There are many different types of mechanical seals, and understanding those differences can help with choosing the right seal for a given application.
By assembly, cartridge seals arrive as pre-assembled units containing the seal faces, secondary seals, gland, sleeve, and hardware. They reduce installation error and simplify maintenance. Component seals are installed as individual parts, which allows them to fit tighter spaces and offers more material flexibility, but they require a higher level of installation precision. Split seals divide across the shaft axis so the seal can be replaced without disassembling the equipment, a significant advantage wherever downtime is costly.
By arrangement, single seals use one pair of seal faces and work well where leakage risk and fluid hazard are moderate. Double seals use two sets of faces with a barrier or buffer fluid between them, and are specified when the process fluid is hazardous, abrasive, or requires zero atmospheric leakage.
By design, pusher seals use springs that compress axially as the faces wear, with a dynamic O-ring that moves along the shaft. Non-pusher seals (bellows seals) replace the dynamic O-ring with a metal or elastomeric bellows, making them better suited to high-temperature service and fluids that coke or crystallize.
Specialty seals cover applications with extreme temperatures, high pressures, corrosive environments, or dry-running conditions. In oil and gas compressor service, this includes gas liftoff seals, where a thin film of pressurized gas separates the faces during operation.