Delivery head (of centrifugal pumps). DIN 24 260, Part 1 (September 1986) gives the following definition and notes: The delivery head H in metres is "the useful mechanical work transferred from the pump to the pumped liquid relative to its weight... At constant pump speed and constant flow rate, H is not dependent on the density of the pumped liquid but is generally dependent on its viscosity..." By contrast, the important factor for determining the sealing pressure" is the density and not the viscosity.