Air compressor - is it still a must have tool?

[FuzzFace2]

I would be lost without mine. I have both electric and air tools and use them equally. Just depends on the job at hand. I also have a 12000 # four post lift that I would also be lost without. I wish I had bought it 20 years ago LOL.

Gary, I know the off road guys use them a lot.

I also seen where they use the tube bumpers as air tanks.

93F350, sounds like you have a nicely set up shop.

Dave ----

[Gary Lewis]

Gary, I know the off road guys use them a lot.

I also seen where they use the tube bumpers as air tanks.

93F350, sounds like you have a nicely set up shop.

Dave ----

DeWayne - I agree that a lift and a compressor are wonderful additions to a shop.

Dave - Yes, the off-roaders use them as they need to let the air pressure in the tires down significantly while off road, and then bring it up again to hit the road. And the little 12v compressors just aren't up to the task. I remember having a low tire on my '72 F250 when camping once, and we played at least two hands of Canasta while my 12v job brought the air pressure up just a little bit. So, airing up 4 big tires would take forever with one of them.

As for tube bumpers being used as the reservoir, they also use the roll bars for that. But that would take someone with far better welding skills than I.

[fljab]

DeWayne - I agree that a lift and a compressor are wonderful additions to a shop.

Dave - Yes, the off-roaders use them as they need to let the air pressure in the tires down significantly while off road, and then bring it up again to hit the road. And the little 12v compressors just aren't up to the task. I remember having a low tire on my '72 F250 when camping once, and we played at least two hands of Canasta while my 12v job brought the air pressure up just a little bit. So, airing up 4 big tires would take forever with one of them.

As for tube bumpers being used as the reservoir, they also use the roll bars for that. But that would take someone with far better welding skills than I.

I carry one of the Slime 12V air compressors on my bike when on trips, and even then it does a barely adequate job and is really only for emergencies. If the pressure is low I normally just put quarters in a gas station inflater and use that.

I worked fluid systems for a living for many yrs and plumbed in quite a few compressed air line systems in facilities @ KSC over the course of 20+ yrs. In my old garage (at another property) I had installed hard lines and drops in several places in the shop. I was running it off a 60 gallon, 6 hp single stage oil-less compressor (never buy one of those!). I blew that one up so bought a better one - still single stage but with oil in the crankcase - and used the old tank for an additional 60 gallons on top of the one on the new compressor. Running some tools really eats up the air and unless you have a high cfm 2 stage Quincy, or a screw compressor, they eventually get behind and take a while to catch up.

As a side note, when I first hired in @ KSC, we had 2 big piston compressors at each shuttle pad (the shuttle pads were the old Apollo moon rocket pads, and Pad A is now SpaceX). At Pad A were 2 opposed piston Ingersol-rands, and a same model IR plus a Chicago pneumatic (when they were good, before HF used the name) at Pad B. The Chicago was a great compressor and the legend passed down to me was that it was either designed for or was taken out of a WW2 era submarine. That compressor required very little maintenance and ran great. The IRs on the other hand were always breaking and it seems we had one apart constantly and would often have to scramble and mix/match parts to get them all online for an upcoming launch. We replaced them all with 740 cfm Quincy screw compressors in the 90s and wow, what a difference. There were certain evolutions on the pad where part of the work order called us out to put both compressors on line manually, but after the change it was no longer needed.

At my new house I didn't get around to plumbing in lines, and have for yrs been using a little 4 gallon HF pancake compressor for doing basic things like tires, but have gone electric for everything else. I have some good battery tools, but also corded drills and grinders that have great power and run all day. Also, and this surprised me, I got an old electric impact from my father in law and it works better than my air driven ones. I've since bought a new one and use it for anything where an impact is needed and it works great. One common job I need to do regular are the blades on my riding mower. The air impact won't budge the big nuts holding them on, but the electric one will buzz those things right off. Granted, I never did own a top of the line IR or other premium air impact.

