As we all know, mainly by the metering pump driven by power, fluid delivery and regulation of three parts. The power drive mechanism drives the diaphragm to reciprocate through the mechanical linkage system. The diaphragm (piston) will be sucked in by the conveying fluid in the first half of the stroke and will be drained out of the pump head in the second half of the stroke. Therefore, the frequency of the stroke reciprocation or The stroke length of a reciprocating movement can achieve the purpose of regulating the fluid delivery volume. Precision machining accuracy to ensure that each pump to achieve the precise measurement of the medium being delivered. Because of its power-driven and fluid delivery methods are different, metering pump can be roughly divided into two major types of plunger and diaphragm. 1, plunger metering pump There are two common valve pump and valveless pump. Plunger metering pump because of its simple structure and high temperature and pressure and other advantages have been widely used in the field of petrochemicals. Aiming at the shortage of high-pressure medium under the condition of high pressure, the valve-less rotary plunger metering pump has been paid more and more attention. It is widely used in high viscosity medium such as syrup, chocolate and oil additives Metering added. Due to the structural disadvantage of being unable to achieve complete isolation between the metering medium and the pump lubricant, the plunger metering pump suffers from a number of limitations in high contamination prevention fluid metering applications. 2, diaphragm metering pump As the name suggests, the diaphragm metering pump uses a special design and processing of flexible diaphragm to replace the piston, the reciprocating motion of the drive mechanism to achieve the suction - discharge process. Due to the isolation of the diaphragm, the structural isolation between the fluid being metered and the drive lubrication mechanism is truly achieved. High-tech structural design and selection of new materials have greatly increased diaphragm life, coupled with the excellent corrosion resistance of composite materials, diaphragm metering pumps have now become the main pump in fluid metering applications. In the diaphragm metering pump family members, hydraulic driven diaphragm pump due to the use of oil evenly driven diaphragm, overcomes the mechanical direct drive pump diaphragm over-concentration shortcomings, to enhance the diaphragm life and maximum pressure. In order to overcome the possible malfunction caused by diaphragm breakage in single-diaphragm metering pump, some metering pumps are equipped with diaphragm breakage to achieve automatic interlock protection when the diaphragm ruptures. The measurement of the pump head with double-diaphragm structure further improves its safety Suitable for applications that are particularly sensitive to safety. As a diaphragm metering pump, electromagnetically driven metering pump generates pulsating driving force with electromagnet, which saves the motor and transmission mechanism, makes the system small and compact and is an important branch of low pressure metering pump with small range.