ISO/TR 6307:2023

TECHNICAL ISO/TR
REPORT 6307
First edition
2023-09
Effect of conductivity on multipass
testing as per ISO 4548-12:2017
Effet de la conductivité sur les essais multi-passes selon l'ISO 4548-
12:2017
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Reference filter testing .1
5 Flat sheet media study .4
6 Commercially available filter study .5
7 Oil analysis .8
8 Summary of ISO 4548-12 discussions regarding conductivity .9
8.1 General . 9
8.2 Summary of uncertainties in ISO 4548-12 . 9
8.3 Summary of comparison on conductivity: ISO 16889, ISO 19438, and ISO 4548-12 . 9
9 Conclusions .10
Bibliography .11
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 70, Internal combustion engines
Subcommittee SC 7, Tests for lubricating oil filters.
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iv
Introduction
ISO 4548-12:2000 and ISO 4548-12:2017 state that oil (MIL-PRF-5606, AIR 3520 and other suitable
fluids) conductivity is to be set to “at least 1 000 pS/m” prior to conducting a lubricating oil filter, with a
recommended level of “1 500 pS/m +/- 500 pS/m.” Prior to the revision of ISO 4548-12:2000 (started in
2016), fluid conductivity had received increasing attention. Some labs reported issues with maintaining
fluid conductivity during these tests and discussed the effects conductivity can have on filter capacity
results. Testing showed the fluid conductivity can decrease during a test, which corresponded to an
increase in filter capacity. A task force was established within ISO/TC70/SC7/WG2 to investigate
this issue. Findings from this work are summarized in this document. The root cause of the fluid
conductivity problem was not discovered and most labs did not report any issues with maintaining
conductivity during ISO 4548-12 testing.
Experiments were conducted by one laboratory, oil was examined by two laboratories, and survey
results were sent from nine laboratories. Three sets of experiments were conducted including testing
with flat sheet samples and commercially available filters to examine the effect of fluid conductivity
change. Fresh and aged oil were examined to see if any components of the fluid were depleted during
normal use.
v
TECHNICAL REPORT ISO/TR 6307:2023(E)
Effect of conductivity on multipass testing as per ISO 4548-
12:2017
1 Scope
This document outlines the importance of conductivity in multi-pass filter testing per ISO 4548-12. This
information also applies to filters tested per other multi-pass filter test standards, such as ISO 16889
and ISO 19438. Filters tested according to each method can experience similar changes in performance
during the fluid conductivity changes outlined within this document.
The objectives of this document are to clarify the following issues:
— Examine how conductivity affects filter capacity test results when filters are tested per
ISO 4548-12:2017.
— Compare findings to ISO 4548-12:2017 operating parameters.
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 4548-1, Methods of test for full-flow lubricating oil filters for internal combustion engines — Part 1:
Differential pressure/flow characteristics
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4548-1 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/
4 Reference filter testing
This issue was first reported after a lab used “reference filters” to monitor the consistency of their
multi-pass test system. These are typical production spin-on filters, but specifically manufactured to
limit filter-to-filter variation. These reference filters are constructed with synthetic media and a media
area of 3 039 cm . These filters are typically used as hydraulic/transmission oil filters on heavy-duty
diesel engines for off-road equipment.
From 2012 to 2015, this lab gathered data from periodic testing of these reference filters per
ISO 16889:2008 (Figure 1). Initial and final conductivity were logged during this testing. Test
technicians noticed final conductivity would significantly drop during some tests, corresponding with
a higher than expected capacity. Specific parameters of this testing are shown below.
Key
X final conductivity (pS/m)
Y retained capacity (g)
Flow Rate: 75 lpm
BUGL: 10 mg/l of A3 dust per ISO 12103-1:2016
Terminal dP: 345 kPa
Expected capacity: 60 – 70 g
Expected performance: β200 = 14 μm(c) / β1,000 = 19 μm(c)
Figure 1 — Reference filter capacity versus final conductivity
When a reference filter test results were outside of the expected results (tolerance), the fluid in the test
system would be changed. This fixed the issue and allowed the reference filter to test within expected
results. Reference filter testing has continued at this lab, but in 2015 more attention was paid to fluid
change-outs of the test system. Reference filters were tested in old oil (used for some time and ready to
be changed) and new oil, at different levels of initial conductivity (results shown in Figure 2). Figure 2
also shows the results from testing reference filters throughout 2015 as “Historical Data.” This is
normal lab practice for monitoring the status of the test system and fluid.
The 2016 Study conducted with old and new oil was done at initial conductivity levels of 1 000 pS/m,
1 500 pS/m, and 2 000 pS/m. The reference filter capacity results were significantly higher than
historical results when tested with the old fluid, signifying the need for the fluid to be changed. This
old fluid was left in the test system for the 2016 study. The new fluid was a fresh batch of oil, removed
from the drum, added to the test system, and additized with conductivity improving fluid to establish
the initial conductivity level(s).
Key
X final conductivity (pS/m)
Y retained capacity (g)
historical data (conductivity was not actively maintained)
new oil, 2016 study (conductivity was not actively maintained)
old oil, 2016 study (conductivity was not actively maintained)
Figure 2 — Reference filter capacity vs final conductivity from 2016 Study when conductivity
was not maintained and historical data.
A method (conductivity dosing system) for maintaining oil conductivity was developed and tested in
2016 to see how maintaining the conductivity would affect reference filter performance. Conductivity
1)
improving/increasing fluid (Stadis 450 ) was continuously added in small doses during each multi-pass
test (up to 50 ml) to not significantly affect the fluid level of the main tank. This dosing was consistent
throughout each test as the conductivity was actively controlled. Conductivity was monitored
with an in-line conductivity sensor that provided real-time feedback. Initial and final conductivity
measurements were also taken with a hand-held conductivity meter in the main tank, as specified
in ISO 4548-12. All conductivity data presented in this report was measured in the main tank with a
hand-held conductivity sensor. This method was effective at maintaining an oil conductivity within ±
200 pS/m of the initial conductivity during each test. The new oil was not actively maintained because
the final conductivity did not decrease significantly during the current work testing. Testing with the
“new” oil was conducted over the course of one (1) week. The results are shown below in Figure 3.
1) Stadis 450 is the trademark of a product supplied by Innospec. This information is given for the convenience of
users of this document and does not constitute an endorsement by ISO of the product named. Equivalent products
may be used if they can be shown to lead to the same results.
Key
X final conductivity (pS/m)
Y retained capacity (g)
historical data (conductivity was not actively maintained)
new oil, 2016 study (conductivity was not actively maintained)
old oil, 2016 study (conductivity was actively maintained)
Figure 3 — Reference filter capacity vs final conductivity 2016 Study when conductivity was
maintained and historical data.
Figure 2 and 3 show the importance of maintaining conductivity for obtaining consistent and reliable
test results in multi-pass testing (such a
...