ISO 21250-4:2020

INTERNATIONAL ISO
STANDARD 21250-4
First edition
2020-07
Rolling bearings — Noise testing of
rolling bearing greases —
Part 4:
Test and evaluation method NQ
Roulements — Essais de bruit de graisse pour roulement —
Partie 4: Méthode d’essai et interpretation NQ
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, abbreviated terms and subscripts . 2
5 Calculation method . 2
5.1 Signal processing. 2
5.2 Peak detection . 2
6 Test method NQ . 4
6.1 Measuring principle . 4
6.2 Testing procedure . 4
7 Evaluation of results . 5
Annex A (informative) Test machine . 6
Annex B (informative) Calibration . 9
Bibliography .10
Foreword
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electrotechnical standardization.
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This document was prepared by Technical Committee ISO/TC 4, Rolling bearings.
A list of all parts in the ISO 21250 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv © ISO 2020 – All rights reserved

Introduction
The rolling bearing life theory emphasizes the use of pure and homogeneous lubricants as essential for
a long bearing service life. The lubrication of rolling bearings is described in several national standards.
[4]
The GfT worksheet 3 contains theoretical and practical knowledge of rolling bearing lubrication.
Grease lubrication is the most common type of rolling bearing lubrication. The purity grade of rolling
bearing grease is influenced by thickeners, base oils, additives and solid lubricant additives as well
as the manufacturing process and is reflected in the running noise. Therefore, noise testing of rolling
bearing greases is recommended.
In addition, grease noise testing in accordance with this document allows the grease manufacturers
to develop low-noise lubricants with better damping properties. This document can also support the
rolling bearing manufacturers and end-users in the selection of low-noise grease with better damping
properties.
This document covers requirements for the testing assembly and the test machine of method NQ to
determine and assess the noise characteristics of rolling bearing grease jointly with ISO 21250-1,
ISO 21250-2 and ISO 21250-3.
INTERNATIONAL STANDARD ISO 21250-4:2020(E)
Rolling bearings — Noise testing of rolling bearing
greases —
Part 4:
Test and evaluation method NQ
1 Scope
This document specifies the testing and evaluation method of rolling bearing grease noise in accordance
with the method NQ.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 492, Rolling bearings — Radial bearings — Geometrical product specifications (GPS) and tolerance values
ISO 5593, Rolling bearings — Vocabulary
ISO 15242-1:2015, Rolling bearings — Measuring methods for vibration — Part 1: Fundamentals
ISO 15242-2:2015, Rolling bearings — Measuring methods for vibration — Part 2: Radial ball bearings
with cylindrical bore and outside surface
ISO 21250-1:2020, Rolling bearings — Noise testing of rolling bearing greases — Part 1: Basic principles,
testing assembly and test machine
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5593, ISO 15242-1, ISO 21250-1
and the following apply.
ISO and IEC maintain terminological databases
...