High level of metering accuracy

These pumps achieve high levels of accuracy, repeatability and linearity, while delivering precise, constant flow by using special hydraulic oil management systems. 

Wanner explains that to maintain accuracy in a hydraulically-actuated metering pump, the volume of oil on the non-process side of the diaphragm must remain constant. Hydra-Cell pumps have a replenishment valve in every piston assembly which operates on the suction stroke, thus ensuring optimum actuating oil volume on every diaphragm pressure stroke to provide accuracy that exceeds the performance demands of API 675.

Electronic variable speed drives or mechanical speed variators are used to control flow, while the hydraulic management system protects the diaphragm against dry running and vacuum or blocked inlet conditions.