ISO 14085-2:2015

INTERNATIONAL ISO
STANDARD 14085-2
First edition
2015-03-01
Aerospace series — Hydraulic filter
elements — Test methods —
Part 2:
Conditioning
Série aérospatiale — Eléments filtrants hydrauliques — Méthode
d’essais —
Partie 2: Vieillissement accéléré
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 . 2
5 Test equipment and materials . 2
6 Accuracy of measuring instruments and test conditions . 3
7 Summary of information required prior to testing . 4
8 Thermal conditioning test . 4
8.1 Preliminary preparation . 4
8.2 Thermal conditioning test procedure . 4
9 Cold start test . 5
9.1 Preliminary preparation . 5
9.2 Cold start test procedure . 7
10 Reporting . 8
11 Identification statement . 8
Annex A (informative) Cold Start Test Equipment . 9
Annex B (informative) Test Results Sheet .12
Bibliography .13
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 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: Initial 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 on the performance, reliability, and safety of the system, and needs to be controlled to levels
that are considered appropriate for the system concerned.
Different principles are used to control the contamination level of the fluid by removing solid contaminant
particles; one of them uses 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.
Filter elements are designed to withstand a range of thermal stresses, such as low and high temperature
extremes, and system demands at low temperature (cold starts) whereby hydraulic fluid passes through
the element at a greatly increased viscosity. These thermal stresses test both the chemical and thermal
stability of the filter element. These cold starts test the ability of the filter element to withstand the high
differential pressures and potential weakness at low temperatures without subsequent loss of integrity
or performance.
These stresses will be encountered within the lifetime of any filter element fitted in an aerospace
hydraulic system. It is, therefore, necessary to check that having been subjected to such conditions; the
filter element continues to provide adequate filtration, while also maintaining structural integrity.
This part of ISO 14085 provides a procedure by which to introduce such thermal stresses and to
condition a filter element prior to any subsequent qualification testing. This enables the purchaser of
the filter element to be secure in the knowledge that the product will withstand such thermal stresses
in addition to other qualification requirements without failure.
INTERNATIONAL STANDARD ISO 14085-2:2015(E)
Aerospace series — Hydraulic filter elements — Test
methods —
Part 2:
Conditioning
1 Scope
This part of ISO 14085 specifies
— a procedure to thermally condition a hydraulic filter element to presumed aerospace hydraulic
system stresses,
— a test procedure to complete cold soaks, hot soaks, and temperature variation in a combined manner,
and
— a test procedure to simulate cold starts.
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.
This part of ISO 14085 is intended to provide a test procedure that yields reproducible thermal test
conditioning of a hydraulic filter element, for simulation of the thermal stresses typically encountered
in an aerospace hydraulic system.
The conditioning test procedures defined in this part of ISO 14085 are intended to be used prior to
performance tests as specified in other parts of this International Standard.
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 4021, Hydraulic fluid power — Particulate contamination analysis — Extraction of fluid samples from
lines of an operating system
ISO 5598, Fluid power systems and components — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5598 and the following apply.
3.1
cold soak
prolonged immersion of a filter element in stationary fluid at the lowest expected system fluid temperature
3.2
cold start
application of a rapid increase in flow and differential pressure (3.3), followed by a brief maintaining of
the differential pressure (3.3), with cold fluid at a high viscosity
3.3
differential pressure
Δp
difference between the inlet and outlet pressures of the component under test, as measured under
specified conditions
3.4
fabrication integrity
physical acceptability of a filter element to meet the specification designated by the filter supplier
3.5
hot soak
prolonged immersion of a filter element in stationary fluid at the highest expected system fluid temperature
3.6
material safety data sheet
MSDS
specification sheet defining physical aspects, characteristics, and health and safety data for a substance
4 Symbols
The graphical symbols used in this part of ISO 14085 are in accordance with ISO 1219-1.
5 Test equipment and materials
5.1 Hot and cold soak test fluid, shall be the same as the system operating fluid, or shall be another
compatible fluid agreed upon between the supplier and purchaser.
