ISO 23369:2022

Hydraulic fluid power - Multi-pass method of evaluating filtration performance of a filter element under cyclic flow conditions

This document specifies: a) A multi-pass filtration performance test under cyclic flow conditions with continuous contaminant injection for hydraulic fluid power filter elements. b) A procedure for determining the contaminant capacity, particulate removal and differential pressure characteristics. c) A test currently applicable to hydraulic fluid power filter elements that exhibit an average filtration ratio greater than or equal to 75 for particle sizes ≤25 µm(c), and a final test system reservoir gravimetric level of less than 200 mg/L. It is necessary to determine by validation the range of flow rates and the lower particle size limit that can be used in test facilities. d) A test using ISO 12103‑1 A3 medium test dust contaminant and a test fluid. This document provides a test procedure that yields reproducible test data for appraising the filtration performance of a hydraulic fluid power filter element without influence of electrostatic charge. This document is applicable to three test conditions: - Base upstream gravimetric level of 3 mg/L; - Base upstream gravimetric level of 10 mg/L; - Base upstream gravimetric level of 15 mg/L.

Transmissions hydrauliques — Évaluation des performances d’un élément filtrant par la méthode de filtration multi-passe sous débit cyclique

Le présent document spécifie: a) un essai d’évaluation des performances de filtration d’éléments filtrants de transmissions hydrauliques, multi-passe sous débit cyclique, avec injection continue de polluants; b) un mode opératoire permettant de déterminer leur capacité de rétention des polluants, ainsi que leurs caractéristiques en matière d’élimination des particules et de pression différentielle; c) un essai applicable à l’heure actuelle aux éléments filtrants de transmissions hydrauliques ayant un rapport de filtration moyen égal ou supérieur à 75 pour les tailles de particules inférieures ou égales à 25 µm(c) et une concentration finale dans le réservoir du circuit d’essai inférieure à 200 mg/l. Il est nécessaire de déterminer par validation la plage des débits et la limite inférieure de taille de particules pouvant être utilisées avec les installations d’essai; d) un essai utilisant le contaminant ISO12103-1 A3 «Medium Test Dust» («poussière d’essai moyenne») comme polluant, ainsi qu’un fluide d’essai. Le présent document fournit un mode opératoire d’essai générant des données d’essai reproductibles pour l’évaluation des performances de filtration d’un élément filtrant de transmission hydraulique non soumis à l’influence de charges électrostatiques. Le présent document est applicable à trois conditions d’essai: 1) essai réalisé avec une concentration amont de base de 3 mg/l; 2) essai réalisé avec une concentration amont de base de 15 mg/l; 3) essai réalisé avec une concentration amont de base de 15 mg/l.

General Information

• Status: Published
• Publication Date: 18-Dec-2022
• ICS: 23.100.60 - Filters, seals and contamination of fluids
• Technical Committee: ISO/TC 131/SC 6 - Contamination control
• Drafting Committee: ISO/TC 131/SC 6 - Contamination control
• Current Stage: 6060 - International Standard published
• Start Date: 19-Dec-2022
• Due Date: 26-Oct-2023
• Completion Date: 19-Dec-2022

Relations

• Revises: ISO 23369:2021 - Hydraulic fluid power - Multi-pass method of evaluating filtration performance of a filter element under cyclic flow conditions
• Effective Date: 06-Jun-2022

Overview

ISO 23369:2022 - Hydraulic fluid power: Multi-pass method of evaluating filtration performance of a filter element under cyclic flow conditions specifies a reproducible laboratory procedure to evaluate hydraulic filter elements when subjected to cyclic (varying) flow. The standard defines a multi-pass filtration test with continuous contaminant injection to determine contaminant capacity, particulate removal performance, and differential pressure behaviour of filter elements used in hydraulic fluid power systems. It complements steady‑state multi-pass tests (e.g., ISO 16889) by addressing real-world cyclic flow effects.

Key topics and requirements

• Test method: Multi-pass filtration under cyclic flow with continuous contaminant injection and periodic fluid sampling to measure particulate removal.
• Target elements: Applicable to filter elements with an average filtration ratio ≥ 75 for particle sizes ≤ 25 µm(c).
• Contaminant and fluid: Uses ISO 12103-1 A3 (Arizona) medium test dust and a specified test fluid (see Annex A of the standard).
• Gravimetric baseline levels: Three base upstream gravimetric test conditions - 3 mg/L, 10 mg/L, and 15 mg/L.
• System limits: Final test system reservoir gravimetric level must be < 200 mg/L; injection systems and flow ranges must be validated for each test facility.
• Cyclic flow parameters: Recommended cycle rate is 0.1 Hz (industry default); testing at other frequencies is allowed if agreed, but only 0.1 Hz results may be claimed as “in accordance with ISO 23369.”
• Measured outputs: Contaminant mass injected, retained capacity, filtration ratios (particle‑size resolved), and differential pressure (clean, terminal, and assembly pressures).
• Repeatability controls: Procedures to avoid electrostatic effects on particle counts, accuracy/validation of injection and test circuits, and sampling methods are included.

