77
As a policy of continual improvement, STAUFF reserves the right to alter the specification without prior notice.
201.031
Date of Issue: 06 November 2018
11.9 New ISO Medium Test Dust and its effect on ISO Contamination Control
Standards
When General Motors gave advance warning to the International Standards Organization (ISO) that it
was intending to stop the production of AC Fine Test Dust (ACFTD), work commenced immediately on
finding an improved replacement dust. ACFTD was used extensively within the fluid power and
automotive industries for calibrating Automatic Particle Counters (APCs) and for the testing of
components.
APCs are used for testing oil filters, and also for contaminant sensitivity testing of hydraulic components.
For 25 years, APCs have been the main stay in the measurement of solid particles in hydraulic fluids.
The growth in demand for measuring fluid cleanliness in a variety of industrial processes, including fluid
power, has resulted in APCs moving from the laboratory environment out into the factory. In fact, they
are now a critical part of many production processes. It is therefore essential that the data they provide is
both accurate and consistent.
Calibration
ACFTD has been used as an artificial contaminant since the 1960s and its original particle size
distribution was determined using an optical microscope. This particle size distribution subsequently
formed the basis of ISO 4402, the method for calibrating APCs. Due to the limitations of that method of
measurement, the particle size distribution was questioned below ab
out 5μm. It was also not traceable to
any national standard of measurement -
a critical requirement for today’s quality management systems.
There was also an absence of formal controls over the distribution of the test dust, and batch-to-batch
variability was much greater than is acceptable nowadays.
ISO therefore defined the requirements for the replacement for ACFTD and asked the National Institute
of Standards and Technology (NIST) in the USA to produce a standard, traceable reference material.
The new
dust’s particle size distribution has been accurately determined with the aid of modern scanning
electron microscope and image analysis techniques.
ISO Medium Test Dust Benefits
The new ISO Medium Test Dust (ISO MTD) consists of similar materials to the old ACFTD, but to
minimize particle counting errors, it is of a slightly coarser grade because ACFTD included too many
particles smaller than 5μm which gave problems during testing.
ISO MTD is produced to a standard distribution and stringent quality control procedures, thereby
ensuring excellent batch-to-batch repeatability. These procedures, combined with a revised ISO APC
calibration method give:
- A traceable and controlled reference test dust with greatly reduced variation in particle size distribution.
This gives the trace-ability required by ISO 9000, QS9000 and similar quality management systems.
- A procedure for determining the performance of APCs so that minimum acceptable levels can be set by
the user.
- Improved calibration techniques and procedures.
- More accurate calibration.
- Improved levels of particle count reproducibility with different equipment.
- More accurate and consistent filter test results.
Effect on Industry
The introduction of ISO MTD has necessitated changes to certain ISO standards.
The standards affected include:
Содержание LPM-II-plus
Страница 1: ...Manual Particle Monitor LPM II plus...
