Hey guys!! Kicking around the idea of upgrading to a different air compressor. Right now I have a 25 gal. 2 stage craftsman unit, which as served me well over the years, the only complaint i have is that it's not so good with die grinders and DAs. So what do I need to look for? More cfm rating? Or a bigger tank? It would seem to me that a bigger tank would make it last longer before it would need to run, but then take longer to run until its filled. True? I tryied to search this but found what seems like a lot more BS than fact. Thanks guys!!!
Please explain air compressors
- Thread starter Gus68
- Start date
crewchief888
Well-known member
more cfm is what you need.
more cfm usually means a bigger tank, 220v, more peak pressure, and more money.
more cfm usually means a bigger tank, 220v, more peak pressure, and more money.
Kevin54
MEMBER EMERITUS
What size do you have now?
As far as running DA's and such, they're air hogs. I have a 5hp Ingersoll-Rand, 80 gallon 2 Stage that keeps up to most things except DA's. It doesn't cycle a lot, but it still cycles more than I would like. It may be the fact too, that I have it in the garage and when it kicks on, it's loud like and air compressor should be that bothers me. I don't have to wait on it, but the cycling noise is irritating. If I ever get a chance to add on, it's going into another section so I don't have to hear it.
BTW....like I said, I don't have to wait on it for a DA, but even air files and painting, I've never had to wait on it to catch up. It seems to pump up rather quickly. I'm sold on the IR. I'd like to hear from others that have the 80's but with larger motors myself.
As far as running DA's and such, they're air hogs. I have a 5hp Ingersoll-Rand, 80 gallon 2 Stage that keeps up to most things except DA's. It doesn't cycle a lot, but it still cycles more than I would like. It may be the fact too, that I have it in the garage and when it kicks on, it's loud like and air compressor should be that bothers me. I don't have to wait on it, but the cycling noise is irritating. If I ever get a chance to add on, it's going into another section so I don't have to hear it.
BTW....like I said, I don't have to wait on it for a DA, but even air files and painting, I've never had to wait on it to catch up. It seems to pump up rather quickly. I'm sold on the IR. I'd like to hear from others that have the 80's but with larger motors myself.
A bigger tank helps high CFM/low duty cycle tools like impact guns that tend to run in bursts.
However the tools you mention are high CFM/high duty cycle tools. In that case you want the pump's output to meet or exceed the tool's air consumption.
(ex: My Sioux DA consumes a whopping 15 CFM and my 5 HP/60 gallon IR compressor just barely keeps up.)
Instead of buying a new high capacity compressor you might want to look at an electric die grinder and DA.
However the tools you mention are high CFM/high duty cycle tools. In that case you want the pump's output to meet or exceed the tool's air consumption.
(ex: My Sioux DA consumes a whopping 15 CFM and my 5 HP/60 gallon IR compressor just barely keeps up.)
Instead of buying a new high capacity compressor you might want to look at an electric die grinder and DA.
do you mean 2 CYLINDER or 2 STAGE?? I have a hard time believing you have a 2 stage pump on only a 25 gallon tank; it is most likely 2 CYLINDER but only a SINGLE stage.. if it was a 2 stage, you wouldnt be complaining about not being so good with Da's or die grinders unless you are running multiples at the same time. If that's the case then you need more reserve, as in either a bigger tank or even a 2nd tank...
Most 2 stage compressors run at least a 60-80 gallon tank.
If yours now is a single stage I would seriously look to a real 2 stage.
Yes it IS a 2 stage (least thats what it says on it) and oilless, like I said, I have had the thing for about 8 years, and for normall mechanic work, I can't complain. But for die grinders and cut off wheels, it has a hard time keeping up. I never thought about a second tank, that sounds interesting, tell me more!!!
egnorant
Well-known member
Ugh...what is a DA? Kinda looking at upgrading my compressor and wonder if I use one!
Bruce
Bruce
Dual Action Sander. They consume a huge amount of air and tend to be used continuously.
wedge40
Well-known member
Thanks for asking Bruce. I managed to find it after googling for a few minutes.
