Face Materials

Mechanical Seal Face Materials FSA Knowledge Series

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Abstract This Fluid Sealing Association Knowledge Series training presentation provides an overview of materials use for primary and mating rings in mechanical seals. This overview includes:​

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Most common materials available

▪ ▪

​Distinguishing characteristics and properties Application-specific considerations

Causes of Mechanical Seal Failure ▪ Seal Face materials are estimated to contribute to less than 9% of all mechanical seal failures.

▪ A significant portion of those failures are associated with improper material selection for the application, not the materials themselves.

8%

9%

40%

19% 24%

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System Operations

Mechanical

Seal Components

Other

System Design

Based on “third party” published data.

Materials Overview 5

Face Materials

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▪

Mechanical Carbon

▪

Alumina

▪

Tungsten carbide

▪

Silicon carbide

▪

Other

Mechanical Carbon: Raw Materials Raw Materials Filler (20-80%)

–

Natural Graphite, Synthetic Graphite, Petroleum Coke, Lampblack

Binder (15-50%)

–

Synthetic Resins, Coal Tar Pitch, Petroleum Pitch, Metals, Carbohydrates

Additives (0-10%) –

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Film Formers, Abrasives, Antioxidants, Graphitizing Aids

Mechanical Carbon: Process Overview

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Effects of Composition on Physical Characteristics

Carbon

CarbonGraphite

Improved Chemical Resistance 9

Graphite

Effects of Impregnations on Physical Characteristics

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Mechanical Carbon: Effects of Impregnation on Tribology

8 7 6 5 4 3 2 1 0

0.30 0.25 0.20 0.15 0.10 0.05 0.00

Impregnation Wear Ratio 11

Friction

Friction

Wear Ratio (x10-9)

Carbon-Graphite (70:30) 375 psi contact, 75 fpm, Air Block on SAE 4620 Ring

Mechanical Carbon: Run-In effects ▪ ▪

▪

▪

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Break-in period is associated with all contacting face seals after which a steady state condition can be expected.

This break-in is affected by: ▪ Flatness of both faces ▪ Surface finish of both faces ▪ Contact Pressure ▪ Temperature ▪ Medium More graphitic materials will inherently transfer material to harder mating material.

Lack of lubrication during break-in (i.e. dry run) will tend to exaggerate the severity of the break-in.

Mechanical Carbon: Materials Selection

Impregnation

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Service

Thermoset Resin

General duty to 260°C / 500°F in Water, Coolants, Fuels, Oils, Light Chemical solutions, Food and Drug

Carbon

Highly corrosive environments

Antimony

Steam, Light Hydro-carbons, Higher duty

Film Formers (Fluorides etc.)

Dry running, Cryogenics, Vacuum

Oxidation Inhibitors (Phosphates etc.)

Higher temperature and speed, Turbine engine applications to 245 m/s / 800 ft/sec. and 540°C / 1000°F

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Conditions When Carbon Materials Should Not Be Used ▪ Certain Oxidizing Chemicals ▪ Temperatures Higher than 650°C / 1200°F with Oxygen Present ▪ Abrasives in the interface ▪ Dry Running (No Absorbable Gas) in the Absence of Film Formers

Dry Gas

Aqueous Oil/Solvents

Carbon

Fundamental Conditions for Satisfactory Carbon Operation ▪ Presence of Absorbable Gas ▪ Proper Carbon Material Selection ▪ Proper Running Surface Preparation ▪ Proper Mating Material Selection

Graphite

Mechanical Carbon: Materials Selection

Cryogenic

200

600

800

Temperature °F

1000

Mechanical Carbon: Net Face Contact Pressure Limits 600 500

Face Pressure Limits (PSI)

400 300 200 100 0 Air, Methane, Steam, Carbon Dioxide,etc.

Water, Gasoline, Methanol, Kerosene

Light Oils

Face Materials: Grade Application Grade Recommendation Information

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▪

Application conditions

▪

Think “Mating Pairs”

▪

Consider materials presently used in application ▪

Do the present materials work?

▪

Issues with the present application?

