译文：
计量泵作为化学品精密投加的理想设备，广泛应用于石化、化工、油气田、电力、造纸、制药、环保、水处理等行业。计量泵的背压阀，一般有两种用途。 1.用于防止液体在重力作用下自流(或虹吸)，这时候一般选用大于液体自身压力即可，如防止液位为2米药箱中的液体自流,可选用压力大于0.02MPa的背压阀，一般计量泵选用0.1MPa即可。 2.用于稳定计量泵的流量，如某些计量泵的流量随压力变化较大，可在计量泵的出口处设置背压阀，使计量泵的输出流量稳定，这时一般选择背压阀的压力为计量泵的实际使用压力或略小于计量泵的使用压力。 出口管道上的单向阀用于防止液体回流，背压阀用于保持计量泵出口有一恒定压力。由于计量泵的往复运动,驱动部分有一定的撞击声属正常现象,GB/T7782-1996《计量泵》规定在距泵1米处的噪音不在于75分贝（当然越小越好），声音异常，可能有以下原因： a.泵使用压力超出泵的额定压力（管道上的单向阀不畅通时可能出现此现象，可以在计量泵出口至单向阀前安装一压力表检查计量泵出口压力）。 b.蜗杆轴承损坏。 3.由于零件磨损导致安装隙增大。

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原文：
Precision metering pumps for chemical dosing ideal device, widely used in petrochemical, chemical, oil and gas, power, paper, pharmaceutical, environmental protection, water treatment and other industries. Metering pump back pressure valve, generally have two purposes. 1. Is used to prevent the liquid in the gravity gravity (or siphon), which is generally used when the pressure can be greater than the liquid itself, such as the medicine cabinet to prevent the liquid level to 2 meters of liquid gravity, the pressure can be used more than 0.02MPa of back pressure valve, metering pump generally can use 0.1MPa. 2. To stabilize the flow of metering pumps, metering pumps, as some changes in the flow with higher pressure can be measured to set the exit of the pump back pressure valve, so that the output of metering pump flow rate stability, this time, select the back-pressure valve The pressure of the actual use of a metering pump metering pump pressure or slightly less than the use of pressure. One-way valve on the outlet pipe to prevent liquid back, back-pressure valve for the metering pump to maintain a constant pressure. As the reciprocating metering pump, driving a certain part of a crash is normal, GB/T7782-1996 "metering pump," the provisions of 1 m away from the pump is not the noise of 75 dB (of course, the smaller the better), sound anomalies may have the following reasons: a. pump using the pump pressure exceeds the rated pressure (one-way valve on the pipe blocked this phenomenon may occur when, in the metering pump can be exported to the one-way check valve before the installation of a metering pump outlet pressure gauge). b. worm bearing damage. 3. As part installation gap leading to increased wear.