Compressor types for air, 8:1 compression, oil free?

[fastline12]

I am trying to work with some ideas for an emergency use air compressor up to 8:1 compressor and possibly run oil free? I am familiar with the "oiless" piston designs common at big box stores but I am also looking at a sliding vane type. Issue is I seem to find them up to about 2 bar ONLY as a dry compressor, then they jump right up with oil and the works like a rotary.

I am curious if a sliding vane system can be done to run dry to these pressures in one stage? This is NOT a continuous use unit and I am sure heating could be an issue. We have other ways to keep it cool if needed, just need compact and find piston types to be rather bulky for their performance.

 

[MikeHalloran]

A fortune awaits the person who can solve the tribological problems associated with sliding vane compressors at high speed and high pressure. Many fortunes have been squandered in the effort. As you suggested, heat is a major part of the problem, as is wear.

Speaking of wear, note that siding vane compressors normally produce a lot of dust as wear products, so if you are thinking of using one for breathing air, think again.



Mike Halloran
Pembroke Pines, FL, USA

 

[fastline12]

I appreciate the reply. No on the breathing and and we intended to filter it.

I notice commercial shop air systems not in the USA offer vane systems but looks like they run oil mist just like twin screw and need post separation.

Is piston really the only way?

 

[ScottyUK]

I don't think you're limited to piston only. Atlas Copco have a number of screw, scroll and tooth compressors in the 8x - 10x compression range, depending on how big you want to go. The smallest are in the 2HP - 3HP region, the big ones are 'big'. The ones in the brochure I'm looking at are for the marine market but I bet there are equivalents for on-shore applications.

 

[fastline12]

Scotty, do you have any links? 2-3HP might be about the range we are looking. I have not seen scroll used outside the HVAC markets, that is interesting. I also am not familiar with gear compressors. I would assume these would be very similar to roots?

 

[MintJulep]

I come across the Atlas-Copco railroad oil-less scroll web page every few years.

I've never seen one "in the wild" however.

 

[ScottyUK]

fastline12,

Here's a link to their British website:

http://www.atlascopco.co.uk/ukus/products/navigationbyproduct/ProductGroup.aspx?id=1472896.

Looks pretty similar to the stuff I had to hand, slightly newer looking design.

 

[tbuelna]

There are many types of screw or Lysholm type machines that can fill a receiver with air at 8 bar without using oil. They are not as efficient as piston or vane compressors, but their rotors operate without contact, so no oil is required in the working space.

 

[TD2K]

Check with Altas Copco, I'm almost certain I put in an oil free instrument air compressor from 11.5 psia to about 100+ psig (will have to check the data sheet tomorrow). Centrifugal unit, 3000 scfm outlet rating. What type of flow are you looking for?