What are the working principles and structural characteristics of diaphragm pumps
Working principle and structure of diaphragm pump
Diaphragm pump is a special form of displacement pump. It relies on the back and forth agitation of a diaphragm to change the volume of the working chamber to suck and discharge liquid.
Diaphragm pump is mainly composed of transmission part and diaphragm cylinder head. The transmission part is a driving mechanism that drives the diaphragm to agitate back and forth. Its transmission forms include mechanical transmission, hydraulic transmission and pneumatic transmission. Among them, hydraulic transmission is widely used. Figure 1 shows a hydraulically driven diaphragm pump. The working part of the diaphragm pump is mainly composed of a crank connecting rod mechanism (not shown in Figure 1), plunger, cylinder, diaphragm, pump body, suction valve, and discharge valve. , The drive mechanism composed of crankshaft connecting rod, plunger and hydraulic cylinder is very similar to reciprocating plunger pump.
Figure 1 Hydraulic drive diaphragm pump
1- discharge valve; 2- pump body; 3- plunger;
4-liquid cylinder; 5-diaphragm; 6-suction valve
When the diaphragm pump is working, the crank connecting rod mechanism is driven by the electric motor to drive the plunger to reciprocate. The movement of the plunger is transmitted to the diaphragm through the working fluid (usually oil) in the cylinder, causing the diaphragm to move back and forth.
The cylinder head of the diaphragm pump mainly has a diaphragm to separate the liquid to be transported from the working fluid. When the diaphragm moves to one side of the transmission mechanism, the working chamber in the pump cylinder sucks the liquid under negative pressure; when the diaphragm moves to the other side, Then discharge the liquid. The liquid to be transported is separated from the working fluid by the diaphragm in the pump cylinder, and only contacts the pump cylinder, suction valve, discharge valve and the inner side of the diaphragm, without contacting the plunger and sealing device, which makes the column Important parts such as plugs work completely in oil medium and are in good working condition.
The diaphragm must not only have good flexibility, but also have good corrosion resistance, usually made of polytetrafluoroethylene, rubber and other materials.
The pot-bottom-shaped parts with meshes on both sides of the diaphragm are installed to prevent the diaphragm from locally deforming too much, and are generally called diaphragm restrictors.
Diaphragm pumps have good sealing performance, can easily achieve leak-free operation, and can be used to transport corrosive liquids such as acids, alkalis, salts and high viscosity liquids.
Classification and characteristics of diaphragm pumps
Diaphragm pumps can be divided into single diaphragm pumps, double diaphragm pumps, tube diaphragm pumps and mechanical diaphragm pumps according to their diaphragm forms. The single diaphragm pump is shown in Figure 2 and the double diaphragm pump is shown in Figure 3.
Figure 2 Single diaphragm pump
1- plunger; 2- packing; 3- fill tank; 4- diaphragm
Figure 3 Double diaphragm pump
According to the structure of the hydraulic end of the diaphragm pump, it is divided into two types: hydraulic diaphragm pump and mechanical diaphragm pump. The plunger of the hydraulic diaphragm pump is not in contact with the diaphragm, and the hydraulic end is divided into an infusion chamber and a hydraulic chamber. The infusion cavity is connected to the pump suction and discharge valves, and the hydraulic cavity is filled with hydraulic oil (light oil) and communicates with the hydraulic oil tank (charge tank) at the upper end of the pump body. When the plunger moves back and forth, the hydraulic oil transmits the pressure to the diaphragm and causes it to be flexed and deformed to change the volume, play the role of transporting liquid, and meet the requirements of accurate measurement. The diaphragm of the mechanical diaphragm pump is connected with the plunger mechanism without a hydraulic oil system. The forward and backward movement of the plunger directly drives the front and back flexure and deformation of the diaphragm, thus playing the role of transporting liquid. The difference and characteristics of mechanical diaphragm pump and hydraulic diaphragm pump are shown in Table
