Hydraulic movement mainly refers to the unified setting of an oil station, and then the oil is distributed to each hydraulic actuator, mainly used in the factory more dense valve area. Gas-liquid linkage is often used in dispersed areas and is not easy to lay cables, and the medium in the pipeline is compressed gas (such as the west-to-East gas pipeline), using the compressed gas in the pipeline as the power, driving oil to the actuator.Electro-hydraulic linkage is rare, and an actuator corresponds to a motor that increases the pressure of the drive oil to make the valve move.
Pneumatic devices, hydraulic devices are mostly composed of compressed gas or hydraulic pressure cylinders), a small number of pneumatic motors or hydraulic motors driven by the deceleration mechanism into. The former is widely used as a partial rotary and linear reciprocating drive; the latter can be used as a multi-ring rotary drive, and some can be common with electric devices. They all have the characteristics of compact ﹑ opening and closing, suitable for indoor or corrosive ﹑ flammable and explosive environment; The disadvantage is that the piping is more complex and not suitable for long-distance control. The pressure of the pneumatic device is generally (4~6) x105 PA, the output is small.The hydraulic device adopts high pressure and has greater output.
The electric device uses an electric motor to drive the deceleration mechanism to drive the valve device. Some are driven by electric magnetism valves (see solenoid valves). The electric device of the valve has two types of multi-rotary type and partial rotary type. It is characterized by convenient power supply ﹑ easy to adjust ﹑ output, suitable for remote control and automatic control needs, more widely used.However, in the design and manufacture, it is necessary to consider the influence of outdoor ﹑ flammable and explosive environmental conditions on electric devices, and the structure is more complex.
The gas-liquid linkage device and the electro-hydraulic linkage device consist of a compressed gas or electric power as the power source of the hydraulic mechanism. Common is part of the rotary type, which is characterized by rapid action ﹑ the output of large, can drive large caliber valves. This device is commonly used for truncation valves or emergency automatic truncation valves for long-distance pipelines for oil and natural gas.