Selection of sanitary diaphragm valve type and mode of action

The choice of sanitary diaphragm valve type and mode of action There are many types of sanitary diaphragm valve body, which is the most important link in the selection of diaphragm valve. Commonly used are straight single seat, straight double seat, angle, diaphragm, small flow, three-way, 10 kinds of eccentric rotation, butterfly, sleeve, spherical, etc. Before selecting a valve, carefully analyze the medium, process conditions and parameters of the control process, collect enough data, understand the system's requirements for the diaphragm valve, and determine the type of valve to be used based on the collected data. When choosing, you can consider from the following aspects: (1) The shape and structure of the valve core are mainly considered based on the selected flow characteristics and unbalanced force. (2) Wear resistance When the fluid medium is a suspension containing a high concentration of abrasive particles, the valve core and valve seat joint surface will be severely rubbed every time it is closed. Therefore, the flow path of the valve must be smooth, and the internal material of the valve must be hard. (3) Corrosion resistance As the medium is corrosive, if the regulating function can be satisfied, try to choose a valve with a simple structure. (4) The temperature and pressure of the medium. When the temperature and pressure of the medium are high and the change is large, the valve core and valve seat material should be selected for small changes in temperature and pressure. (5) Prevent flash vaporization and cavitation Flash vaporization and cavitation only occur in liquid media. In the actual production process, flashing and cavitation not only affect the calculation of the flow coefficient, but also cause vibration and noise, which will shorten the service life of the valve. Therefore, the valve should be prevented from flashing and cavitation when selecting the valve. Regardless of the type of actuator, its output force is the effective force used to overcome the load (mainly refers to the effect of unbalanced force and unbalanced torque plus friction, sealing force, gravity and other related forces). Therefore, in order to make the diaphragm pump work normally, the equipped actuator must be able to generate enough output force to overcome various resistances and ensure a high degree of sealing and valve opening. For double-acting pneumatic, hydraulic, and electric actuators, there is generally no return spring. The magnitude of the force has nothing to do with its running direction. Therefore, the key to selecting an actuator is to understand the maximum output force and the motor's rotational torque. For single-acting pneumatic actuators, the output force is related to the opening of the valve, and the force appearing on the diaphragm valve will also affect the motion characteristics, so it is required to establish a force balance across the opening range of the diaphragm valve. After determining the output power of the actuator, select the corresponding actuator according to the requirements of the process environment. For explosion-proof requirements on site, pneumatic actuators should be selected, and the junction box is explosion-proof, and electric actuators cannot be selected. If there is no explosion-proof requirement, both pneumatic and electric actuators can be used, but in terms of energy saving, electric actuators should be used as much as possible. For hydraulic actuators, they are not as widely used as pneumatic and electric actuators, but they have the characteristics of high adjustment accuracy, fast action speed and smoothness. Therefore, in some cases, in order to achieve better adjustment effects, hydraulic actuators must be selected. Institutions, such as the speed adjustment of the transparent machine in the power plant, the temperature adjustment control of the catalytic device reactor of the oil refinery, etc. The action mode of sanitary diaphragm valve is the direct-flow rubber-lined diaphragm valve. The action mode is only available when the pneumatic actuator is selected. Its action mode is formed by the combination of the positive and negative effects of the actuator and the positive and negative effects of the valve. There are 4 types of combinations, namely, positive (air-to-close type), positive and negative (air-to-open type), anyway (air-to-open type), and reverse (air-to-close type). The diaphragm valve action mode formed by these four combinations has air There are two types: on and off. For the choice of diaphragm valve action mode, mainly consider from three aspects: a) process production safety; b) the characteristics of the medium; c) ensure product quality and minimize economic losses.