PISTON AND SYSTEM FLUID SPEED RELATIVE TO PORT SIZE
AND CUSHION REQUIREMENTS
Page 15
FORCE AND FORCE REDUCTION CHARTS
PISTON / FLUID VELOCITY
SERIES
R
The chart to the right provides a guide in determining the adequacy of stan-
dard cylinder ports relative to application. The information provides piston speed in
feet per minute, by bore size for standard NPTF ports, system connected using
Schedule 80 pipe with a fluid velocity of 15 feet per second.
Piston speed is a function of fluid velocity in the connecting lines, generally
expressed in gallons per minute (GPM) and measured as the input/exhaust flow
through the cylinder cap end port.
System fluid velocity should not exceed 15 feet per second in order to min-
imize the effect of fluid turbulence, pressure drop and hydraulic shock loading. If
fluid velocity through the cylinder ports exceeds 15 feet per second, consider port
enlargement or twin ports.
Circumstances involving heavy loads or piston speeds in excess of 20 feet
per minute wherein the piston completes full stroke, cushions are recommended.
Cylinder cushions increase cylinder life, reduce piston impact speeds and hydraulic
shock.