Wedge
egnorant
Well-known member
Thanks, I tried the search and google but it didn't work out.
Bruce
Bruce
mitusa
Well-known member
I'm no expert on air compressors, but I think the "two stage" option is mainly used to boost air psi..... the second cylinder takes air from the first cylinder which has been compressed to a certain psi and then compresses it some more, to achieve a high psi such as 175 psi.
I have an IR two stage two cylinder 5 hp 80 gal air compressor. It will handle a DA but DA's are like others have stated, air hogs. If you are going to use them for extended time periods, I would suggest at least something similar to what I have. HTHs
I have an IR two stage two cylinder 5 hp 80 gal air compressor. It will handle a DA but DA's are like others have stated, air hogs. If you are going to use them for extended time periods, I would suggest at least something similar to what I have. HTHs
nevet hearfd of an oilless 2 stage all the s stage units I can ever remember seeing were standard piston type with an oil sump.
My particular one is a 5HP 80 gallon 2 stage 4 cylinder Emglo... 3 cylinders act as the 1st stage, compress the aid and push it to the 4th cylinder which compresses it further which is where the added pressure capability comes from. my compressor unit itself is a "V-4" configuration. (like half of a V-8 engine)
My particular one is a 5HP 80 gallon 2 stage 4 cylinder Emglo... 3 cylinders act as the 1st stage, compress the aid and push it to the 4th cylinder which compresses it further which is where the added pressure capability comes from. my compressor unit itself is a "V-4" configuration. (like half of a V-8 engine)
DirtRoad
Well-known member
I highly doubt its a two stage, ive been wrong before though
How about a pic of it?
How about a pic of it?
I too am put off by the "compressor industry" of today. All those ratings at the big box stores - very confusing. This is what I sorted out in the best way I can explain: the cfm/min rating MAY be the amount of air processed. Try to find the cfm/min DELIVERED.
I had a 3 hp Ingersoll Rand/60 gallon tank that was a disappointment - but I was running a blasting cabinet. It took a few minutes just to fill up the tank, even without running any tools. It stayed with my old garage, will make someone a great compressor for the normal week end use.
I was looking for a 5 HP compressor, but ran across a 7.5 HP Saylor Beall that was on closeout, so I jumped on it. It had an 80 gallon tank, probably a little small for that size, but that is probably why it was still available. My point is that a good compressor will keep up with the demand, a "too small" compressor will just run all the time.
Noise: in my opinion, "oil" is quieter than "oil less", slow pumps are quieter than fast pumps. I am looking forward to the "chunka chunka" rather than the "whirrrrrr".
Northern tool has a nice 5 hp vertical compressor worth checking out.
So, go bigger rather than smaller, slower pump rather than faster. Any tank size will work.
Don't have mine hooked up yet, still finishing up the garage. Soon, though, soon......
I had a 3 hp Ingersoll Rand/60 gallon tank that was a disappointment - but I was running a blasting cabinet. It took a few minutes just to fill up the tank, even without running any tools. It stayed with my old garage, will make someone a great compressor for the normal week end use.
I was looking for a 5 HP compressor, but ran across a 7.5 HP Saylor Beall that was on closeout, so I jumped on it. It had an 80 gallon tank, probably a little small for that size, but that is probably why it was still available. My point is that a good compressor will keep up with the demand, a "too small" compressor will just run all the time.
Noise: in my opinion, "oil" is quieter than "oil less", slow pumps are quieter than fast pumps. I am looking forward to the "chunka chunka" rather than the "whirrrrrr".
Northern tool has a nice 5 hp vertical compressor worth checking out.
So, go bigger rather than smaller, slower pump rather than faster. Any tank size will work.
Don't have mine hooked up yet, still finishing up the garage. Soon, though, soon......