If I was to spend the $$ and do it right, I'd start by getting a Quincy 2 stage compressor, those are the best from my experience. Who knows these days though with manufacturing more and more being done in Offshore, but they were far better than any other make by a wide margin if sized and used right when I was working on them.

And, I wish I had a 2 or 4 post lift!

 

[Gary Lewis]

I carry one of the Slime 12V air compressors on my bike when on trips, and even then it does a barely adequate job and is really only for emergencies. If the pressure is low I normally just put quarters in a gas station inflater and use that.

I worked fluid systems for a living for many yrs and plumbed in quite a few compressed air line systems in facilities @ KSC over the course of 20+ yrs. In my old garage (at another property) I had installed hard lines and drops in several places in the shop. I was running it off a 60 gallon, 6 hp single stage oil-less compressor (never buy one of those!). I blew that one up so bought a better one - still single stage but with oil in the crankcase - and used the old tank for an additional 60 gallons on top of the one on the new compressor. Running some tools really eats up the air and unless you have a high cfm 2 stage Quincy, or a screw compressor, they eventually get behind and take a while to catch up.

As a side note, when I first hired in @ KSC, we had 2 big piston compressors at each shuttle pad (the shuttle pads were the old Apollo moon rocket pads, and Pad A is now SpaceX). At Pad A were 2 opposed piston Ingersol-rands, and a same model IR plus a Chicago pneumatic (when they were good, before HF used the name) at Pad B. The Chicago was a great compressor and the legend passed down to me was that it was either designed for or was taken out of a WW2 era submarine. That compressor required very little maintenance and ran great. The IRs on the other hand were always breaking and it seems we had one apart constantly and would often have to scramble and mix/match parts to get them all online for an upcoming launch. We replaced them all with 740 cfm Quincy screw compressors in the 90s and wow, what a difference. There were certain evolutions on the pad where part of the work order called us out to put both compressors on line manually, but after the change it was no longer needed.

At my new house I didn't get around to plumbing in lines, and have for yrs been using a little 4 gallon HF pancake compressor for doing basic things like tires, but have gone electric for everything else. I have some good battery tools, but also corded drills and grinders that have great power and run all day. Also, and this surprised me, I got an old electric impact from my father in law and it works better than my air driven ones. I've since bought a new one and use it for anything where an impact is needed and it works great. One common job I need to do regular are the blades on my riding mower. The air impact won't budge the big nuts holding them on, but the electric one will buzz those things right off. Granted, I never did own a top of the line IR or other premium air impact.

If I was to spend the $$ and do it right, I'd start by getting a Quincy 2 stage compressor, those are the best from my experience. Who knows these days though with manufacturing more and more being done in Offshore, but they were far better than any other make by a wide margin if sized and used right when I was working on them.

And, I wish I had a 2 or 4 post lift!

Jim - I have a 6HP Craftsman I'm loading up today to give to my brother. It is the noisiest compressor I've ever been around!

So, when I was looking at compressors it was going to be a twin-piston two stage unit. I looked at the Quincy, Curtis, and IR, but then called Eagle and talked to a tech. He asked questions about that I do and said "You don't want a two-stage but a single-stage". After describing the difference in pressure vs CFM I bought their 7.5 HP and 30 CFM compressor and have loved it. 👍

[fljab]

Jim - I have a 6HP Craftsman I'm loading up today to give to my brother. It is the noisiest compressor I've ever been around!

So, when I was looking at compressors it was going to be a twin-piston two stage unit. I looked at the Quincy, Curtis, and IR, but then called Eagle and talked to a tech. He asked questions about that I do and said "You don't want a two-stage but a single-stage". After describing the difference in pressure vs CFM I bought their 7.5 HP and 30 CFM compressor and have loved it. 👍

Warning, ramble alert!

