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This Fluid Sealing Association Knowledge Series training presentation provides an overview of the different materials of construction of mechanical seals. This section lists typical face, secondary seal, and metal materials:
▪ Many different materials
▪ Wide range of physical properties
▪ Many requirements unique to mechanical seals
Face Materials
Face materials are selected for their:
▪ Tribological (wear) characteristics
▪ Mechanical properties to withstand pressure loads
▪ Chemical compatibility with process fluids
Typical materials include:
Carbon
Tungsten Carbide
Alumina Oxide
Face Materials
Other possible face materials:
Secondary Seals
▪ Secondary seals provide sealing between seal components (e.g. O-rings)
▪ Normally elastomeric in nature
▪ Often define temperature limits of seals
Secondary Seals
Secondary
Seal Materials
Typical materials include (but not limited to):
▪ Fluorocarbons (FKM) (Viton®)
▪ Nitrile (NBR – Buna N)
▪ Ethylene Propylene (EPR or EPDM)
▪ Chloroprene (Neoprene®)
▪ Perfluoroelastomers (FFKM)
▪ TFE Propylene (Aflas®)
▪ PTFE (Teflon®)
▪ Flexible graphite
Viton ® is a registered trademark of DuPont Performance Elastomers
Neoprene ® is a registered trademark of DuPont Performance Elastomers
Aflas ® is a registered trademark of Asahi Glass Company, Limited
Teflon ® is a registered trademark of Chemours
Metallic Components
Metallic components typically include the adaptive hardware used to support the seal faces and attach the seal assembly to the equipment.
Seal Gland Plate
Seal Face Carrier Springs
Seal Sleeve
Retaining Rings
Collar
Metallic Components
Selection of metallic components is heavily dependent on compatibility/performance in the pumped fluid. Some common metal used for mechanical seals include:
▪ 304 Stainless Steel
▪ 316 Stainless Steel
▪ Alloy 20Cb3 (Carpenter 20 CB3®)
▪ Alloy C-276, Alloy B (Hastelloy® C-276, Hastelloy® B)
▪ Alloy 600 and Alloy 718 (Inconel® 600, Inconel® 718)
▪ Alloy 400 (Monel® 400)
▪ Duplex and Super Duplex Stainless Steel (SAF 2205®, SAF 2507®)
▪ Nickel, Tantalum, Titanium
Carpenter 20 CB-3® is a registered trademark of Carpenter Technologies
Hastelloy ® is a registered trademark of Haynes International Inc
Monel ®, Inconel ® are registered trademarks of the Special Metals Corporation group of companies
SAF 2205 ®, SAF 2507 ® are registered trademarks of the Sandvik Group of companies
Compatibility Guides
Compatibility of materials in particular fluid is important as it often changes with temperature and fluid concentration. Guides for material compatibility can be found:
▪ Hydraulic Institute - Mechanical Seals for Pumps: Application Guidelines
▪ Seal manufacturer application guide
▪ Industry references (e.g. NACE, Compass Publications)
▪ Material Suppliers
Compatibility Guides
Some caution should be noted when using material compatibility guides
▪ Not all rating systems are equivalent
▪ Compatibility test conditions may not represent actual conditions
▪ Effects of conditions may not be considered (e.g. temperature, concentration, aeration, velocity)
▪ Mixtures of fluids can be difficult to establish compatibility
Actual performance of a material in the field is the best indicator of compatibility
