how the air compressor works - types of air compressors

8/19/2019 How the Air Compressor Works - Types of Air Compressors

1/10

HOME

More than a tool for inflating tires, it's an alternative power sourcefor your shop.

How It Works: The Air Compressor

MAR 18, 2015

By Thomas Klenck

mailto:?subject=How%20It%20Works%3A%20The%20Air%20Compressor&body=/home/improvement/energy-efficient/1275131http://www.twitter.com/share?url=/home/improvement/energy-efficient/1275131&text=How+It+Works%3A+The+Air+Compressor&via=PopMechhttp://pinterest.com/pin/create/button/?url=/home/improvement/energy-efficient/1275131&media=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&description=How+It+Works%3A+The+Air+Compressor%20%20-%20PopularMechanics.comhttp://www.popularmechanics.com/author/7153/thomas-klenck/http://www.facebook.com/v2.0/dialog/feed?app_id=218456798186610&name=How+It+Works%3A+The+Air+Compressor&description=More+than+a+tool+for+inflating+tires%2C+it%27s+an+alternative+power+source+for+your+shop.&display=popup&link=/home/improvement/energy-efficient/1275131&picture=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&redirect_uri=/home/improvement/energy-efficient/1275131&version=v2.0http://www.popularmechanics.com/http://www.popularmechanics.com/home/http://www.popularmechanics.com/author/7153/thomas-klenck/


2/10

We Recommend

HOW TO PUT UP CHRISTMAS LIGHTS: 7 ESSENTIAL TIPS AND LOOKS

Years ago, it was common for shops to have a central power source that drove all the tools

through a system of belts, wheels and driveshafts. The power was routed around the work

space by mechanical means. While the belts and shafts may be gone, many shops still use a

mechanical system to move power around the shop. It's based on the energy stored in air

that's under pressure, and the heart of the system is the air compressor.

You'll find air compressors used in a wide range of situations—from corner gas stations to

major manufacturing plants. And, more and more, air compressors are finding their way into

home workshops, basements and garages. Models sized to handle every job, from inflating

pool toys to powering tools such as nail guns, sanders, drills, impact wrenches, staplers and

spray guns are now available through local home centers, tool dealers and mail-order

catalogs.

The big advantage of air power is that each tool doesn't need its own bulky motor. Instead, a

single motor on the compressor converts the electrical energy into kinetic energy. This makes

for light, compact, easy-to-handle tools that run quietly and have fewer parts that wear out.

Advertisement - Continue Reading Below

http://www.popularmechanics.com/home/outdoor-projects/how-to/g1684/how-to-hang-outdoor-christmas-lights/


3/10

Air compressor types

While there are compressors that use rotating impellers to generate air pressure, positive-

displacement compressors are more common and include the models used by homeowners,

woodworkers, mechanics and contractors. Here, air pressure is increased by reducing the

size of the space that contains the air. Most of the compressors you'll run across do this job

with a reciprocating piston.

http://www.twitter.com/share?url=/home/improvement/energy-efficient/1275131&text=How+It+Works%3A+The+Air+Compressor&via=PopMechhttp://pinterest.com/pin/create/button/?url=/home/improvement/energy-efficient/1275131&media=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&description=How+It+Works%3A+The+Air+Compressor%20%20-%20PopularMechanics.comhttp://www.facebook.com/v2.0/dialog/feed?app_id=218456798186610&name=How+It+Works%3A+The+Air+Compressor&description=More+than+a+tool+for+inflating+tires%2C+it%27s+an+alternative+power+source+for+your+shop.&display=popup&link=/home/improvement/energy-efficient/1275131&picture=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&redirect_uri=/home/improvement/energy-efficient/1275131&version=v2.0mailto:?subject=How%20It%20Works%3A%20The%20Air%20Compressor&body=/home/improvement/energy-efficient/1275131


4/10

Like a small internal combustion engine, a conventional piston compressor has a crankshaft,

a connecting rod and piston, a cylinder and a valve head. The crankshaft is driven by either

an electric motor or a gas engine. While there are small models that are comprised of just the

pump and motor, most compressors have an air tank to hold a quantity of air within a preset

pressure range. The compressed air in the tank drives the air tools, and the motor cycles on

and off to automatically maintain pressure in the tank.

At the top of the cylinder, you'll find a valve head that holds the inlet and discharge valves.

Both are simply thin metal flaps–one mounted underneath and one mounted on top of the

valve plate. As the piston moves down, a vacuum is created above it. This allows outside air

at atmospheric pressure to push open the inlet valve and fill the area above the piston. As the

piston moves up, the air above it compresses, holds the inlet valve shut and pushes the

discharge valve open. The air moves from the discharge port to the tank. With each stroke,

more air enters the tank and the pressure rises.

