1 Output considerations

Regardless of the type of actuator, its output force is the effective force used 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 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 large output force and the rotating 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 air diaphragm pump will also affect the movement characteristics, so it is required to establish a force balance across the opening range of the diaphragm pump.

2 Determination of the type of actuator
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, it is not as widely used as pneumatic and electric actuators, but it has the characteristics of high adjustment accuracy, fast action speed and smoothness. Therefore, in some cases, in order to achieve better adjustment results, 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 choice of valve body is an important part of the choice of diaphragm pump. There are many types of Air diaphragm pump valve bodies. Commonly used are straight single-seat, straight double-seat, angle, diaphragm, small flow, three-way, eccentric rotation, butterfly, sleeve, spherical, etc. 10 types. 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 pump, and determine the type of valve to be used based on the collected data. In the specific selection, the following aspects can be considered:

(1) The spool shape and structure 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, it is best to choose a valve with a simple structure if it can meet the adjustment function.

(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 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, when selecting the valve, prevent the valve from flashing and cavitation.

Diaphragm pump, also known as control pump, is the main type of actuator. It changes the fluid flow by receiving the control signal output by the adjustment control unit and using power operation. Diaphragm pumps are generally composed of actuators and valves. According to the power used by the actuator, diaphragm pumps can be divided into three types: pneumatic, electric, and hydraulic, namely pneumatic Air diaphragm pump with compressed air as power source, electric diaphragm pumps with electricity as power source, and liquid medium (Such as oil, etc.) Pressure-driven electro-hydraulic diaphragm pumps. In addition, according to their functions and characteristics, there are solenoid valves, electronic, intelligent, and fieldbus diaphragm pumps. Diaphragm pumps have many types and structures, and they are constantly updated and changed. Generally speaking, the valve is universal, which can be matched with pneumatic actuators, electric actuators or other actuators.