A 2 stage will yield higher over all pressures in the system as a general rule, and more cfm out. It just depends on what you want. With higher pressure systems you need higher pressure components through out as a 2 stage is often 150-175 but some go to 250, and single stage are 110-125. Higher pressures equal both more storage for the same size tank (60 gallons of 175 psi is more than 60 gallons of 125), but it also equals power. If I was setting it up would put a regulator on the output of the tank and set at 100-125, but also have a bypass line to get full pressure when you need that extra oomph for an impact or whatever. A safer alternative would be to have a valved off QD directly on the receiver vs pressurizing the entire system to 175+.

Like with building horsepower in a truck or car, the higher you go then the more the entire driveline needs to be upgraded to support it. Again, if it were me would still probably go with a 2 stage with output at 150ish for the extra storage and power it offers when you need it, but it's not so much that building the system (and supporting air tools) would be exorbitant. For that matter, you could set up a pressure switch to turn on and off at any pressure you wanted for the most part, but you wouldn't want it to be drastically different than the designed pressure capacity of the compressor.

A common example of higher pressure storage is a scuba tank. The breathing air is at what, 2200 or so? That is reduced to a breathable pressure at the depth you're at, ie shallow depths it lasts much longer than deeper. Sea level is ~14.7 psia, and every 33' adds another atmosphere of 14.7 psia.

Another consideration is correct sizing of the compressor output for what is needed in that particular shop/environment. We often put in compressors that were way oversize to what a shop needed, but that is what was spec'd because the engineers @ KSC liked overkill. In many cases we had big maintenace problems with water not only in the system, but in the compressor itself. It would never run long or often enough to burn off or evaporate the water vapor, and that would end up in the oil of the compressor. We had huge problems with milky oil and would change the fluid on those often. Many times you'd get pure water for a good bit before the whitish sludge would start coming out, then we would refill with oil, run it, drain, and then fill up and leave it to try and get as much of that out as we could. Again, the Quincy's tolerated this much better than the IRs.

So, the short end of this rather lengthy writeup is that it's not only about cfm output, but storage and power/torque also, all of which should be considered when building a system. I am not in any way saying the 30 cfm single stage is inadequate for what you need, far from it. I mean, I've been using that little 4 gallon pancake compressor for over 10 yrs! I need something bigger to paint with, but it does what I need it to do for the most part. I get rambling sometimes when it comes to pressure systems as I lived it for a long time. My step mother was in the hospital a few months back and one time when I was up in the room the air breathing gas mixture guy came in and was adjusting the mix and output for her particular need (she had pneumonia). Anyway, I ended up getting in a fairly long, technical conversation that had all the rest of the relatives and others coming in and out in complete bewilderment, but he and I completely understood each other. I guess we all get to geek out on some subjects LoL....

 

[Gary Lewis]

Warning, ramble alert!

A 2 stage will yield higher over all pressures in the system as a general rule, and more cfm out. It just depends on what you want. With higher pressure systems you need higher pressure components through out as a 2 stage is often 150-175 but some go to 250, and single stage are 110-125. Higher pressures equal both more storage for the same size tank (60 gallons of 175 psi is more than 60 gallons of 125), but it also equals power. If I was setting it up would put a regulator on the output of the tank and set at 100-125, but also have a bypass line to get full pressure when you need that extra oomph for an impact or whatever. A safer alternative would be to have a valved off QD directly on the receiver vs pressurizing the entire system to 175+.

Like with building horsepower in a truck or car, the higher you go then the more the entire driveline needs to be upgraded to support it. Again, if it were me would still probably go with a 2 stage with output at 150ish for the extra storage and power it offers when you need it, but it's not so much that building the system (and supporting air tools) would be exorbitant. For that matter, you could set up a pressure switch to turn on and off at any pressure you wanted for the most part, but you wouldn't want it to be drastically different than the designed pressure capacity of the compressor.

A common example of higher pressure storage is a scuba tank. The breathing air is at what, 2200 or so? That is reduced to a breathable pressure at the depth you're at, ie shallow depths it lasts much longer than deeper. Sea level is ~14.7 psia, and every 33' adds another atmosphere of 14.7 psia.

