How Metering Pumps Work...

The pumped product is in contact with a diaphragm and isolated from the pump thrust mechanism. The hydraulic diaphragm is placed between two liquids (process product and hydraulic oil) and is subject to compression on its thickness only. The hydraulic system (behind the diaphragm) transmits the volume displaced by a reciprocating piston causing a regular flexure of the diaphragm resulting in a spherical segment whose volume corresponds to the volume displaced by the piston. Suction and compression stages are carried out by the piston. The hydraulic system of all hydraulic diaphragm
metering pumps is of the “intelligent diaphragm” type, also called “mechanical oil replenishment”.

Besides the safety valve, this system is provided with air bleed valve and mechanically operated oil replenishing valve.