Diaphragm pump category and type selection

According to the power used by its actuator, the diaphragm pump can be divided into three kinds: pneumatic, electric and hydraulic, that is, the pneumatic diaphragm pump with compressed air as the power source, the electric diaphragm pump with electric power source, and the electro-hydraulic diaphragm pump powered by the pressure of the liquid medium (such as oil, etc.). In addition, according to its function and characteristics, There are also solenoid valves, electronic, intelligent, field bus diaphragm pumps. There are many types of diaphragm pump products, and the structure is also diverse, and it is constantly updated and changed. Generally speaking, the valve is universal and can be matched with the pneumatic actuator, or with the electric actuator or other actuator.
Diaphragm pump type selection
1, diaphragm pump valve body type selection The selection of valve body is the most important link in the selection of diaphragm pump. There are many kinds of diaphragm pump valve body, commonly used are straight single seat, straight double seat, corner, diaphragm, small flow, tee, eccentric rotation, butterfly, sleeve, ball and other 10 kinds. Before selecting the valve, it is necessary to carefully analyze the media, process conditions and parameters of the control process, collect enough data, understand the requirements of the system for the diaphragm pump, and determine the type of valve to be used according to the collected data. In the specific choice, can be considered from the following aspects:
(1) The spool shape structure is mainly considered according to the selected flow characteristics and unbalance force.
(2) Wear resistance When the fluid medium is a suspension containing a high concentration of wear particles, the spool and seat joint surface will be subjected to serious friction each time it is closed. Therefore, the flow path of the valve should be smooth, and the internal material of the valve should be hard.
(3) Corrosion resistance Because the medium is corrosive, in the case of meeting the adjustment function, try to choose a simple valve 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 with small temperature and pressure changes of the spool and valve seat should be selected.
(5) Prevent flash and cavitation Flash and cavitation are only produced in liquid media. In the actual production process, flash and cavitation not only affect the calculation of flow coefficient, but also form vibration and noise, so that the service life of the valve is shorter, so the valve should be prevented from flash and cavitation when selecting the valve.
2. Selection of diaphragm pump actuator
(1) Consideration of output force
Regardless of the type of actuator, its output force is effective for overcoming the load (mainly refers to the unbalanced force and unbalanced moment plus the role of friction, sealing force, gravity and other related forces). Therefore, in order to make the diaphragm pump work normally, the actuator should be able to produce enough output force to overcome various resistance to ensure a high seal and the opening of the valve.
For double-acting pneumatic, hydraulic and electric actuators, there is generally no return spring. The size of the force has nothing to do with its direction of operation, so the key to selecting the actuator is to find out the maximum output force and the rotational torque of the motor. For single-acting pneumatic actuators, the output force is related to the opening of the valve, and the force appearing on the diaphragm pump will also affect the motion characteristics, so it is required to establish a force balance across the opening range of the diaphragm pump.
(2) Determination of the type of executive mechanism
After determining the output force of the actuator, select the corresponding actuator according to the requirements of the process environment. When there are explosion-proof requirements on the site, the pneumatic actuator should be selected, and the junction box is explosion-proof, and the electric actuator cannot be selected. If there is no explosion-proof requirement, pneumatic and electric actuators can be selected, but from the perspective of energy saving, electric actuators should be selected as far as possible. For the hydraulic actuator, its use is not as extensive as the pneumatic and electric actuator, but it has the characteristics of high adjustment accuracy, fast action speed and smooth, so in some cases; In order to achieve a better regulation effect, it is necessary to choose a hydraulic actuator, such as the speed regulation of the transparent machine in the power plant, the temperature regulation control of the catalytic unit reactor in the refinery.