What are the precautions for the four ball method of lubricant bearing capacity?
Precautions for Four-Ball Method Lubricant Load-Capacity Testing
1. Test Equipment & Materials
Steel Ball Specifications: Standard-sized steel balls (typically 12.7mm diameter) must be used, with surface hardness and finish meeting requirements.
Four-Ball Machine Calibration: Before testing, verify the equipment's rotational speed (1400–1500 rpm) and loading system (lever or hydraulic) accuracy to ensure stable load application.
2. Test Condition Control
Temperature & Time: Maintain constant ambient temperature (e.g., 25±1°C), with each test strictly limited to 10 seconds to prevent overheating.
Lubricant Volume: Ensure the lubricant fully submerges the contact points of all four balls for adequate lubrication.
3. Key Parameter Measurement
Maximum Non-Seizure Load (PB): Gradually increase the load until the rotating ball stops, recording the critical value to reflect oil film strength.
Sintering Load (PD): Continue loading until friction components weld, then immediately terminate the test to prevent equipment damage.
Wear Scar Diameter: Measure the fixed ball's wear scar diameter post-test using a microscope, averaging three replicate tests.
4. Safety & Operational Protocols
Protective Measures: Wear protective gear due to potential high temperatures or metal debris.
Data Recording: Document load, speed, and wear scar diameter meticulously for traceability.
5. Compliance with Standards
Adhere to GB/T 3142-2019 (China) or ASTM D2783 (International), selecting relevant parameters based on lubricant application.
6. Common Issues
Reproducibility Variance: If results vary significantly, inspect ball wear or machine stability.
Lubricant Suitability: High-viscosity or solid-additive lubricants may require parameter adjustments.
Strict adherence to standardized procedures, emphasizing equipment calibration, environmental control, and data accuracy, ensures reliable lubricant load-capacity evaluation.
SH120 automatic four ball machine grease wear resistance tester is in the form of sliding friction, under the condition of extremely high point contact pressure, mainly used to evaluate the bearing capacity of lubricants.
In practical application, different evaluation indexes can be selected according to different uses of lubricants.
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