How should the diaphragm pump be selected?

1. Diaphragm pump selection

　　 The valve body selection of the diaphragm pump is the most important link in the selection of the diaphragm pump. Diaphragm pumps have many kinds of valves. Commonly used are straight-through single-seat, straight-through two-seat, angle, diaphragm, small flow, three-way, eccentric rotation, butterfly, sleeve, spherical, etc. 10 types. Before choosing a valve, you should carefully analyze the control process medium, process conditions and parameters, collect enough data, understand the requirements of the diaphragm pump system, and determine the type of valve used based on the collected data. When making specific choices, you can consider the following aspects:

　　(1) The shape and structure of the valve core are mainly 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, severe friction will occur every time the valve core and valve seat are closed. Therefore, the flow of the valve should be stable, and the internal material of the valve should be hard.

　　 (3) Due to the corrosiveness of the medium, a valve with a simple structure should be selected as far as possible under the condition of satisfying the adjustment function.

　　(4) When the temperature and pressure of the medium are high and change a lot, the valve core and seat materials should be selected as the valve with little temperature and pressure change.

　　(5) Prevent flashing and cavitation only 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, and shorten the service life of the valve. Therefore, flashing and cavitation should be prevented when selecting valves.

　　 Second, the choice of diaphragm pump

         (1) The output force of the actuator, regardless of its type, is the effective force to overcome the load (mainly refers to the unbalanced force and unbalanced moment plus friction, sealing force, gravity and other related forces). Therefore, in order to make the diaphragm pump work normally, the supporting actuator should be able to produce enough output force, overcome various resistances, and ensure high sealing performance and valve opening. For double-acting pneumatic, hydraulic and electric actuators, there is usually no return spring. The magnitude of the force has nothing to do with the direction of action. Therefore, the key to selecting an actuator is to find the maximum output force and torque of the motor. For single-acting pneumatic actuators, the output force is related to the valve opening, and the force on the diaphragm pump will also affect its movement characteristics. Therefore, it is necessary to establish a force balance in the entire opening range of the diaphragm pump.

         (2) After the output force of the actuator is determined by the type of the actuator, select the corresponding actuator according to the requirements of the process environment. On-site explosion-proof requirements use pneumatic actuators, junction boxes are explosion-proof, and electric actuators cannot be used. If there is no explosion-proof requirement, pneumatic and electric actuators can be used, but considering energy saving, electric actuators should be used as much as possible. In hydraulic actuators, its application is not as extensive as pneumatic and electric actuators, but its adjustment accuracy is high.