw pumps just wear out.

Noise wise, there not exactly silent, but its more like a vacuum sound and even a crude enclosure really muffles it, it has nothing like the slap - low base of a piston pump hence way more neighbor friendly. with mine shut in a different room yes you hear it running but i can still here a neighbors cheap piston compressor about 100 feet away thats way more irritating and louder.

If noise is bnot a issue piston pumps can be cheap but few things will beat screws for efficiency once you get north of 10Hp, bellow that and vane can offer some long term advantages.

In big industrial sizes,200hp+,piston multistage units are more energy efficient ,and produce far less waste heat=waste energy.....The big issue with piston machines is they need a foundation.....a screw doesnt,no vibration,just sits on thin concrete floor.....Big piston units liquefy wet soils common in industrial areas.

Above screw HP I have seen "turbo" compressor.

IIRC IR big motor, with big gear on end 20" (in gear case with pump oil lube)
and 3 ordinary looking engine turbochargers all
plugged into the gearbox.

Arranged around the big gear, they were maybe 3".

No oil injection and filter out problems.

yeah, but that sure as fuck does not scale down well, i forget the actually hp needs of a turbo, but its scary high for a given engines output power. dread to think how much HP one of thoes sucks to get 120psi BOOST!!!

More than a few of the larger old print stuff have worked on used blowers with a circa 12" centrifugal wheel like out of a water pump, would get some serious volume at just a few PSI and they just ran forever being direct drive on a 2 pole motor. Certainly way less agro long term than any of the carbon vane pumps and just as much performance. Got no doubt thats the way to go if you want air in the hundred + hp range and like you say no mantinace - no oil simplicity sure takes some beating, hell im almost willing to be the turbo charger guts are relatively cheap to make too compared to a typical vane or piston pump.

Agree 100%
However, seeing how it works alongside (and dumps into the same pipe)
as some large recips, I can only surmise the total cost of operation
is less.

I actually like those little hydrovane units (under 10 hp) and
wish they would be sold over here (and at a competitive price)
But the Eaton and other chinese screw compressors are ruining this
part of the business.

Spud said:

Noise and compactness of package is why I am not interested in piston compressors. The Air center by Kaeser or the equivalent model by Atlas Copco are very compact.

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My 3hp (old) Quincy is very quiet, barely louder than the motor by it's self. As for size, the total package is about double the height of the tank alone(40 gallon). It fits neatly under the stairs to the second floor. A friend has a modern 5 hp screw that is very loud if operated without the sound enclosure. And about the same size. Pick your poison.....