The advantages & disadvantages of pneumatic valves and electric valves
The working principle of pneumatic valve use compressed air to drive the movement of multiple groups of combined pneumatic piston in the actuator, transmits force to the beam and the characteristics of the inner curve track, drives the air core spindle to rotate, the compressed air disc is transmitted to each cylinder, changes the inlet and outlet position to change the rotation direction of the spindle, it adjusts the number of cylinder combinations according to the requirements of the rotating torque required by the load (valve). Drive the load (valve) work. Two five-way solenoid valve is usually used with double-acting pneumatic actuator, two is two positions controllable: open - off, five is five channels of ventilation, of which one is connected with the air source, two are connected with the inlet and outlet of the external air chamber of the double-acting cylinder, and two are connected with the inlet and outlet of the internal air chamber. The specific working principle can be referred to the working principle of the double-acting pneumatic actuator. Due to the increasing number of control methods and means, there are many methods used to control pneumatic actuators in actual industrial processes and industrial controls.
First, valve reliability . We are used to think that the reliability of pneumatic valves is high, the reliability of electric valves is poor. However, the new generation of electric valve actuators uses new circuit integration technology to abandon the previous fatal weakness, so that the actuator can be used for an average of 5-10 years, so as to reach or exceed the service life of the pneumatic valve. Therefore, in terms of reliability, the two types of valves have their own advantages.
Second, the field power source in the explosion-proof requirements of the occasion most of the use of pneumatic valve actuator - one of the advantages of pneumatic valve is intrinsically safe explosion-proof, and the shortcomings are obvious - the need to establish a more perfect pneumatic mechanism, increasing the configuration cost. The electric valve actuator can use local materials, and the electric valve is preferred when the explosion-proof requirement is not high and the air source is inconvenient.
The technical indicators of electric valve actuator and pneumatic valve actuator + valve positioner are basically the same. The prices of the two types of products, whether domestic or import are similar. The pneumatic valve needs to be configured with air compressor stations and other air source facilities, so the selection of electric valves has an advantage in price.
The selection of the actuator with obvious output is determined according to the type of valve and the allowable pressure difference. Therefore, the specific selection should be determined according to the actual situation which needs to be flexible.
At the level of fire and explosion prevention, the pneumatic actuator + valve positioner is far superior to the electric actuator: 1. Only a few electric actuators can be produced as explosion-proof series. 2. Highly flammable, explosive and other special occasions are usually not allowed to use electric actuators.
