ISO 21250-1:2020

Overview

ISO 21250-1:2020 - "Rolling bearings - Noise testing of rolling bearing greases - Part 1" specifies the basic principles, testing assembly and test machine requirements for assessing noise characteristics of rolling bearing greases. It defines core terminology and symbols (for example GD = grease damping, NL = noise level, NP = noise peak, SUN = start‑up noise) and sets the framework used by the companion test methods ISO 21250-2 (BQ+), ISO 21250-3 (MQ) and ISO 21250-4 (NQ). The standard is primarily applicable to unused greases, especially NLGI classes 1–3 and greases conforming to ISO 12924.

Key topics and technical requirements

• Scope and purpose: establishes measurement principle and test-machine requirements for meaningful comparison of grease noise and damping properties.
• Terminology & symbols: uniform definitions for noise metrics (noise level, noise peak, peak count, grease damping) used across BQ+/MQ/NQ methods.
• Measurement bands: identifies frequency bands relevant to grease noise analysis (M-band, H-band; L-band noted but not used for grease testing in this part).
• Test assembly and machine: mechanical arrangement, transducer type and mounting, spindle speed and loading considerations to ensure repeatable results (see Parts 2–4 for method-specific parameters).
• Evaluation methods: concepts for calculating grease damping (GD), peak analysis and start‑up noise (SUN) evaluation.
• Test setup and specimen: guidance on test bearings, grease quantity and mounting to ensure comparable test conditions.
• Signals, recording & display: requirements for measurement acquisition, smoothing and counting methods used in peak analysis.
• Calibration and uncertainty: calibration levels, calibrators and error estimation to support reliable, comparable test data.

Applications and users

ISO 21250-1:2020 is intended for:

• Grease manufacturers developing low‑noise formulations and improving damping properties.
• Bearing manufacturers and design engineers selecting greases for low-noise applications (e.g., electric motors, fans, appliances).
• Independent test laboratories and quality‑control teams establishing reproducible noise-test methods.
• R&D teams evaluating effects of base oil, thickener and additives on bearing noise.

Practical benefits include standardized comparison of grease damping, support for product development, and informed lubricant selection to reduce operational noise and improve end‑product NVH performance.

Related standards

• ISO 21250-2: Test and evaluation method BQ+
• ISO 21250-3: Test and evaluation method MQ
• ISO 21250-4: Test and evaluation method NQ
• ISO 12924 (grease classification) and relevant bearing standards (ISO 492, ISO 15242-1)

Keywords: ISO 21250-1:2020, rolling bearings, noise testing, grease damping, BQ+, MQ, NQ, grease noise, test machine, NLGI.