[TheForge] air compressors, CFM, and psig

[terry l. ridder]

hello;


i am still researching air compressors and have not found a good
explanation or chart for determining the CFM for a given psig for an air
compressor.

for any given air compressor take the last one i last below, the
ingersoll-rand, is 50 CFM at 175 psig. what does that equate to at 40
psig? what does that equate to at 90 psig?

the 40 psig is what my paint sprayer works at.
the 90 psig is what my 3/8inch air ratchet works at.

air compressor specifications generally list

IndustrialAir 80 Gallon Hi-Flo Single Stage Air Compressor
http://www.farmandfleet.com/catalog/product.aspx?i=605037&h=050104001
<begin quote>
IndustrialAir
80 Gallon Hi-Flo Single Stage Air Comp
Mfr #: ILA4708065
Blain #: 605037     Price: $778.99

Capacity: 80 gallon tank
Maximum pressure: 155 PSI
CFM @ 40 PSI: 16.1
CFM @ 90 PSI: 14.0
Volts: 208-240
Power: 4.7 HP
Dimensions: 31.5" x 34.75" x 77"
Weight: 540 lb
UL & CSA certified
<end   quote>

IndustrialAir 80 Gallon 2 - Stage Industrial Compressor
http://www.farmandfleet.com/catalog/product.aspx?i=605035&h=050104001
<begin quote>
IndustrialAir
80 Gallon 2 - Stage Industrial Compressor
Mfr #: IV5248069
Blain #: 605035     Price: $1,269.99
                Sale Price: $1,199.99 Through 5/10/2009

Capacity: 80 gallon tank
Maximum pressure: 175 PSI
CFM @ 100 PSI: 17.5
CFM @ 175 PSI: 15.8
Volts: 208-240
Phase: single
Power: 5.2 HP
Dimensions: 31.5" x 34.75" x 77"
Weight: 610 lb 
<end   quote>

Ingersoll Rand Electric Stationary Air Compressor
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200319399_200319399
<begin quote>
Ingersoll Rand Electric Stationary Air Compressor (Fully Packaged) -
15 HP, 50 CFM At 175 PSI, 230 Volts
Item# 1592042C
  Was $4991.99
Sale $4989.99 <--big sale a whole $2.00 usd off the regular price.

Max. PSI    175
Volts   230
Amps    39
HP  15
Motor Phase(s)  3
Stages  2
Air Tank Size (gal.)    120
Tank Description    Horizontal
Pump    Two stage, splash lubricated, belt-driven
Air Outlet Size (in.)   1
Drain System    Automatic
Portable or Stationary  Stationary
Dimensions L x W x H (in.)  78 x 30 x 56
Ship Wt. 1117.0 lbs
<end   quote>

sidenote: nearly every air compressor manufactuer makes the same mistake
and just use 'psi' when it should either be 'psig' for pounds per square
inch gauge or 'psia' for pounds per square inch absolute. just using psi
is meaningless.

what is a type-30 air compressor? northern tools and other web sites
throw that term around but never define it.


-- 
terry l. ridder ><>