Is compressor Maximum Pressure important?

[mdbrandy]

I'm comparing all sorts of compressors (reading all the threads I can in the forums), and I haven't come across the answer to whether the maximum compressor pressure is important. I'm looking at an Ingersoll Rand compressor:
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_211720_211720
that seems to have good specs; 30 amp motor, 18.1 CFM at 90 psi, for about $800 with free shipping, but the max pressure on the unit is only 135 psi. Seems very low pressure compared to most other compressors. Is CFM more important, or tank pressure? I'd love to spend $1200 - $1500 on a nice 2 stage Quincy, Belaire, etc., but I don't think I can swing that.

I use some air tools, I've done a bit of blasting in a small cabinet, and I'm preparing to HVLP paint.

Thanks for any input.

Mark

[Serge]

The higher the pressure the more air you have in your tank, thus a bigger reserve. That's the advantage of the higher pressure. Also, the pressure differential with your working pressure will help the compressor stay on top of things. At 135 psi, these are the newer breed, the old models were 125 I believe, so that's 10 in your pocket...

You should be fine for a one tool at a time operation. It will work hard though and in some instance, you might have to wait for your compressor to catch up with grinders, angle grinders and sanders. Paint guns you should be allright. But expect this compressor to produce alot of water if you use it hard like with a grinder or sander as it will get very hot and the hot compressed air will contain much water in humid climates (in NV you would be allright!...) So pipe in conscequence, with proper care and a water trap and filters you will be fine.

A good investment is an automatic drain that will empty water from the compressor at set interval (it's a timer on a valve).

Have you looked at more robust units used? You can usually find good deals in bigger compressors used. I think you could get a nice one for $800...

Just my 2 cents.

Serge

[mdbrandy]

The higher the pressure the more air you have in your tank, thus a bigger reserve. That's the advantage of the higher pressure. Also, the pressure differential with your working pressure will help the compressor stay on top of things. At 135 psi, these are the newer breed, the old models were 125 I believe, so that's 10 in your pocket...

You should be fine for a one tool at a time operation. It will work hard though and in some instance, you might have to wait for your compressor to catch up with grinders, angle grinders and sanders. Paint guns you should be allright. But expect this compressor to produce alot of water if you use it hard like with a grinder or sander as it will get very hot and the hot compressed air will contain much water in humid climates (in NV you would be allright!...) So pipe in conscequence, with proper care and a water trap and filters you will be fine.

A good investment is an automatic drain that will empty water from the compressor at set interval (it's a timer on a valve).

Have you looked at more robust units used? You can usually find good deals in bigger compressors used. I think you could get a nice one for $800...

Just my 2 cents.

Serge

I'm just a hobbyist, so it'll always be one tool at a time...

I've read other suggestions to look at more robust used units, but I'm not sure where to look. I live in Central Illinois (Champaign), and there's nothing in the newspaper classifieds. I'm 150 miles plus or minus from Chicago, Indianapolis and St. Louis, but I'm not sure how I'd find things there yet. I've been doing some internet searching, but haven't come across any appropriate units on the few "used" sites that I have encountered. If there are any known "used tool" sites that anyone can point to, that would be great!

Thanks.

Mark

[DougE]

I was in the same position when I looked for my compressor. I eventually bought the one you linked and while I don't use it every day, it has served me well.

I don't do a lot of body work anymore, but when I do it supports me. I spray with a GTI that drinks 14.7 cfm at 30 psi and the compressor doesn't lag at all. As Serge said, though, make sure you have adequate water traps and drains and it should be OK.

I wasn't able to find any used equipment that I wanted so I went with new. May have just been that I didn't know where to look...

[stealth1]

That does look like a good overall compressor for the money, a lot of CFM for the money. I agree that the used units are usually hard to find and you don't really know if it has been used hard plus most of the time the larger units will be three phase and if your not a large commercial shop you usually don't have access to three phase power.