Okay, I found that Northern one I referred to, it was $1199 when I was looking, now $1499. Two stage, 5 hp
I thought this was a good compromise, especially at the sale price.
http://www.northerntool.com/shop/tools/product_200596486_200596486
And here is a chart that shows cfm displaced vs delivered (Saylor Beall web site):
Spacing doesn't work out here, but the numbers are in this order, the last three number are CFM diplaced, CFM delivered, shipping weight:
motor HP ASME Tank Size Splash Lubricated Model Pressure Lubricated Model Pump RPM CFM Displaced @175 psi CFM Delivered @175 psi Shipping Weight (lbs)
1.5 60 715-60 PL-715-60 400 7.8 5.8 524
2 60 720-60 PL-720-60 510 10 7.5 545
3 80 730-80 PL-730-80 540 14.8 11.1 612
5 80 735-80 PL-735-80 845 23 17.3 628
7.5 80 745-80 PL-745-80 655 35.4 26.9 729
10 120 755-120 PL-755-120 845 46 34.4 875
15 120 451512 PL-451512 830 63.7 51 1195
20 200 92020 PL-92020 605 92.8 76.1 1643
25 200 92520 PL-92520 710 109 89.6 1657
30 240 93024 PL-93024 830 127.4 101.1 1893
I thought this was a good compromise, especially at the sale price.
http://www.northerntool.com/shop/tools/product_200596486_200596486
And here is a chart that shows cfm displaced vs delivered (Saylor Beall web site):
Spacing doesn't work out here, but the numbers are in this order, the last three number are CFM diplaced, CFM delivered, shipping weight:
motor HP ASME Tank Size Splash Lubricated Model Pressure Lubricated Model Pump RPM CFM Displaced @175 psi CFM Delivered @175 psi Shipping Weight (lbs)
1.5 60 715-60 PL-715-60 400 7.8 5.8 524
2 60 720-60 PL-720-60 510 10 7.5 545
3 80 730-80 PL-730-80 540 14.8 11.1 612
5 80 735-80 PL-735-80 845 23 17.3 628
7.5 80 745-80 PL-745-80 655 35.4 26.9 729
10 120 755-120 PL-755-120 845 46 34.4 875
15 120 451512 PL-451512 830 63.7 51 1195
20 200 92020 PL-92020 605 92.8 76.1 1643
25 200 92520 PL-92520 710 109 89.6 1657
30 240 93024 PL-93024 830 127.4 101.1 1893
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kaffine
Well-known member
My guess is this is the one he has.
http://www.searsoutlet.com/d/product_details.jsp?md=ct_md&pid=9142&mode=seeAll
5mall5nail5
Well-known member
I have an oilless 2 stage from Cman Pro. It's great. It's a 25 gal 2 stage 175 psi unit, oil less
^^^ same one I have
Cryptic1911
Well-known member
More cfm's are nice as that's how much air the pump itself can flow when it's running (and you're out of stored air in the tank), so if you have a constant draw on it, you need a pump with enough cfm's to keep the tool going and pump the tank back up at the same time. What is also needed is a larger tank for more volume, but also equally important is the max / peak PSI that the pump can stuff in that tank. That's your potential stored energy, and while running off of stored air in the tank, the cfm ratings don't matter since the pump doesn't come into play (until it kicks on). When running off stored air, all you are limited by is the diameter of the fittings and air lines
I have a CH 60 gallon, with an advertised 5 HP motor which I doubt. It probably puts out about 3 HP. I think the 5 HP rating may be a peak rating at start up. Having said all that, it runs my floor model blast cabinet and DA fairly easily. Constant use will drain it down to about 90 PSI, but it quickly fills back up to 120. I only paid a little over $650 for this compressor at Harbor Freight about 20 years ago, so I think I got my use out of it.
Al Bundy
Well-known member
y20dth
Well-known member
you can buy the same one you allready have and put it in parallel.
Fixnair
Well-known member
The advertising guys for the big box stores have ruined our industry! Tank size has really very little to do with your compressor providing you with enough air to get a job done. What you need is CFM. Single stage compressors, the most popular today and the cheapest, compress the air in one stroke of the piston to it's final output pressure. They are most efficient around 75 PSIG. Efficiency drops off from there and is very inefficient @ 125. (Ef @ 75 PSI =70% and only 45% @ 125PSI.) efficiency is actual delivered air compared to piston swept volume expressed as a %
A two stage compressor compresses the air in the first stage up to about 40 PSIG. Then deposited the air into an inter cooler where the heat of compression is given up to the atmosphere. The inter cooler delivers cooled air to the second stage cylinder where it is compressed again up to a final discharge of up to 300 PSIG. You could have more stages after the first two depending on how high you want to go. I've worked on compressors for the Navy working @10,000PSIG. Normally two stage compressors only go up to 175 PSIG and are rated at 60% efficiency. A single stage @ 175 would only achieve probably 20% ef.