Applications and users

ISO 23369:2022 is practical for:

• Filter manufacturers - product development, validation and performance claims for applications where flow is cyclic.
• Test laboratories - standardized test protocols for comparative evaluation and quality control.
• OEMs and system designers - selecting filters matched to hydraulic system duty cycles and contamination tolerance.
• Maintenance and reliability engineers - understanding filter lifetime under realistic cyclic conditions and planning element replacement strategies.
• Procurement/specifiers - specifying test-proven filtration performance for contracts and tenders.

Use cases include R&D comparisons, acceptance testing, supplier verification, and risk assessment for hydraulic systems in mobile equipment, industrial machinery, and transmission hydraulics.

Related standards

• ISO 16889 - steady-state multi-pass filtration test (complementary)
• ISO 12103‑1 - Arizona test dust (A3)
• ISO 11171 - particle counter calibration
• ISO 4405 - gravimetric contamination determination
• ISO 3968, ISO 4021, ISO 2942 - supporting methods for differential pressure, sampling, and integrity checks

Keywords: ISO 23369:2022, hydraulic fluid power, cyclic flow, filtration performance, multi-pass method, filter element testing, ISO 12103-1 A3, gravimetric level, filtration ratio.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23369
Second edition
2022-12
Hydraulic fluid power — Multi-
pass method of evaluating filtration
performance of a filter element under
cyclic flow conditions
Transmissions hydrauliques — Évaluation des performances d’un
élément filtrant par la méthode de filtration multi-passe sous débit
cyclique
Reference number
© ISO 2022
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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 4
5 General procedure .5
6 Test equipment .5
7 Measurement accuracy and test condition variation . 7
8 Filter performance test circuit validation procedures . 8
8.1 General . 8
8.2 Filter test system validation . 8
8.3 Contaminant injection system validation . 9
9 Summary of information required prior to testing a filter element .9
10 Preliminary test preparation .10
10.1 Test filter assembly . 10
10.2 Contaminant injection system . . 10
10.3 Filter test system . 11
11 Filter performance test .12
12 Calculations .14
13 Data presentation .17
14 Identification statement (reference to this document) .18
Annex A (normative) Base test fluid properties .19
Annex B (informative) Test system design guide .21
Annex C (informative) Example report, calculations and graphs .26
Bibliography .35
iii
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.
This second edition cancels and replaces the first edition (ISO 23369:2021), which has been technically
revised.
The main changes are as follows:
— calculation of ramp time.
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
Introduction
In hydraulic fluid power systems, one of the functions of the hydraulic fluid is to separate and lubricate
the moving parts of components. The presence of solid particulate contamination produces wear,
resulting in loss of efficiency, reduced component life and subsequent unreliability.
A hydraulic filter is provided to control the number of particles circulating within the system to a level
that is commensurate with the degree of sensitivity of the components to contaminants and the level of
reliability required by the users.
Test procedures enable the comparison of the relative performance of filters so that the most
appropriate filter can be selected. The performance characteristics of a filter are a function of the
element (its medium and geometry) and the housing (its general configuration and seal design).
In practice, a filter is subjected to a continuous flow of contaminant entrained in the hydraulic fluid until
some specified terminal differential pressure (relief-valve cracking pressure of differential-pressure
indicator setting) is reached.
Both the length of operating time (prior to reaching terminal pressure) and the contaminant level at
any point in the system are functions of the rate of contaminant addition (ingression plus generation
rates) and the performance characteristics of the filter.
Therefore, a realistic laboratory test establishes the relative performance of a filter by providing the
test filter with a continuous supply of ingressed contaminant and allowing the periodic monitoring of
the filtration performance characteristics of the filter. A standard multi-pass method for evaluating
the performance of hydraulic fluid power filter elements under steady-state flow conditions has
been developed as ISO 16889. That test procedure provides a basis for the comparison of the relative
performance characteristics of various filter elements. The results from such a test, however, might not
be directly applicable to most actual operating conditions.
In actual operation, a hydraulic fluid power filter is generally not subjected to steady-state flow but
to varying degrees of cyclic flow. Tests have shown that, in many instances, the filtration capabilities
of an element are severely reduced when subjected to varying cyclic flow conditions. It is therefore
important to evaluate the filtration performance of a filter for applications under cyclic flow conditions.
The cyclic flow multi-pass test procedure for hydraulic filters specified in this document has been
developed to supplement the basic steady-state flow test (ISO 16889) for filter elements that are
expected to be placed in service with cyclic flow. The recommended flow cycle rate of 0,1 Hz is a result
