Gland sealing is the standard form of sealing adopted for many slurry pump applications due to it's relative robustness, gradual failure mode and ease of maintenance.
ANATOMY OF A GLAND SEAL
A gland seal is comprised of a chamber (Stuffing Box) which houses stationary sealing components such as Lantern Rings, Neck Rings and Gland Packing. The chamber allows for flushing water to be feed into the sealing area through a feed hole. Passing through the centre of the chamber is a shaft which may have a sacrificial wear sleeve which rotates against the stationary packing in the sealing chamber or stuffing box. Pressure is applied between the packing and shaft sleeve through a gland follower which when tightened compresses the packing, this forms a sealing line between the sleeve and the packing, between the pressure in the pump and atmosphere outside the pump.
Naturally this friction creates heat for which the the purpose of flushing water is to do what it says, flush and cool the sealing line between the stationary and rotating parts. Within a slurry pump which can pump not only solids laden product but also acidic or alkaline solutions allowances need to be made to reduce not only the effects of friction between the sleeve and packing but also corrosion and erosion.