SFA: What's the Answer?
How Big an Air Compressor?
Does anyone know what size air compressor I would need in terms of HP, CFM, gallons, to run a Park Industries PRO-EDGE® III and two hand polishers?
The PRO-EDGE uses very little air; just a "slug" of air when raising or lowering the hold-down clamps.
The hand polishers are what will use a lot of air, typically 10-15 CFM @ 90 psi. Size your compressor for the number of air grinders you expect to have. A compressor big enough to run the grinders will easily accommodate the ProEdge.
When I started my shop I ran it for a couple of years on two Home Depot $450 air compressors. They were rated for "continuous duty" but wore out in about 18 months while still under warranty. Replaced for free.
Custom Stone Interiors
St. Cloud, Minn.
"I spent most of my money on motorcycles, women, and beer. The rest I wasted." author unknown
No matter what, oversize.
Some polishers can use up to 19 cu ft/min; check with the manufacturer for specifics.
Reciprocating compressors are not meant to run continuously, and the demand placed on them by polishers will burn them up in short order if you do not oversize them. I'd consider having an auxiliary air tank or have two in-line.
Or, save your money for a screw or vein compressor.
I have been running my Kaiser screw compressor for over 20 years without anything except regular maintenance.
Slabworks of Montana
NSI, SFA, USGBC
"What we leave behind is not what is engraved in stone monuments, but what is woven into the lives of others" - Pericles
I'm running a saw (almost no air use), PRO-EDGE II with multiple air leaks, a vac lifter, and 2 air polishers on one 7.5HP, 2-stage, 80 gallon-reciprocating compressor. I had two, but one is currently down so it's acting as a reservoir at the moment. It'll work hard while everything is running at once but that isn't too often. The compressor pre-dates me at the shop and I started four years ago.
Production Manager, Austin Stone Works
"If you don't know where to start, go back to the beginning" - Alphonse Soady
I’m looking for a Gardner Denver screw compressor. Need one pretty quick since one of my air compressors just went down. It’s been something I knew was coming. But wondering if I should buy new? Slightly used preferably. And honestly what’s the cost usually for a 15-25 HP one?
Check with your power company. Our electric supplier just bought us a brand-new 25HP variable drive.
I would buy new and have a warranty.
Why not buy the same size that just went down, or slightly larger?
Why did your power company just go and buy you a new one? Out of curiosity. And because I had two 80-gal rotaries seriesed up. Works good. Just runs 'em hard. I’d rather get something I know I’m not going to have issues with. Like a screw drive.
I like to think they bought it because I am a nice guy.
The reality is that we are in a high-use area and the company is replacing incentivizing the replacement of older, less-efficient equipment. They are paying for many compressors for many in our industry.
It is cheaper for the power company to replace older equipment to bring down the usage, rather than build more generating plants.
Within the past few years they replaced all our lights/fixtures to the new energy-efficient models in the shop & showroom (12,000 ft²) & bought a new compressor. Probably 250 4' bulbs and 100 8' bulbs. Fixtures and bulbs.
An important part of your air system is a dryer. I bought a remanufactured one from the OEM in Michigan 14 years ago and never had a problem. Found it on eBay. Water in the air will wreck your pneumatically operated devices so the dryer is not really optional.
My rule of thumb is that you need 5HP of compressor for every air polisher you plan to run.
Stone Innovations, Inc.
Plover, Wis. USA
"The difference between an obstacle and an opportunity is our attitude towards it. Every opportunity has a difficulty, and every difficulty has an opportunity.