of an industry survey and a broad range of test results. If much higher cycle rates are expected in
actual service, the test should be conducted at that frequency to produce more meaningful results. The
procedure specified in this document may be applied at a cycle rate other than 0,1 Hz, if agreed upon
between the supplier and user. However, only values resulting from testing at the 0,1 Hz cycle rate may
be reported as having been determined in accordance with this document.
Fluid samples are extracted from the test system to evaluate the filter element’s particulate removal
characteristics. To prevent this sampling from adversely affecting the test results, a lower limit is
placed upon the rated flow rate of filter elements that should be tested with this procedure.
The current maximum flow rate specified in this document is based upon the maximum gravimetric
level of injection systems that have been qualified to date.
v
INTERNATIONAL STANDARD ISO 23369:2022(E)
Hydraulic fluid power — Multi-pass method of evaluating
filtration performance of a filter element under cyclic flow
conditions
1 Scope
This document specifies:
a) A multi-pass filtration performance test under cyclic flow conditions with continuous contaminant
injection for hydraulic fluid power filter elements.
b) A procedure for determining the contaminant capacity, particulate removal and differential
pressure characteristics.
c) A test currently applicable to hydraulic fluid power filter elements that exhibit an average filtration
ratio greater than or equal to 75 for particle sizes ≤25 µm(c), and a final test system reservoir
gravimetric level of less than 200 mg/L. It is necessary to determine by validation the range of flow
rates and the lower particle size limit that can be used in test facilities.
d) A test using ISO 12103-1 A3 medium test dust contaminant and a test fluid.
This document provides a test procedure that yields reproducible test data for appraising the filtration
performance of a hydraulic fluid power filter element without influence of electrostatic charge.
This document is applicable to three test conditions:
— Base upstream gravimetric level of 3 mg/L;
— Base upstream gravimetric level of 10 mg/L;
— Base upstream gravimetric level of 15 mg/L.
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 2160, Petroleum products — Corrosiveness to copper — Copper strip test
ISO 2942, Hydraulic fluid power — Filter elements — Verification of fabrication integrity and determination
of the first bubble point
ISO 3722, Hydraulic fluid power — Fluid sample containers — Qualifying and controlling cleaning methods
ISO 3968, Hydraulic fluid power — Filters — Evaluation of differential pressure versus flow
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 11171, Hydraulic fluid power — Calibration of automatic particle counters for liquids
ISO 11943:2021, Hydraulic fluid power — Online automatic particle-counting systems for liquids —
Methods of calibration and validation
ISO 12103-1, Road vehicles — Test contaminants for filter evaluation — Part 1: Arizona test dust
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology 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/
3.1
contaminant mass injected
m
i
mass of specific particulate contaminant injected into the test circuit to obtain the terminal differential
pressure
3.2
differential pressure
difference between the tested component inlet and outlet pressures as measured under the specified
conditions
Note 1 to entry: See Figure 1 for a graphical depiction of differential pressure terms.
3.3
clean assembly differential pressure
difference between the tested component inlet and outlet pressures as measured with a clean filter
housing containing a clean filter element
3.4
clean element differential pressure
differential pressure of the clean element calculated as the difference between the clean assembly
differential pressure (3.3) and the housing differential pressure (3.6)
3.5
final assembly differential pressure
assembly differential pressure at the end of a test, equal to the sum of the housing differential pressure
and the terminal element differential pressure
3.6
housing differential pressure
differential pressure of the filter housing without an element
3.7
terminal element differential pressure
maximum differential pressure across the filter element as designated by the manufacturer to limit
useful performance
3.8
rest conductivity
electrical conductivity at the initial instant of current measurement after a DC voltage is impressed
between electrodes
Note 1 to entry: Rest conductivity is the reciprocal of the resistance of uncharged fluid in the absence of ionic
depletion or polarization.
3.9
retained capacity
m
R
mass of specific particulate contaminant effectively retained by the filter element when terminal
element differential pressure is reached
3.10
cyclic flow
change of flow from the specified rated flow rate to 25 % of rated flow rate at a specified frequency and
waveform
Key
differential pressure ΔP )
()
2 test time or contaminant mass injected
3 final assembly differential pressure (end of test)
4 terminal element differential pressure
clean element differential pressure at q
max
housing differential pressure at q
max
clean assembly differential pressure at q
max
Figure 1 — Differential pressure conventions for multi-pass test under cyclic flow conditions
4 Symbols
Table 1 — Symbols
Symbol Unit Description
overall average upstream count of particles larger than size x
particles per millilitre
A
u,x
