Why measure cleanliness???

1. 1
Part Technical
Cleanliness XX.XXXX
Blocking of Bearing
Turbocharger, Piston, Axle
Blocking of Valves
ABS, Hydraulics
Part Cleanliness… WHY???
Blocking of Nozzles
Injectors, Fuel System
Electric Short Circuit
Boards, Processors
• Smaller tolerances
make systems more
sensitive to dirt.
• Cleanliness and
system life times are
correlated.
• Large residue
particles (killer
particles) may cause
function loss.
• Both Exhaust and
Noise, are correlated
with smooth
(unscratched)
surfaces.

2. 2
Component Cleanliness of Fluid
Systems in Automotive Complying
with ISO Standards
Abstract:
As the presence of particulate
contamination in the lubricant
is the major cause of failures
and short component life of
fluid systems, companies in a
variety of industries are
focusing attention in
achieving and maintaining
system cleanliness. The
presence of machining and
assembly debris in the fluid
system at start-up and during
the initial running phase will
cause a substantial increase
in the wear rates of the
system, further generating
large particles, with the
consequential loss in
performance and component
life. It will also increase the
probability of sudden and
catastrophic failure of the
system. To achieve clean
components requires
appropriate manufacturing,
cleaning and measurement
processes. Accurate
assessment of the
effectiveness of components
and parts cleanliness is
related to given contaminant
extraction methods, analysis
and data reporting. ISO
standards are continually
being developed to control
procedures and implement a
consistent cleanliness
evaluation process.
This article explains the
processes in these standards
and how similar procedures
have been adapted to suit the
requirements of the above
industries. It also gives
guidance and
recommendations on the
implementation of these
standards so that the best
use can be made of them.
1. Introduction
The need for component
cleanliness was first identified in
the 1960s when the aircraft
industry started using hydraulic
flight systems. The last 10 years
has seen more and more
industrial sectors implement
component cleanliness programs
as they realize the technical and
commercial benefits.
Foreword:
The fluid power industry was the major developer of ISO
standards through ISOTC131/SC6 until 2002 when the
automotive industry embarked on a project to develop their
own standards through ISOTC22/SC5. Although the
processes used would be very similar to those developed by
TC131/SC6, the automotive industry considered that their
requirements were sufficiently different to warrant new
standards. For example, the automotive industry focus is on
the incidence of small numbers of large particles (>1000 μm
- so called ‘killer particles’) residual after production as they
could have serious safety consequences, whereas these
particles should be filtered out of fluid power systems during
production.
This split development has led to small differences in both
terminology and procedures. For instance, the process of
removing particles from components is called ‘extraction’ in
ISO16232.
This document summarizes the standard practices related to
contaminant extraction, collection, analysis and data
reporting for cleanliness evaluation of manufactured parts
and components, specifically being applied to the fluid
systems (lube, fuel and hydraulics) in automotive and fluid
power markets.
2. Contaminant Extraction Methods
2.1 Extraction selection with geometry
The selection of the most suitable extraction method(s) is
guided by the followed principles:
• Extraction method must be selected for the geometry of
the component so that the extraction liquid can reach
the controlled surfaces.

