SANY SSY009115264 SY750 Track Bottom Roller Assembly-Heavy-duty crawler excavator undercarriage parts manufacturer-HELI(cqctrack)

1. Component Identification & Functional Definition

The Track Bottom Roller Assembly (OEM Part Number: SSY009115264) is a primary load-bearing component within the lower track structure of the SANY SY750 ultra-class heavy-duty mining excavator. Manufactured by HELI (CQCTRACK) as a precision-engineered replacement assembly, this component—also referred to as a lower roller or track roller—is mounted directly to the track frame and forms the primary contact interface between the machine’s substantial weight and the track chain. Its core function is to support the machine’s entire operational weight while facilitating smooth track movement across the most severe terrain.

2. Primary Operational Role & Performance Requirements

For a machine of the SY750′s scale (~75-85 tons class), the bottom roller operates under extreme conditions, necessitating exceptional engineering:

• Primary Load Bearing: Directly supports the static and dynamic weight of the excavator, transmitting ground reaction forces upward through the track frame. It must withstand immense radial loads during digging, lifting, and travel.
• Track Chain Guidance & Stability: Provides a continuous, hardened path for the track chain’s link assemblies and bushings to travel upon, maintaining lateral stability and preventing derailment under high lateral stresses.
• Shock & Vibration Dampening: Acts as the first line of defense in absorbing impact loads from uneven ground, rock benches, and other obstacles, protecting the entire undercarriage and upper structure from shock-induced damage and operator fatigue.
• Contaminant Management: Its design and sealing system must aggressively exclude abrasive particulates (silica, metallic dust) and moisture, which are the primary agents of premature wear and bearing failure in mining environments.

3. Detailed Structural Engineering & Material Specifications

HELI’s manufacturing process for this assembly employs heavy-duty specifications tailored for mining applications:

• Roller Body & Flanges:
  • Material: Forged from high-alloy, boron-added steel (e.g., 50B or similar). This provides an optimal balance of hardenability, toughness, and wear resistance.
  • Heat Treatment: The outer running surface and flanges undergo deep case hardening via carburizing, followed by tempering. This creates an ultra-hard wear surface (HRC 58-63) with a depth sufficient to endure years of abrasive contact, backed by a tough, shock-absorbing core.
  • Machining: CNC machining ensures precise concentricity, flange profile, and sealing surface integrity. The flange height and thickness are designed to contain the specific track chain used on the SY750.
• Shaft & Bearing System:
  • Shaft: Fabricated from quenched and tempered alloy steel (42CrMo4). The bearing journals are precision-ground, and often treated with induction hardening or plasma nitriding to resist fretting corrosion and wear.
  • Bearing Configuration: Utilizes extra-large, double-row tapered roller bearings or spherical roller bearings with enhanced dynamic load ratings. These are pre-loaded and set to handle the extreme multi-directional forces of a mining excavator.
  • Mounting: The shaft is typically a press-fit or bolted flange design, securely fixed within the roller body to prevent rotation and ensure all torque is transferred through the bearings.
• Advanced Sealing Technology:
  • A multi-layered, cartridge-type seal is standard. This system typically integrates:
    1. A primary radial lip seal made of hydrogenated nitrile (HNBR) for high temperature and chemical resistance.
    2. A secondary floating face seal or metal-to-metal labyrinth.
    3. An external slinger and dust lip to deflect larger debris.
  • The sealed cavity is packed with high-viscosity, shear-stable lithium complex grease containing solid lubricant additives (e.g., molybdenum disulfide) for boundary lubrication protection.
• Lubrication & Maintenance Design: Features a heavy-duty grease fitting for scheduled replenishment. Some designs may incorporate a grease relief valve to prevent seal damage from over-pressurization.

4. Manufacturing Profile: HELI (CQCTRACK) Capabilities

HELI’s production of this component leverages its specialization in ultra-large undercarriage parts:

• Process Vertical Integration: Full control from steel alloy selection and closed-die forging, to machining, thermal processing, and assembly.
• Forging & Heat Treatment: Utilizes large-tonnage forging presses to achieve superior grain flow. Computer-controlled carburizing furnaces and tempering lines ensure consistent, deep case hardness.
• Quality & Testing Protocol:
  • Material Certification: Full traceability with chemical and mechanical test reports.
  • Non-Destructive Testing (NDT): Dye penetrant (DPI) or magnetic particle inspection (MPI) of all critical surfaces post-forging and machining.
  • Dimensional Verification: Coordinate Measuring Machine (CMM) inspection of final geometry.
  • Performance Testing: Rotational torque testing and seal pressure testing on a sampling basis to validate assembly integrity.

5. Application, Compatibility & Service Information

• Primary Model Application: SANY SY750 Crawler Excavator (Mining Configuration).
• System Integration: Multiple units are mounted along the bottom flange of the track frame, directly supporting the track chain’s lower strand.
• Wear Life & Inspection: Service life is a critical cost-per-hour metric. Wear is measured on the roller outer diameter and flange thickness. Regular inspection for seal leaks, irregular wear patterns, or loss of rotation is essential.
• Replacement Guidelines: Due to the severe operating environment, bottom rollers are typically replaced in sets per side. For optimal undercarriage life and performance, their replacement should be synchronized with the wear state of the track chain, sprocket, and idler to prevent accelerated wear on new components.
• Operational Best Practice: Maintaining proper track tension and avoiding continuous travel on severe, sharp-edged rock are crucial to maximizing roller life.

6. Conclusion

The SANY SSY009115264 SY750 Track Bottom Roller Assembly manufactured by HELI (CQCTRACK) is engineered as a critical durability component for one of the largest mining excavators in its class. Its design philosophy emphasizes maximum service life under continuous, high-load, high-contamination conditions through the use of premium forged materials, deep-case heat treatment, a high-capacity bearing system, and a robust multi-stage seal. For mine maintenance managers and equipment owners, this component represents a reliable, performance-validated alternative that supports the demanding productivity and availability requirements of modern mining operations, contributing directly to lower total cost of ownership for the SANY SY750 excavator.