overall average downstream count of particles larger than size x
particles per millilitre
A
d,x
filtration ratio at particle size x (ISO 11171 calibration)
a
α –
x()c
filtration ratio at particle size x and time interval t
–
α
xt,
α –
average filtration ratio at particle size x (ISO 11171 calibration)
x()c
a
litres per second
rise and fall ramp flow rate acceleration
squared
milligrams per litre average base upstream gravimetric level
c
b
'
milligrams per litre desired base upstream gravimetric level
c
b
milligrams per litre average injection gravimetric level
c
i
'
milligrams per litre desired injection gravimetric level
c
i
milligrams per litre test reservoir gravimetric level at 80 % assembly differential pressure
c
m
grams mass of contaminant needed for injection
grams estimated filter element contaminant capacity (mass injected)
m
e
m grams contaminant mass injected
i
grams contaminant mass injected at element differential pressure
m
P
m grams retained capacity
R
N – number of counts in specific time period
particles per millilitre number of upstream particles larger than size x at count i
N
u,xi,
number of downstream particles larger than size x at count i
N particles per millilitre
d,xi,
average upstream count of particles larger than size x at time interval
particles per millilitre
N
u,xt,
t
average downstream count of particles larger than size x at time
particles per millilitre
N
d,xt,
interval t
p
Pa or kPa (bar) Pressure
ΔP
Pa or kPa (bar) differential pressure
q
litres per minute test flow rate
q litres per minute average test flow rate
q litres per minute minimum test flow rate (25 % of q )
min max
q litres per minute maximum test flow rate
max
q litres per minute discarded downstream sample flow rate
d
litres per minute average injection flow rate
q
i
'
litres per minute desired injection flow rate
q
i
litres per minute discarded upstream sample flow rate
q
u
t
minutes test time
t minutes predicted test time
pr
minutes final test time
t
f
a
The subscript (c) signifies that the filtration ratio, α , and the average filtration ratio, α , are determined in
x()c x()c
accordance with the method in this document using automatic particle counters calibrated in accordance with ISO 11171.
TTaabblle 1 e 1 ((ccoonnttiinnueuedd))
Symbol Unit Description
minutes test time at element differential pressure
t
P
seconds fall ramp time
t
F
seconds rise ramp time
t
R
′ seconds predicted test time
t
V litres final measured injection system volume
if
litres initial measured injection system volume
V
ii
V litres minimum required operating injection system volume
min
litres final measured filter test system volume
V
tf
V litres minimum validated injection system volume
v
micrometres particle sizes
xx,
x micrometres interpolated particle size
int
a
The subscript (c) signifies that the filtration ratio, α , and the average filtration ratio, α , are determined in
x()c x()c
accordance with the method in this document using automatic particle counters calibrated in accordance with ISO 11171.
5 General procedure
5.1 Set up and maintain apparatus in accordance with Clauses 6 and 7.
5.2 Validate equipment in accordance with Clause 8.
5.3 Run all tests in accordance with Clauses 9, 10 and 11.
5.4 Analyse test data in accordance with Clause 12.
5.5 Present data from Clauses 10, 11 and 12 in accordance with the requirements of Clause 13.
6 Test equipment
6.1 Calibrated timer, a digital or mechanical stopwatch calibrated by a facility meeting the
requirements of ISO/IEC 17025.
6.2 Automatic particle counter(s) (APC), calibrated in accordance with ISO 11171.
6.3 ISO medium test dust (ISO MTD) (in accordance with ISO 12103-1, A3 medium test dust), dried
at 110 °C to 150 °C for not less than 1 h for quantities less than 200 g. For use in the test system, mix the
test dust into the test fluid, mechanically agitate, then disperse ultrasonically in an ultrasonic bath that
2 2
has a power density of 3 000 W/m to 10 000 W/m .
For quantities greater than 200 g, dry for at least 30 min per additional 100 g. For use in the test system,
mix the test dust into the test fluid, mechanically agitate, then disperse ultrasonically with a power
2 2
density of 3 000 W/m to 10 000 W/m .
NOTE 1 This dust is commercially available. For availability of ISO medium test dust, contact the ISO Central
Secretariat or member bodies of ISO.
6.4 Online particle counting system (if necessary) with optional dilution system that has been
validated in accordance with ISO 11943.
6.5 Sample bottles, containing less than 20 particles larger than 6 µm(c) per millilitre of bottle
volume, qualified in accordance with ISO 3722, to collect samples for gravimetric analyses.
6.6 Petroleum base test fluid, with properties as specified in Annex A.
NOTE 1 The use of this hydraulic fluid ensures greater reproducibility of results and is based upon current
practices, other accepted filter standards and its world-wide availability.
NOTE 2 The addition of an anti-static agent to this test fluid can affect the test results.
6.7 Filter performance test circuit, composed of a filter test system and a contaminant injection
system.
6.7.1 Filter test system, consisting of:
a) a reservoir, pump, fluid conditioning apparatus and instrumentation that are capable of
accommodating the range of flow rates, pressures and volumes required by the procedure and
capable of meeting the validation requirements of Clause 8;
b) a clean-up filter capable of providing an initial system contamination level as specified in Table 3;
c) a configuration that is relatively insensitive to the intended contaminant level and capable of