Another good compressor for $800 is at SAMS CLUB if you have one of those near you (Wal-mart's big brother) they have a Delta 80 gallon with about the same CFM specs and it is a very robust looking unit, heavy piping etc. and I have talked with people that run small shops off of these compressors and so far they are up to 5 years with no problems at all. Just my two cents if you have a Sams you might stop in, they also do payment plans in house which for that compressor is about $20 a month ! If it is not in stock they can usually get it for you and if I remember right it was like $780 so right at what your looking for with a larger tank. Happy shopping..............:D

[mdbrandy]

That does look like a good overall compressor for the money, a lot of CFM for the money. I agree that the used units are usually hard to find and you don't really know if it has been used hard plus most of the time the larger units will be three phase and if your not a large commercial shop you usually don't have access to three phase power.

Another good compressor for $800 is at SAMS CLUB if you have one of those near you (Wal-mart's big brother) they have a Delta 80 gallon with about the same CFM specs and it is a very robust looking unit, heavy piping etc. and I have talked with people that run small shops off of these compressors and so far they are up to 5 years with no problems at all. Just my two cents if you have a Sams you might stop in, they also do payment plans in house which for that compressor is about $20 a month ! If it is not in stock they can usually get it for you and if I remember right it was like $780 so right at what your looking for with a larger tank. Happy shopping..............:D

We do have a Sams club, and my wife is a member. I hadn't thought to look there. But now I will :).

Thanks.

Mark

[mdbrandy]

Unfortunately, the Sam's here in town has nothing bigger than a little 2 tank portable Bostich unit. I think I saw the Delta on Sam's online, but it said "in store only", and unfortunately, once I selected a store, I can't find one anywhere within 100 miles (or more) that lists it. Only Coleman Powermate compressors. And now I can't "unselect" a store, so I can't even find the Delta anymore. If I wasn't a programmer myself, I'd be cussing out whomever programmed the Sam's Club shopping site...

[Mooch]

My compressor is rated at 32CFM at 175 psi .But ever since I bought it 15 or so years ago I have always set it at 150 psi . I believe it will lengthen the life of the pump and so far so good. Very seldom will you ever use over 100 psi anyway.
I believe the compressor you are talking about will work just fine for you.
Serge is a pro and uses his much more and longer than us. Mooch

[mdbrandy]

My compressor is rated at 32CFM at 175 psi .But ever since I bought it 15 or so years ago I have always set it at 150 psi . I believe it will lengthen the life of the pump and so far so good. Very seldom will you ever use over 100 psi anyway.
I believe the compressor you are talking about will work just fine for you.
Serge is a pro and uses his much more and longer than us. Mooch

I know I won't need any absolute pressures over 100psi, but the point about more pressure equalling more reserve air is a good one. The ideal gas law gives you that. But the consensus seems to be that for a hobbyist, the ingersoll-rand machine should do the job, if having to work a little hard once in a while. That's good to know. I'll be researching a bit longer - I hope to buy within a couple weeks. Need to be ready to work/paint by mid to late summer.

Oh, and the pros are the ones with the most experience, so I'm always happy to get their advice!

Thanks.

Mark

[dclark]

I have that IR compressor that you're looking at. It does very well for me. I have been cutting sheet metel and sanding on my truck all spring long, no problems. Although I do have about 75 feet of 1.5 inch galvanized pipe run which gives me another 50 or so gallons of air. Why don,t you go to farm and fleet there in Urbana( I'm from Danville) and check out the 2 stage Porter Cable they have for about 850-900 dollars. It's 60 or 80 gallons. Better choice than the single stage IR. I would have done that myself but didn't think I wanted to drive to Danville in the winter with it in the back of my truck. Good luck!

[stealth1]

I agree with dcclark that Farm and fleet will often have good deals, they have a Porter Cable 80 gallon with 175psi MAX and does 17.4cfm@100psi with a V-style pump for $750 on sale right now. The Ingersoll Rand looks like a great deal, just trying to give you some options........best of luck

[mdbrandy]

I have that IR compressor that you're looking at. It does very well for me. I have been cutting sheet metel and sanding on my truck all spring long, no problems. Although I do have about 75 feet of 1.5 inch galvanized pipe run which gives me another 50 or so gallons of air. Why don,t you go to farm and fleet there in Urbana( I'm from Danville) and check out the 2 stage Porter Cable they have for about 850-900 dollars. It's 60 or 80 gallons. Better choice than the single stage IR. I would have done that myself but didn't think I wanted to drive to Danville in the winter with it in the back of my truck. Good luck!

