Materials

Mechanical Seal Materials

At Vulcan Seals, we provide comprehensive material information to ensure you choose the right seals for your applications. Our resources empower you with the knowledge needed to make informed decisions.

The capability, performance and life of a mechanical seal are significantly influenced by the grade, quality and combination of materials. The selection of the mechanical seal type and materials are dependent upon the equipment and application parameters. The following is an introductory guide to the standard materials offered on Vulcan Seals mechanical seals. Further material grade options and applications technical support is available from Vulcan Seals.

Seal Faces

Seal Faces are the primary sealing surfaces of a mechanical seal, typically running pairs selection of the correct seal face materials is critical to ensure effective sealing performance. All Seal Faces have positive and negative factors, consideration of all application parameters is recommended.

Carbon

‍Carbon is considered the most effective sealing face material when paired with a significantly harder material. It is commercially attractive and available in multiple quality levels. Carbon is considered a soft and brittle seal face so is not recommended for use in media with solid particulate.

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The above diagram shows the increasing performance in terms of ability to self-lubricate, wear and chemical resistance of the standard Vulcan Seals Carbon grades.
  • ‍VCP1‍

Double Phenolic Resin Impregnated Carbon Graphite, provides exceptional sealing performance and value, VCP1 is the standard grade offered on majority of Vulcan Seals standard seal ranges.

  • ‍VCD1

Double Phenolic Resin Impregnated Carbon Graphite, offering the exceptional sealing performance and value of VCP1, with addition of being specified and tested for use in potable water, FDA and EC food contact regulations.

  • ‍VCT1

Triple Phenolic Resin Impregnated Carbon Graphite, for higher-end wear performance in demanding applications, particularly effective in applications with marginal lubrication or in more aggressive chemical medias. VCT1 is specified as the standard Carbon for Vulcan Seals, seal ranges specifically intended for chemical equipment, such as Vulcan Seals Type 1609 and Vulcan Seals Type 1659.

  • ‍VCA1

Antimony Impregnated Carbon Graphite, offers the most effective performance in applications with poor, or temporarily absent, lubrication and cooling to the Seal Faces. For example, medias of elevated temperature.

Due to the potential health hazards posed by the impregnation leaching from the Carbon into the media, VCA1 Carbon should not be specified for food, beverage or ingredient production for humans or animals.  

Metals

  • ‍Stainless Steel

304 Stainless Steel monolithic seal heads or stationary faces are an economical option for light duty applications. 316 Stainless Steel is available for food and more aggressive chemical applications. Due to limited resistance to physical damage Stainless Steel Seal Faces must be paired with a Carbon seal face. Stainless Steel is considered a soft seal face so is not recommended for use in media with solid particulate.

  • ‍VIN1

Ni-resist iron offers an extremely wear resistant and thermally stable alternative to Stainless Steel for lubricating applications with temperature fluctuations. Ni-resist is not suitable for chemically active medias, due to reactive nature of the iron and nickel alloy, leading to seal face degradation.

Alumina Ceramic

  • ‍VAW1

High purity 99.5% Alumina Ceramic is an economic seal face option suitable for general application. Alumina Ceramic offers exceptional chemical and wear resistance due high level of hardness and inert chemical nature. However, it is liable to physical and thermal shock fracture, making it not suitable for medias with solid particulate, low lubrication or sudden temperature changes.

Silicon Carbide

Silicon Carbide is considered the most tribologically effective sealing face material when paired with a Carbon material. Increasingly commercially attractive and available in multiple grades, each offering unique properties. Silicon Carbide is the hardest and most wear resistant seal face and material, also offers exceptional chemical capability. For lubricating medias with high solid particulates two Silicon Carbide Seal Faces paired together is the recommended option.

The above diagram broadly shows the increasing performance in terms of ability to self-lubricate.

For further details on each grade please refer to the Vulcan Seals dedicated Silicon Carbide page.

