Materials of Construction

Materials of Construction FSA Knowledge Series

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Abstract 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

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Face Materials Face materials are selected for their: ▪

Tribological (wear) characteristics

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Mechanical properties to withstand pressure loads

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Chemical compatibility with process fluids

Typical materials include:

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Carbon

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Tungsten Carbide

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Nickel bound

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Cobalt bound Alumina Oxide

▪ Silicon Carbide Reaction bonded Alpha sintered Porous alpha sintered Composite silicon carbide

Face Materials Other possible face materials: ▪ Metals ▪ Bronze ▪ 17-4 PH ▪ Cast Iron ▪ Ni-Resist Iron ▪ Engineered Plastics ▪ Glass Filled PTFE

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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

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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 7

Metallic Components Metallic components typically include the adaptive hardware used to support the seal faces and attach the seal assembly to the equipment.

Retaining Rings Seal Gland Plate

Seal Face Carrier Springs Seal Sleeve

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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:

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304 Stainless Steel

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316 Stainless Steel

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Alloy 20Cb3 (Carpenter 20 CB3®)

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Alloy C-276, Alloy B (Hastelloy® C-276, Hastelloy® B)

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Alloy 600 and Alloy 718 (Inconel® 600, Inconel® 718)

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Alloy 400 (Monel® 400)

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Duplex and Super Duplex Stainless Steel (SAF 2205®, SAF 2507®)

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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

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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

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THANKS!

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