Metering pumps, also known as dosing pumps or proportioning pumps, are a type of special positive displacement pump used to convey liquids, especially corrosive ones, that can meet various strict process requirements. The flow rate can be continuously adjusted within the range of 0-100%, making it possible to maintain a constant flow rate independent of the discharge pressure. Metering pumps are a type of fluid transfer machinery that can simultaneously achieve the functions of conveying, measuring, and regulating, thereby simplifying the production process. By using multiple metering pumps, several media can be accurately mixed in the process flow at precise ratios. Due to its outstanding performance, metering pumps are now widely used in various industrial fields such as petrochemicals, pharmaceuticals, and food production.
Classification of metering pumps:
- According to the flow-through part:
- (1) Plunger/piston type
- (2) Mechanical diaphragm type
- (3) Hydraulic diaphragm type
- According to the driving mode:
- (1) Motor-driven
- (2) Electromagnetic-driven
- According to the working mode:
- (1) Reciprocating type
- (2) Rotary type
- (3) Gear type
- According to pump characteristics:
- (1) Extra-large pump base
- (2) Large pump base
- (3) Medium pump base
- (4) Small pump base
- (5) Micro pump base
Other classification methods include: electric control type, pneumatic control type, thermal insulation type, heating type, high viscosity type, and other principle characteristics.
Structure of metering pump
The structure of a metering pump typically consists of three main components: an electric motor, a transmission box, and a cylinder body. The transmission box is composed of a turbine-worm mechanism, a stroke adjustment mechanism, and a crank-connecting rod mechanism. The high adjustment stroke is achieved by rotating the adjustment handwheel to change the eccentricity of the moving shaft, thereby changing the stroke of the plunger (or piston). The cylinder body component consists of a pump head, a suction valve group, a discharge valve group, a plunger (or piston), and a packing seal component.
Work principle of metering pump
The motor drives the worm through the coupling, and the main shaft and eccentric wheel rotate through the worm gear reduction. The sliding adjustment seat of the bow-shaped connecting rod moves back and forth driven by the eccentric wheel. When the plunger moves backward to the dead point, a vacuum gradually forms in the pump chamber, the suction valve opens, and liquid is sucked in. When the plunger moves forward to the dead point, the suction valve closes, the discharge valve opens, and the liquid is discharged as the plunger further moves forward. The pump works in a reciprocating manner to continuously discharge a pressurized and quantified amount of liquid.