1.) Maintain the quality and quantity of hydraulic oil
In hydraulic diaphragm metering pump the hydraulic oil does several things to ensure proper operation of the pump. First it develops the pressure to displace the diaphragm which in turn moves the chemical. Secondly the oil also lubricates the internals of the pump. Additionally it also keeps the diaphragm from taking any mechanical stress due to pressure imbalance. Hence it is important to make sure that the quantity of the oil is up to the level recommended by the manufacturer. Usually there are markings on the pump itself to show the optimal level of the oil. Then make sure the oil does not have any contamination from external or internal sources. If there is water, chemical or even air (frothing) in the oil it changes the physical and chemical properties of the oil which damages the pump components. If there are any solid particles such as dirt, metal filings or chips these will start wearing on wear parts such as gears and plungers. That wear will cause either leak paths or cause the mating parts to fall out of tolerance affecting the performance and accuracy of the pump.
2.) Prevent any restrictions on the suction line.
These pumps work on hydraulically balanced diaphragm principle. The pressure created by the process fluid is matched by the pressure created by the hydraulics of the pump. The hydraulics of the pump generates enough pressure to overcome and push the process liquid out. If during the operation of the pump the suction is restricted and the process side of the pump either does not fill up quickly, there is a pressure imbalance which slams the diaphragm against the contour plate (lower pressured process side). If this happens often enough and with an increasing pressure imbalance the diaphragm will eventually fail by extruding through the holes of the contour plate. Hence it is highly recommended to use a large (in diameter), unobstructed and short (in length) suction line.