meeting the validation requirements of Clause 8;
d) a configuration that does not alter the test contaminant particle size distribution over the
anticipated test duration and that is capable of meeting the validation requirements of Clause 8;
e) pressure taps in accordance with the requirements of ISO 3968;
f) fluid sampling sections upstream and downstream of the test filter, in accordance with the
requirements of ISO 4021;
g) cyclic flow bypass line equipped with an automatically controlled shut-off valve (e.g., an electrically-
actuated ball valve or poppet type valve or alternative system (e.g., direct drive), which have been
shown to be satisfactory for this application) capable of producing the required flow rate cycle at
the designated frequency.
NOTE For typical configurations that have proved to be satisfactory, see the filter test system design guide
in Annex B.
6.7.2 Contaminant injection system, consisting of:
a) a reservoir, pump, fluid conditioning apparatus and instrumentation that are capable of
accommodating the range of flow rates, pressures and volumes required by the procedure and
capable of meeting the validation requirements of Clause 8;
b) a configuration that is relatively insensitive to the intended contaminant level and capable of
meeting the validation requirements of Clause 8;
c) a configuration that does not alter the test contaminant particle size distribution over the
anticipated test duration and capable of meeting the validation requirements of Clause 8;
d) a fluid sampling section in accordance with the requirements of ISO 4021.
NOTE For typical configurations that have proved to be satisfactory, see the contaminant injection system
design guide in Annex B.
6.8 Membrane filters and associated equipment, suitable for conducting gravimetric
contamination analysis in accordance with ISO 4405.
7 Measurement accuracy and test condition variation
7.1 Use and maintain instrument accuracy and test conditions within the limits given in Table 2.
Table 2 — Instrument accuracy and test condition variation
Instrument accu- Allowed test condition
Test parameter SI unit
racy (±) of reading variation (±)
Conductivity pS/m 10 % 1 500 pS/m ± 500 pS/m
Differential pressure Pa or kPa (bar) 5 % —
Base upstream gravimetric level mg/L — 10 %
Injection flow rate mL/min 2 % 5 %
Test flow rate L/min 2 % 5 %
a
APC sensor and dilution flow rates mL/min 1,5 % 3 %
b 2 2
Kinematic viscosity mm /s 2 % 1 mm /s
Mass g 0,1 mg —
c
Temperature °C 1 °C 2 °C
Time s 0,1 s —
Injection system volume L 2 % —
Filter test system volume L 2 % 5 %
a
Sensor flow variation to be included in the overall 10 % allowed between sensors.
b 2
1 mm /s = 1 cSt
c
Or as required to guarantee the viscosity tolerance.
7.2 Maintain specific test parameters within the limits given in Table 3, depending on the test
condition being conducted.
Table 3 — Test condition values
Filter test condition
Parameter
Condition 1 Condition 2 Condition 3
Initial contamination level for filter test Less than 1 % of the minimum level specified in ISO 11943:2021,
system Table C.2 measured at the smallest particle size to be counted.
Initial contamination level for injection
Less than 1 % of injection gravimetric level.
system
Base upstream gravimetric level, based on
(3 ± 0,3) mg/L (10 ± 1,0) mg/L (15 ± 1,5) mg/L
a
the average test flow rate while cycling, q
Minimum of five sizes selected to cover the presumed filter
b performance range from α = 2 to α = 1 000. Typical sizes
Recommended particle sizes to be counted x()c x()c
are: (4, 5, 6, 7, 8, 10, 12, 14, 20, 25, 30) µm(c).
Sampling and counting method Online automatic particle counting
From q to q at a frequency of 0,1 Hz (6 cycles/min) in
max min
Cyclic flow rate conditions
accordance with the waveform specified in Figure 2.
a
When comparing test results between two filters, the base upstream gravimetric level and the wave form shall be the
same.
b
Particle sizes where α is low (α = 2, 10…) can be unobtainable for fine filters, and particle sizes where α is high
(α = 200, 1 000) can be unobtainable for coarser filters.
8 Filter performance test circuit validation procedures
8.1 General
These validation procedures reveal the effectiveness of the filter performance test circuit to maintain
contaminant entrainment and prevent contaminant size modification.
8.2 Filter test system validation
8.2.1 Install a conduit in place of the filter housing during validation. The conduit shall be selected so
that is produces the maximum differential pressure expected during testing.
NOTE An orifice with a 60° inlet and outlet is recommended.
8.2.2 Validation shall be performed at the cyclic flow rate that includes the lowest minimum test flow
rate ( q ) and highest maximum test flow rate ( q ) at which the filter test system is to be operated.
min max
The minimum test flow rate shall be 25 % of the maximum test flow rate.
8.2.3 Validate the cyclic flow at 0,1 Hz (6 cycles/min), unless otherwise specified.
8.2.4 Adjust the total fluid volume of the filter test system (exclusive of the clean-up filter circuit)
such that it is numerically within the range of 25 % to 50 % of the maximum volume flow rate, with a
minimum of 5 L.
It is recommended that the system be validated with a fluid volume numerically equal to 50 % of the
maximum test volume flow rate for flow rates less than or equal to 60 L/min, or 25 % of the maximum
test volume flow rate for flow rates greater than 60 L/min.
NOTE This is the ratio of volume to flow rate required by the filter test procedure (see 10.3.4).
