Select a Compressor and get the most for your money

Getting the most for your money when selecting a compressor.

Particulates also build up in piping causing pressure drop and excessive tool wear. Oil, usually in the form of vapors or mists, combines with particulates to clog tools. It may also build up in piping and cause significant pressure drop.

Do not forget to include high quality, automatic drain traps in the system. If the filtered and separated contaminants are not removed, they will find their way into the system again.

Piston vs. rotary compressor

Piston compressors are still commonly found in hangars. A piston compressor may provide adequate flow for a short period, but its allowable duty cycle must be considered. The duty cycle is the percentage of time a compressor may operate without the risk of overheating and causing excessive wear to the compressor. Most small piston compressors have an allowable duty cycle of 60 to 70 percent. For this reason, piston compressors are usually oversized to allow the compressor to periodically shut down and cool off because of the relatively high operating temperatures.

Rotary vane and screw compressors have a 100 percent allowable duty cycle with lower operating temperatures of only 170-200 F, compared to 300-400 F in a piston.

Reliability and maintenance over time

Compressor reliability, maintenance requirements, and productivity are essential considerations. Consider how a compressor performs as time passes. Pistons, cylinders, rings, and valves wear over time, causing the compressor to deliver less air, and send more lubricating oil past the rings into the compressed air system and right to the point-of-use. Preventive maintenance will slow this process, and rebuilding the compressor will reverse the gradual loss of flow and reduce the oil carry-over. However, it can be expensive.

Rotary screw compressors do not wear because the rotors do not touch each other or the rotor housing. Some screw compressors can operate for more than 50,000 hours before requiring an overhaul -- that's more than 10 times as long as a typical piston compressor and they are much quieter too!

A thorough system analysis goes a long way in building a reliable, cost-effective system. Carefully consider each system component and its impact on the application. Remember, value is more than initial price and purchasing quality equipment now will save time and money for years to come.

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