Cartridge seals are designed for rapid installation on and removal from pump shafts. The cartridge seal is an arrangement of seal components on a shaft sleeve and in a seal gland constituting a single unit that is usually assembled and pre-set at the factory. Both bellows and spring-type seals can be cartridge-arranged if the pump stuffing box is large enough.

Cartridge seal units offer major maintenance advantages. Replacement is rapid and there is far less risk of assembly error and assembly damage than with conventional mechanical seal mounting.