The diaphragm valve type selection
The diaphragm valve body type selection is the most important link in diaphragm valve selection. The diaphragm valve body has a lot variety, most commonly are ten kinds: throughway single seat, throughway double seat, angular, diaphragm, small flow, three-way, eccentric rotation, butterfly shape, sleeve, ball, etc. Before the valve selection, we should take careful analysis of controlling process media and technology condition and parameters, collecting enough data, understanding the system requests to diaphragm valves, according to the collected data to determine the valve type that will be used. When in the specified choice, we can consider from the following aspects:
(1) Valve core shape structure is mainly considered according to the selected flow characteristics and unbalance force factors.
(2) Abrasion resistance when the fluid medium contains high concentrations abrasive particles in suspension, the valve core, seat will be serious friction when closed. Therefore, the valve flow path should be smooth, the internal material should be hard.
(3) Corrosion-resistant due to corrosive media, under the circumstances of meeting the regulatory function, the best choice is simple valve.
(4) medium temperature and pressure when the medium temperature and pressure are high and change a lot, you should select valve core and valve seat material that affected a little by small changes of temperature and pressure valves.
(5) to prevent flashing and cavitation flashing and cavitation are p only roduced in liquid medium. In the actual producting process, the flashing and cavitation are not only affect the calculation of flow coefficient, but also form vibration and noise, shorten the valve service life, so when selecting valves, we should prevent the valve producing flashing and cavitation .
No matter what type actuators is, the output power are used to overcome the load effective (mainly refers to the unbalanced force and unbalanced moment added with friction, sealing force, gravity force and other relevant effects). Therefore, in order to the properly working of diaphragm pump, the equipped actuators must be able to generate sufficient output force to overcome resistance and ensure high degree sealing and the valve opening. For the double-acting pneumatic, hydraulic, electric actuator, generally without reset spring. The size of the force has nothing to do with its running direction, therefore, the key to selecting actuators is to understand the maximum output power and the motor rotational torque. For single function pneumatic actuator, the output force is related to the valve opening degree, force appeared on diaphragm valve will also affect the motion characteristics, thus requiring to establish the force balance in the entire range of the diaphragm valveopening degree.
After confirming the actuator output force, based on the process use of environmental requirements, select the appropriate actuator. For the scene, where explosion-proof requirements, should use pneumatic actuator, and the junction box is the explosion-proof type, can not select electric actuator. If there is no explosion-proof requirements, either pneumatic or electric actuator can be selected, but from the energy-saving considerations, we should try to use electric actuator. For the hydraulic actuator, its use is less than pneumatic, electric actuator, but it has high adjustable precision, high speed movement and smooth characteristics, therefore, in some cases, in order to achieve better regulation, it is necessary to select the hydraulic actuator, such as power plants and transparent machine regulating speed, the refinery's catalytic device reactor temperature adjustment control,etc.
Diaphragm Valves acting mode choice
The oblique rubber lined diaphragm valve acting mode is only existing when selecting the pneumatic actuator, its acting mode is through the pros and cons of the actuators and valve to combine and form. There are four kinds of combination that is pros and pros (gas off type), pros and cons (gas open type), cons and pros (gas open type), cons and cons (gas off type), through the these four kinds of combination of diaphragm valve acting mode has gas open and off two kinds. The choice of diaphragm valve acting mode, mainly from three aspects to consider: a) process production safety; b) the medium characteristics; c) to ensure product quality, minimize economic losses.
