Aerospace series — Fluid systems and components — Methods for system sampling and measuring the solid particle contamination in hydraulic fluids

This document specifies best practice for sampling hydraulic fluid from aircraft hydraulic systems and other hydraulic systems associated with aerospace purposes.

Série aérospatiale — Systèmes de fluides et éléments constitutifs — Méthodes de prélèvement et de mesure de la contamination particulaire solide dans un fluide hydraulique

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Status
Published
Publication Date
07-Aug-2018
Current Stage
6060 - International Standard published
Start Date
08-Aug-2018
Completion Date
08-Aug-2018
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INTERNATIONAL ISO
STANDARD 5884
Second edition
2018-08
Aerospace series — Fluid systems
and components — Methods for
system sampling and measuring
the solid particle contamination in
hydraulic fluids
Série aérospatiale — Systèmes de fluides et éléments constitutifs
— Méthodes de prélèvement et de mesure de la contamination
particulaire solide dans un fluide hydraulique
Reference number
ISO 5884:2018(E)
ISO 2018
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ISO 5884:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018

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.
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Published in Switzerland
ii © ISO 2018 – All rights reserved
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ISO 5884:2018(E)
Contents Page

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

0 Introduction ...............................................................................................................................................................................................................v

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

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

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

4 Sampling apparatus .......................................................................................................................................................................................... 1

4.1 General ........................................................................................................................................................................................................... 1

4.2 Sampling apparatus characteristics ...................................................................................................................................... 2

4.2.1 Manual sampling apparatus ................................................................................................................................... 2

4.2.2 Automated sampling apparatus .......................................................................................................................... 2

4.3 Sample apparatus preparation ......... ......................................................................................................................................... 3

4.3.1 General...................................................................................................................................................................................... 3

4.3.2 Solvents .................................................................................................................................................................................... 4

4.3.3 Cleaning procedure for sampling apparatus ........................................................................................... 5

4.3.4 Cleaning procedure for sample bottles ........................................................................................................ 5

4.3.5 Checking and controlling cleaning methods ............................................................................................ 6

5 Sampling ........................................................................................................................................................................................................................ 6

5.1 General ........................................................................................................................................................................................................... 6

5.2 Recommendations for sampling point location ......................................................................................................... 6

5.3 Sampling frequency ............................................................................................................................................................................ 7

5.4 Sampling methods ............................................................................................................................................................................... 7

5.4.1 General...................................................................................................................................................................................... 7

5.4.2 Sampling method A — Field monitor/PCM system ........................................................................... 7

5.4.3 Sampling method B — Sampling valve (using sample bottles) ............................................... 8

5.4.4 Sampling method C — Reservoir sampling with vacuum pump and tubing ............... 9

5.4.5 Sampling method D — Reservoir sampling with direct bottle dipping ........................... 9

5.5 Sample marking ..................................................................................................................................................................................10

6 Sample analysis methods .........................................................................................................................................................................10

7 Test reporting .......................................................................................................................................................................................................10

7.1 General ........................................................................................................................................................................................................10

7.2 Test report form ..................................................................................................................................................................................10

7.3 Minimum data to be included in the test report form .......................................................................................11

7.4 Example test report .........................................................................................................................................................................11

Annex A (informative) Example test report template ......................................................................................................................12

Bibliography .............................................................................................................................................................................................................................13

© ISO 2018 – All rights reserved iii
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ISO 5884:2018(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 on 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 the following

URL: www .iso .org/iso/foreword .html.

This document was prepared by ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 10, Aerospace

fluid systems and components.

This second edition cancels and replaces the first edition (ISO 5884:1987), which has been technically

revised. The main changes compared to the previous edition are as follows:
— update of the document to be in line with current ISO rules;
— improved layout and clarity in definition;

— removal of sample analysis detail, with reference to relevant ISO method instead;

— improved sampling point recommendations;
— improved clarity of sampling methods and recommendations for preference.

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 2018 – All rights reserved
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ISO 5884:2018(E)
0 Introduction
0.1 General

The design of modern hydraulic equipment for aerospace purposes, its use and performance are widely

determined by the type and condition of the applicable hydraulic fluids.

The quality and serviceability of hydraulic fluids are dependent on various factors (e.g. thermal stability,

viscosity), but in particular on the level of solid particle contamination. Regular fluid contamination

testing is required to determine if the fluid is maintained within specified limits that are set by the

aircraft manufacturer or hydraulic system operator.

