Hydraulic systems are crucial across many sectors of business from construction to aerospace. A hydraulic system relies on the quality of its parts and here we will look at the six main components that go to make the hydraulic system.
1. Reservoir
This is the storage tank that contains the fluid, vital for maintaining a constant supply of hydraulic fluid. It will also help cool the system by dissipating any heat generated. They are mostly made of either plastic or metal and can be located in various places around the system.
2. The pump
The pump is the very heart of a hydraulic system. It takes the fluid from the reservoir and generates the pressure required to keep it moving through the system.
Depending on the requirements of the system, a wide variety of different types of pumps can be used, such as piston pumps or geared pumps, centrifugal pumps or diaphragm pumps. A detailed comparison of the various pumps can be found here:
3. Valves
The valves are used to regulate the flow of fluid through the system. They can be directional flow valves or pressure control valves.
4. Actuators
Actuators are what convert the hydraulic pressure into the mechanical force needed. They will move various components, such as the hydraulic cylinders and motors.
5. Hoses and fittings
These connect the components of the system. They will be chosen in order to cope with such things as the temperature range and the pressure the system operates within.
A hydraulic power unit is a self-contained unit, and all the components will be pre-assembled and chosen to work within the limits of the unit. A Hydraulic Power Unit can be adapted for a wide range of industrial applications.
6. Hydraulic Fluid
If the pump is the heart of the system, then the fluid is very much the lifeblood of it. Depending on what the capacities of the system are, the fluid will be chosen for such things as viscosity or the temperature range it can safely operate in. Most hydraulic fluid is mineral oil-based stock.
Common types of hydraulic system
The components in a hydraulic system are arranged in different ways depending on the job. Pumps convert mechanical power into hydraulic energy, with gear pumps and fixed or variable displacement piston pumps the main types. Hydraulic motors turn pressure and flow into torque and rotation, while cylinders push force in a straight line that can be reversed.
Aviation systems draw fluid from a reservoir, pressurise it to drive other components and then return it. Their main parts are the pump, reservoir, actuating cylinder, pressure relief valve and heat exchanger.
In an open-centre system, fluid flows from the actuator back to the reservoir when idle, letting fresh fluid reach the pump inlet. It uses a directional control valve and generates less heat. In a closed-loop system the fluid flows continuously between pump and actuator without passing through the reservoir. A feed pump takes the place of the directional control valve, and the result is very precise actuation.
Mobile and stationary systems, pumps and fluid
Hydraulic systems fall into two broad groups, mobile and stationary. Mobile systems, such as those on construction machinery, usually use a petrol or diesel engine to drive the hydraulic pumps, which then power the motors, actuators and other parts. Stationary systems use an electric motor to drive the pumps instead.
Vane pumps and gear pumps are two of the most common pump types. In an adjustable vane pump, changing the position of the rotor within its housing alters how much fluid leaves the pump, and when the two are centred the flow drops to zero. On the output side, a single acting cylinder applies force in one direction only.
The fluid itself needs care. It is held in a reservoir that helps keep contaminants out, and it should be protected from the weather. Fluid that oxidises loses its effectiveness and forms a sludge that can interfere with valves and restrict flow passages, so choosing the right fluid for the system matters as much as choosing the right components.