As the ideal equipment for chemical precision injection, metering pumps are now widely used in petrochemical, chemical, oil and gas fields, power, papermaking, pharmaceutical, environmental protection, water treatment and other industries. Dosing pump back pressure valve, there are two general purposes. 1. Used to prevent the gravity flow of gravity under gravity (or siphon), this time generally greater than the pressure of the liquid itself can be used, such as to prevent the liquid level of 2 meters medicine tank gravity, the pressure can be greater than 0.02MPa back pressure Valve, the general metering pump can be used 0.1MPa. 2. Used to stabilize the metering pump flow, such as some metering pump flow with the pressure changes larger, can be set in the metering pump outlet back pressure valve, the metering pump output flow stability, then generally choose back pressure valve The pressure for the metering pump actual use pressure or slightly less than the metering pump working pressure. The check valve in the outlet pipe is used to prevent backflow of the liquid and the back pressure valve is used to maintain a constant pressure at the metering pump outlet. Due to the reciprocating movement of the metering pump, the driving part has a certain impact sound phenomenon is normal, GB / T7782-1996 "metering pump" provisions in the distance of 1 meter from the pump noise is not 75 dB (of course, the smaller the better), but The abnormal sound you have mentioned may be caused by the following reasons: a. The pressure of the pump exceeds the rated pressure of the pump (This phenomenon may occur when the check valve on the pipe is not smooth, and you can install a pressure before the check valve outlet to the check valve Table check metering pump outlet pressure). b. Worm bearing damage. 3 due to wear and tear caused by increased wear and tear parts.