The proper selection of a mechanical seal can be made only if the full operating conditions are known. Identification of the exact liquid to be handled is the first step in seal selection.

　　Metal parts must be corrosion resistant, usually plated steel, bronze, stainless steel, or Hastelloy.

　　Mating faces must also resist corrosion and wear. Carbon, ceramic, silicon carbide or tungsten carbide may be considered.

　　Stationary sealing members of Buna, EPR, Viton and Teflon are common.

　　Pressure:

　　The proper type of seal, balanced or unbalanced, is based on the pressure on the seal and on the seal size.

　　Temperature:

　　Can determine the use of the sealing members as materials must be selected to handle liquid temperature.

　　Characteristics of the Liquid:

　　Abrasive liquids create excessive wear and shorten seal life.

　　Double seals, or clear liquid flushing from an external source, allow the use of mechanical seals on these difficult liquids.

　　For best results with double (or tandem) seals handling abrasive, the inboard seal faces should be a hard material, such as silicon carbide vs. silicon carbide, while the outboard seal faces should have maximum lubricity, such as silicon carbide vs. carbon graphite.