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Vickers by Danfoss Target-Pro 2 Analyzer and Sampler Operation Manual V-PP-MC-0002-E
July 2023
Appendix
New ISO Standard Test Dust and its
effect on ISO Contamination Control Standards
For more than 25 years, the measurement of solid particles
in hydraulic fluids hasdepended on AC Fine Test Dust
(ACFTD), a product manufactured by General Motors.
ACFTD was used for calibrating Automatic Particle Counters
(APCs), testing components such as oil filters, and testing
the contaminant sensitivity of hydraulic components.
The particle size distribution of ACFTD, determined using an
optical microscope, formed the basisof ISO 4402—the
method for calibrating APCs. The limitations of optical micro-
scopes meant that distribution was uncertain at particle
sizes smaller than 5 microns. Consistency between batches
was also a regular concern.
After General Motors decided to stop making ACFTD, the
International Organization for Standardization (ISO) defined
requirements for a replacement, and asked the National
Institute of Standards and Technology (NIST ) to produce a
standard, traceable reference substance. The new dust’s
particle size distribution has been accurately determined
with the aid of scanning electron microscopes and image
analysis techniques.
New Test Dust Benefits
The new ISO Medium Test Dust (ISOMTD) uses similar
materials to ACFTD, but in a slightly coarser grade to reduce
particle counting errors. ISOMTD is produced to a standard
distribution and stringent quality control procedures for reli-
able consistency. In addition, production of ISOMTD
includes a revised ISO APC calibration method.
The result is a controlled reference test dust with uniform
particle size distribution. It provides the traceability required
by ISO 9000, QS9000 and similar quality management sys-
tems. A procedure for determining the performance of
APCs means the user can set minimum acceptablelevels.
Benefits include improved calibration techniques and proce-
dures, greater particle count reproducibility with different
equipment, and more accurate and consistent filter test
results.
Effect on Industry
T H E
I N T R O D U C T I O N
O F
I S O M T D
H A S
R E Q U I R E D
C H A N G E S
C E R T A I N
I S O
S T A N D A R D S .
T H E S E
I N C L U D E :
ISO 4402
1991
Hydraulic fluid power Calibration
of liquid automatic
particle counters
ISO 4406
1987
Hydraulic fluid power
Code for defining the level of
contamination by solid particles
ISO 4572
1981
Hydraulic fluid power Filters
Multi-pass method for evaluating filtration
performance of filter elements
To prevent confusion over which standards to use, ISO is
updating 4402 to ISO 11171, and 4572 to ISO 16889. ISO
standards written for the new test dust will use a new iden-
tifier, ‘(c)’. Micron sizes according to ISO 11171 will be
expressed as ‘µm(c)’ and Beta ratios according to ISO
16889 will be expressed as ‘Bx(c)’,e.g. ‘B5(c)’.
In the new ISO 4406, new calibration sizes are used to give
the same cleanliness codes as the ‘old’ calibration sizes of 5
and 15 microns. This will prevent the need to change sys-
tem cleanliness specifications.
The proposed cleanliness codes for APCs will be formed from
three particle counts at 4, 6 and 14 microns, with 6 and 14
microns corresponding closely to the previous 5 and
15 micron measurements. Users may still quote just two
counts of 6 microns and 14 microns for APCs.
Counts derived by microscope counting methods are not
affected, so the particle sizes used for microscopy, at 5 and
15 microns, will remain unchanged. The only real effect
users will experience is improved particle count accuracy;
there will be no change in filter performance or ISO cleanli-
ness levels.
