Diaphragm metering pump is composed of actuator and valve, diaphragm pump selection in the specific choice, can be considered from the following aspects:

1, the spool shape and structure are mainly based on the selected flow characteristics and unbalanced forces and other factors

2, wear resistance, when the fluid medium is a suspension containing high concentration of abrasive particles, the valve core, valve seat joint surface each closure will be seriously friction. Therefore, the valve flow path to smooth, the internal material of the valve to be hard

3, corrosion resistance as a corrosive medium, to meet regulatory function in the case, try to choose simple valve.

4, the medium temperature and pressure when the medium temperature, high pressure and great change, valve core and valve seat should use the material by the temperature and pressure changes in the small valve.

5, to prevent flashing and flashing and cavitation cavitation produced only in liquid medium. In the actual production process, steam and air not only affects the calculation of flow coefficient, but also the formation of vibration and noise, shorten the life of the valve, so the choice should be to prevent the valve valve produces flash steam and cavitation.

(1) the diaphragm valve type selection

The body of the diaphragm pump selection is one of the most important part of choice. Many types of diaphragm valve, commonly used through single seat, through two seater, angular, diaphragm, small flow, three links, eccentric rotation, butterfly, sleeve type, spherical and other 10 kinds. In the choice of the valve prior to the control process of the medium through careful analysis, process conditions and parameters, to collect sufficient data to understand the system requirements on the diaphragm, according to the data collected to determine the type of valve to be used. In the specific choice, can be considered from the following aspects:

A, wear resistance, when the fluid medium is a suspension containing high concentration of abrasive particles, the valve core, valve seat joint surface each closure will be seriously friction. Therefore, the valve flow path to smooth, the internal material of the valve to be hard

B, corrosion resistance as a corrosive medium, to meet regulatory function in the case, try to choose simple valve.

C, disc shape of the structure mainly based on the choice of flow characteristics and considerations such as power imbalances.

D, the medium temperature and pressure when the medium temperature, high pressure and great change, valve core and valve seat should use the material by the temperature and pressure changes in the small valve.

E, to prevent flashing and flashing and cavitation cavitation produced only in liquid medium. In the actual production process, steam and air not only affects the calculation of flow coefficient, but also the formation of vibration and noise, shorten the life of the valve, so the choice should be to prevent the valve valve produces flash steam and cavitation.

(2) selection of actuating mechanism of diaphragm pump

A, the consideration of output force

No matter what type of actuator, the output power are used to overcome the effective load (mainly refers to the imbalance force and torque and friction, sealing force, gravity and the role of the force). Therefore, in order to work diaphragm pump is equipped with the implementing agencies to be able to generate sufficient output power to overcome resistance and ensure a high degree of sealing and the valve opening.

For double acting pneumatic, hydraulic, electric actuator, generally not reset spring. The size of the force and the direction it has nothing to do, therefore, is that the rotary ininguting agencies to ascertain the maximum output power and torque motor. For single acting pneumatic actuator, output force and the valve opening the degree of emergence of the force on the diaphragm will also affect the motion characteristics, therefore requires a force opening in the diaphragm area balance.

B, determination of actuator type

The implementation of the output power is determined, according to the use of environmental technology requirements, select the appropriate enforcement agency. For the scene, explosion-proof requirements, should use pneumatic actuator, and explosion-proof junction box, can not choose the electric actuator. If there is no explosion-proof requirements, pneumatic and electric actuators can be used, but from energy considerations, should try to use the electric actuator for the hydraulic actuator, its use as pneumatic, electric actuators widely, but with high accuracy of regulation, characteristics, movement speed and stationary so, in some cases, in order to achieve better regulation, must use the hydraulic actuator such as power plants and transparent machine speed regulation, the refinery catalytic reactor temperature control.