Hydraulic fluid power — Impact and use of ISO 11171:2016 µm(b) and µm(c) particle size designations on particle count and filter test data

This document explains the use of the two acceptable methods of reporting particle size, µm(c) and µm(b), that are defined in ISO 11171:2016. It also explains the reasons for the existence of two alternative size reporting methods and its implications with respect to particle count and filter Beta Ratio data.

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Status
Published
Publication Date
05-Sep-2019
Current Stage
6060 - International Standard published
Start Date
06-Sep-2019
Completion Date
06-Sep-2019
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ISO/TR 22681:2019 - Hydraulic fluid power -- Impact and use of ISO 11171:2016 µm(b) and µm(c) particle size designations on particle count and filter test data
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TECHNICAL ISO/TR
REPORT 22681
First edition
2019-09
Hydraulic fluid power — Impact and
use of ISO 11171:2016 µm(b) and
µm(c) particle size designations on
particle count and filter test data
Reference number
ISO/TR 22681:2019(E)
ISO 2019
---------------------- Page: 1 ----------------------
ISO/TR 22681:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
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ISO/TR 22681:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Origins of the particle size shift ............................................................................................................................................................ 1

5 Implications of the particle size shift .............................................................................................................................................. 3

6 Use of revised ISO 11171 ............................................................................................................................................................................. 6

Bibliography ................................................................................................................................................................................................................................ 8

© ISO 2019 – All rights reserved iii
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ISO/TR 22681:2019(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso

.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee

SC 6, Contamination control.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved
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ISO/TR 22681:2019(E)
Introduction

A minor revision to ISO 11171:2010 was approved during 2016. The revision was necessitated by a

particle size shift resulting from the replacement of the particle counter calibration material, National

Institute of Standards and Technology (NIST) SRM 2806a, with SRM 2806b. Prior to this revision,

particle count data based upon ISO 11171 was reported in units of µm(c). Following the introduction

of SRM 2806b, users of particle count data in the absence of this revision could not discern whether

particle sizes being reported were based upon SRM 2806a or SRM 2806b. Hypothetically, a particle size

reported as 20 µm(c) could actually be as large as 20 µm or as small as 18 µm depending upon whether

SRM 2806a or SRM 2806b were used. This approximately 10 % shift in particle size can become

significant in terms of the actual numbers of particles counted.

To minimize confusion and provide for clear communication, ISO 11171:2010, 6.8 and 7.1 were revised

to provide a means for reporting particle size that clearly identifies the basis for reported particle

size and provides the industry with tools to relate past SRM 2806a and new SRM 2806b data without

extensive revisions to existing standards, specifications, and other literature. It provides a historically

consistent, traceable definition of µm(c), while allowing an option to report sizes in terms of a defined

µm(b) as needed. This document summarizes the underlying reasons for the minor revision and its

practical impact on the industry.
© ISO 2019 – All rights reserved v
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TECHNICAL REPORT ISO/TR 22681:2019(E)
Hydraulic fluid power — Impact and use of ISO 11171:2016
µm(b) and µm(c) particle size designations on particle
count and filter test data
1 Scope

This document explains the use of the two acceptable methods of reporting particle size, µm(c)

and µm(b), that are defined in ISO 11171:2016. It also explains the reasons for the existence of two

alternative size reporting methods and its implications with respect to particle count and filter Beta

Ratio data.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Origins of the particle size shift

ISO 11171 provides direct traceability to the standard international (SI) definition of a metre through

NIST SRM 2806. ISO 11171 has been widely used to calibrate automatic particle counters (APCs) for

hydraulic, lube oil, diesel fuel, and other non-aqueous liquid applications since 1999. NIST SRM 2806 is

the primary calibration material used in this document.

During 2010, the original supply of SRM 2806, also sold as SRM 2806a, was exhausted. For ease of

communication, the term “SRM 2806a” is used henceforth in this document to refer to both designations,

SRM 2806 and SRM 2806a, of the original calibration material.

During 2014, its replacement, SRM 2806b, was released. The SRM 2806b production and certification

process was overseen by an international group of experts from ISO/TC 131/SC 6. The specifications for

SRM 2806b were better defined than those for SRM 2806a and it was produced by a different supplier.

Advances in sample preparation and metrology were used to produce and certify SRM 2806b. A critical

difference between SRM 2806a and SRM 2806b is that particle sizing was done manually from SEM

micrographs with SRM 2806a, while automated image analysis was used with SRM 2806b.

This allowed an order of magnitude of more particles to be analysed and in a manner not subject to

human bias. The end result was a certified calibration material, SRM 2806b, with better precision in

the size distribution and a reduction in uncertainty compared to its predecessor, SRM 2806a.

© ISO 2019 – All rights reserved 1
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ISO/TR 22681:2019(E)

An international round robin of ISO 11171 found that particle size, as defined using SRM 2806b

compared to SRM 2806a, had shifted. The relationship between SRM 2806a and SRM 2806b sizes was

determined from data submitted by 15 participating labs and is given by the following formula:

d = 0,898 d
c b
where

d is the particle size in µm(c) obtained using an APC calibrated with SRM 2806 and SRM 2806a;

d is the particle size in µm(b) obtained using an APC calibrated with SRM 2806b.

As a result of the minor revision to ISO 11171, particle size reported in µm(c) is traceable to SRM 2806a

using the conversion equation, or by direct measurement using an APC calibrated with SRM 2806a

or SRM 2806a-traceable secondary samples in the case of data generated prior to 2016. Particle sizes

traceable to SRM 2806b are reported in units of µm(b). Users of particle count data have the option to

report particle size in units of either µm(c) or µm(b), or both, as appropriate. This particle size shift is

within the published uncertainty of SRM 2806a, but it is great enough to affect particle count and filter

test data. The magnitude of the particle size shift is illustrated graphically in Figure 1.

In Figure 1, particle size in µm(c) as determined using ISO 11171 and SRM 2806a is plotted on the

X-axis. The corresponding particle size as determined using other means, i.e. using SRM 2806b or AC

Fine Test Dust, is plotted on the Y-axis. The bold line shows the relationship between µm(c) and µm(b).

The relationship passes through the origin with a slope of 1,114.

For reference, the thin line shows the relationship between µm(c) and µm sizes determined using the

obsolete ISO 4402 calibration method and AC Fine Test Dust. This relationship does not pass through

the origin and the slope is steeper. Figure 1 demonstrates that the particle size shift with SRM 2806b

is significant, yet less than what was observed when the industry transitioned from ISO 4402 to

ISO 11171.
1) Withdrawn standard.
2 © ISO 2019 – All rights reserved
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ISO/TR 22681:2019(E)
Key
Y particle size µm
X particle size, µm (c)
1 µm(b) ISO 11171
2 AC fine test dust, ISO 4402

Figure 1 — Relationship between particle sizes defined using SRM 2806a and those obtained

using SRM 2806b, and using AC Fine Test Dust
5 Implications of the particle size shift

Prior to the revision in ISO 11171, there was no convenient method for users of particle count data to

determine whether or not their data was affected by the particle size shift. Users could not tell whether

particle count results were based upon SRM 2806a or SRM 2806b calibrations. As a result of the revision,

in most cases particle count and size data reported in units of µm(c) can be used in the same manner

that was don
...

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