What You Need To Know About Compressed Air Systems

What You Need To Know About Compressed Air Systems

Compressed air is​ used in​ many operations and​ processes and​ as​ a​ source of​ energy for​ heating, ventilating, and​ air conditioning (HVAC) and​ process actuators and​ motors. it​ may also be supplied for​ low pressure systems and​ used for​ pneumatic control. Air can be compressed in​ several different ways and​ supplied at​ varying pressures and​ degrees of​ filtration depending on its use.

A typical compressed air system is​ capable of​ producing instrument quality air for​ pneumatic HVAC controls, tools, conveying systems, and​ general plant air. the​ system consists of​ a​ single motor driven single stage rotary screw compressor with inlet air filter, a​ safety relief valve, aftercooler, air/oil separator, air receiver with safety relief valve, prefilter, air dryer, afterfilter, oil/water traps, and​ oil/water separator.

Compressors are most often supplied skid mounted as​ a​ packaged unit.Theassembled package includes all major components, controls, and​ a​ sound attenuation enclosure. the​ unit only requires mounting to​ a​ foundation,hook up to​ system piping, connection to​ the​ oil water separator, and​ power connection.

There are various types of​ compressors: Rotary helical screw air compressors are positive displacement machines. Atwin-screw compressor consists of​ accurately matched rotors [one lobe (male) and​ one helix (female)] that mesh closely when rotating within a​ close tolerance common housing. One rotor is​ motor driven while the​ other is​ gear driven, turning it​ in​ a​ counter-rotating motion.

The rotors uncover inlet posts at​ one end allowing air to​ flow in. as​ the​ rotors continue to​ rotate the​ air is​ compressed by the​ minishing volume between the​ rotors . at​ the​ end of​ the​ rotors, ports allow the​ now compressed air to​ exit. One or​ more stages may be used.

These compressors are used in​ systems up to​ 3000 cubic feet per minute (cfm). They are usually oil injected to​ increase sealing, lubricate rotors, and​ provide cooling. They can also be oil free. One or​ two stages can be used. They have
a low initial cost, no pulsation, are almost free of​ vibration, and​ do not require special foundations.

Centrifugal compressors compress air as​ it​ enters the​ center of​ a​ fluted casting, housing a​ rotating impeller. the​ impeller imparts kinetic energy to​ the​ gas which turns into potential energy as​ the​ gas velocity slows, thus increasing pressure. Compression is​ a​ continuous process. One or​ more stages may be used.

Centrifugal compressors are used in​ large systems up to​ 15,000 cfm. a​ blow-off silencer is​ needed to​ control noise. Centrifugal compressors require no ubrication in​ contact with the​ air stream and​ therefore provide oil free air.

Reciprocating or​ positive displacement compressors use a​ piston in​ a​ cylinder to​ compress air up to​ a​ capacity of​ 6,000 cfm . Air enters the​ cylinder through a​ valve when the​ piston is​ going down. the​ valve closes when the​ piston starts to​ go up. as​ the​ piston approaches the​ top ofthe cylinder, the​ air is​ compressed by the​ decreasing volume. an​ exhaust valve opens when the​ piston is​ near the​ top of​ the​ cylinder allowing the​ compressed air to​ exit. the​ cycle is​ them repeated.

Rotary sliding vane compressors use a​ rotor eccentrically mounted in​ a​ cylinder. the​ rotor has eight or​ more slots cut along its length .Vanes are placed in​ the​ slots. as​ the​ rotor rotates, the​ vanes move out from centrifugal force. as​ the​ rotor continues through a​ rotation, the​ rotor housing causes the​ vanes to​ move back in​ the​ slot ofthe rotor.

The volume of​ air between the​ housing, eccentrically mounted rotor, and​ two vanes changes as​ the​ rotor rotates, compressing the​ air.

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