Glossary · Pneumatics and hydraulics
Hydraulic cylinder
Also known as: Hydraulic ram, Hydraulic actuator
German: Hydraulikzylinder
In hydraulics, a hydraulic cylinder is a linear actuator in which pressurized hydraulic fluid acts on a piston to produce a linear force and motion.
- Fluid power
In one sentence
A hydraulic cylinder is a linear actuator in which pressurized oil acts on a piston to produce large linear forces.
Example
A press uses a double-acting hydraulic cylinder with a load-holding valve and position sensor to close the tool.
How it applies
- Engineering: Force equals pressure times piston area; high forces at compact size are the main reason to use hydraulics. Load-holding valves, cushioning and seals are part of the design.
- Commissioning: Air is bled from the cylinder and lines; speeds, pressures and position sensing are set.
- Maintenance: Seals and rod surfaces are wear parts; external leaks show on the rod. Loads must be lowered or mechanically secured before work.
- Documentation: Warn that a cylinder can move unexpectedly if a hose or valve fails, and that loads held by hydraulic pressure must be mechanically secured before anyone works under them. Describe bleeding and pressure release.
Hydraulic vs. pneumatic cylinder
A hydraulic cylinder uses nearly incompressible oil, so it is stiff and powerful. A Pneumatic cylinder uses compressible air; it is faster, cleaner and cheaper, but less stiff and weaker.