A mechanical seal's power consumption consists of its face friction and the power consumed by the turbulence of liquid inside its stuffing box. Turbulence generated by rotation of the mechanical seal is enhanced by non-enclosed springs, recesses and inlets for cooling or flushing liquid. The power consumption of the rotating water eddy can be calculated approximately as

P_v = 1.02 · 10^-6 · n^2.8 · D^3.6 · e

where:

n = Speed (min^-1)

D = Outer diameter of the rotating part of the seal (m)

e = Axial length of the rotating part of the seal (m)

P_v = Power loss (KW)

The diagram shows that turbulence losses do not contribute significantly to a mechanical seal's total power consumption until the circumferential speed exceeds 25 to 30 m/s.