Pneumatic diaphragm pump is a new type of conveying machinery. It uses compressed air as the power source. It can pump all kinds of corrosive liquids, liquids with particles, high viscosity, volatile, flammable, and highly toxic liquids. . Its performance parameters are similar to the WLLDENPVMPS of the Federal Republic of Germany and the MARlOWPUMPS of the United States.
Diaphragm pump valve body type selection Valve body selection is an important link in the selection of diaphragm pumps. There are many types of valve bodies in diaphragm pumps, and 10 types are commonly used: straight-through single-seater, straight-through double-seater, angular, diaphragm, small flow, three-way, eccentric rotation, butterfly, sleeve, and spherical. Before choosing a valve, it is necessary to 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.
The action mode of the diaphragm pump is only available when the pneumatic actuator is selected, and its action mode is formed by the combination of the positive and negative actions of the actuator and the positive and negative actions of the valve. There are 4 types of combinations, positive and negative (air-to-close type), positive and negative (air-to-open type), reverse (air-to-open type), and reverse-reverse (air-to-close type). On and off. For the choice of diaphragm pump action mode, three aspects are mainly considered: a) safety of process production; b) characteristics of medium; c) guarantee of product quality and small economic loss.
The action mode of the electric diaphragm pump is only available when the pneumatic actuator is selected, and its action mode is formed by the combination of the positive and negative actions of the actuator and the positive and negative actions of the valve. There are 4 types of combinations, positive and negative (air-to-close type), positive and negative (air-to-open type), reverse (air-to-open type), and reverse-reverse (air-to-close type). The action modes of the diaphragm pump formed by these four combinations are: air On and off. For the selection of the action mode of the diaphragm pump, three aspects are mainly considered: a) safety of process production; b) characteristics of the medium; c) guarantee of product quality and small economic loss.
The flow characteristic of the electric diaphragm pump refers to the relationship between the relative flow of the medium flowing through the valve and the displacement (relative opening of the valve). The ideal flow characteristics mainly include straight line, equal percentage (logarithmic), parabolic and quick opening. Commonly used ideal flow characteristics are only straight line, equal percentage (logarithmic), and quick opening. The parabolic flow characteristic is between straight line and equal percentage, which can generally be replaced by equal percentage characteristic, while the quick opening characteristic is mainly used in two-position adjustment and program control, so the choice of diaphragm pump characteristics is actually straight line and equal percentage flow characteristic s Choice.
The selection of the flow characteristics of the electric diaphragm pump can be calculated theoretically, but the methods and equations used are very complicated. At present, empirical criteria are mostly used, specifically considering the following aspects: ① analyze and select from the adjustment quality of the regulating system; ② consider from the process piping situation; ③ analyze from the load change situation.
If the flow characteristics of the diaphragm pump are selected, the shape and structure of the valve core can be determined according to its flow characteristics. However, for diaphragm valves, butterfly valves, etc., due to their structural characteristics, it is impossible to achieve the desired effect by changing the shape of the valve core. The required flow characteristics can be achieved by changing the shape of the feedback cam of the valve positioner.
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