I actually did go look at that Porter Cable unit. So far I had only seen one mention of Porter Cable compressors on any web forum (not this one), and it was negative. Not a thorough analysis, I know. But I'm still researching, and it is still a possibility.

Thanks!

Mark

[dclark]

I actually did go look at that Porter Cable unit. So far I had only seen one mention of Porter Cable compressors on any web forum (not this one), and it was negative. Not a thorough analysis, I know. But I'm still researching, and it is still a possibility.

Thanks!

Mark
Don't know anything about their compressors but if they're anything like their tools you can't go wrong. right up there with dewalt.

[nsjuice]

WOw.

New here, and already .. I've absorbed so much information.

THanks for the Compressor link. I'm opening up shop soon.. and I'm glad to have seen it.

I need some advice on this IR compressor. I want to run 2 compressors in my 3k sqft. shop. the IR for the paint booth, and a higher rated CFM for shop use.

Does anyone have any objections to this?

Will the IR suffice for Paint gun use? I currently shoot with a IWatat LV400

THanks for any help, and I apologize if I've hijacked this topic.


Awesome Forum and Members.

[dclark]

This IR compressor we are talking about is more for the home hobbyist. It's big but I would want a two stage for a shop. I'm no expert on compressors but I don't think this one would suffice for production work. Hopefully some of these guys who paint for a living will chime in here and point you toward a good compressor for higher volume of work. Good luck!

[mdbrandy]

I actually did go look at that Porter Cable unit. So far I had only seen one mention of Porter Cable compressors on any web forum (not this one), and it was negative. Not a thorough analysis, I know. But I'm still researching, and it is still a possibility.

Thanks!

Mark
I did a little more digging on the Porter Cable Compressor that I can get locally. The specs are:

Model No. C7550
Horsepower Peak 7.0
Voltage-Single Phase 240V
Minimum Branch Circuit Requirement 30 amps
23 amp motor (nameplate)
*Fuse Type Time Delay
Air Tank Capacity, Gallons 80 ASME, Vertical
Approximate Cut-in Pressure 140 PSIG
Approximate Cut-out Pressure 175 PSIG
SCFM @ 100 psig 15.6
SCFM @ 175 psig 15.2

The IR that I was looking at is:

Motor: 5.0 HP/11.5 Peak HP - single phase motor
Volts: 230 Volts/30 Amps
PSI: 18.1CFM @ 90PSI/ 15.5CFM @ 135PSI
Max PSI: 135 PSI
Tank Size: 60-gallon vertical
Pump: Oil lube cast iron belt driven pump
Air Outlet: 1/2in. NPT
100% continuous duty
Drain System: Manual Drain
Start Up Kit: 1592008; sold separately
Dimensions: 20in.L x 30in.W x 71in.H
U.S.A.
Model SS5L5

So the CFM around 90/100 psi is higher with the IR. But the tank and max pressure are bigger/higher with the Porter Cable. ARRGH! Too many choices. They are both about the same price. Is the 2 stage/80 gallon likely a better machine than the 1 stage/60 gallon for all-around use?

Thanks.

Mark

[dclark]

I did extensive research on posts before I bought mine. There are guys out there much smarter than me that can explain the difference between 2 vs. 1 stage.Even though the air pressure specs look higher on the single stage it doesn't provide the same cfm's, don't ask me why, it's just what I have learned. There are other paint forums that you can research for your answers if you are looking for specifics. I do know that a 2 stage is the much better choice . You won't run out of air with an 80 gallon 2 stage for the home hobbyists. I get along good with my 80 gal single stage IR but like I said, I have alot of pipe plumbed for additional reserve. I wish I had a 2 stage. Better to have two much and not need it than to not have enough and wish you had it. IMO you should go with the porter cable. Same price, good brand name and way more air availability.You'll never be dissapointed.

[mdbrandy]

Interesting thread here:

http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=8;t=000039;p=0

A "newbie" tutiorial on compressors.