3. 3
• Extraction method must be directed to only remove
particles from the controlled surfaces.
• Component geometry must allow the particle to be
transported away by the extraction method.
• Extraction method must be validated.
ISO18413 provides recommendations for selection of
contaminant extraction methods:
- Pump/Motor - End-use simulation method.
- Valve Cylinder - End-use simulation method.
- Manifolds/System - End-use simulation method.
- Gear/Shaft/Plates - Pressure rinse or ultrasonic.
- Spool/Pistons - Pressure rinse or ultrasonic.
- Reservoir - Pressure rinse or agitation.
- Hose/Pipe - Agitation or ultrasonic.
To obtain repeatable results, the process attributes must be
consistent.
2.2 Agitation extraction method (Slosh test)
The contaminants are extracted by partially filling the
component with a known volume of test liquid (between 30
to 50% of the component volume), sealing its openings, and
agitating or ‘sloshing’ it in order to detach the particles from
the controlled surfaces and suspend them in the test liquid
for subsequent analysis.
The efficacy of the agitation method depends on type of
agitation, duration of agitation and choice of test liquid.
This method is only suitable for hollow components like
hoses or pipes whose size is such that they can be readily
and consistently agitated.
Applicable standards: ISO16232 Part 2; ISO18413 Clause
5.3
2.3 Pressure rinse extraction method
The contaminants are extracted from the controlled surfaces
of the component by pressure rinsing with a jet of filtered test
liquid which removes the particles from the surfaces and
carries them away for subsequent analysis.
The pressure rinse liquid dispenser is a device for providing
clean test liquid at a suitable pressure and a flow rate
capable of extracting the particles in an effective manner.
The efficacy of pressure rinsing depends on pressure, flow
rate, distance, angle, shape and size of the nozzle, rinsing
time and liquid volume per unit area.
Applicable standards: ISO16232 Part 3; ISO18413 Clause
5.4
2.4 Ultrasonic vibration extraction method
The contaminant is removed by subjecting the item to
ultrasonic vibration. The principal characteristics of the
ultrasonic equipment are power, frequency and bath size. In
general, by applying transducers to the floor or wall surfaces
3. Extractions for cylindrical pipe of hydraulic,
lube and fuel components
This section outlines the extraction methods to assess
the cleanliness of the wetted inner side of cylindrical or
pipe type of hydraulic, lube, fuel components and
subassemblies.
3.1 Extractions of the contaminant from passages or
holes of component
The functional test method, according to ISO16232 and
ISO18413, is able to properly and effectively detach the
particles that are residual in narrow flush passages like drain
or return lines in a manifold block or casings.
3.2 Extractions of the contaminant from inside of
hydraulic tube and hose
Flushing rig complying with ISO16232 Part 5 is best to
validate cleanliness of hoses and pipes and this needs a
flow rate to give turbulence in the pipe with a Reynolds
Number (Re) of >4000 i.e. well into the turbulent regime.
And a variable delivery pump is desirable to suit component
size.
The viscosity used in these test rigs is usually higher than
usual extraction liquids because of the minimum viscosity
required by the circulating pump. The rig should also
include on-line particle counting so that the progress of
flushing can be continuously monitored and terminated
when a RCL is achieved. This approach can achieve
considerable savings in costs over more ‘conventional’
methods of collection.
It is recommended that at least 10 mL extraction liquid/cm2
of wetted surface area is used for pressure rinsing hoses
and pipes. If the calculated amount of extraction fluid is less
than 2 litres, then 2 litre shall be used or if it exceeds 20 litre,
20 litre shall be used, unless otherwise specified.
4. Protocol and Validation for Contaminant
Extraction
4.1 Package during transportation
If particles are detached during transportation of the test
components and/or from packaging, these have to be
included in the cleanliness test. They are collected using
appropriate extraction method(s). During handling and
storage of test components, it shall be safeguarded that no
contaminants are deposited on or removed from controlled
surfaces. To prevent loss of particles during transport it may
be necessary to seal openings in the test components with
either tape or a suitable plug.
Applicable standards: ISO16232 Part 2, 3, 4 & 5
4.2 Blank test
• A blank test is performed to verify that the
environment, operating conditions, and equipment
used in the extraction procedure do not contribute a

4. 4
significant amount of contamination to the
component being analysed. To ensure process
consistency, a blank test should be performed at
regular intervals using identical test parameters.
• For the determination of system blank values,
identical conditions as experienced during testing
of the component are applied but with the
component omitted (see 3.3).
• If the blank level exceeds 10% of the cleanliness of
the component (presumed or measured), then
either the process or environment is too dirty and
re-cleaning is necessary, or the contamination
level of the component is to low and it is necessary
to increase the number of test components
analysed in order to collect more contaminants and
thus fulfil the 10% limit.
4.3 Validation of contamination extraction process
It is essential that the contamination extraction procedure is
validated, so that its effectiveness is confirmed.
Extraction Step
Figure 1. Validating the extraction process.
The process is:
•Determine the most suitable extraction method and
the operating parameters.
•Perform two extractions and for each of two
samples to establish either the total mass of
contaminants or total number of particles. Note that
ISO16232 requires the extraction of three samples.
For particle numbers, this should include the total
numbers of particles larger than
•the smallest particle sizes specified in the
inspection document.
•Divide the result of last sample by the sum of all the
results obtained.
•If the value obtained is less than 10% of this sum,
the end point is reached, and the extraction is
complete. The cleanliness level of the component
is the sum of the extractions.
•If the value obtained is >10%, further extraction is
necessary. If six extractions have been performed
without reaching the 10% value, then the extraction
parameters are not suitable and will have to be
modified.
➢ The component is made cleaner.
5. Analysis Methods
5.1 General
A variety of standard, contaminant analysis methods and
data reporting formats are available to produce the required
part or component cleanliness data.
Both ISO16232 and ISO18413 describe three basic
contaminant analysis methods: gravimetric particle size,
distribution and chemical composition. Largest particle
size is included in particle size evaluation.
The major difference separating ISO16232 and other
standards is the requirement to analyze all of the
extraction liquid so that all particles in the extraction are
analyzed and the larger (‘killer’) particles, typically at
much lower concentrations, are not missed. Because of
this need, the microscopic procedures of ISO16232 are
completely automated using image analysis.
5.2 Gravimetric analysis method
Extraction, filtration, drying, and weighing
Precision components must be free of contaminants to work
properly. Parts that are made with unclean components can
fail prematurely. Technical cleanliness is the process of
measuring the level of contamination from these particles to
help ensure high-quality finished products. In the first of this
six-part blog series, we will take a close look at the first step
of the technical cleanliness workflow—preparation
(extraction, filtration, drying, and weighing). First, let’s look at
where preparation fits into the overall technical cleanliness
inspection process:
• Preparation
o Extraction
o Filtration
o Drying and weighing
• Inspection
o Image acquisition
o Particle detection
o Particle size measurement and
classification
o Particle count extrapolation and
normalization
o Contamination level calculation
o Cleanliness code definition
o Maximum approval check
o Separation of reflective and nonreflective
particles
o Fibre identification
o Results review
o Reporting
➢ Extraction
The components to be tested are placed in an extraction
cabinet in a clean room, and any contaminant particles or
0
10
20
30
40
50
60
70
80
90
100
110
1 2 3 4 5 6
CleaninessValues(Ci)
Number of Samples
DECLINING CURVE
Decay
CriterionBlank Level

