ISO 4406:2017

INTERNATIONAL ISO
STANDARD 4406
Third edition
2017-08
Corrected version
2018-03
Hydraulic fluid power — Fluids
— Method for coding the level of
contamination by solid particles
Transmissions hydrauliques — Fluides — Méthode de codification du
niveau de pollution particulaire solide
Reference number
©
ISO 2017
© ISO 2017
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Code definition . 1
3.1 General . 1
3.2 Basis of code . 2
3.3 Allocation of scale numbers . 2
3.4 Determination of code using automatic particle counter analysis . 3
3.5 Determination of code using microscope sizing . 4
4 Identification statement (reference to this document) . 4
Annex A (normative) Graphical presentation of the code number . 5
Foreword
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URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee
SC 6, Contamination control.
This third edition cancels and replaces the second edition (ISO 4406:1999), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— All year references for ISO 11171 have been removed to ensure that only the most recent version
of ISO 11171 is used. This is needed to ensure consistency in the usage and definition of the µm(c)
particle sizes used in this document.
— All year references for ISO 4407 and ISO 11500 have been removed to ensure that only the most
recent version of these standards are used.
This corrected version of ISO 4406:2017 incorporates the following corrections.
Following the first (and only) sentence in 3.4.5, the following text has been added: "Graphical
presentation of ISO Code results shall be as described in Annex A.”
Following the first (and only) sentence in 3.5.4, the following text has been added: "Graphical
presentation of ISO Code results shall be as described in Annex A.”
Figure A.1 has been replaced by a new Figure A.1 which includes the missing exponent in Y.
iv © ISO 2017 – All rights reserved

Introduction
In hydraulic fluid power systems, power is transmitted, and controlled, through a liquid under pressure
within an enclosed circuit. Solid particle contaminant is always present in the hydraulic fluid and the
amount needs to be determined because the contaminant may cause serious problems.
INTERNATIONAL STANDARD ISO 4406:2017(E)
Hydraulic fluid power — Fluids — Method for coding the
level of contamination by solid particles
1 Scope
This document specifies the code to be used in defining the quantity of solid particles in the fluid used
in a given hydraulic fluid power system.
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 4407, Hydraulic fluid power — Fluid contamination — Determination of particulate contamination by
the counting method using an optical microscope
ISO 11171, Hydraulic fluid power — Calibration of automatic particle counters for liquids
ISO 11500, Hydraulic fluid power — Determination of the particulate contamination level of a liquid sample
by automatic particle counting using the light-extinction principle
3 Code definition
3.1 General
The purpose of this code is to simplify the reporting of particle count data by converting the numbers
of particles into broad classes or codes, where an increase in one code is generally a doubling of the
contamination level.
The original code, in accordance with the first edition of this document, stated the
...