Hydraulic cylinder displacement is the power variable that measures the amount of hydraulic oil moved within your cylinder during one cycle. This measurement will help you to establish your cylinder’s speed of operation. As displacement impacts virtually every aspect of a hydraulic system, knowing how to calculate volumetric displacement in your cylinder is essential to your equipment’s efficiency, capacity, and overall lifespan.
Hydraulic cylinder displacement is crucial because it will impact which pump volume, motor size, volume flow, and other factors are best for your equipment. Additionally, certain displacement values are required for cylinders to function safely and effectively in extreme environments or tough markets. Volumetric displacement is also key in establishing position-sensing sensors for cylinders used in construction, harvesting and agricultural equipment, and other industrial machinery.
What to Know Before Calculating Volumetric Displacement
Before learning how to calculate the displacement of a hydraulic cylinder, you will need to find or calculate the following values and measurements:
- Piston Diameter. Begin by measuring the piston, also called the bore. However, be sure that you are measuring the actual piston, not the outside of the hydraulic cylinder.
- Piston Radius. Multiply the piston diameter by 2 and square the result to determine the radius (r2).
- Piston Area. Using the previous values, you can calculate the piston area (A) by multiplying pi (π) by the radius.
- Cylinder Stroke. Hydraulic cylinder stroke is the traveling distance between your cylinder’s extended length and retracted length. To find the correct value, subtract the retracted length from the extended length.
Hydraulic Cylinder Displacement Formula
Calculating hydraulic cylinder displacement can be accomplished with an easy and straightforward formula. Simply multiply the area of the piston (A) by the cylinder stroke (S) to determine displacement (Q):
Let’s work through an example. Say a hydraulic cylinder has a piston area of 12.57 in2 and a stroke of 30”. In this case, the volumetric displacement formula would read:
In this scenario, the volumetric displacement of this particular cylinder would be approximately 377.1 in3. If your application or market prefers to measure volumetric displacement by gallons, divide by 231 to reach 1.63 gallons.