ISO 14085-4:2015

Aerospace series - Hydraulic filter elements - Test methods - Part 4: Verification of collapse/burst pressure rating

ISO 14085-4:2015 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. ISO 14085-4:2015 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.

Série aérospatiale — Eléments filtrants hydrauliques — Méthode d'essais — Partie 4: Vérification de la résistance à l'éclatement/écrasement

General Information

• Status: Published
• Publication Date: 25-Feb-2015
• ICS: 49.080 - Aerospace fluid systems and components
• Technical Committee: ISO/TC 20/SC 10 - Aerospace fluid systems and components
• Drafting Committee: ISO/TC 20/SC 10/WG 8 - Hydraulic fluids and fluid contamination control
• Current Stage: 9020 - International Standard under periodical review
• Start Date: 15-Oct-2025
• Completion Date: 15-Oct-2025

Overview

ISO 14085-4:2015 specifies a standardized test method for verifying the collapse/burst pressure rating of aerospace hydraulic filter elements. The procedure quantifies a filter element’s ability to withstand a designated differential pressure in the intended flow direction by flowing contaminated fluid through the element until collapse/burst occurs or the maximum expected differential pressure is reached. The test may be run alone following a fabrication integrity check (ISO 2942) or continued after an efficiency test per ISO 14085-3.

Key topics and requirements

• Scope and purpose: Verifies structural resistance of hydraulic filter elements to high differential pressures caused by clogging or transient events (cold starts, decompression surges). Not intended to replicate full in-service conditions.
• Test circuit & equipment: Typical components include reservoir, pump (±5% flow stability), test housing, differential pressure transducer (40–100 Hz recording or equivalent), flow meter, contaminant injection system and optional online particle counter (calibrated per ISO 11943).
• Test media and contaminant: Test fluid as defined in ISO 14085-3 Annex A; contaminant is ISO 12103-1, A2 (ISO Fine Test Dust).
• Procedure highlights:
  • Option to continue from an ISO 14085-3 efficiency test or start after fabrication integrity (ISO 2942).
  • Maintain test flow (50–100% of nominal or manufacturer’s rated flow) and temperature (15 °C–40 °C unless specified).
  • Inject contaminant continuously or intermittently; record differential pressure versus contaminant mass added until specified collapse/burst pressure or failure.
  • Pressure relief valve (if fitted) should be set ≥150% of the specified final collapse/burst pressure.
• Acceptance criteria:
  • No visual structural failure when retested per ISO 2942.
  • No abrupt decrease in slope of the differential pressure versus contaminant mass curve prior to the specified rating (transients excluded).

Applications and users

• Filter element manufacturers validating design robustness and publishing collapse/burst ratings.
• Aerospace OEMs and system integrators specifying filter performance for hydraulic fluid power systems.
• Independent test laboratories performing comparative performance evaluations.
• Quality, certification and maintenance engineers assessing filter selection for safety-critical hydraulic systems. Practical uses include product qualification, comparative benchmarking of filter elements, and ensuring filters meet design constraints for differential pressure resistance in aerospace hydraulic applications.

Related standards

• ISO 14085 series (Parts 1–6) - test sequence, conditioning, efficiency, collapse/burst, flow fatigue, cleanliness.
• ISO 2942 - fabrication integrity and first bubble point.
• ISO 12103-1 (A2) - test contaminant specification.
• ISO 11943 - calibration/validation of particle counters.
• ISO 5598 and ISO 1219-1 - vocabulary and graphical symbols.

Keywords: ISO 14085-4:2015, collapse/burst pressure, hydraulic filter elements, aerospace test methods, differential pressure, filter testing, ISO 14085-3, ISO 2942.

Standards Content (Sample)

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
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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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 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
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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.
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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
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on the ISO list of patent declarations received (see www.iso.org/patents).
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For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
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
...