[stealth1]

mdbrandy,

Great link about compressors, I especially enjoyed the story of the gas station guy and the old Quincy compressor with no oil ! :eek:

[SuthnCustoms]

this isnt a suggestion about what one to buy but just a personal experiance on a Porter Cable
I bought a 60 gallon 2 stage porter cable about 4 years ago to use for air tools around the house for 450.00..it has yet to let me down & use it ALOT..was kind of concerned about it keeping up with painting once i started painting on my own..it keeps up just fine with my finishline III gun & the cheap walmart special cambel hausfeld 1/4 tip gun ive used in the past before i got the devilbiss gun..ive also used it alot for an air ratchet..air grinders & such for work on cars & building/fabricating slot of things around here..it keeps up just fine with those too..for the price i dont think anyone can go wrong with a porter cable unless money isnt the issue ..one thing ive done with mine is buy a cheap fan from a dollar store & put it directly on the compressor cylinder to keep it cooler in the hot summer months around here

[Phil V]

SCFM @ 100 psig 15.6
SCFM @ 175 psig 15.2

There is no way those figures are accurate, it has to be a misprint or the company had a brain fart when they came up with those initial figures. If a compressor is at around 15 cfm @ 175 psi then its going to close to 19 cfm @ 100 psi. Also if its putting out 15 cfm @ 100 psi then it will be around 11 cfm @ 75 psi. The higher the psi the lower the cfm, the compressor has to work harder to make those higher pressures, so the cfm will be lower.

To the guy getting setup with a 3,000 square foot shop for commerical use.
If you are setting up your shop to make money then you can justify the cost of a commerical/industrial air compressor like a Quincy etc. I bought a Quincy 5 hp, two stage, 80 gallon tank compressor new 22 years ago for $1800. It has operated flawlessly just about everyday in my commercial body/paint shop. I could have bought a less expensive compressor for around $1,000 to $1,200 and would likely be on my third compressor by now.
This is one of those instances where spending more mone to start with saves you money in the long run. Not to mention the down time and aggravation when a lesser expensive compressor goes bad. In any autobody/paint environment the air compressor is by far the most important tool in the shop, a good one can make your life a lot easier and a bad or marginal compressor can make your life miserable.

For the other guys, in most cases a 2 stage compressor is better than a single stage. The best advice I can give you is buy the most expensive largerst compressor you can afford (even if you have to borrow a little money). I don't like the saying "you get what you pay for" because in many cases its just not true. BUT when it comes to compressors that rule just about always applies.

[mdbrandy]

SCFM @ 100 psig 15.6
SCFM @ 175 psig 15.2

There is no way those figures are accurate, it has to be a misprint or the company had a brain fart when they came up with those initial figures. If a compressor is at around 15 cfm @ 175 psi then its going to close to 19 cfm @ 100 psi. Also if its putting out 15 cfm @ 100 psi then it will be around 11 cfm @ 75 psi. The higher the psi the lower the cfm, the compressor has to work harder to make those higher pressures, so the cfm will be lower.

Is that from experience, or is there actually a way to calculate it with a 2 stage compressor? I thought it was a little strange myself, but if you go to the actual Porter Cable site:

http://www.portercable.com/index.asp?e=547&p=5507

it gives a couple more numbers:

SCFM Air Delivery
@40 PSI: 16.4
@90 PSI: 15.2

Which don't quite match up with the other figures given on the side of the compressor (the ones you note above I got right off the compressor tank label).

Any ideas on how to verify these numbers? Should I worry about the inconsistencies here? I'd tend to trust the nameplate info over the web advertisements.

A few other pieces of info are that the motor is a "WEG" made in Brazil, runs at 3450 rpm drawing 23.0 amps, and the pump runs at 1400 rpm.

Thanks for the discussions - there's so much info out there, it helps to focus on some of the issues.