Typical compressors come in 1- or 2-cylinder versions to suit the requirements of the tools

they power. On the homeowner/contractor level, most of the 2-cylinder models operate just

like single-cylinder versions, except that there are two strokes per revolution instead of one.

Some commercial 2-cylinder compressors are 2-stage compressors–one piston pumps air

into a second cylinder that further increases pressure.

Compressors use a pressure switch to stop the motor when tank pressure reaches a preset

limit–about 125 psi for many single-stage models. Most of the time, though, you don't need

that much pressure. Therefore, the air line will include a regulator that you set to match the

pressure requirements of the tool you're using. A gauge before the regulator monitors tank

pressure and a gauge after the regulator monitors air-line pressure. In addition, the tank has

a safety valve that opens if the pressure switch malfunctions. The pressure switch may also

incorporate an unloader valve that reduces tank pressure when the compressor is turned off.

Many articulated-piston compressors are oil lubricated. That is, they have an oil bath that

splash-lubricates the bearings and cylinder walls as the crank rotates. The pistons have rings

that help keep the compressed air on top of the piston and keep the lubricating oil away from

the air. Rings, though, are not completely effective, so some oil will enter the compressed air

in aerosol form.

Having oil in the air isn't necessarily a problem. Many air tools require oiling, and inline oilers

are often added to increase a uniform supply to the tool. On the down side, these models


5/10

require regular oil checks, periodic oil changes and they must be operated on a level surface.

Most of all, there are some tools and situations that require oilfree air. Spray painting with oil

in the airstream will cause finish problems. And many new woodworking air tools such as

nailers and sanders are designed to be oilfree so there's no chance of fouling wood surfaces

with oil. While solutions to the airborne oil problem include using an oil separator or filter in

the air line, a better idea is to use an oilfree compressor that uses permanently lubricated

bearings in place of the oil bath.

A variation on the automotive-type piston compressor is a model that uses a one-piece

piston/connecting rod. Because there is no wrist pin, the piston leans from side to side as the

eccentric journal on the shaft moves it up and down. A seal around the piston maintains

contact with the cylinder walls and prevents air leakage.

Where air requirements are modest, a diaphragm compressor can be effective. In this design,

a membrane between the piston and the compression chamber seals off the air and prevents

leakage.

Compressor power

One of the factors used to designate compressor power is motor horsepower. However, this

isn't the best indicator. You really need to know the amount of air the compressor can deliver

at a specific pressure.

The rate at which a compressor can deliver a volume of air is noted in cubic feet per minute

(cfm). Because atmospheric pressure plays a role in how fast air moves into the cylinder, cfm

will vary with atmospheric pressure. It also varies with the temperature and humidity of the air.

To set an even playing field, makers calculate standard cubic feet per minute (scfm) as cfm at

sea level with 68 degrees F air at 36% relative humidity. Scfm ratings are given at a specific

pressure–3.0 scfm at 90 psi, for example. If you reduce pressure, scfm goes up, and vice

versa.

You also may run across a rating called displacement cfm. This figure is the product of

mailto:?subject=How%20It%20Works%3A%20The%20Air%20Compressor&body=/home/improvement/energy-efficient/1275131http://pinterest.com/pin/create/button/?url=/home/improvement/energy-efficient/1275131&media=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&description=How+It+Works%3A+The+Air+Compressor%20%20-%20PopularMechanics.comhttp://www.facebook.com/v2.0/dialog/feed?app_id=218456798186610&name=How+It+Works%3A+The+Air+Compressor&description=More+than+a+tool+for+inflating+tires%2C+it%27s+an+alternative+power+source+for+your+shop.&display=popup&link=/home/improvement/energy-efficient/1275131&picture=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&redirect_uri=/home/improvement/energy-efficient/1275131&version=v2.0http://www.twitter.com/share?url=/home/improvement/energy-efficient/1275131&text=How+It+Works%3A+The+Air+Compressor&via=PopMech


6/10

CommentJoin the conversation

cylinder displacement and motor rpm. In comparison with scfm, it provides an index of

compressor pump efficiency.

The cfm and psi ratings are important because they indicate the tools that a particular

compressor can drive. When choosing a compressor, make sure it can supply the amount of

air and the pressure that your tools need.