Tank size only serves to shorten the start/stop cycling in your machine. For a three horsepower machine you would want a 30 gal. Receiver min and 60 gallon max. A 5 HP 60 gal is min and 80 gal is max. Most domestic compressors make about 4.5 SCFM of air per horsepower. Given that look for a three HP unit that will deliver around 13CFM, a 5 HP @23CFM.
Never buy an oiless compressor. They require ten times more service during their lifetime.
Well now you probably know more than you want so I'll get off.
A two stage compressor compresses the air in the first stage up to about 40 PSIG. Then deposited the air into an inter cooler where the heat of compression is given up to the atmosphere. The inter cooler delivers cooled air to the second stage cylinder where it is compressed again up to a final discharge of up to 300 PSIG. You could have more stages after the first two depending on how high you want to go. I've worked on compressors for the Navy working @10,000PSIG. Normally two stage compressors only go up to 175 PSIG and are rated at 60% efficiency. A single stage @ 175 would only achieve probably 20% ef.
Tank size only serves to shorten the start/stop cycling in your machine. For a three horsepower machine you would want a 30 gal. Receiver min and 60 gallon max. A 5 HP 60 gal is min and 80 gal is max. Most domestic compressors make about 4.5 SCFM of air per horsepower. Given that look for a three HP unit that will deliver around 13CFM, a 5 HP @23CFM.
Never buy an oiless compressor. They require ten times more service during their lifetime.
Well now you probably know more than you want so I'll get off.
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Fixnair
Well-known member
An oiless compressor is going to wear out much faster than a lubricated machine. A piston running in a lubricated cylinder really never wears out because the oil keeps them separated, in theory at least.
Now consider an oil free machine, the rod bearing is a sealed ball bearing on the big end and a Teflon bushing on the small end. Neither style is known for long service life. Now the piston is an aluminum piston which carries a large Teflon ring. Teflon has a large rate of expansion therefore must allow a lot of room for expansion and when cold is very loose and makes lots of noise. Teflon also wears a hundred times faster as a Piston ring than cast iron in lubricant as a piston ring.
Over the life of a lubricated compressor you will have replaced the oil free unit several times.
You could add storage tank to your system but think about what it gives you. You do get a little longer run time for your tool but the trade off is your compressor runs an equally longer time to replace what you used. So what did your expenditure of money get you? You could pipe the extra tank anywhere in the system. Compressed air is pretty dumb and doesn't care where the tank is.
What you need is a larger compressor and that requires a larger motor.
Now consider an oil free machine, the rod bearing is a sealed ball bearing on the big end and a Teflon bushing on the small end. Neither style is known for long service life. Now the piston is an aluminum piston which carries a large Teflon ring. Teflon has a large rate of expansion therefore must allow a lot of room for expansion and when cold is very loose and makes lots of noise. Teflon also wears a hundred times faster as a Piston ring than cast iron in lubricant as a piston ring.
Over the life of a lubricated compressor you will have replaced the oil free unit several times.
You could add storage tank to your system but think about what it gives you. You do get a little longer run time for your tool but the trade off is your compressor runs an equally longer time to replace what you used. So what did your expenditure of money get you? You could pipe the extra tank anywhere in the system. Compressed air is pretty dumb and doesn't care where the tank is.
What you need is a larger compressor and that requires a larger motor.
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Curious if these were Davey's?? Were those used exclusively for normal air . . . . or also modified for CNG (compressed natural gas)??
These are multi-stage like 4 . . . right??
