ISO 14085-4:2015

INTERNATIONAL ISO
STANDARD 14085-4
First edition
2015-03-01
Aerospace series — Hydraulic filter
elements — Test methods —
Part 4:
Verification of collapse/burst
pressure rating
Série aérospatiale — Eléments filtrants hydrauliques — Méthode
d’essais —
Partie 4: Vérification de la résistance à l’éclatement/écrasement
Reference number
©
ISO 2015
© ISO 2015
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Test circuit and equipment . 2
6 Accuracy of measurements and variations of test conditions. 3
7 Test procedure . 3
8 Reporting . 4
9 Acceptance criteria . 5
Annex A (informative) Test data report form . 6
Annex B (informative) Examples of abrupt decrease in the slope of the differential pressure
versus contaminant mass added curve and increase in particle counts .7
Bibliography . 9
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
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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).
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 10, Aerospace fluid systems and components.
ISO 14085 consists of the following parts, under the general title Aerospace series — Hydraulic filter
elements — Test methods:
— Part 1: Test sequence
— Part 2: Conditioning
— Part 3: Filtration efficiency and retention capacity
— Part 4: Verification of collapse/burst pressure rating
— Part 5: Resistance to flow fatigue
— Part 6: Cleanliness level
iv © ISO 2015 – All rights reserved

Introduction
In aerospace hydraulic fluid power systems, power is transmitted and controlled through a liquid
under pressure. The liquid is both a lubricant and power-transmitting medium. The presence of solid
contaminant particles in the liquid interferes with the ability of the hydraulic fluid to lubricate, and
causes wear and malfunction of the components. The extent of contamination in the fluid has a direct
bearing in the performance, reliability, and safety of the system, and needs to be controlled to levels that
are considered appropriate for the system concerned.
Filters are used to control the contamination level of the fluid by removing solid contaminant particles,
typically consisting of a filter element enclosed in a filter housing. The filter element is the porous device
that performs the actual process of filtration. The complete assembly is designated as a filter.
As a filter element removes contaminant due to its efficiency, the filter element clogs and its differential
pressure increases to values which can affect its structural integrity. The capability of the filter element
to maintain a specified fluid cleanliness level depends on its performance and structural integrity, which
can both be affected if the filter element differential pressure becomes too high.
A collapse/burst test quantifies the resistance of the filter element to high differential pressures that
can occur both due to filter clogging, as well as that occurring in non-steady state operating conditions
such as cold starts and decompression surges.
This part of ISO 14085 provides a procedure to verify that a filter element can withstand a designated
high differential pressure without failure.
INTERNATIONAL STANDARD ISO 14085-4:2015(E)
Aerospace series — Hydraulic filter elements — Test
methods —
Part 4:
Verification of collapse/burst pressure rating
1 Scope
This part of ISO 14085 describes a method for verifying the collapse/burst pressure rating of an
aerospace hydraulic fluid power filter element. This represents the capability of a filter element to
withstand a designated differential pressure in the normal (intended) direction of flow, created by
flowing contaminated fluid through the filter element until either collapse/burst occurs or the maximum
expected differential pressure is reached without element failure.
The collapse/burst pressure test can be conducted in conjunction with an efficiency test performed
according to the procedure defined in the ISO 14085-3 by continuing the contaminant injection until the
designated filter element differential pressure is reached.
This part of ISO 14085 is not intended to qualify a filter element under replicate conditions of service;
this can only be done by a specific test protocol developed for the purpose, including actual conditions
of use, for example the operating fluid or contamination.
The tests data resulting from application of this part of ISO 14085 can be used to compare the performance
of aerospace hydraulic filter elements.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 1219-1, Fluid power systems and components — Graphical symbols and circuit diagrams — Part 1:
Graphical symbols for conventional use and data-processing applications
ISO 2942, Hydraulic fluid power — Filter elements — Verification of fabrication integrity and determination
of the first bubble point
ISO 5598, Fluid power systems and components — Vocabulary
ISO 11943, Hydraulic fluid power — On-line automatic particle-counting systems for liquids — Methods of
calibration and validation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5598 and the following apply.
3.1
free-flow dummy element
duplicate test filter element with its media layers removed to replicate the flow pattern in the housing
generated by the test filter element
4 Symbols and abbreviated terms
Graphic symbols used are in accordance with ISO 1219-1.
5 Test circuit and equipment
5.1 Test stand: Use a test stand and components similar to that depicted in Figure 1 to perform the
collapse/burst test. Critical components of the test system are described below.
Key
A contaminant injection system 7 shut-off valve
B filter test system 8 clean-up filter
1 reservoir 9 check valve
2 pump 10 flow meter
3 relief valve 11 temperature controller
4 temperature gauge 12 diffuser
5 test filter 13 flow control valve
6 differential pressure (Δp) transducer 14 alternate contaminant injection point
...