30

mailto:?subject=How%20It%20Works%3A%20The%20Air%20Compressor&body=/home/improvement/energy-efficient/1275131http://www.twitter.com/share?url=/home/improvement/energy-efficient/1275131&text=How+It+Works%3A+The+Air+Compressor&via=PopMechhttp://pinterest.com/pin/create/button/?url=/home/improvement/energy-efficient/1275131&media=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&description=How+It+Works%3A+The+Air+Compressor%20%20-%20PopularMechanics.comhttp://www.popularmechanics.com/flight/a14291/the-stratolaunch-plane-is-truly-massive/?mag=pop&click=yrhttp://www.twitter.com/share?url=/home/improvement/energy-efficient/1275131&text=How+It+Works%3A+The+Air+Compressor&via=PopMechhttp://www.popularmechanics.com/cars/motorcycles/a14237/3-motorcycles-you-need-to-know-right-now/?mag=pop&click=yrhttp://www.popularmechanics.com/home/a13882/ingenious-diy-air-conditioners/?mag=pop&click=yrhttp://www.popularmechanics.com/cars/motorcycles/a14237/3-motorcycles-you-need-to-know-right-now/?mag=pop&click=yrmailto:?subject=How%20It%20Works%3A%20The%20Air%20Compressor&body=/home/improvement/energy-efficient/1275131http://www.facebook.com/v2.0/dialog/feed?app_id=218456798186610&name=How+It+Works%3A+The+Air+Compressor&description=More+than+a+tool+for+inflating+tires%2C+it%27s+an+alternative+power+source+for+your+shop.&display=popup&link=/home/improvement/energy-efficient/1275131&picture=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&redirect_uri=/home/improvement/energy-efficient/1275131&version=v2.0http://www.facebook.com/v2.0/dialog/feed?app_id=218456798186610&name=How+It+Works%3A+The+Air+Compressor&description=More+than+a+tool+for+inflating+tires%2C+it%27s+an+alternative+power+source+for+your+shop.&display=popup&link=/home/improvement/energy-efficient/1275131&picture=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&redirect_uri=/home/improvement/energy-efficient/1275131&version=v2.0http://www.popularmechanics.com/flight/a14291/the-stratolaunch-plane-is-truly-massive/?mag=pop&click=yrhttp://pinterest.com/pin/create/button/?url=/home/improvement/energy-efficient/1275131&media=http://pop.h-cdn.co/assets/cm/15/05/54c8014b7f0cf_-_tb_lg_9802hihwa2-de.gif&description=How+It+Works%3A+The+Air+Compressor%20%20-%20PopularMechanics.comhttp://www.popularmechanics.com/home/a13882/ingenious-diy-air-conditioners/?mag=pop&click=yr


7/10

RECOMMENDED

3 Motorcycles You Need to

Know Right Now

The Most Creative Air

Conditioners ever

This Will Be the World's

Largest Plane

What do you think?