Another consideration is correct sizing of the compressor output for what is needed in that particular shop/environment. We often put in compressors that were way oversize to what a shop needed, but that is what was spec'd because the engineers @ KSC liked overkill. In many cases we had big maintenace problems with water not only in the system, but in the compressor itself. It would never run long or often enough to burn off or evaporate the water vapor, and that would end up in the oil of the compressor. We had huge problems with milky oil and would change the fluid on those often. Many times you'd get pure water for a good bit before the whitish sludge would start coming out, then we would refill with oil, run it, drain, and then fill up and leave it to try and get as much of that out as we could. Again, the Quincy's tolerated this much better than the IRs.

So, the short end of this rather lengthy writeup is that it's not only about cfm output, but storage and power/torque also, all of which should be considered when building a system. I am not in any way saying the 30 cfm single stage is inadequate for what you need, far from it. I mean, I've been using that little 4 gallon pancake compressor for over 10 yrs! I need something bigger to paint with, but it does what I need it to do for the most part. I get rambling sometimes when it comes to pressure systems as I lived it for a long time. My step mother was in the hospital a few months back and one time when I was up in the room the air breathing gas mixture guy came in and was adjusting the mix and output for her particular need (she had pneumonia). Anyway, I ended up getting in a fairly long, technical conversation that had all the rest of the relatives and others coming in and out in complete bewilderment, but he and I completely understood each other. I guess we all get to geek out on some subjects LoL....

Jim - My understanding is that a 2-stage will give higher pressures, as you said, but lower CFM than a single-stage with the same size motor.

The way I believe it works is that a single-stage has both cylinders pumping directly into the tank. But a 2-stage has the large primary cylinder pumping into the smaller secondary cylinder. So the volume is less but the pressure is higher. Here's how Jenny describes it:

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. Typically, a single stage pump will have a higher CFM (Cubic Feet per Minute) rating than a two stage pump because every cylinder is drawing in air and compressing it with air during every rotation.

Two stage air compressors work in a very similar manner with the primary difference being that they compress the air in 2 steps or stages. During the first step or stage, air is drawn in and compressed to an intermediate pressure. After being compressed in the first stage, the air is piped, usually through an intercooler where the air is allowed to cool, to be compressed in the final or second stage. Two stage compressors are normally good for pressures up to 200psi. Two stage pumps are more efficient at higher pressures because the air is cooled between the stages.

As for oversizing a compressor, I'm sure that is very possible. But, the guidance I found helpful was to find your max CFM usage and buy a compressor that will provide twice that volume. That way the compressor will cycle on and off when you are running full-tilt, and during the off phase the air can cool in the tank and the compressor itself can cool. And it is easier to get moisture out of cool air than hot air.

That's how I sized my compressor and it has worked remarkably well. I can run my blast cabinet hard and the compressor will still cycle. And I really use the blast cabinet in my restorations as I like to powder coat everything, so every part has to go through the cabinet.

[fljab]

Jim - My understanding is that a 2-stage will give higher pressures, as you said, but lower CFM than a single-stage with the same size motor.

The way I believe it works is that a single-stage has both cylinders pumping directly into the tank. But a 2-stage has the large primary cylinder pumping into the smaller secondary cylinder. So the volume is less but the pressure is higher. Here's how Jenny describes it:

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. Typically, a single stage pump will have a higher CFM (Cubic Feet per Minute) rating than a two stage pump because every cylinder is drawing in air and compressing it with air during every rotation.

Two stage air compressors work in a very similar manner with the primary difference being that they compress the air in 2 steps or stages. During the first step or stage, air is drawn in and compressed to an intermediate pressure. After being compressed in the first stage, the air is piped, usually through an intercooler where the air is allowed to cool, to be compressed in the final or second stage. Two stage compressors are normally good for pressures up to 200psi. Two stage pumps are more efficient at higher pressures because the air is cooled between the stages.

