A Primer on Hydraulic Cylinders

If you work in construction, manufacturing or agriculture—or if you own a car or have ever flown on a plane—you’ve encountered machines that rely on hydraulic cylinders. Though simple in design, they’ve proven invaluable throughout commercial and industrial uses. Because of how common they are, it can pay off to know a bit about how they work—and what to do when they stop working.

How Hydraulic Cylinders Work

All hydraulic systems work on one basic principle: most liquids are incompressible, so applied forces are transferred through them. Because pressure remains constant, these forces scale with the cross-sectional area that they’re flowing through. Hydraulic cylinders, working in tandem with a hydraulic pump, apply this principle to generating unidirectional force. The internal piston divides the cylinder into two chambers, moving back and forth as fluid is pumped through the system into one or the other. Force generated by the piston is multiplied relative to the force necessary to pump the fluid.

Common Causes of Hydraulic Failures

Various hydraulic seals are necessary to keep the hydraulic fluid from leaking, which would result in power loss. These seals often bear the brunt of the system’s constant internal pressure, and a broken seal compromises the cylinder’s function. Seals naturally wear over time, but they can degrade more quickly if used in the incorrect environment. A seal needs to be made of a material that can withstand the expected pressure while also resisting chemical attack from surrounding fluid and thermal damage from heat generated.

Applications of Hydraulic Cylinders

Hydraulic cylinders provide a compact and highly efficient means of linear force multiplication, a feat with an immense range of applications. Because of this, hydraulics are invaluable throughout various industries. Construction and civil engineering are major examples, with hydraulic cylinders and pumps driving heavy equipment such as bulldozers, excavators, pavers and dump trucks. The aerospace industry also employs them in devices like wing flaps or landing gears, and your automobile likely uses hydraulics in its suspension.