In order to obtain consistent and comparable test results, the test methods detailed in this document

should be used.

As a result of the rapid development and improvement of hydraulic systems and their components,

which meet critical requirements, the problem of solid particle contamination of hydraulic fluids has

steadily increased. The need for maintaining a specified standard of fluid cleanliness in hydraulic

systems requires continuous control of the number and size of the solid particle contaminants.

0.2 Solid particle contamination

Solid particle contaminants can be the cause of abrasion and wearing, thereby shortening the life of the

components in a hydraulic system.
In a hydraulic system:

a) components are subject to erosion (primarily in components with higher fluid velocities);

b) all moving parts are subject to wear by abrasion; and

c) control valves are subject to silting (settlement of fine particles on the control bore).

0.3 Causes of solid particle contamination

Solid particle contamination of hydraulic fluids can be system-generated, introduced from the outside,

in-built or maintenance-generated, for example:
a) dust particles in the air;
b) metal particles, produced during the manufacture of parts;
c) sand residues on castings;
d) abrasion of seals;
e) oxide layers on welding seams and on heat-formed or heat-treated steel parts;
f) chemical and physical changes in the condition of hydraulic fluids;

g) maintenance of hydraulic systems (e.g. fibres, secondary contamination, etc.);

h) wear of components from abrasion, adhesion and fatigue; and
i) ingress of particles via piston gland seals.
0.4 Layout of this document
This document is sub-divided into the following clauses:
— Sampling apparatus (Clause 4):
— Characteristics;
© ISO 2018 – All rights reserved v
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ISO 5884:2018(E)
— Preparation;
— Sampling (Clause 5):
— Recommendations for sampling point location;
— Recommendation of sampling frequency;
— Sampling methods;
— Recommendation of sample marking;
— Sample analysis methods (Clause 6);
— Test report recommendations (Clause 7).
vi © ISO 2018 – All rights reserved
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INTERNATIONAL STANDARD ISO 5884:2018(E)
Aerospace series — Fluid systems and components —
Methods for system sampling and measuring the solid
particle contamination in hydraulic fluids
1 Scope

This document specifies best practice for sampling hydraulic fluid from aircraft hydraulic systems and

other hydraulic systems associated with aerospace purposes.
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 3696, Water for analytical laboratory use — Specification and test methods

ISO 3722, Hydraulic fluid power — Fluid sample containers — Qualifying and controlling cleaning methods

ISO 4021, Hydraulic fluid power — Particulate contamination analysis — Extraction of fluid samples from

lines of an operating system

ISO 4405, Hydraulic fluid power — Fluid contamination — Determination of particulate contamination by

the gravimetric method

ISO 4406, Hydraulic fluid power — Fluids — Method for coding the level of contamination by solid particles

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 11218, Aerospace — Cleanliness classification for hydraulic fluids

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 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 https: //www .electropedia .org/
4 Sampling apparatus
4.1 General

When establishing the solid particle contamination of hydraulic fluids, the test results can be adversely

affected by not sufficiently taking account of the need for an optimum cleanliness.

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ISO 5884:2018(E)

To obtain meaningful results, reproducible at any place and at any time, it is essential to ensure that

the sampling equipment is carefully prepared and maintained throughout the sampling process to

prevent any addition of solid particle contamination to the hydraulic fluid sample taken. This is because

additional solid particle contamination can be caused by using apparatus inadequately cleaned for the

measurement.

All apparatus used for determination of the solid particle contamination level of hydraulic fluids shall

be thoroughly cleaned before use in accordance with the procedure specified in 4.3.3.

It is important that for all sampling apparatus, due consideration is given to the suitability and resistance

to both the cleaning fluid used to prepare the sample apparatus and to the fluid to be sampled. This is

especially important when considering the compatibility differences between mineral oil /synthetic

hydrocarbon and Phosphate Ester–based hydraulic fluids.
4.2 Sampling apparatus characteristics
4.2.1 Manual sampling apparatus
4.2.1.1 General

Most system fluid samples can be obtained with the use of a simple sample bottle and tubing (if

necessary) to transfer the fluid from the sampling point to the bottle.

It is preferable to purchase suitable sample bottles that meet the provisions of ISO 3722. The system

operator shall specify the required cleanliness level.

