CAT® SEALS

Introduction

For over 60 years, Caterpillar has been a leading manufacturer of metal face seals, providing robust solutions for demanding applications across various industries. Cat Seals are engineered to protect critical components like bearings and gears from extreme environments, including abrasive conditions, chemicals, water, and temperature fluctuations. They offer long service life with minimal maintenance, increasing equipment uptime and productivity.

Types of Seals

Caterpillar offers two primary seal designs:

• Cat Duo-Cone™ Seals: These seals utilize elastomeric toric rings and metal sealing rings, requiring less radial space in a housing. They incorporate a round toric and are known for their reliability in diverse applications.
• Cat Heavy Duty Dual Face Seals: These seals feature a square bore housing design and a Belleville Washer load ring. They are designed for demanding environments and offer advantages like no requirement for assembly tools or lubricants.

Key Features and Benefits

• Corrosion-resistant seal rings
• Precision machined, self-renewing sealing surfaces
• Minimal face load variations
• Specialized seal and load ring materials to match application requirements
• Extended service life, often exceeding 30,000 hours without maintenance
• Protection against abrasive materials and contaminants
• Permit the use of oil as a lubricant, reducing friction and wear

Application Engineering

Caterpillar engineers are available to assist with sealing requirements. Users can complete an application data sheet and provide drawings for tailored seal recommendations.

Product Design Review

Seal Ring Materials

Caterpillar offers a variety of seal ring materials engineered for specific performance characteristics:

C6: Ideal for high-speed applications requiring superior corrosion resistance.

Stellite: Designed for harsh environments with abrasive and corrosive elements, suitable for moderate rotational speeds.

NiHard: Offers slightly greater pressure-velocity characteristics than Stellite but with less wear and corrosion resistance.

Formed Seals: Versatile for applications not requiring extreme corrosion/abrasion resistance, used in axle, winch, and final drive applications.

Forged Seals: Available for undercarriage applications where minor wear is present and cost is critical.

Load Ring Materials

Common load ring materials include:

Nitrile (NBR): Offers maximum abrasion resistance, suitable for standard axle, final drive, and undercarriage applications.

Low-Temperature Nitrile (LT-NBR): Developed for highly abrasive, low-temperature applications.

Silicone: Used in extreme high or low temperature applications.

Hydrogenated Nitrile (HNBR): Offers better temperature resistance to permanent deformation than standard Nitrile.

Fluoroelastomer (FKM): Suitable for extremely high temperatures.

Design Information

The performance of Cat Seals is influenced by several design factors:

Load Deflection

The combination of seal ring dimensions and elastomeric materials dictates allowable operating conditions. Proper seal selection and design consultation with Caterpillar Engineering is recommended.

Speed Capability

Face load is related to application speed. Factors like seal material, diameter, temperature, lubricant viscosity, and centrifugal force influence performance. Higher speeds can generate heat, affecting lubricant and elastomer properties.

Seal Wear Measurement

Cast Cat Seals automatically compensate for wear by forming a contact band that widens as wear occurs. Formed seals tend to wear axially due to increased flexibility.

Lubricant Requirements

Cat Seals require lubrication, preferably mineral-based oils (10WT to 90WT). Lubricant provides cooling and lubrication to the sealing faces. Ensure cavities are clean and not overfilled (max 90%) to allow for thermal expansion.

Operating Environment Considerations

Factors like mud packing, abrasive conditions (dust, sand, rock), and exposure to chemicals or extreme temperatures can affect seal life and require appropriate material selection and protective measures.

Cat Duo-Cone Seals

Cat Duo-Cone seals are available in various radial cross sections and ramp angles to suit different operating environments. They are commonly used in undercarriage, axle, wheel, and final drive applications.

Seal Group Size (Class) Options

Seals are categorized by Class (A through L), based on toric size and housing ramp angle, offering tailored performance for specific applications. For example:

• Class A (4.30mm): Limited applications with tight constraints.
• Class C (9.47mm): Common in moving undercarriages for crawler tractors and excavators.
• Class D (12.70mm): Widely used in axle, wheel, and final drive applications.
• Class K (Heavy Duty Dual Face): Features a square bore housing and Belleville Washer for demanding environments.

Detailed specification tables listing Seal Group, Seal Number, Class, OD, ID, Ring, Toric, and Ramp Angle are available for numerous configurations.

Cat Duo-Cone Seal Ramp Angles

Ramp angles are designed to tailor seal performance:

• 8° Seal Ramp: For high-pressure differentials, offering increased toric retention.
• 15° Seal Ramp: Most common, offering resistance to internal pressure, used in final drive, axle, and wheel applications.
• 20° Seal Ramp: Resists internal pressures and requires less axial room, common in undercarriage applications.

Cat Heavy Duty Dual Faced Seals

Class K Cat Heavy Duty Dual Faced Seals utilize a square bore housing and a Belleville Washer load ring. They are designed for demanding environments and are used in undercarriage, axles, final drives, gear boxes, and wheels.

Detailed specification tables listing Seal Group, Seal Number, O.D., Smaller O.D., I.D., Shaft Dia, Seal Material, and Belleville Washer are available for numerous configurations.

Installation

Cat Duo-Cone Seals Installation

Proper installation is crucial for seal longevity. Key steps include:

• Assembly Contents: (2) Metal Seal Rings, (2) Elastomeric Toric Rings.
• Terminology: Understanding components like Seal Ring, Rubber Toric, Housing Retainer Lip, etc.
• Handling: Protect seal faces; avoid nicks or cuts on torics.
• Housing Preparation: Ensure housings are clean, free from foreign material, and use a lint-free wipe with a non-petroleum solvent.
• Seal Preparation: Dampen torics with approved lubricants like Isopropyl Alcohol. Silicone torics may benefit from brief freezing.
• Installation Process: Use installation tools to seat seals squarely. Apply a thin film of oil to sealing faces.
• Final Assembly: Ensure housings are aligned and concentric. Slowly bring housings together to avoid damage.

Cat Heavy Duty Dual Faced Seals Installation

Proper installation ensures optimal performance:

• Assembly Contents: (2) Metal Seal Rings, (2) Rubber Belleville Washers.
• Terminology: Understanding components like Belleville Washers, Square Bore, Shaft, Sealing Surface.
• Handling: Protect seal faces; ensure all parts are free of grease, oil, dirt, and scale.
• Housing Preparation: Clean housings with a lint-free wipe and non-petroleum solvent.
• Seal Preparation: Install Belleville washer with the inside diameter radius contacting the neck to flange radius of the seal ring.
• Installation Process: Push seal halves into the housing until fully seated. Use a non-petroleum solvent on washers if needed.
• Final Assembly: Align housings concentrically. Slowly bring together. Rotate members to set seals.

Application Data Sheet

Caterpillar provides an Application Data Sheet to gather detailed information for seal selection. This includes data on rotating/oscillating action, sealing system parameters, pressure, lubrication, operating environment, and assembly requirements. The completed sheet can be sent to Caterpillar at catseals@cat.com.