8.2.5 Validate the online particle counting system and dilution systems, if used, in accordance with
ISO 11943 while the filter test system is under cyclic flow conditions.
8.2.6 Establish a background fluid contamination level that is less than that specified in Table 3.
8.2.7 Contaminate the system fluid for each test condition (1, 2, or 3) to be used to the base upstream
gravimetric level as shown in Table 3, using ISO 12103-1, A3 medium test dust.
8.2.8 Verify that the flow rate through each particle counting sensor is equal to the value used for the
particle counter calibration and is within the limits of Table 2.
8.2.9 Circulate the fluid in the test system for 60 min, conducting continuous online automatic
particle counts from the upstream sampling section for a period of 60 min. Sample flow from this
section shall not be interrupted for the duration of the validation. If dilution is used, the fluid that has
passed through the sensor shall not be returned to the reservoir.
8.2.10 Record cumulative online particle counts at equal time intervals not to exceed 1 min for the
duration of the 60-min test at the particle sizes shown in Table 3.
8.2.11 Accept the validation only if:
a) the online particle counting system and dilution system were successfully validated in accordance
with ISO 11943; and
b) the particle count obtained for a given size at each sample interval does not deviate more than
15 % from the average particle count from all sample intervals for that size; and
c) the average of all cumulative particle counts per millilitre are within the range of acceptable counts
shown in ISO 11943.
8.3 Contaminant injection system validation
8.3.1 Validate the contaminant injection system at the maximum gravimetric level, maximum
injection system volume, minimum injection flow rate, and for a length of time required to deplete the
complete usable volume.
8.3.2 Prepare the contaminant injection system to contain the required amount of test contaminant
and required fluid volume consistent with the configuration of that system.
NOTE All ancillary procedures used in preparation of the contaminant injection system become part of the
validation procedure. Alteration of these procedures requires revalidation of the system.
8.3.3 Add the test dust to the contaminant injection system and circulate for a minimum of 15 min.
8.3.4 Start the timer and initiate injection flow from the contaminant injection system, collecting this
flow externally from the system. Obtain an initial sample at this point and measure the injection flow
rate.
8.3.5 Maintain the injection flow rate within ± 5 % of the desired injection flow rate.
8.3.6 Obtain samples of the injection flow, and measure the injection flow rate at 30, 60, 90 and
120 min or at least four equal intervals depending upon the depletion rate of the system.
8.3.7 Analyse the gravimetric level of each sample obtained in 8.3.6 in accordance with ISO 4405.
8.3.8 Measure the volume fluid remaining in the injection system at the end of the validation test.
This is the minimum validation volume, V
v
8.3.9 Accept the validation only if:
a) the gravimetric level of each sample obtained in 8.3.6 is within ±10 % of the gravimetric level
determined in 8.3.1 and the variation between samples does not exceed ±5 % of the mean; and
b) the injection flow rate at each sample point is within ±5% of the selected validation flow rate
(8.3.1), and the variation between sample flow rates does not exceed ±5 % of the average; and
c) the volume of fluid remaining in the injection system, V (8.3.8) plus the quantity [average injection
v
flow rate (12.11) times total injection time (8.3.6)] is within ±10 % of the initial volume (8.3.2).
9 Summary of information required prior to testing a filter element
The following information shall be established before submitting a particular filter element to the test
specified in this document:
a) fabrication integrity test pressure (in accordance with ISO 2942);
b) filter element maximum test flow ( q ) as determined by the manufacturer;
max
c) terminal element differential pressure;
d) presumed particle size values for specific filtration ratios;
e) presumed value of the filter element capacity (mass injected) ( m )
.
e
10 Preliminary test preparation
10.1 Test filter assembly
10.1.1 Ensure that test fluid cannot bypass the filter element in the housing to be evaluated.
10.1.2 Subject the test filter element to a fabrication integrity test in accordance with ISO 2942.
The element shall be disqualified from further testing if it fails to exhibit at least the designated test
pressure.
10.1.3 Where applicable, allow the fluid to evaporate from the test filter element before installing it in
the test filter housing.
NOTE 1 The test fluid specified in Annex A can be used for fabrication integrity testing.
NOTE 2 If the element is not readily accessible, as in the case of a spin-on configuration, the fabrication
integrity test can be conducted following the multi-pass test, with the element removed. However, a low and,
perhaps, unacceptable first bubble point value determined in such a case does not mean that such a value would
have been obtained if the fabrication integrity test had been conducted before the multi-pass test.
NOTE 3 If the tested element fails the fabrication integrity test, then the corresponding cyclic flow results
should be considered invalid, since there is no evidence that the element would have initially passed the test.
10.2 Contaminant injection system
10.2.1 Calculate the average test flow rate ( q ) using Formula (1):
qq +
 