Fixnair
Well-known member
Sorry to be so tardy in getting back to you but most of the HP stuff on the west last then was I/R, Worthington or Rix. I have worked on some Davey stuff for the Air Force. Mostly ground support equipment.
theoldwizard1
Well-known member
While this is the most common design for oil-less compressors it is not the only design. There is the wobble piston and diaphragm.
(1).jpg)
Lubed compressors, especially those that use cast iron cylinder and are pressure lubed have fantastic durability. However, I would not write off all oil-less compressors.
Shadowdog500
Well-known member
Check out this site on how to choose an air compressor.
http://www.jennyproductsinc.com/howtochoose.html
I got by with a 2 hp, 25 gallon craftman compressor for decades. It will run impacts, and air ratchets, etc, no problem, but I only started to run into problems when I got a blast cabinet and needed to blow out my new sprinkler system.
The big benefit with two stage is that it gives you higher pressure. Instead of 140 psi air you get 200 psi air. Do you need higher pressure in the shop? I don't. The drawback is that you get lower CFM out of the pump, so once you exhaust the tank in a few minutes with your blast cabinet the pump can't keep up.
A typical 5HP two stage pump has a large piston for the first squeeze then a second smaller piston in series to squeeze it a little more . A 5 HP single stage compressor usually has two big pistons in parallel that squeeze a lot more air to a lower pressure. So the pressure don't get up to 200PSI, but it can compress a lot more air to 135PSI.
I bought a single stage 5hp 60 gallon compressor and it will keep up with anything I do in my shop.
Chris
http://www.jennyproductsinc.com/howtochoose.html
I got by with a 2 hp, 25 gallon craftman compressor for decades. It will run impacts, and air ratchets, etc, no problem, but I only started to run into problems when I got a blast cabinet and needed to blow out my new sprinkler system.
The big benefit with two stage is that it gives you higher pressure. Instead of 140 psi air you get 200 psi air. Do you need higher pressure in the shop? I don't. The drawback is that you get lower CFM out of the pump, so once you exhaust the tank in a few minutes with your blast cabinet the pump can't keep up.
A typical 5HP two stage pump has a large piston for the first squeeze then a second smaller piston in series to squeeze it a little more . A 5 HP single stage compressor usually has two big pistons in parallel that squeeze a lot more air to a lower pressure. So the pressure don't get up to 200PSI, but it can compress a lot more air to 135PSI.
I bought a single stage 5hp 60 gallon compressor and it will keep up with anything I do in my shop.
Chris
Jvvmusme
Well-known member
District Attorney ?
Shadowdog500
Well-known member
Yeah, district attorneys and politicians tend to go through a lot of hot air!!!
You need at least a 10HP compressor to keep up with them!
Chris
porschedude996TT
Well-known member
I do also, two stage air screw compressor, oil-less. It is more like an axial jet engine than a pump.
Jvvmusme
Well-known member
I have a 45 gallon tank, a 110 volt 2 HP motor with a single stage 2 cylinder (65 mm pistons) compressor. When I use a 10 lb sodablaster from HB the psi drops to 60-70 psi and will not go up until I stop using the blaster. Meanwhile the compressor will run continuously.
Where can I improve my compressor ?
Where can I improve my compressor ?
onewaydave
Well-known member
Fixnair has it pegged.
But here is how I think of the tank. It is a reservoir so that the compressor doesn't run all the time. The pump could be used to run tools without any tank. But it would run constantly while the tool is used. The tank doesn't know what tools you are using and cannot regulate the output to the tool. So if you are only using 2 cfm but the pump is rated at 13 cfm, it would run the high out put all the time. A tank allows the pump to build up pressure and volume in a storage capacity that will run tools less than 13 cfm for "awhile" and when the pressure/volume in the tank is low the pump will cycle on, build up the storage faster than it is being used and then shut off.
Now, if you use a tool at the max output of the pump, the reservoir will be used up and the pump will try to fill the tank. But as you are using the storage as fast as or faster than, it can't keep up. Therefore it runs all the time. If you use a tool that consumed the pressure/volume faster than the pump can put out, you have wait time in addition.
So not only do you have to match the pump to the tank you should match it to the tool(s) used.
