ISO 21250-3:2020

Overview

ISO 21250-3:2020 - "Rolling bearings - Noise testing of rolling bearing greases - Part 3: Test and evaluation method MQ" defines the MQ test procedure for assessing the noise behaviour of greases used in rolling bearings. The standard specifies the test sequence, measurement principles, calculation methods and the rating scale used to assign a grease noise class. It is intended to be used together with other parts of the ISO 21250 series and relevant measurement standards.

Key Topics and Requirements

• Method MQ test sequence
  • Manual pre-greasing of bearings (feeder or spatula); five greased bearings tested in sequence.
  • Each bearing measured for 64 s (including run‑in), total process ~320 s.
  • Reference measurements on preserved, ungreased bearings are required before greased comparison tests.
• Measurement parameters
  • Frequency bands used: M-band (300 Hz–1 800 Hz) and H-band (1 800 Hz–10 000 Hz). L-band is not used for grease noise.
  • Sampling rate: 8 readings per second (256 points per 32 s interval).
  • Test machine warmed up to a spindle housing temperature of 30 °C before testing.
• Evaluation metrics
  • Noise peak values (NP) and noise level (NL) in defined intervals (0–32 s, 32–64 s).
  • Grease damping factors (GD) calculated per ISO 21250‑1 formulae.
  • Grease noise classes (I–IV, >IV) assigned by mapping worst-case NP and GD values for each bearing; final class is the arithmetic mean of five bearings with specified rounding rules.
• Examples and acceptance
  • The standard gives examples of test bearings, axial loads and permissible reference noise limits (e.g., 608 and 6202 bearings with specified axial loads and NL/NP thresholds).
  • Annexes provide sample test setups, bearing preparation and plausibility checks.

Applications and Who Uses It

• Grease manufacturers - R&D and formulation teams use MQ testing to develop low‑noise greases and quantify damping performance.
• Rolling bearing manufacturers - select and verify lubricant compatibility and acoustic performance during product development and quality control.
• Test laboratories and OEMs - perform standardized comparative testing for supplier qualification, acceptance criteria and specification writing.
• Noise-sensitive industries - automotive, electric motors, HVAC and precision machinery benefit from selecting greases characterized by ISO 21250‑3 to reduce operational noise.

Related Standards

• ISO 21250-1:2020 - Basic principles, testing assembly and test machine
• ISO 21250-2, ISO 21250-4 - Other parts of the grease noise testing series
• ISO 5593 - Rolling bearings - Vocabulary
• ISO 15242-1 - Measuring methods for vibration - Fundamentals

Keywords: ISO 21250-3, rolling bearings, grease noise testing, method MQ, grease noise class, damping factor, noise peak, bearing lubrication, test procedure.