Size from the machine’s required thrust at the worst linkage position, not from a familiar bore. The core relationship is force = pressure × effective area, but available pressure and effective area change with circuit direction.
1. Convert Machine Load to Cylinder Thrust
Payload and cylinder force differ when levers and angles are involved. Use the worst geometry and include friction/acceleration as appropriate.
2. Choose Working Pressure
Use expected pressure at the cylinder under flow. Keep relief pressure as a protection setting unless the circuit defines it as the working point.
3. Calculate Bore
Divide required thrust by working pressure to get piston area, convert area to diameter, choose a practical bore and repeat the force check.
4. Check Retraction and Speed
Retraction uses annulus area, producing different force and speed. Flow demand rises with effective area for a given velocity.
5. Screen Rod Buckling
Long compression strokes require a column-stability check based on rod stiffness, effective length and mounting.
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Frequently Asked Questions
What number comes first?
Required cylinder thrust at worst geometry plus pressure available at the actuator.
Why not use relief pressure?
It is a protection setting and may not equal normal pressure at the cylinder.
Why do extend/retract differ?
The rod removes pressure area on retraction.
How does bore affect speed?
A larger area needs more flow for the same speed.
When check buckling?
For slender rods carrying compression over long effective length.
Discuss Your Hydraulic Requirement
Send bore, stroke, mounting, pressure, ports, load and duty details. For replacements, include photos and critical measurements.