Examples of Hydraulic Power

Hydraulic power is derived from using pressurized fluid to actuate machinery. Hydraulic systems (or circuits) are employed in many different applications and can produce tremendous power. Hydraulic circuits can be very compact and provide power remotely through extended tubing or hoses. This versatility allows the circuit to have pumps and motors in one location while the actual work is done relatively far away. With this design advantage, hydraulic circuits produce power for different types of work while using minimal space.

Closed Circuit

• Cars have hydraulic circuits for actuating various systems: brakes, steering and transmission. Automobile hydraulic systems are closed circuits, meaning the fluid is completely contained and rarely adjusted. Fluids are added when levels are low, but this is usually the result of leaks and not as a result of normal operation. Also, closed hydraulic systems do not require filtration. The circuit is clean before being sealed and remains sealed throughout operation.

Open Circuit

• Heavy equipment using hydraulic actuation have open circuits. When a bulldozer lifts its blade or a backhoe moves the bucket, pistons are actuated to perform the necessary work. Because the piston is exposed, there is a possibility of contamination entering the hydraulic cylinder and the hydraulic circuit.

  Open hydraulic circuits require filtration and regular filter changes. Configured similarly to a car's oil or air filter, the hydraulic filter is rated in microns (millionths of a meter) as to the size of particulate matter filtered from the fluid. The proper rated filter is necessary to ensure proper fluid flow in the circuit while at the same time removing damaging contamination.

Flow Rate

• Hydraulic circuits of different types are measured by the flow rate through the circuit. Whether measured in gallons or liters, the circuit is rated as either high flow or low flow. Low-flow rate hydraulic circuits are applied when circuits do regular repetitive work. Paper-making machines, steel processing equipment and other heavy manufacturing machines often use low-flow rate hydraulic circuits for primary power sources. Low-flow rates on these constantly operating machines provide necessary power, while reducing the need for regular maintenance on seals, fittings and installed pressure regulators.

  High-flow rate circuits are installed for more on-demand needs such as heavy equipment. Any installation involving a hydraulic piston on machines ranging from bulldozers to garbage trucks to levelers on the Space Shuttle launching pad involve a high-flow rate hydraulic circuit. The high-flow rate ensures a more rapid response to operator input.