How Does a Hydraulic Cylinder Work? Basic Principle and Components

A hydraulic cylinder is an actuator that converts pressurized hydraulic fluid into linear motion.
It is used in presses, mobile machinery, industrial automation and many other systems.

Main Components

• Barrel – The tube that contains the pressurized oil.
• Piston – The moving element that receives the hydraulic force.
• Rod – Transfers the piston force to the outside.
• Seals – O‑rings, rod seals, wipers.
• Mountings – Clevis, trunnion, foot mounts, etc.

Working Principle

1. The pump delivers oil to one side of the piston at a specific pressure.
2. The oil applies force on the piston surface.
3. According to F = P × A, force depends on pressure (P) and piston area (A).
4. The rod transfers this force as linear motion.
5. A directional control valve reverses the flow to retract the cylinder.

Design Considerations

• Selecting piston diameter according to required force
• Material and wall thickness vs. working pressure
• Buckling check for long rods
• Seal compatibility with fluid and temperature
• Mounting style according to stroke and load

Simple Example

For a cylinder working at 100 bar with an 80 mm piston diameter:

• Piston area: A ≈ 0.005 m²
• Force: F = 100 × 10⁵ Pa × 0.005 m² ≈ 50 kN (about 5 tons)

This gives a quick idea of the force capacity for a given pressure and bore size.