▪

Economics of present materials

▪

Purchase quantities of present materials

▪

Evaluation requirements for new material

▪

Additional information on application

Face Materials: Typical Mating Pairs Light & Heavy Duty Hydro-Carbon Applications ▪

Antimony Impregnated Carbon vs. Reaction Bonded SiC

Highly Corrosive Applications ▪

Impregnated Graphite vs. Self Sintered SiC

Steam Application ▪

Impregnated Carbon vs. Reaction Bonded SiC

▪

Antimony Impregnated Carbon vs. Reaction Bonded SiC

Hot Water Applications ▪

Impregnated Carbon vs. Reaction Bonded SiC

Dry Gas Applications ▪ Antimony Impregnated Carbon vs. Reaction Bonded SiC 17

Face Materials: Application Tribological Materials Carbon Graphite

Silicon Carbide

Tungsten Carbide Alumina

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• Lubricity • Corrosion Resistance • Abrasion Resistance • Stiffness • Corrosion Resistance • High Performance (P-V) • Toughness • Abrasion Resistance • Stiffness • Abrasion Resistance • Stiffness

Primary Disadvantage • Abrasion

• Brittleness

• Corrosion • Thermal Shock

Metal

• Ease of Fabrication

• Lower Performance

Coatings

• Applicable to Various Material

• Delamination • Wear-through

Not Self Lubricating

Primary Advantage

Alumina: Material Processing

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Raw Materials

Alumina, Ceramic oxides, binders

Powder Preparation

Wet Ball Mill, Spray Dry

Forming a Compact

Dry Pressing, Iso-pressing, Extrusion, CIM

Making it a Solid

High Fire Sinter, 1440 -1650°C

Diamond Grinding

OD, bore, face grinding, lapping & polishing

View /Packing

Inspection & Packing

Alumina: Materials Options

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99.5% White Alumina

97% White Alumina

96% Brown Alumina

88% Pink Alumina

Enhanced chemical resistance

General duty

Pump shafts, bearings, and seal faces

Medical Applications

Alumina: Characteristics Prime Features ▪ Exceptionally hard-wearing

▪ Excellent abrasion resistance ▪ High compressive and flexural strengths ▪ Dense, non-porous and vacuum tight ▪ Excellent dimensional stability across very wide temperature range

▪ Resists chemical attack at higher purity levels

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Tungsten Carbide: Processing

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Raw Materials

Tungsten Carbide, Metal binders

Forming a Compact

Dry Pressing, Iso-pressing

Making it a Solid

High Fire Sinter, >2,000°C

Diamond Grinding

OD, bore, face grinding, lapping & polishing

View /Packing

Inspection & Packing

Tungsten Carbide: Material Types Considered a Cemented Carbide Binder determines corrosion resistance:

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▪

Cobalt Bound – Least corrosion resistant

▪

Nickel Bound – Preferred for most sealing applications (~6% binder)

▪

TiC-Ni Bound – Highest corrosion resistance.

Tungsten Carbide: Characteristics Prime Features

▪ Tough (non-brittle) ▪ Exceptionally hard-wearing ▪ Excellent abrasion resistance

▪ High compressive and flexural strengths ▪ Dense, non-porous and vacuum tight

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Silicon Carbide: Processing

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Raw Materials

Silicon Carbide, Carbon, binders

Powder Preparation

Spray Dry

Forming a Compact

Dry Pressing, Iso-pressing

Making it a Solid

High Fire Sinter, >2,000°C

Diamond Grinding

OD, bore, face grinding, lapping & polishing

View /Packing

Inspection & Packing

Silicon Carbide: Reaction Bonded Reaction Bonded SiC (SiSiC) • SiC + C + Si  SiC + SiC

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Silicon Carbide

Silicon

Silicon Carbide: Reaction Bonded + Graphite Reaction Bonded SiC with Graphite (SiSiC-G) • SiC + C + Si  SiC

Silicon Carbide

Silicon

Graphite

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Silicon Carbide: Self Sintered Self Sintered SiC (SiC)

Etched 28

Polished

Face Materials: Increasing capability ▪ Improved Performance in Marginally Lubricated Conditions

▪ Capability for Dry-Run Survivability ▪ Enhanced Pressure-Velocity (P·V) Capability in Hardface combinations ▪ Thermal Shock Resistance

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Face Materials: Superior Tribology ▪ Surface Roughness is required for contacting hardface materials.

▪ External Operation ▪ Matte Lapping (0.18-0.33 μm / 7 - 13 μin Ra) improves surface capabilities temporarily by ‘roughing up’ the surface ▪ Inherently rougher surface finish with a composite

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Silicon Carbide: Sintered SiC + Graphite

Uniform Matrix

Well Bound Interface

Dense Graphite Agglomerate

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Thermal Shock Resistance

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Enhanced Pressure-Velocity (P·V) Capability Controlled face topography, coupled with increased thermal conductivity, improve contacting hardface combinations’ capability

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THANKS!

www.fluidsealing.com

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