Single or two stage compressor for sandblasting?

AMCguy · Jan 5, 2018

I've gone long enough without a big compressor. It's time to start shopping for a 5 - 7.5hp 220 volt unit.

I don't do bodywork or paint, but that might change.

I don't media blast but that is about to change. I want a good sized cabinet and I need an adequate air supply. I want the most air I can get for the money.

I understand the difference between single stage and two stage. What I don't understand is why I need to compress my air to 175 psi if I only need say 50 psi to pressure blast and maybe 90-100 for siphon blasting. All the air tools I currently own are 100psi or below as well.

Wouldn't I get more usable air for my media blast cabinet with a single stage? Don't I want cfms more than pressure?

All the industrial 5-7.5hp units I've seen have a big slow turning two stage head. I really like them. It seems the single stage units are two, three and four cylinder and run at a higher rpm. They seem to cost less but look kinda cheap as well. Are they really just big toys? I'm confused.

creativecars · Jan 5, 2018

You want two stage, if you compare data the two stage is a more efficient pump and you get CFM and pressure with a better pump. The pressure can be regulated down, but you cant get the CFM out of a single stage like you can with the two stage.

Schurkey · Jan 6, 2018

If you want 90 psi at the sand blaster, you'd better have a heap more than that in the tank. Most single-stage compressors don't even turn the motor/compressor back on until the tank is getting close to 90.

redmondjp · Jan 6, 2018

I'm sure that not everybody will agree on this, but there are a few high-flowing single-stage pumps out that will work fine for sandblasting - they often have three cylinders on them and I've seen flow ratings in the 17cfm range if not more (I think I've seen one model which is around 23cfm). The main thing is having a unit that has a high enough duty cycle, as well as a setup which allows for proper air cooling and moisture removal.

CGT80 · Jan 6, 2018

2 stage is the way to go. 60-80 gallons at 175 psi is a lot more air than 60-80 gallons at 130 psi. For intermittent tasks, you will have more reserve and won't have the compressor cycling too often. If you end up with small hoses, filters, regulators, etc., they can eat up pressure. It is easy to regulate down.

With single stage, the pressure at the tool can end up too low by time the compressor turns on.

Blasting is hell on compressors. Bigger is better.

The **** blast guns are popular and I run the 20-24 cfm (large) tips. My compressor is an old 2 stage that was rated at 17.4 cfm at 175, not 90 psi. An online calculator says it produces 20 cfm, based on the fill time. It is a 5hp 80 gallon and it runs from 140-170 psi right now. It will catch up with that blast tip and shut off for about 2 minutes at a time, at 100 psi at the blast cabinet. I'm thrilled with it. It seems I would need a bigger gun to flow more air, but it blasts very quickly compared to a 10 cfm 60 gallon compressor I used to have, while running small or medium tips.

If I had to buy another compressor, it would probably be a 7.5 hp two stage. If a second person was working with me, it would come in useful. I wouldn't mind replacing my 80 gallon tank with a 120 gallon. It would extend the run time from 1 minute to 1.5 minutes to take the tank from 140-170 psi and it wouldn't cycle as much and I would have more air late at night when I don't want to run the compressor. Cycling often is said to be harder on the compressor and motor than continuous use.

Packard V8 · Jan 6, 2018

I want the most air I can get for the money. . . I understand the difference between single stage and two stage. What I don't understand is why I need to compress my air to 175 psi if I only need say 50 psi to pressure blast and maybe 90-100 for siphon blasting. All the air tools I currently own are 100psi or below as well.

Your logic is correct. Maybe you want a larger tank. As mentioned above, if tank volume is limited, a two stage would be better for short time demand of high CFM than single stage, but large CFM demand industrial compressors are often single stage. Why did IR and others bother to make their large single stage compressors? Look at the larger T30s. The single stage will be rated at higher CFM at 100 PSI continuous duty than will the same horsepower two stage.

Single stage air compressors work by drawing air in and subsequently compressing the air to its final pressure in single piston stroke. Single stage air compressors can attain pressures of up to 150 PSI, but most are more efficient at 100 - 125 PSI. Typically, a single stage pump will have a higher sustained CFM rating than a two stage pump of the same horsepower because every cylinder is drawing in air and compressing it with air during every rotation. If one assumes the compressor will be in continuous operation during blasting, a single stage can make sense.

jack vines

iagsxr · Jan 6, 2018

My Eaton has a continuous run switch for blasting.

