In hydraulic pump the process liquid is isolated from plunger by hydraulic oil and a diaphragm. Normally Teflon is used as a diaphragm material due to its flexibility and corrosion resistivity.

Hydraulic diaphragm pumps are recommended for the applications where the leakage is not at all permitted. It provides an integral safety valve which can automatically protect the diaphragm while the fluctuation in the line.