Cartridge Mechanical Seals
Cartridge mechanical seals and component seals use similar components, but the stationary components of cartridge seals are preassembled in a housing, and the rotating components are preassembled on a shaft-mounted sleeve that is sealed with an O-ring. The cartridge seal housing typically replaces the gland cover plate and seals to the pump housing with a gasket, an O-ring or other elastomer. Since cartridge mechanical seal components are preassembled onto the sleeve and into the cartridge housing.
The amount of spring tension applied to the seal faces is an important factor that affects successful seal installation. On component seals, technicians can set this tension manually by adjusting the length of the installed seal spring. With cartridge mechanical seals, the spring tension is preset. To ensure the proper tension, a retaining device holds the rotating and stationary elements in alignment until after the seal is mounted.
While the details of whether a cartridge mechanical seal can be fitted to an application are complex, one criterion is whether the seal installs from the wet side or dry side of the seal chamber. Pumps with a seal that installs from the wet side, behind the impeller, are generally not candidates for cartridge mechanical seals. In addition, submersible pumps, which are usually fitted with dual component seals, cannot be converted to cartridge mechanical seals
because the seals install from the wet side of the pump.