The attention points in the process of pneumatic control valve selection

Pneumatic - valve factory inspection, mainly static characteristic test, including basic error, rated travel deviation, return difference, starting point and end point deviation, dead zone, repeatability error, sealing, leakage, etc. , all these were made in the case of no-load test, actually they are on the workbench to measuring results gained by the valve, but the result is difficult to explain the pneumatic control valve in the actual running conditions will show what kind of performance. Pneumatic control valve body types of options: pneumatic control valve body is a lot of more phyletic, the commonly used types of the body is through single-seat, direct two-seater, angular, diaphragm, small flow rate, tee, eccentric rotating, butterfly, sleeve, spherical, etc. In specific choices, to do the following: ( 1) Mainly based on the selected valve core shape of flow characteristic and factors such as unbalanced force. ( 2) Wear resistance when fluid medium is suspending liquid containing high concentrations of wear particles, the interior of the valve material is hard. ( 3) Corrosion resistance due to the corrosive medium, to choose structure simple valves. ( 4) Medium temperature, pressure, when the medium temperature, high pressure and large, should choose the valve core and valve seat materials by temperature, pressure changes small valves. ( 5) Prevent flash flash and cavitation and cavitation produced only in a liquid medium. In actual production process, flash and cavitation will form the vibration and noise, shorten the service life of the valve, therefore when selecting valves should prevent the valve from flash and cavitation. Pneumatic control valve actuator selection in order to make the pneumatic - valve to work properly, with the implementation of the mechanism to produce enough output power to ensure highly seal and valve opening. For double-acting pneumatic, hydraulic, electric actuators, are generally not reset spring. The size of the force has nothing to do with its direction, therefore, the selection of the actuator is the key to find out the biggest output force and rotational torque of the motor. For single acting pneumatic actuators, the output power is associated with the opening of the valve, pneumatic control valve on the emergence of the force will also affect the movement characteristics, therefore needs to be established in the pneumatic - valve opening range force balance. Determine the type of actuator on the actuator output force is determined, according to the process using the environment requirements, choose the corresponding actuator. For the scene have explosion-proof requirements, should choose pneumatic actuators. From the aspects of energy saving consideration, should try to choose electric actuators. If the adjustment of high precision, can choose hydraulic actuators. Such as power plants transparent machine speed regulation, the refinery catalytic unit reactor temperature regulation control and so on. Pneumatic control valve of the effect way to choose the way to the role of the pneumatic control valve only have when choosing pneumatic actuators, the role of way through positive and negative effect and positive effect of the valve actuator portfolio formation. There are four that are positive (combination Gas closed type) , positive and negative, Gas type) And anyway, Gas type) And reflect ( Gas closed type) , through these four combination way have the function of pneumatic control valve open and close two kinds. For the choice of the ways of pneumatic control valve function, mainly from three aspects: a) Process safety; b) The characteristics of medium; c) Ensure product quality and economic loss is minimal