According to the movement mode of the driving mechanism, the valve driving device is divided into two types: straight stroke and angle stroke. According to the driving structure, the valve driving device is divided into:
1. Diaphragm type.
2. Cylinder type.
① Piston cylinder type.
② Piston rack type.
③ Piston rod type.
④ Piston fork type.
⑤ Piston screw type.
3. Vane type.
4. Air engine type.
5. Film and ratchet combination.
Features of various valve drives:
Advantages of electric device:
1. Strong applicability, not affected by ambient temperature.
2. Wide range of output torque.
3. It is easy to control and can freely use DC, AC, shortwave, pulse and other signals. It is suitable for amplification, memory, logical judgment and calculation.
4. Ultra miniaturization possible.
5. Mechanical self-locking.
6. Easy to install.
7. Convenient maintenance.
Disadvantages of electric devices:
1. Complex structure.
2. Mechanical efficiency is low, generally only 25% – 60%.
3. Output speed cannot be too low or too high.
4. Susceptible to changes in supply voltage and frequency.
Advantages of hydraulic device:
1. Simple structure, compact and small size.
2. Large output force.
3. Easy to obtain low speed or high speed, stepless speed change.
4. Remote automatic control.
5、 Due to the viscosity of hydraulic oil, it has high efficiency, self-lubricating and antirust properties.
1. Change of oil temperature change of oil viscosity.
2. Hydraulic components and pipes are easy to leak.
3. The maintenance is not convenient.
4. Not suitable for various operations on signals.
Advantages of pneumatic device:
1. Simple structure.
2. Gas source is easy to obtain.
3. High switching speed can be obtained.
4. Governor can be installed to adjust the switch speed as required.
5. Large compressibility of gas, elastic when closing.
1. Compared with the hydraulic device, it has a larger structure and is not suitable for valves with large diameter and high pressure.
2. Because of the compressibility of the gas, the speed is not easy to be uniform.
Selection of valve driving mode:
The selection basis of valve driving mode is:
Valve form, specification and structure,
Valve opening and closing torque (pipeline pressure, large differential pressure of valve), thrust,
Environmental temperature and fluid problems,
Usage and times,
Opening and closing speed and time,
Stem diameter, pitch, direction of rotation,
Power source parameters: electric power supply voltage, phase number, frequency; pneumatic air source pressure, hydraulic pressure,
Special considerations: low temperature, anti-corrosion, explosion-proof, waterproof, fireproof, radiation proof, etc.