80 gal. air compressor buying advice ?

[CKurtz]

I'm in the market for an 80 gal. vertical air compressor in the $800 to $1400 dollar range and between 5 and 7. 5 hp.



I'm looking for something that will go to at least 140 lbs of pressure @ around 17cfm or more.



I've looked all over the place and on line and I've come up with these questions.



1 Cast iron or aluminum pump/cyl/head ?

2 Single phase or more on the motor ?

3 Single stage or more on the compressor ?

4 Lubrication type ?

5 What brand names are good ones ?





Any info or anything else I should consider would be appreciated.

 

[Paychk]

1) Complete cast iron compressor (not just iron cylinder bore)

2) Unless you have 3 phase power you are limited to single

3) The only way to get 140 psi in the holding tank is a two stage compressor

4) Pressure lube is best, but those are very expensive

5) Gardner Denver, Champion, Quincy, Bel Aire, some Ingersoll-Rand



The slower the compressor head runs, the longer it will last.



What ever you do, don't use PVC for the piping system!

 

[QRTRHRS]

Dunno about the brand but be very very careful about buying FOB. More often than not, air compressors are poorly packaged for shipping. I can't tell you how many I have seen damaged in shipment. It's not so bad when there are a lot of them loaded together so they support and stabilize each other. It is when you order one and it is jammed in with other freight.

 

[QRTRHRS]

One other point.

Use vibration dampers when you bolt it to the floor. They look like simple blocks of rubber say 4x4x3/4" or so but are a special composite. They relieve the stress on the legs. Many compressor sources sell them.

 

[CKurtz]

Thanks for the advise so far guy's.

I have a 4' x 4' cement slab that I poured next to my shop when I poured the foundation.

It is on the outside of the shop and I was planning on putting the compressor there on some rubber pads of some kind and anchoring it down to the concrete.

I was then going to build walls and a roof around it with good ventilation and of course a door.

I have already wired a 220 circut out to it for power.

I was planning on using 1/2 inch black or galvanized pipe for the inside of the shop along the ceiling and down to different places inside for air lines.

Someone suggested I use schedule 40 PVC but I think for an air system up to 175lbs of pressure the PVC would make me a little nervous.

 

[Un-Hemi]

What I use is 1/2" copper water pipe 'cuz it's easier to solder the connections than cut threads, it doesn't rust, and it dissipates heat well. Plastic pipe should not be used for air, IMO. I also regulate to about 100psi at the compressor because almost everything that runs on air is spec'd for 90psi. I can't imagine where 175psi would be used for anything outside of the storage tank.



If I were to purchase another compressor (unlikely, because the one I have will outlast me), I doubt that I would purchase a 2-stage. Compressing air to 175psi introduces a lot of heat that must be disposed of. I have measured the outlet air temperature at 275 degrees!



Having said that, my compressor is a Speedair 5Z397. It serves me well. Cast iron, two-stage. 80gal. 220V single phase. Splash-oiled, but that's OK; most of the affordable ones are. Oil can and should be changed often.



Another consideration is that the 5Z397 has a 5hp motor, and runs about 22 Amps under load; good wiring is a must.



Spend lots of your money on water removal. Compressing air automatically takes it to 100% humidity, and water is a bad thing.

 

[Philip]

Don't use PVC for your piping. I also recommend the copper pipe. I use 3/4" in my garage. It goes up faster than pipe does. You also won't have rust problems later in the life of the system.



When you are looking at brands. Check the RPM the compressor runs at. Find the lowest compressor RPM you can for the same CFM flow rating. Low RPM means a long life compressor.



Go with a 220 volt single phase compressor. I would recommend getting one with mechanical contactors. This way the motor will be overload protected better. Noncontactor compressors use the air pressure switch to controll the motor. This leads to a faster death of the pressure switches.



I am partial to the Ingersol Rand series compressors. I have a Type 30 model two stage. It is 5 HP low RPM compressor. If you look at this line. In the 5 HP model there are three different compressors listed. The difference is compressor RPM's. They make a 1500 RPM> 1200RPM>750RPM. The low RPM is the highest priced one.

I can't imagine where 175psi would be used for anything outside of the storage tank.

LOL you ever needed to break off large dia bolts before. Even tho most air tools are rated for 100 PSI. Some tools will double the power at higher pressures. I use IR 231 impacts wrenches. At 100 PSI I can't break any bolts above 3/8". At 175 PSI I can snap 5/8's bolts off if I need to. This saves time not having to dig out the cutting torch. Just turn up the air regulator if the need comes up.

 

[Sled Puller]

Quincy is my dream compressor, but I have a surplus compressor now, that has served me well for 10 years or so. Kept up with a decent size sandblaster and plays with air tools. 23 cfm, dual stage, 5hp.





Use metal pipe, as it aids in water removal.



www.tptools.com



That company explains a lot about air compressors, and even has diagrams on proper air line,water removeal, oiler installation. Use them for reference, but shop elsewhere$$$$!

They do run sales during car show season that you can get a deal.



If you want to build one:



http://www.surpluscenter.com/sort.asp?UID=2004051210171762&catname=air&keyword=APBP

 

[Sled Puller]

http://www.tptools.com/statictext/airline-piping-diagram.pdf



That explains in detail why metal pipe. My friends laughed at me when I built mine with black pipe, they said it would draw moisture, lol. Hehehhe!



TiP doesn't like copper either, but a local shop here built a system from copper 20 years ago and it has never leaked.





Good link about air consumption:

http://www.tptools.com/statictext/air_consum.asp

 

[MFalkinham]

Excellent advice so far.....



I would add that you might also consider an older, used industrial air compressor. With the high number of factories and small businesses closing, there is a good selection of them on the secondary market, including ebay.



I bought my compressor from a motorcycle repair shop that was closing. It has a 5hp 220v single phase motor, and a huge cast-iron two-stage industrial pump that holds 2-gallons of oil, compared with the 2-quarts capacity of typical new pumps. Although finding spare parts could be a problem, they are made to run all day long in a commercial setting, so lighter home shop usage probably won't wear one out.



- Mike

 

[MFalkinham]

Excellent advice so far.....



I would add that you might also consider an older, used industrial air compressor. With the high number of factories and small businesses closing, there is a good selection of them on the secondary market, including ebay.



I bought my compressor from a motorcycle repair shop that was closing. It has a 5hp 220v single phase motor, and a huge cast-iron two-stage industrial pump that holds 2-gallons of oil, compared with the 2-quarts capacity of typical new pumps. Although finding spare parts could be a problem, they are made to run all day long in a commercial setting, so lighter home shop usage probably won't wear one out.



- Mike

 

[Philip]

Grade M copper has a burst rating of 600 PSI. If the person does his part on the soldering. Copper isn't an issue on 175 PSI. I know of a few shops around here with copper based systems over 20 years old.



If you read TiP's artical. It states that the steel pipe will cool the air charge and allow the water to condense. Copper does this better than steel.



If you decide on copper. Do not use rolled copper pipe. Use rigid copper.