maxmin
q = (1)
 
 
'
10.2.2 Select a desired base upstream gravimetric level ( c ) from Table 3 such that the predicted test
b
′
time, t , calculated using Formula (2) is preferably in the range of 1 h to 3 h, based on the simple average
test flow rate q , calculated using Formula (1).
10.2.3 Predicted test times of less than 1 h or longer than 3 h are acceptable as long as the selected test
condition 1, 2, or 3 is maintained.
1 000× m
e
′
t = (2)
'
cq ×
b
where q (flow rate) is calculated using Formula (1).
NOTE A second filter element is tested for capacity analysis if the value of the estimated capacity of the test
element is not supplied by the filter manufacturer.
10.2.4 Calculate the minimum required operating injection system volume that is compatible with the
predicted test time, t′ , and a desired value for the injection flow using Formula (3):
'
Vt=× 12,' × qV+ (3)
()
mini v
The volume calculated using Formula (3) ensures a sufficient quantity of contaminated fluid to load
the test filter element plus 20 % for adequate circulation throughout the test. Larger injection system
volumes may be used.
'
A value for the injection flow rate ( q ) of 0,25 L/min is commonly used and ensures that the downstream
i
sample flow expelled from the filter test system does not significantly influence the test results. Lower
or higher injection flow rates may be used provided that the base upstream gravimetric level is
maintained.
'
10.2.5 Calculate the desired gravimetric level ( c ) of the injection system fluid using Formula (4):
i
'
cq×
' b
c = (4)
i
'
q
i
10.2.6 Adjust the total initial volume, V , of the contaminant injection system (measured at the test
ii
temperature) to the value calculated in 10.2.4 and record the result on the report sheet given in
Table C.3.
10.2.7 Calculate the mass of contaminant needed for the contaminant injection system (m) using
Formula (5):
'
cV×
iii
m = (5)
1 000
10.2.8 Prior to the addition of the ISO 12103-1, A3 medium test dust to the contaminant injection
system, verify that the background fluid contamination level is less than specified in Table 3.
10.2.9 Prepare the contaminant injection system to contain the quantity of fluid, V , and ISO 12103-1,
ii
A3 medium test dust (m) (see 10.2.7) using the same procedure that was used for the contamination
injection system validation (see 8.2).
10.2.10 Adjust the injection flow rate at a stabilized temperature to within ±5 % of the value
selected in 10.2.3 and maintain that value throughout the test. Record the injection flow rate on the
report sheet given in Table C.3. During setup, return the injection system sampling flow directly to the
injection reservoir.
10.3 Filter test system
10.3.1 Install the filter housing (without test element) in the filter test system and thoroughly bleed off
air.
10.3.2 It is recommended that the rest conductivity of the test fluid should be checked and maintained
in the range of 1 500 pS/m ± 500 pS/m (see ASTM D-4308). This can be accomplished by the addition of
an anti-static agent. The addition of an anti-static agent can affect the test results. Use of an anti-static
agent that has a date code older than 18 months is not recommended.
10.3.3 Circulate the fluid in the filter test system at maximum test flow rate and at a test temperature
2 2
such that the fluid viscosity is maintained at 15 mm /s ± 1,0 mm /s; record the temperature and
differential pressure of the empty filter housing in accordance with ISO 3968.
10.3.4 Adjust the total fluid volume of the filter test system (exclusive of the clean-up filter circuit)
such that its value in litres is numerically between 25 % and 50 % of the designated maximum test flow
rate through the filter, in L/min, with a minimum of 5 L.
10.3.5 If the designated maximum test volume flow rate is less than or equal to 60 L/min, it is
recommended that the filter test system fluid volume be numerically equal to 50 % of the maximum
test volume flow rate. If the designated maximum test volume flow rate is greater than 60 L/min, it is
recommended that the filter test system fluid volume be numerically equal to 25 % of the maximum
test volume flow rate.
10.3.6 Repeatable test results require that the system volume be maintained constant. The specified