Mark

[John McGraw]

I would not even consider buying a single stage compressor system. If you look further in Nothern's catalog, you will find another IR compressor that would be a much better choice. It is a 7.5 hp T-30 compressor. This is the compressor that I use in my shop, and I am tickled pink with it. It pumps out 24 SCFM, and runs quiet for a compressor this large.
A single stage compressor will make very large CFM's with pretty small motors, but the CFM drops like a rock as the pressure increases. 2 stage compressors make high CFM at high pressures, but the CFM does not go up very much as the pressure drops. I can run a blast cabinet at 120 PSI and never run the pressure down on this compressor! That being said, If you are never going to need hgh pressure, you could get by with a single stage unit, and it can make huge volumes of air if you keep the tank pressure low and spin the pump fast.
In reality, you will find that you do use high pressure a lot more than you think you will. A grinder is not really happy if it is not running at 90-100 PSI, and my air file tends to stall at much below 90 PSI. As the air makes it's way through your shop piping, dryers, and filters, you will have substantial pressure drop as well. I have almost a 20 PSI pressure drop on my distribution system when using a high volume tool like a grinder of blast cabinet. Buy the most compressor you can afford, and you will never be sorry.
I have bought some of the 5 hp 2 stage inexpensive units before, but the pumps run at a high speed and they are loud and tend to wear out at a much faster rate. I expect that the IR T-30 is the last compressor I will ever own, and I think that at about $1500, it is a bargain. The 7.5 hp is the largest compressor motor that can be run on single phase power, and 24 to 25 CFM is about as good as you are going to get without going to a duplex type compressor with two pumps and two motors. There are several Cast iron compressors that are comparable to the T-30, but they are all about the same price. Quincy also makes a very good, long-lived compressor.

Regards, John McGraw

[mdbrandy]

I would not even consider buying a single stage compressor system. If you look further in Nothern's catalog, you will find another IR compressor that would be a much better choice. It is a 7.5 hp T-30 compressor. This is the compressor that I use in my shop, and I am tickled pink with it. It pumps out 24 SCFM, and runs quiet for a compressor this large.
A single stage compressor will make very large CFM's with pretty small motors, but the CFM drops like a rock as the pressure increases. 2 stage compressors make high CFM at high pressures, but the CFM does not go up very much as the pressure drops. I can run a blast cabinet at 120 PSI and never run the pressure down on this compressor! That being said, If you are never going to need hgh pressure, you could get by with a single stage unit, and it can make huge volumes of air if you keep the tank pressure low and spin the pump fast.
In reality, you will find that you do use high pressure a lot more than you think you will. A grinder is not really happy if it is not running at 90-100 PSI, and my air file tends to stall at much below 90 PSI. As the air makes it's way through your shop piping, dryers, and filters, you will have substantial pressure drop as well. I have almost a 20 PSI pressure drop on my distribution system when using a high volume tool like a grinder of blast cabinet. Buy the most compressor you can afford, and you will never be sorry.
I have bought some of the 5 hp 2 stage inexpensive units before, but the pumps run at a high speed and they are loud and tend to wear out at a much faster rate. I expect that the IR T-30 is the last compressor I will ever own, and I think that at about $1500, it is a bargain. The 7.5 hp is the largest compressor motor that can be run on single phase power, and 24 to 25 CFM is about as good as you are going to get without going to a duplex type compressor with two pumps and two motors. There are several Cast iron compressors that are comparable to the T-30, but they are all about the same price. Quincy also makes a very good, long-lived compressor.

Regards, John McGraw

It appears as though you are talking about this one:

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200318469_200318469

At $1899.99, it is quite out of the question for me price-wise, especially since I just today lost a $2500 opportunity this summer that might have paid for more of a machine (teaching computer programming - nothing to do with a compressor :). I am just about sold with going with a smaller 2 stage machine, and so far I have not gotten any solid negatives about the Porter Cable 2-stage that we've mentioned in this thread. As a hobbyist (and a busy one), if I used it more than 200 hours in a year, I'd be lucky (lucky meaning I would have gotten a lot of hobby time over the year!). Maybe 10 years down the road, when all the kids are out of college, I'll have more time, more space, and with any luck, more money! So hopefully an $800 2-stage machine would last 10 years worth of 200 hour running years. Then I can sink $2000 into a "real" compressor if I want to.

It's all good advice. When I win the lottery, I'll take it :). Oh-I guess I'd have to play the lottery in order to win!

Thanks.

