Experimental study on transient frictional features of herringbone-grooved mechanical face seals in start-up and stop stages

Evolutions of frictional features of herringbone-grooved face seals during start-up and stop stages are focused on. Transient frictional torques are measured for outer-diameter-side, middle and inner-diameter-side grooved seals and a smooth-face seal based on a formerly developed dedicated test rig. Development of fluid carrying capacity can be deduced for all four seals according to torque evolutions, and lift-off mechanisms are analyzed. Hydrodynamic effect gets smaller with grooves apart from pressurized fluid side, and thereby hydrostatic effect due to face coning by heat generation dominates the fluid film formation as it is for the smooth-face seal. Thermal characteristic time due to thermal lag effect is smaller than accelerating periods. The squeeze effect indicated by the smaller torque of stop stages is also playing a role in transient operation. •Transient frictional torque evolutions are measured for herringbone-grooved face seals.•Full-film lubrication could arise in out-groove and middle-groove seals during starting up.•Torque evolutions of inner-groove seal are close to those of smooth-face seal.•Hydrostatic effect dominates the fluid film generation when hydrodynamic effect is limited.•Squeeze effect is indicated by the lower frictional torque during stop stages.