First, the plunger metering pump features: 1, the price is lower. 2, the flow rate of up to 76m3 / h, the flow rate of 10% to 100% of the range, measurement accuracy of ± 1%, the maximum pressure up to 350MPa. When the outlet pressure changes, the flow rate is almost unchanged. 3, can transport high viscosity medium, not suitable for conveying corrosive slurry and dangerous chemicals. 4, the shaft seal for the packing seal, there is leakage, the need to periodically adjust the packing. Filler and plunger wear, need to be pressure ring flushing and discharge packing. 5, no safety relief device. Second, the mechanical diaphragm metering pump features: 1, the price is lower. 2, no seal, no leakage. 3, can transport high-viscosity media, abrasive slurry and hazardous chemicals. 4, the diaphragm withstand high stress, lower diaphragm life. 5, the outlet pressure below 2MPa, the flow of a smaller scope; measurement accuracy of ± 5%, when the pressure from the smallest to the largest, the flow changes up to 10%. 6, no safety relief device. Third, the hydraulic diaphragm metering pump features: 1, no passive seal, no leakage, safety relief device, easy maintenance. 2, pressure up to 35MPa; flow rate in the range of 10: 1, measurement accuracy of ± 1%; pressure increased by 6.9MPa, the flow decreased by 5% to 10%. 3, the higher the price. 4, suitable for medium viscosity medium. Fourth, bellows metering pump features: 1, the price is lower. 2, no seal, no leakage. 3, the most suitable for conveying vacuum, high temperature, low temperature medium, the outlet pressure below 0.4MPa G, lower measurement accuracy.