Common problems and solutions for metering pump piping systems

Problem 1: When there is no pressure at the outlet of the metering pump, the actual flow rate is much higher than the rated flow rate, and the flow rate hardly changes when adjusting.

Solution: Install a back pressure valve at the outlet of the metering pump. The back pressure valve can stabilize the flow rate of the metering pump while maintaining stable pipeline pressure, ensuring metering accuracy.

Problem 2: Large vibration occurs in the outlet piping after the pump is started.

Solution: Install a pulsation dampener at the outlet of the metering pump (preferably used in conjunction with a back pressure valve if there is no pressure at the outlet of the metering pump). Inertia resistance of the fluid discharged from the outlet at the moment the pump starts can cause pulsating impact force on the pipeline. This is a unique phenomenon of reciprocating pumps caused by sudden acceleration of liquid in the pipeline. A pulsation dampener can effectively prevent pipeline vibration caused by pulsation.

Problem 3: The fluid cannot be discharged or the pressure cannot be increased, and the flow rate is unstable after the pump is started.

Solution: There are many reasons why the metering pump cannot discharge the liquid, such as damaged diaphragm or blocked pipeline. If the motor and plunger are working properly, the reason for the failure to increase pressure is usually impurities in the liquid, which prevents the valve ball and seat from sealing completely, resulting in failure to increase pressure and unstable flow rate. Therefore, it is recommended to install a filter to prevent impurities from entering the pipeline.

Problem 4: (a) The liquid in the storage tank still flows out of the pump head after the pump is stopped. (b) Siphoning occurs when the metering pump is dosing.

Solution: Install a back pressure valve at the outlet of the metering pump. The self-flow is generally due to the liquid level in the storage tank being higher than the position of the pump head, causing the self-flow phenomenon. The back pressure valve can effectively prevent the occurrence of self-flow or siphoning.

Problem 5: Large pressure fluctuations occur in the outlet piping of the pump, affecting metering accuracy and the use of precision instruments.

Solution: Install a pulsation dampener near the pump outlet, preferably used in conjunction with a back pressure valve. Installing a pulsation dampener of suitable volume can reduce more than 90% of the pulsations, making the fluid after the dampener flow out smoothly.