More From

HOME

http://www.popularmechanics.com/home/food-drink/g2092/best-meat-cuts-to-grill/https://beap.gemini.yahoo.com/mbclk?bv=1.0.0&es=wSS5yKUGIS9l17pf5bZtKnZwNSHSptGiGsaquqK.k1N274OoaPKY7gLN3GAwgxqf2DjadRBt6dtYvbkEv6YTvcbkcKP3sGEqTE17nJPIz2tOIqGdwgFfeMPVtVuZFBsP71ogYVqUarp8afshv5a2jY0UdewFt6UUv_ZMplclTPyqsdMzrnvJ1Wsm6sxFG8glV5eg0qw7wrvpyYGQs0HrbFV0spEmlHeo6WKwtHDqBuJlPxsJkg.z_sawtfYY9F1qi6.3sU0wQ0GDpxwloX.CNMt6c1a5PVkSnfSRlRT4mL7vPGEpPFlXApgIN46Y0ddDawtm3stuaJUXpys9H6fbvEem9WfWOlIdEqJ5ODCMR_tP.EpXpexu_6TemzqF125NzSVa8qYM_W8SwoE4Kwjt5cyAt7R3Ye_UJbSAqHy2JAI_u2X1ZC2A2c6gkEjavMskfYrQMI5IMVvOuioU5PLRbitz6MYPSjw3%26lp=http://info.yahoo.com/privacy/us/yahoo/relevantads.htmlhttp://www.popularmechanics.com/homehttp://www.popularmechanics.com/flight/a14291/the-stratolaunch-plane-is-truly-massive/?mag=pop&click=yrhttp://www.popularmechanics.com/home/food-drink/g2092/best-meat-cuts-to-grill/https://yahoo.com/https://beap.gemini.yahoo.com/mbclk?bv=1.0.0&es=58qIxpsGIS9zjtAvtBWlSTDIWuYDrB0Nw2PBxjqWg8vXOragD5SpEeNoPOrK3CBG24H6Luhrs3OkvJuMMfa9M_tbGPfAG4qV2mUtTOHa5sOlDPYoVQr2EevqKalBCD8nnsV0K92KnkPOdIUcoQnyN7lEyz4Rm9UxGRgUMFs0diXdYwlseiVabl.PNzN.huDYUG3gUWl6zFa1zThBTS5QdBpvQiu80rjwPQ4DjsAtnxjxsFSxxQ7_UwgbIw2o5cuxKOnwf4_T6t8W7a9XRmC7JYwcSdzz5lOEto4oa6v6QTxiohSSASLdjzI9j_c1J81MDKFtMtDhioGFPFaYknzLmolODxXViba_iGfXT.tKmwp4sAwZL6icYl9SAPQR2qT6Fjv.4gv1g73Exyq2qSm1j.ziX.eTEsn_yQxcRY14IIG4O65BZdobM9K7V.Rch9Xfo8gOTIHbjAIZAR_MlrNYNqc4lys3YE_vLhlkbhow49pHEXMKpQwH%26lp=http://www.popularmechanics.com/technology/startups/advertorial/a15/grant-delgatty-his-moment-of-invention/?mag=pop&click=yrhttp://www.popularmechanics.com/cars/motorcycles/a14237/3-motorcycles-you-need-to-know-right-now/?mag=pop&click=yrhttps://beap.gemini.yahoo.com/mbclk?bv=1.0.0&es=wSS5yKUGIS9l17pf5bZtKnZwNSHSptGiGsaquqK.k1N274OoaPKY7gLN3GAwgxqf2DjadRBt6dtYvbkEv6YTvcbkcKP3sGEqTE17nJPIz2tOIqGdwgFfeMPVtVuZFBsP71ogYVqUarp8afshv5a2jY0UdewFt6UUv_ZMplclTPyqsdMzrnvJ1Wsm6sxFG8glV5eg0qw7wrvpyYGQs0HrbFV0spEmlHeo6WKwtHDqBuJlPxsJkg.z_sawtfYY9F1qi6.3sU0wQ0GDpxwloX.CNMt6c1a5PVkSnfSRlRT4mL7vPGEpPFlXApgIN46Y0ddDawtm3stuaJUXpys9H6fbvEem9WfWOlIdEqJ5ODCMR_tP.EpXpexu_6TemzqF125NzSVa8qYM_W8SwoE4Kwjt5cyAt7R3Ye_UJbSAqHy2JAI_u2X1ZC2A2c6gkEjavMskfYrQMI5IMVvOuioU5PLRbitz6MYPSjw3%26lp=https://beap.gemini.yahoo.com/mbclk?bv=1.0.0&es=58qIxpsGIS9zjtAvtBWlSTDIWuYDrB0Nw2PBxjqWg8vXOragD5SpEeNoPOrK3CBG24H6Luhrs3OkvJuMMfa9M_tbGPfAG4qV2mUtTOHa5sOlDPYoVQr2EevqKalBCD8nnsV0K92KnkPOdIUcoQnyN7lEyz4Rm9UxGRgUMFs0diXdYwlseiVabl.PNzN.huDYUG3gUWl6zFa1zThBTS5QdBpvQiu80rjwPQ4DjsAtnxjxsFSxxQ7_UwgbIw2o5cuxKOnwf4_T6t8W7a9XRmC7JYwcSdzz5lOEto4oa6v6QTxiohSSASLdjzI9j_c1J81MDKFtMtDhioGFPFaYknzLmolODxXViba_iGfXT.tKmwp4sAwZL6icYl9SAPQR2qT6Fjv.4gv1g73Exyq2qSm1j.ziX.eTEsn_yQxcRY14IIG4O65BZdobM9K7V.Rch9Xfo8gOTIHbjAIZAR_MlrNYNqc4lys3YE_vLhlkbhow49pHEXMKpQwH%26lp=http://www.popularmechanics.com/technology/startups/advertorial/a15/grant-delgatty-his-moment-of-invention/?mag=pop&click=yrhttp://info.yahoo.com/privacy/us/yahoo/relevantads.htmlhttp://www.popularmechanics.com/home/a13882/ingenious-diy-air-conditioners/?mag=pop&click=yr


