Metal bellows are constructed by welding “leaflets” into a series of “convolutions”. This series of convolutions is referred to as the “Bellows Core”.
Since almost all seals utilize the process liquid or gas to lubricate the seal faces, they are designed to leak. Process liquids and gases containing hazardous vapors, dangerous toxic chemicals or flammable petroleum must not be allowed to leak into the atmosphere or onto the ground. In these applications a second "containment" seal is placed after the primary seal along the pump shaft. The space in between these two seals is filled with a neutral or compatible liquid or gas [Generally nitrogen] called a "buffer [Unpressurized]" or "barrier [Pressurized]" fluid.
A "cartridge seal" is a prepackaged seal that is common in more complex applications. Cartridge seals were originally designed for installation in equipment where a component type seal was difficult due to the design of the equipment. A cartridge type mechanical seal is a pre-assembled package of seal components making installation much easier with fewer points for potential installation errors to occur.
All mechanical seals must contain the four elements: 1) Primary sealing surfaces, 2) Secondary sealing surfaces, 3) a means of actuation and 4) a means of drive.
