Contents
Displacement
When air is drawn into a compressor, the pistons or rotors compress it into a smaller space, increasing its pressure. In an air compressor, displacement refers to the total volume of air moved or “swept out” by the pistons or rotors in a single cycle, typically measured in cubic feet per minute (CFM). It’s the amount of air a compressor can take in and push through the system each minute during normal operation.
Understanding displacement helps operators choose the right compressor for their needs. It’s one of the key specifications that determines a system’s airflow capacity and overall performance. A compressor with a larger displacement can move more air, making it better suited for demanding industrial environments where a consistent air supply is essential.
FAQs
While displacement measures how much air the machine’s pistons or rotors can move, FAD (also known as “delivered air”) reflects how much usable compressed air is actually available after compression losses, valve timing and leakage are factored in.
Displacement is typically expressed in cubic feet per minute (CFM). The CFM calculation depends on the bore, stroke and number of cylinders (in a reciprocating compressor) or the rotor dimensions and speed (in a rotary screw model).
For example, in a piston compressor, displacement can be estimated by multiplying the area of the piston head by the stroke length, then multiplying that result by the number of cylinders and the number of revolutions per minute (RPM).
Understanding how to calculate displacement helps ensure proper air compressor sizing. A compressor that’s too small may not supply enough air to power end-use equipment, while one that’s too large can waste energy and increase operating costs.
In a reciprocating compressor, piston displacement directly impacts how much air the unit can produce. Higher piston displacement usually means higher airflow potential, but efficiency depends on several factors, including compression ratio, valve design and temperature control.
Piston diameter, stroke length, number of cylinders and operating speed all contribute to total compressor displacement.
Selecting the right size ensures your system runs efficiently without overloading or wasting power. In addition to displacement capacity, consider every air-powered tool or process in your operation. Check each item’s required CFM and pounds per square inch (PSI) rating. Calculate the CFM of all tools that could be operating at the same time to determine the minimum airflow capacity.
Consider that your business may grow over time. You may want to choose an air compressor that can grow with you or has slightly more CFM than you need right now. If you need additional help choosing the right solutions for your business, Quincy Compressor can assist you. You can browse our online resources or contact us for additional assistance.