Hydraulics and pneumatics are two different ways of moving machines. In both cases, a pump and actuator are used. The difference between the two is in the substance being pressurized and the specific application.
Hydraulics
Hydraulics use a pressable fluid such as mineral oil, ethylene glycol, water, or fire-resistant movements at a high temperature and help control and transmit power. Hydraulic systems require a pump and, like pneumatic systems, use specific valves to control the force and speed of the actuators. Hydraulics are used at 65 bar to 345 bar or over 700 bar for specialised applications. The word hydraulics is derived from the Greek words hydor (water) and aulos (pipe). A hydraulic system includes a cylinder, piston, various pumps, and valves that control the direction of flow, and of course the compressed fluid.
Hydraulic systems are generally larger and more complex than pneumatic systems and require more space because a large container is required to hold the fluid. The larger size goes hand in hand with greater pressure, which often makes a hydraulic system more expensive than pneumatics. Hydraulic systems are also slower than pneumatic systems, because the oil has a thicker substance and requires more energy to get through the pipes. Examples of hydraulic applications include:
- Elevators
- Dams
- Machine tools
- Amusement park rides
- Wind turbines
- Wheelchair elevators
- Digging arms for excavators
- Forging metal parts
- Wing valves on aircraft
- Hydraulic braking system in cars
- Lifting cars
Pneumatics
Pneumatics uses, instead of liquids, a compressible gas such as air or other types of pressable pure gases and can be used to influence the mechanical movement of both small hand-held devices and large machines. A pneumatic system is composed of several components, including air tanks, a gas compressor, transition lines, cylinders, hoses and of course the gas itself. Solenoid valves regulate the airflow, converting the gas into mechanical energy. Pneumatics are mainly used with pressures of approx. 5.5 bar to 6.9 bar. The compressed air is stored in storage tanks before it is used.
Pneumatic systems are mainly used for shock absorption. You often see pneumatic applications in sectors such as construction, robotics, food production and distribution, medical applications, mining, biotechnology, transport and manufacturing. Examples of applications include:
- Air compressors
- Vacuum pumps
- HVAC control systems
- Compressed air engines and vehicles
- Pressure sensors, switches, and pumps
- Conveyor belt systems in the pharmaceutical and food industry
- Precision drilling for dentists
- Air brakes used by buses, trucks, and trains
- Nail guns
- Production and assembly lines
- Pneumatic motors, tires, and tools
The difference
In general, hydraulic systems are used for heavy-lifting applications, such as wind turbines, elevators, and aircraft wing flaps. Hydraulic systems operate at higher pressures, which means that more force is generated by small-scale actuators. Pneumatic systems are normally used when moving or assembling products, including food or pharmaceuticals, partly because there is no risk of oil leaks due to burst pipes.
More information about hydraulics and pneumatics? Or do you want to order specific parts for your machine? Contact the specialists at Marvo, we will be happy to help you.