Tubing shall be pre-cleaned or purchased in a condition which is in accordance with a cleanliness level

required by the system operator.

If cleaning manual sampling apparatus is required prior to use, then refer to 4.3.

4.2.1.2 Sample bottles

The sample bottles shall be made from glass or polyethylene terephthalate (PET or PETG). They shall

have a maximum capacity of 250 ml and a minimum capacity of 100 ml. They should be sealed by means

of caps (preferably of phenolic resin with glass bottles) which do not cause contamination. Otherwise, a

non-flaking plastic film compatible with the hydraulic fluid should be used.
4.2.1.3 Sample tubing

The sample tubing (if necessary for sampling of fluid) shall be in accordance with the description given

in ISO 4021.
4.2.2 Automated sampling apparatus
4.2.2.1 General

Automatic sampling of fluid systems can be carried out using equipment such as a field monitor or

portable cleanliness monitor. These systems are preferred to bottle sampling methods as there is a

much lower possibility of contamination of the results, especially in adverse environmental conditions.

Automated sampling monitors shall be flushed prior to use. This can be completed using the system

fluid itself, or a fluid which has a similar viscosity and a cleanliness class better than the requirement

for the system fluid. The volume of fluid used for flushing should be at least twice that of the hose used

to connect the monitor to the hydraulic system.
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ISO 5884:2018(E)
4.2.2.2 Field monitors

Field monitors contain membrane filters suitable for subsequent microscopic analysis (ISO 4407) or

gravimetric analysis (ISO 4405).

The membrane filters shall be pre-installed in the field monitor in a clean environment.

During flushing, the fluid should bypass the membrane and therefore a three-way valve shall direct the

flow from the membrane. Following flushing and prior to sampling, the valve is actuated to direct the

flow to the membrane filter.
4.2.2.3 Laser particle counter systems

Portable laser particle counter systems use light extinction techniques to produce an immediate

analysis of the system cleanliness. The monitors shall be calibrated in accordance with ISO 11171. The

output from the systems is in the form of a coded cleanliness level in accordance with ISO 4406 or

cleanliness classes in accordance with ISO 11218.

NOTE SAE AS 4059 or NAS 1638 can also be taken as equivalent standards to ISO 11218.

ISO 11218 (or SAE AS 4059) should be used in place of NAS 1638, except in special circumstances where

comparison to earlier data is necessary.

These types of monitors are affected by the occurrence of water droplets or air bubbles in the sampled

fluid. Therefore, care shall be taken with the location of the sampling point (5.2).

4.2.2.4 Portable mesh blockage monitors

Portable mesh blockage monitors determine particulate contamination levels by passing a specified

flow of sample fluid through a series of calibrated mesh screens in a specified sequence. Pressure drop

build-up (or flow degradation), which is dependent on particulate contamination levels, is measured

and converted via algorithms into:
— a coded cleanliness level in accordance with ISO 4406; or
— cleanliness classes in accordance with ISO 11218.

NOTE SAE AS 4059 or NAS 1638 can also be taken as equivalent standards to ISO 11218.

ISO 11218 (or SAE AS 4059) should be used in place of NAS 1638, except in special circumstances where

comparison to earlier data is necessary.

These monitors are especially suited to systems in which the fluid is likely to contain free water or air

bubbles and can also be used to measure viscosity, temperature and fluid water content (if equipped

with a water sensor).
4.3 Sample apparatus preparation
4.3.1 General

Sampling apparatus requires careful preparation to achieve a high level of cleanliness and control

prior to use. This ensures that sampled fluid is not contaminated by background contaminant already

present on the sample apparatus itself.

Staff performing any cleaning procedures shall wear lint-free clothes (e.g. cap, smock frock, boots) to

avoid excessive secondary contamination by fibres.

The standard of the workroom shall be such as to ensure that the specified cleanliness standard can be

achieved repeatedly.
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ISO 5884:2018(E)
4.3.2 Solvents
4.3.2.1 General

Liquid solvents shall be used to ensure removal of both solid and liquid contamination of sampling

equipment.

The solvents used shall be verified as physically and chemically compatible with the sampling

equipment and shall not react with the hydraulic oil to be stored in the bottle.

The following solvents are recommended solvents. Other approved equivalents are permitted, but

should be agreed prior to use.
— Solvent Type A: Water in accordance with ISO 3696, Grade 3.
— Solvent Type B: 2-propanol (is
...

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