Tungsten Carbide

Tungsten carbide is considered the most resilient sealing face material and offers exceptional particulate and impact resistance. A high-cost material option selection is only recommended for the most physically demanding application, due to lower tribological performance compared to Silicon Carbide.

  • ‍VTN1 & VTN2

Nickel bound tungsten carbide grades with differential nickel content on rotary and stationary faces to provide create different hardness and surface physical properties, to assist with seal face performance when paired together, and prevent vacuum face-locking during equipment downtime.

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Elastomers

Elastomers are the secondary sealing surfaces of a mechanical seal, typically sealing the mechanical against the equipment hardware. Selection of the correct elastomer is critical to ensure the overall performance of the mechanical seal. All elastomers faces have positive and negative factors, consideration of all application parameters is recommended.

The table below outlines overall range available from Vulcan Seals with Nitrile (NBR), EPDM, and VitonTM/FKM, being the three most commonly available across Vulcan Seals mechanical ranges, covering the majority of industrial applications.

Material Shore Hardness Temperature Range pH Range Typical Application
FFKM (e.g. Kalrez®) 75 Shore A -50°C / +310°C (-58°F / +590°F) 0 - 14 For absolute chemical and temperature capability. Only available in O-ring form, and to special order.
FEP/PFA* 80-95 Shore A -60°C / +205/260°C (-76°F / +401/500°F) 0 - 14 For applications where near universal chemical resistance is required. Only available on specific seal designs.
TFEP Alfas™* 75 Shore A -50°C / +250°C (-23°F / +480°F) 2 - 14 For high-temperature duties; duties involving alternating acid and alkaline environments.
Viton™/FKM 70 Shore A -30°C / +200°C (-22°F / +392°F) 0 - 8 For general acidic and organic chemical duties, including petrochemicals (other than amines, acetates and acrylates, see EP above).
HNBR 75 Shore A -40°C / +150°C (-40°F / +300°F) 5 - 10 For general duties; especially synthetic hydraulic and lubricating oils; duties involving alternating acid and alkaline environments.
EPDM 70 Shore A -40°C / +140°C (-40°F / +284°F) 6 - 14 For general warm to hot water duties; acetic, peroxyacetic and acrylic acid duties (including acetate and acrylate derivatives of these acids); alkaline chemical duties, especially hypochlorite, hydroxides, amines, and other derivatives of ammonia.
Chloroprene (NeopreneTM) 70 Shore A -50°C / +100°C (-58°F / +212°F) 6 - 13 For refrigeration duties involving mineral oil lubricants, especially if ammonia is involved. For synthetic oils see HNBR.
Nitrile 70 Shore A -30°C / +120°C (-22°F / +248°F) 5 - 8 For general duties; especially ambient temperature water duties, mineral oil-based applications.
PTFE* 55 Shore D -250°C / +260°C (-418°F / +508°F) 0 - 14 For applications where near universal chemical resistance is required. Only available on specific seal designs.
*Non elastomeric materials used as secondary seals

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Metal Components

Mechanical seals typically are constructed of metal components to load, drive and activate the primary and secondary seals (Seal Faces and Elastomers).

304 Stainless Steel is the standard alloy Vulcan Seals mechanical seals are constructed from, suitable for the majority of applications. 316 Stainless Steel is specified as standard on seal Types intended for more aggressive chemical applications. In addition, 316 Stainless Steel can be specified on all types where application requires specified FDA and EC food contact materials, or where media is more chemically aggressive.

Vulcan Seals mechanical seals feature polished surfaces to the sheet metal and coil components, providing a fine surface finish that greatly reduces the opportunity for corrosion

As standard smaller coils as featured in mechanical seal design featuring multiple springs and wave springs, higher specification alloys are utilised to improve chemical resistance and reduce coil fatigue. Vulcan Seals mechanical seal Types are available with all metallic components manufactured from higher chemical resistant alloys such as Hastelloy®, Monel® and Duplex® on request.

To review the recommended seal face pair and elastomer combination for your specific application please refer to the Seal Materials Chemical compatibility listing in the Vulcan Seals Mechanical Seals manual.