OccupantRJ · Jan 6, 2018

The air consumption of a suction blast gun is not determined by the blast nozzle size. It is determined by the air jet. I was running a jet that was all my compressor wanted. Air pressure would drop to 75 while blasting. It could not keep up. I changed the air jet to 1/64" smaller, and now the compressor sometimes waits on the cabinet while maintaining a steady 100 psi. I now make my own air jets, and also set up my blast gun adjustments using a vacuum gauge on the grit suction line. I run my two stage compressor at 125 psi.

I am preparing to put my single stage 5 hp back into action, so I will get some good direct comparison as to how it also does. Overall plan is to run them on a flip flop for more cooling time between cycles.

dr_clyde · Jan 6, 2018

A single stage compressor will make a higher volume of air at a lower pressure in a given time period. A two stage will make slightly less air at a higher pressure.

A GOOD single stage will be fine for home blasting use. Quincy, Curtis, Gardener-Denver are my first look. Basically, you want to avoid the oil-less and compressors from the big box store.

A two stage compressor will make a higher pressure, and therefore a higher volume of air, but typically at a lower cfm than a comparable single. This is for pretty much anything other than blasting. Having 80 gallons at 175 psi will last longer and do more work in between cycles than 80 gallons at 100 psi. Two stage compressors are generally better built and more expensive, as they are designed to be used industrially.

Call a air service company. They can hook you up with a good name and be able to answer your demand questions more specifically.

I prefer a screw compressor myself for blasting. Quiet and way, way more air than a reciprocating per HP. But usually out of reach $$ wise for the home shop.

bdk1976 · Jan 6, 2018

I've blasted with a '5' HP (actually about 3) 60 gallon Lowe's special compressor - about 11cfm. Will work for small parts but runs constantly and loads up with moisture quick.

Upgraded to an older Saylor-Beall 5HP (real 5HP) and 120gal tank a couple of years ago. 2 stage - 17+ cfm IIRC. Runs quieter, cooler, and with less moisture problems. This is the smallest I would recommend, and would try to go bigger.

I am also a fan of a larger tank as it can help give the motor a rest and allows for additional cooling as well. I haven't tried it yet, but using a LVLP paint gun I wouldn't be surprised if I could spray a whole coat on a car without having it kick on. Next time I paint I am going to charge the tank, drain water, and see how far I can get before it kicks on while spraying primer. That 120gal tank at 175-ish can store a LOT more energy than a 60gal at 125-135.

lis2323 · Jan 6, 2018

I use a (TRUE) 5 horse Atlas Copco two stage 22 CFM and I would consider this BARE minimum for adequate sandblasting needs. I have a Skat Blast cabinet.

clubairth · Jan 6, 2018

Remember air is compressible. So the higher pressure gives you a LOT more air volume. This will make your compressor last longer because it will cycle less pumping up to 175 psi than it would pumping up to 100 psi.

It's just a better compressor.
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AMCguy · Jan 6, 2018

Thanks for the replies. I'm leaning towards this baby pictured on the right.

http://www.dvcompressors.com/?page_id=2154

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sz0k30 · Jan 6, 2018

A buddy of mine has a blast cabinet similar to the one in Post #11. He had a 5HP, 60 Gal I/R and said the compressor could not keep up with the blaster. He upgraded to a 7.5HP, 80 Gal I/R and says now the compressor easily keeps up with the blaster, but his neighbors complain

that their lights dim when the compressor turns on.

sberry · Jan 6, 2018

Good point about the air jet, I had really forgot about that and was picking my nose about nozzle size and air use at one point, duh.

dkmc · Jan 6, 2018

All the manufacturers literature I have read about Air Compressors says a single stage compressor is recommended for up to 100 psi and not above. Also, a single stage compressors efficiency will drop considerably above 100 psi.

Unlike a Holley Dominator on a stock street engine, bigger IS better when it comes to compressors and blasting. With 5 real HP being about minimum.

matt_i · Jan 6, 2018

AMCguy said:
All the industrial 5-7.5hp units I've seen have a big slow turning two stage head. I really like them. It seems the single stage units are two, three and four cylinder and run at a higher rpm. They seem to cost less but look kinda cheap as well. Are they really just big toys? I'm confused.

The multiple cylinder units eventually move more air via pump.

The two stage is more efficient for higher pressures, typically 175psi is available. But as mentioned that's more of a storage issue.

I don't think I've ever blasted at higher than 100psi before.

So maybe the multi cylinders make sense for you.

MacMcMacmac · Jan 6, 2018

AMCguy said:
Thanks for the replies. I'm leaning towards this baby pictured on the right.

http://www.dvcompressors.com/?page_id=2154

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That is a proper industrial quality machine. It will serve you well.

Single or two stage compressor for sandblasting?

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