What is piston duty cycle?

Knowing about the duty cycle will help you select the right compressor.

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What is piston duty cycle?

What is a duty cycle? Why do I need to think of that when I select a piston compressor? The duty cycle is as important as the flow/cubic feet per minute (CFM) of your compressor. In short it is referring to the frequency of use of the piston compressor. The more your piston compressor is cycling/running, the more duty cycle you need.

Piston Air Compressor

Piston Air Compressor from Atlas Copco

When buying a piston compressor, regardless if it is for DIY/Handyman tasks or for a professional application, usually most focus is placed on the flow/CFM or litres/minute. Commonly we think “I need this much air” and then find a piston compressor that can deliver that much air. But what is often forgotten is the regularity of use, the duty cycle. All piston compressors have a duty cycle, some as low as 25% and some as much as 100%.


What can happen if the compressor runs over its duty cycle? Well, your compressor can malfunction, the piston can seize within the piston housing as it gets too hot and as it cools down it can seize, or the engine can stop to name two common issues. However, rarely is the duty cycle identified as the underlying cause.


How can find the duty cycle of my piston compressors? You can work out the duty cycle of your machine by reading the engine plate of your air compressor. Your compressor’s duty cycle is directly related to the engines duty cycle, and is expressed with an ‘S’ followed by series of numbers. Most smaller piston compressors duty cycles are measured in 10 minute cycles, unless specified. For example if your compressor states “S3-75”, S3 is referring to “Intermittent periodic use” referring to a 10 minute duty cycle, 75 is referring to the mount of running as percentage, in this case 75%. So if the duty cycle says S3-75 it is built to run a maximum 7.5 minutes in every ten minute cycle.


Can a piston compressor have a 100% duty cycle? Yes, there are piston compressors that have 100% duty cycle, the engine on these compressors are rated S1. Atlas Copco’s LE series of Piston compressors have 100% duty cycle. So when you size your piston compressor to your needs do make sure that you take in to account the duty cycle. If you need a constant flow of compressed air, your compressor might need to be sized larger so you can let it “rest” and you can use the stored air in the receiver tank while it is not running.


If you have more questions about our piston compressors or want to find your nearest Atlas Copco piston reseller call us on 1800 023 469.


Piston compressor