A metering pump refers to a pump that can adjust and transport media according to the indications on the flow (or relative stroke length) indicator mechanism (or equipment) through a flow (or stroke length) adjustment mechanism (or device). According to the structural type of the hydraulic end of the metering pump, it is often divided into four types: plunger type, hydraulic diaphragm type, mechanical diaphragm type, and bellows type metering pumps. The plunger type and hydraulic diaphragm type are relatively widely used.

A metering pump is generally a horizontal single acting pump, mainly composed of transmission components (base) and hydraulic cylinder components. The hydraulic cylinder is divided into two categories: plunger metering pumps and diaphragm metering pumps. The common types of machine bases include convex wheel structure and N-axis structure. Other transmission components include electric motors, reduction devices, connecting rods, cross heads, etc. The composition of the hydraulic cylinder is basically the same as that of a regular reciprocating pump.

The commonly used flow regulation methods for metering pumps include adjusting the stroke of the plunger (or piston), adjusting the pump speed, and combining stroke and pump speed. Among them, the stroke regulation method is the most widely used. This method is simple, reliable, and can maintain high measurement accuracy even at low flow rates. There are three ways to adjust the itinerary:

(1) Manual adjustment during parking: Manually adjust the stroke of the metering pump during parking.

(2) Manual adjustment during operation: By changing the axial displacement during pump operation, the crank radius can be indirectly adjusted to achieve the purpose of adjusting the stroke length. Common methods include adjusting the N-shaped crankshaft, adjusting the L-shaped crankshaft, and adjusting the eccentric cam.

(3) Automatic adjustment during operation: There are two common types: pneumatic control and electric control. Pneumatic control is achieved by changing the pressure signal of the gas source to automatically adjust the stroke; Electric control is achieved by changing the electrical signal to automatically adjust the stroke.