5.2 Cold start test fluid, may be the same as the cold soak test fluid, but an alternative may also be
selected with a higher cold temperature viscosity, if agreed upon between the supplier and purchaser.
Using a higher viscosity can reduce the volume of fluid required to conduct the cold start test because
a lower flow is required to achieve the required differential pressure. If an alternative fluid is chosen, it
shall be fully compatible with the filter element and all materials to which it is exposed.
5.3 Differential pressure transducer shall be
a) positioned such that the upstream and downstream connections conform to ISO 3968, with no
bends or restrictions included in the measurement. Pressure taps in accordance with ISO 3968, and
b) connected to a data recording system.
5.4 Temperature transducer shall be
a) located such that the sensing part is located in the internal fluid volume,
b) positioned so that it measures the temperature of the test fluid as close as possible to the upstream
part of the test element,
2 © ISO 2015 – All rights reserved

c) positioned so that the sensor part does not touch the filter element or any part of the filter
element container,
d) connected to a data recording system, and
e) able to withstand the upstream pressure generated during the cold start test.
5.5 Filter element container, used for thermal conditioning tests shall
a) be large enough (in length and width, or diameter) to accommodate at least one test filter element,
If using an open container, the container shall be deep enough for fluid to fully cover the test filter
element by a minimum of 10 mm.
b) have a construction suitable for testing over the full temperature range,
c) have a cover for the container, or shall be a sealed or unsealed housing,
If the container is sealed, it shall either be capable of withstanding any increase in pressure due to
expansion of fluid as it heats up, or shall have a means of venting any increase in pressure.
d) be compatible with all the fluids used in the process, and
e) have a means for inserting a temperature transducer into the test fluid.
5.6 Environmental chamber, capable of achieving and maintaining the required temperatures within the
stated limits and capable of holding the filter element containers (see 5.5). The chamber shall have suitable
thermal controls with a calibrated feedback loop to allow precise control of the chamber temperature.
Alternatively, the hot and cold soaks can be performed using separate oven and freezer units, but the
same limits apply. If separate oven and freezer units are used, thermal shocks shall be avoided.
NOTE The environmental chamber is the preferred option, as this reduces the possibility of thermal shocks
and enables the thermal cycling tests to be performed more quickly as heating and cooling is more effective. It is
also a safer option as it overcomes the need to transfer the thermal container and hence removes the possibility
of fluid spillage or physical contact with the hot or cold surfaces.
5.7 Cold start test equipment. See Annex A for a list of typical equipment necessary to perform the
cold start test.
6 Accuracy of measuring instruments and test conditions
Use and maintain measuring instrument accuracy and test condition variations within the limits
given in Table 1.
Table 1 — Accuracy of measuring instruments and allowed test conditions variations
Permitted variations in test
Instrument accuracy
Test parameter SI Unit conditions
(± of actual value)
(± of target value)
a
Differential pressure kPa 2 % +5 %/-0 %
a
Gauge pressure kPa 2 % 5 %
Flow rate L/min 2 %
0 °C/+4 °C for max. temp
Temperature °C 0,1 °C
-4 °C/0 °C for min. temp
a
100 kPa = 1 bar
7 Summary of information required prior to testing
Prior to applying the requirements of this part of ISO 14085 to a particular hydraulic filter element,
establish the
a) fabrication integrity test pressure (see ISO 2942),
b) required maximum element differential pressure for the cold start test agreed upon between
purchaser and supplier, and
c) required hot and cold test temperatures for the soak test agreed between purchaser and supplier.
8 Thermal conditioning test
8.1 Preliminary preparation
8.1.1 Visually inspect the filter element for any obvious damage.
8.1.2 Carry out a fabrication integrity test on each element in accordance with ISO 2942, if not already
done. Reject the filter element if it is damaged or fails to meet the required minimum bubble point pressure
and restart with a fresh element.
8.1.3 Ensure that the filter element is dry of any fluid before proceeding to 8.1.4.
8.1.4 Place or fit the filter element into the container (see 5.5).
8.1.5 Fill the selected container with clean test fluid, ensuring that the filter element is completely
submerged by at least 10 mm of test fluid, and all air has been purged from
...