Mark

[Len]

Mark
The Porter Cable that you mention is plenty of compressor for most small shop. As far as quality goes I couldn't tell you if it's good or bad. Also check out the American IMC BelAire compressor below, it's in the same price neighborhood and I can vouch for it's quality and should parts or service ever be needed it is readily available.


http://autobodystore.net/Merchant2/graphics/00000001/TN-bel218VW.gif
Bel Air Compressor Link (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=BEL218Vw&Category_Code=C1)

[mdbrandy]

Mark
The Porter Cable that you mention is plenty of compressor for most small shop. As far as quality goes I couldn't tell you if it's good or bad. Also check out the American IMC BelAire compressor below, it's in the same price neighborhood and I can vouch for it's quality and should parts or service ever be needed it is readily available.


http://autobodystore.net/Merchant2/graphics/00000001/TN-bel218VW.gif
Bel Air Compressor Link (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=BEL218Vw&Category_Code=C1)

Thanks for the Link, Len. I have certainly looked at all the Bel Aire compressors, but that one is still about $400 more than the PC that I can get locally, plus I assume there would be somewhere around $200 shipping. It probably is a better machine, but that $400-$600 is earmarked as the majority (or more) of the price of a Hobbyair system. Add another $300 for a good gun, and I'm at about the $1500 that I can afford to spend on a compressor/respirator/gun setup right now. That's essentially my target.

Thanks again.

Mark

[Phil V]

Mark, that porter cable actually should work fine for your needs. I would (or have someone who knows compressors) reset the kick on/kick off pressure of that compressor from the 175 psi to around 150 - 155 psi. For autobody/paint use there is no reason to run a compressor to 175 psi shut off. I dropped the kick on/kick off pressure of my Quincy to 135 kick on and 155 psi kick off. The pump and the electric motor will last appreciably longer because that last 25 psi on a two stage compressor is the hardest that compressor has to work. It works harder, more strain on the elctric motor, more friction with the moving parts of the compressor pump, the pump will run hotter, produce more moisture. By dropping the psi the compressor will cycle a little more often but the end result it will run less.

[Len]

Thanks for the Link, Len. I have certainly looked at all the Bel Aire compressors, but that one is still about $400 more than the PC that I can get locally, plus I assume there would be somewhere around $200 shipping. It probably is a better machine, but that $400-$600 is earmarked as the majority (or more) of the price of a Hobbyair system. Add another $300 for a good gun, and I'm at about the $1500 that I can afford to spend on a compressor/respirator/gun setup right now. That's essentially my target.

Thanks again.

Mark

Most of the 80 gallon IMCs are shipped at no charge but it's still a more expensive compressor. The PC compressor will probably serve you well in a small shop, just be sure to pipe it reasonably will and it should do a good job for you.

[mdbrandy]

Most of the 80 gallon IMCs are shipped at no charge but it's still a more expensive compressor. The PC compressor will probably serve you well in a small shop, just be sure to pipe it reasonably will and it should do a good job for you.

Len - Ah, I hadn't actually investigated the shipping. Since it wasn't "advertised" as such, I just assumed...and we all know what that gets me... :).

Phil V - I have downloaded the Users Manual on the thing; I'll see what it tells me about resetting the pressure. I'm just about ready to go do it, I think...

On the piping, I have "mapped out" a setup in my garage that would involve around a 40 foot run. I've read posts on soldered copper, brazed copper, and black iron. Any opinions on whether threaded black iron is reasonable for a garage shop that only gets used 200 or so hours a year? It would be a lot easier than doing all that soldering or brazing (which I've never done before). I may be out of this house in 5 to 7 years as well, so I can always "upgrade" in the next place...

Thanks for all the opinions. I'm an engineer by occupation, but mostly computer simulations - the guys that work with the machinery on a daily basis are the ones that REALLY know how it works!

Mark

[Phil V]

Back iron pipe is my choice for running air lines. Its easy to setup, no leaks. You can even disassemble it when you move and reassemble it in your new shop (I've done that twice with the air line system currently in my shop). Some will say that the pipe rusts on the inside because its iron/moisture but it has never been an issue for me for the last 20 years with the same piping system.

[mdbrandy]

Back iron pipe is my choice for running air lines. Its easy to setup, no leaks. You can even disassemble it when you move and reassemble it in your new shop (I've done that twice with the air line system currently in my shop). Some will say that the pipe rusts on the inside because its iron/moisture but it has never been an issue for me for the last 20 years with the same piping system.

Excellent! It's always nice to get the answer that you were hoping for! It happens so seldom... :).

Mark