What are Hydraulic Control Systems?

B. Turner

Hydraulic control systems include any controls that use fluid-based operation rather than electronics or pneumatic power. When control units within these systems are shifted, the internal fluid moves throughout the machine's inner workings. As it moves, this non-compressible fluid transfers force throughout the system to shift gears or influence motion. Hydraulic control systems rely on Pascal's law, which states that liquid pressure will remain equally distributed within a sealed system. Many modern machines rely on either hydraulic controls or a hybrid electric-hydraulic system.

Hydraulic controls are based on Pascal's law.
Hydraulic controls are based on Pascal's law.

Many types of equipment rely on some form of hydraulic controls, including aircraft and aerospace vessels. Marine vessels and elevators also use these types of controls, as do hydraulic cranes. Cars and trucks typically contain hydraulic brake systems, and a variety of industrial and manufacturing machines also rely on these controls for safe and effective operation.

Blaise Pascal, a mathematician and physician, established Pascal's law.
Blaise Pascal, a mathematician and physician, established Pascal's law.

Hydraulic control systems can influence the motion or operation of a machine in several ways. The most basic involves manual control, where a human or robotic users flips a switch, pulls a lever or turns a steering wheel. This motion drives hydraulic fluid throughout the system to accomplish the desired action.

Other systems rely on automatic controls rather than manual input. For example, a sensor on a crane may detect heavy loads and automatically send extra fluid towards the crane's lifting system. This fluid in turn creates excess lifting power to safely move the heavy load. Similar systems rely on pressure sensors, electronic eyes, and a variety of additional inputs.

One of the primary advantages to using hydraulic control systems is the ability to handle very large loads or accommodate tremendous forces. Compared to electric or pneumatic control systems, hydraulic controls are better able to handle sudden changes in load while maintaining an even level of power distribution. Hydraulic systems also allow for very precise and accurate handling in more specialized applications. Compared to air-based pneumatic systems, hydraulic controls make it much easier to spot a potential leak due to the visibility of the fluid.

Buyers should also be aware of the potential drawbacks to this system before investing in hydraulic controls. The hydraulic fluid used within these systems can be highly corrosive, and may lead to extended maintenance and repairs over time. Hydraulic control systems also utilize a large number of seals, which could fail or leak. Finally, because this fluid consists primarily of petroleum products, it poses risks to the environment during use and disposal.

Many cranes and other types of heavy equipment rely on fluid-based controls.
Many cranes and other types of heavy equipment rely on fluid-based controls.

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I recently read some interesting information by a hydraulic, pneumatic, lubrication and filtration systems manufacturer and distributor. It talked about basic hydraulics and the reasons for hydraulic pump system failure. It was quite informative!


When dealing with hydraulic powered machinery, maintenance is a must. Hydraulic services are really helpful in preventing damages to occur on your machinery. Different services being offered may charge differently, so it would be best to shop around and look for the best price possible.

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