As for oversizing a compressor, I'm sure that is very possible. But, the guidance I found helpful was to find your max CFM usage and buy a compressor that will provide twice that volume. That way the compressor will cycle on and off when you are running full-tilt, and during the off phase the air can cool in the tank and the compressor itself can cool. And it is easier to get moisture out of cool air than hot air.

That's how I sized my compressor and it has worked remarkably well. I can run my blast cabinet hard and the compressor will still cycle. And I really use the blast cabinet in my restorations as I like to powder coat everything, so every part has to go through the cabinet.

True, for a given electrical (or gas) motor, a single stage will put out more, but cfm output is always rated at a certain pressure output and that needs to be considered. Storing compressed air at 150-200 in a given size receiver is still more reserve capacity than storing 110-125.

I did a quick comparo online of IR compressors, both 5 hp, 230V, single phase, on upright 60 gallon receivers. The single stage drew 21 amps & put out 18.1 cfm @ 90 psi. The 2 stage drew 28 amps & put out 14.7 cfm @ 175 psi. The 2 stage was also ~$300 more. I see also that screw compressors are as small as 3 hp but are more than triple the price of a comparable 2 stage piston unit.

Single stage vs 2 stage is kinda like comparing a F150 to a F250. There is some overlap in engines and capacity, but F250s start out with 351 base engine plus bigger payload and go up from there, while that is getting near the top of the F150 line. If you want to tow a RV for instance, or car trailer, in many cases you can equip a F150 to do what you want for less money, but a F250 would do it in a base model and have way more towing capacity with options not available in a F150.

My little pancake HF compressor makes 110 psi or so and has less than a 1hp motor and single stage go up to (?) not sure, but 5 hp or so. 2 stage compressor start at 5 hp and go up to about as much as you want or need.

I know this is all moot for your system and what you did works great. That is a good rule of the thumb if you can figure out what you need and double it. Bottom line is single stage compressors are cheaper to buy, operate, and maintain plus put out a reasonable amount of pressure and cfm for most applications we need in our home shops, no argument there.

 

[PetesPonies]

True, for a given electrical (or gas) motor, a single stage will put out more, but cfm output is always rated at a certain pressure output and that needs to be considered. Storing compressed air at 150-200 in a given size receiver is still more reserve capacity than storing 110-125.

I did a quick comparo online of IR compressors, both 5 hp, 230V, single phase, on upright 60 gallon receivers. The single stage drew 21 amps & put out 18.1 cfm @ 90 psi. The 2 stage drew 28 amps & put out 14.7 cfm @ 175 psi. The 2 stage was also ~$300 more. I see also that screw compressors are as small as 3 hp but are more than triple the price of a comparable 2 stage piston unit.

Single stage vs 2 stage is kinda like comparing a F150 to a F250. There is some overlap in engines and capacity, but F250s start out with 351 base engine plus bigger payload and go up from there, while that is getting near the top of the F150 line. If you want to tow a RV for instance, or car trailer, in many cases you can equip a F150 to do what you want for less money, but a F250 would do it in a base model and have way more towing capacity with options not available in a F150.

My little pancake HF compressor makes 110 psi or so and has less than a 1hp motor and single stage go up to (?) not sure, but 5 hp or so. 2 stage compressor start at 5 hp and go up to about as much as you want or need.

I know this is all moot for your system and what you did works great. That is a good rule of the thumb if you can figure out what you need and double it. Bottom line is single stage compressors are cheaper to buy, operate, and maintain plus put out a reasonable amount of pressure and cfm for most applications we need in our home shops, no argument there.

I could never do my restoration work if my air powered tools were electric . . nope.

[Gary Lewis]

I could never do my restoration work if my air powered tools were electric . . nope.

I'm curious - would it be the weight, or RPM, or what that would keep battery-powered tools from working for you?

[ArdWrknTrk]

I'm curious - would it be the weight, or RPM, or what that would keep battery-powered tools from working for you?

Spray guns and sand blasters don't work too well on batteries