No I am not saying pressure and volume are the same but they both must be considered. Like horsepower and torque.
The basic principal of GJ applies, here. Calculate exactly what you need based on the tools you'll run, the number of people using those tools at one time and the length of time the tool will be used continuously. Then buy the biggest and most expensive monster you can almost afford. Immediately, on delivery, disassemble it to paint a custom coordinated scheme and modify the system with after coolers and hose reels. By the time you've finished that you will have built up the Garage slush fund and be able to start shopping for the larger unit.
Dave, the enabler.
But here is how I think of the tank. It is a reservoir so that the compressor doesn't run all the time. The pump could be used to run tools without any tank. But it would run constantly while the tool is used. The tank doesn't know what tools you are using and cannot regulate the output to the tool. So if you are only using 2 cfm but the pump is rated at 13 cfm, it would run the high out put all the time. A tank allows the pump to build up pressure and volume in a storage capacity that will run tools less than 13 cfm for "awhile" and when the pressure/volume in the tank is low the pump will cycle on, build up the storage faster than it is being used and then shut off.
Now, if you use a tool at the max output of the pump, the reservoir will be used up and the pump will try to fill the tank. But as you are using the storage as fast as or faster than, it can't keep up. Therefore it runs all the time. If you use a tool that consumed the pressure/volume faster than the pump can put out, you have wait time in addition.
So not only do you have to match the pump to the tank you should match it to the tool(s) used.
No I am not saying pressure and volume are the same but they both must be considered. Like horsepower and torque.
The basic principal of GJ applies, here. Calculate exactly what you need based on the tools you'll run, the number of people using those tools at one time and the length of time the tool will be used continuously. Then buy the biggest and most expensive monster you can almost afford. Immediately, on delivery, disassemble it to paint a custom coordinated scheme and modify the system with after coolers and hose reels. By the time you've finished that you will have built up the Garage slush fund and be able to start shopping for the larger unit.
Dave, the enabler.
theoldwizard1
Well-known member
You need more air volume (CFM). That typically means a bigger pump and a bigger motor.
Noisy sucker, 'aint it? I had a Husky version of this and needed those things airline guys wear on the tarmac.
dmeadow
Well-known member
Hmmm. Here's a thought. If the air is "dumb" to where the tank might be, would this make any sense:
I buy a two-stage 60 gallon compressor (specifically thinking of the HF one). I want two-stage but space issues restrict the size of the tank to 60. However, I have an old 20 gallon compressor that could contribute its tank to the cause.
The biggest air hog in my shop will be a small sandblast cabinet. For everything else, the two-stage 60 gallon tank will be more than enough.
So would it make sense to plumb the 20 gallon tank in series, with an on-off valve, next to the sandblast cabinet so it is only in play when I'm doing the sandblasting?
Is it worth the bother, or would it just be an exercise in extra plumbing?
I buy a two-stage 60 gallon compressor (specifically thinking of the HF one). I want two-stage but space issues restrict the size of the tank to 60. However, I have an old 20 gallon compressor that could contribute its tank to the cause.
The biggest air hog in my shop will be a small sandblast cabinet. For everything else, the two-stage 60 gallon tank will be more than enough.
So would it make sense to plumb the 20 gallon tank in series, with an on-off valve, next to the sandblast cabinet so it is only in play when I'm doing the sandblasting?
Is it worth the bother, or would it just be an exercise in extra plumbing?
theoldwizard1
Well-known member
It will help some, but it will not solve our air volume problem while sand blasting.
Air volume usage has a lot to do with "duty cycle", the percentage of "On" time to "Off" time, of the tool you are using. While you are sand blasting, the air is on continuously. It will just take longer until you consume the air built up inside the 2 tanks before the compressor kicks on and you are back in the same situation.
If you had a 500 gallon tank, it would take even longer before the compressor would kick in, and even longer to refill, but you would still be in the same situation.
sberry
Banned
I have 2 units, uses both tanks but one comp does 95% of the work. The second will come on if demand is high enough, that can be an option but is extra equipment and space for most people especially since a stand alone unit can be had reasonable to satisfy most common work.