8/10

7 Unexpected Cuts of Meat You Should Grill This SummerCheaper, tastier, and more sustainable options for your summer of backyard BBQs. Just add

a nice cold beverage. By Noah Davis

This College Student Built an Awesome Tiny Home to Avoid DebtYou have to see the inside. By Danielle Tullo

http://www.popularmechanics.com/home/outdoor-projects/a16283/college-student-tiny-house/http://www.popularmechanics.com/home/tools/a16301/best-new-tool-flugz-ear-plugs/http://www.popularmechanics.com/home/food-drink/g2092/best-meat-cuts-to-grill/http://www.popularmechanics.com/home/food-drink/g2092/best-meat-cuts-to-grill/http://www.popularmechanics.com/home/outdoor-projects/a16283/college-student-tiny-house/http://www.popularmechanics.com/author/9564/noah-davis/


9/10

Best New Tool: Flugz Ear PlugsFlugz may be pricey, at $25, but can you put a price on your hearing? By Roy Berendsohn

The 5 Best Walk-Behind Mowers, Tested A sturdy walk mower can take the exhaustion out of hours of yardwork. Buy accordingly. By

Beau Grimmett, Dave Noonan, and Roy Berendsohn

http://www.popularmechanics.com/home/lawn-garden/g2089/best-walk-lawn-mowers-tested/http://www.popularmechanics.com/home/tools/a16301/best-new-tool-flugz-ear-plugs/http://www.popularmechanics.com/author/3101/roy-berendsohn/http://www.popularmechanics.com/home/tools/a16301/best-new-tool-flugz-ear-plugs/http://www.popularmechanics.com/home/lawn-garden/g2089/best-walk-lawn-mowers-tested/


10/10

HOME HOME HOW-TO HOW TO HOW IT WORKS: WATER WELL PUMP

HOW IT WORKS: HEAT RECOVERY VENTILATOR HOW IT WORKS: WATER HEATER

HOW IT WORKS: WATER SOFTENER WHEN GOOD TOOLS DIE YOUNG

HOW YOUR HEATING SYSTEM WORKS: A PRIMER

MORE FROM HOME

Newsletter Digital Editions About UsMedia Kit Press Room Contact Us

Community Guidelines Advertise Online About Our Ads

Customer Service Subscribe Other Hearst Subscriptions

Give a Gift Events & Promotions Giveaways

Being Green Why Did I Get This Ad?

©2015 Hearst Communications, Inc. All Rights Reserved.

Privacy Policy Your California Privacy Rights Terms of Use Site Map

A PART OF HEARST DIGITAL MEDIA
https://www.facebook.com/popularmechanicshttp://www.popularmechanics.com/home/tools/reviews/a10746/when-good-tools-die-young-16930312/http://www.popularmechanics.com/about/community-guidelines/https://twitter.com/PopMechhttp://www.popularmechanics.com/homehttps://plus.google.com/+PopularMechanics/postshttp://www.popularmechanics.com/home/how-to/a3782/4294558/http://www.hearst.com/press-room/http://www.popularmechanics.com/about/advertise-online/http://www.popularmechanics.com/sitemap/http://www.popularmechanics.com/home/interior-projects/how-to/a153/1275141/http://www.pinterest.com/popmech/?auto_follow=1http://www.popularmechanics.com/about/contact-us/http://www.popularmechanics.com/home/https://www.youtube.com/user/popmechshow?sub_confirmation=1http://www.popularmechanics.com/promotions/https://preferences.hearstmags.com/brands/POP/u.aspxhttps://subscribe.hearstmags.com/subscribe/splits/popularmechanics/pop_digital_footer_linkhttp://www.popularmechanics.com/about/privacy-policy#californiahttp://www.popularmechanics.com/about/terms-of-usehttp://www.hearst.com/beinggreen/http://www.popularmechanics.com/about/privacy-policyhttp://www.popularmechanics.com/http://www.popularmechanics.com/home/interior-projects/how-to/a150/1275126/http://sweepstakes.popularmechanics.com/http://subscribe.hearstmags.com/circulation/shared/index.htmlhttp://www.popularmechanics.com/home/how-to/a152/1275136/http://www.popularmechanics.com/about/about-us/http://www.popularmechanics.com/content/how-to/https://subscribe.hearstmags.com/subscribe/splits/popularmechanics/pop_sub_footer_linkhttp://www.popularmechanics.com/content/home-how-to/http://www.popularmechanics.com/about/about-our-ads/http://popularmechanicsmediakit.com/https://w1.buysub.com/pubs/HR/POP/POP_nameAddrEntry_combo.jsp?cds_page_id=41200&cds_mag_code=POP&id=1421430180950&lsid=50161143009011357&vid=1http://www.popularmechanics.com/about/oba-policy/http://www.popularmechanics.com/home/interior-projects/how-to/a149/1275121/https://subscribe.hearstmags.com/subscribe/splits/popularmechanics/pop_gift_nav_link_footer

how the air compressor works - types of air compressors

Documents