range of ratios between the test system fluid volume and the test volume flow rate from 1:4 to 1:2
minimizes the physical size of the system reservoir as well as the quantity of test fluid required, while
maximizing the mixing conditions in the reservoir.
10.3.7 Establish a fluid background contamination level less than that specified in Table 3.
10.3.8 Effectuate online automatic particle counting by:
a) Adjusting the upstream sampling flow rate to a value compatible with the sampling procedure
used and the downstream sampling flow rate to within ±5 % of the injection flow rate. Maintain
uninterrupted flow from both sampling points during the entire test.
b) Adjusting the upstream and downstream dilution flow rates if required for online automatic
particle counting, so that at the end of testing, the flow rates and concentrations at the particle
counters are compatible with the instrument requirements; and the upstream and downstream
sensor flow rates should be set and maintained at the values, and within the limits, specified in
8.2.8 and Table 2.
c) Returning the undiluted and unfiltered sampling flow upstream of the test filter directly to the test
reservoir; if the upstream sample is diluted or filtered for online automatic particle counting, the
diluted or filtered fluid should be collected outside of the filter test system. If the upstream sample
flow is diluted or filtered, the downstream sample flow rate to be discarded should be reduced
by a value equal to the upstream sample flow that is collected outside the system. This is to assist
in maintaining a constant system volume that should be kept within ±5 % of the initial system
volume.
d) The upstream and downstream dilution flow rates should be equal to the values chosen in 10.3.8 b
within the limits shown in Table 2.
e) Sensor flow rates should be monitored and recorded throughout the test and maintained within
the limits shown in Table 2.
10.3.9 Adjust the particle counter thresholds to the values selected from Table 3.
11 Filter performance test
11.1 Install the filter element into its housing and subject the assembly to the specified test condition
and reaffirm the fluid level.
11.2 Measure and record the clean assembly differential pressure. Calculate and record the clean
element differential pressure by subtracting the housing differential pressure measured in 10.3.3 from
the clean assembly differential pressure.
11.3 Calculate the final assembly differential pressure corresponding to the final element differential
pressure plus the housing differential pressure.
11.4 Measure and record the initial system contamination level using online particle counting from
upstream of the test filter element.
11.5 Bypass the system clean-up filter if the upstream contamination level is less than that specified
in Table 3. If the upstream contamination level is not less than specified in Table 3 then continue to
utilize the clean-up filter until the upstream contamination level is less than that specified in Table 3.
11.6 Obtain a sample from the contaminant injection system. Label it “Initial injection gravimetric
sample”.
11.7 Measure and verify the injection flow rate. Continuous measurement of the injection flow rate is
required throughout the test to ensure the flow rate is maintained within the specified tolerances.
11.8 Operate the cycling valve in the test system to generate and repeat the flow rate cycle shown in
Figure 2.
Key
X test time (t')
Y test flow rate (q)
Figure 2 — Waveform for multi-pass test under cyclic flow conditions
Up to q ≤ 120 L/min the rise and fall ramp time should be ≤0,2 s. From q > 120 L/min the rise and
max max
fall ramp flow rate acceleration (a) should be ≥ 7,5 L/s . Ramp time should be calculated using
Formula (6)
qq−
maxmin
t = (6)
RF,
60 ×a
NOTE During validation of the test stand, a pressure reading can be used to confirm rise and fall timing as
measured by the flow meters.
11.9 Initiate the filter test as follows:
a) allow the injection flow to enter the filter test system reservoir;
b) start the timer;
c) divert the downstream sample flow from the test system to maintain a constant system volume
within a tolerance
...