5. 5
residues are removed via flood, squirt, rinse, or ultrasonic
bath.
For the vast number of functionally relevant components in
automobiles, extraction with a liquid is suitable. The rinsing
liquid must be compatible with the component as well as the
filtration device.
Note that the extraction cabinet must be cleaned regularly to
avoid becoming a source of contamination. For this reason,
the empty cabinet is flushed several times. The washing
rinse is then filtered and examined for particles. The amount
of residue becomes constant after 3 to 4 washing cycles,
which results in a background value for the given
configuration (rinse, cabinet, and filter). It is sufficient to
weigh the filter membranes to obtain this blank value.
➢ Filtration
The washing rinse is filtered through a membrane, and the
extracted particles are collected on the filter. This filter is
clamped in a holder that is part of the extraction cabinet.
If the washing rinse is an oil, it’s filtered directly. A defined
quantity (about 50 ml) of oil is drawn through a vacuum filter
holder. The particles remain behind on the filter.
It’s important to note that a filter will not usually be covered
completely with residue particles (the border of the filter is
covered by a seal that results in a reduced flow-through
area).
A filter membrane clamped and in use with an extraction
cabinet
Filter sizes vary from 25 mm to 90 mm in diameter. The
typical filter size and quasi-standard for technical cleanliness
is 47 mm. Filter membrane materials include:
• Cellulose: Excellent compatibility with aqueous
solutions
• Polyester: Uniform image background; easy to set
threshold for particle detection
• Glass fiber: Ideal for solutions with high levels of
suspended solids or high viscosity
• Nylon mesh: Very good resistance to almost all
solvents; needs a white support layer as it is
transparent
➢ Drying and Weighing:
The filter membrane is dried in preparation for further
analysis. The rinse fluid or oil can be removed using an
exicator (a desiccator), a drying oven, or dedicated
equipment.
The dried filter membrane (with all impurities on it) is then
weighed using an analytical balance with an integrated
windshield. The gravimetric result gives the first value for the
residue particles, but the size, shape, and other particle
parameters are still unknown.
The weighted filter membrane is next mounted on a filter
holder, ready for the next phase of the technical
cleanliness inspection process—image acquisition.
5.3 Particle counting by microscope
The inspection process includes the following steps:
• Image Acquisition and Stage Movement: The
dried membrane filter is mounted on a motorized
microscope stage so that the images needed for
inspection can be acquired.
• Particle Detection: Membrane filter images are
examined for particles, which appear as dark areas
against a bright background.
• Particle Size Measurement: Detected particles are
measured according to different parameters,
including Maximum Ferret and Equivalent Circle
diameter.
• Particle Size Classification: Once particles have
been measured, they are grouped into different size
classes. The two major size classes are differential
(defined by a minimum and maximum size) and
cumulative (defined only by a minimum particle
size).
• Particle Count Extrapolation: A defined area on
the membrane filter is scanned and checked for
particles. These areas may include filter size (the
total area of the filter), flow-through area (the filter
area covered with particles), maximum scan area
(the maximum possible area to be scanned for
inspection), and inspection area (the actual scan
area defined by the user).
• Particle Count Normalization: The extrapolated
particle count is normalized to the comparison
value, enabling the comparison of multiple
measurements. Normalization methods include
washed area (particle count is normalized on a
1000 cm2
area), washed volume (particle count is
normalized on a 100 cm3
area), washed parts
(particle count is normalized on a single sample

6. 6
part), and filtered fluid (particle count is normalized
on a filtered fluid of 1 ml or 100 ml).
• Contamination Level Calculation: This level of
classification is determined not by particle size but
by the total number of particles in a defined
contamination class (classes are defined for most
international standards).
• Cleanliness Code Definition: Some standards
reduce the representation of measured data to a
brief description. This Cleanliness Code is defined
by the standard and is composed of particle size
classes and contamination levels.
• Maximum Approval Check: Checking for a
maximum approval value is an optional step. If a
maximum value is required, it is specified in the
inspection configuration and may be an absolute
number of particles or a maximum Cleanliness
Code.
• Separation of Reflective and Non-Reflective
Particles: The distinction between metallic and
non-metallic particles is made by determining
whether particles reflect light or not (extremely
important as metallic particles stand to cause much
greater harm than non-metallic particles).
• Fiber Identification: Fibbers detected on the
membrane filter often have a different origin (i.e.,
work clothes or rags) than the other particles found
on the filter. Fibers thus need to be recognized and
analysed or disregarded depending on the standard
being used for assessing the cleanliness
examination.
• Results Review: The following operations are
possible as part of this review: the deletion of items
incorrectly identified as particles; the splitting of
particles located close together and incorrectly
identified as a single large particle; the merging of
particle segments located close together and
incorrectly identified as separate particles; the
correction of incorrect particle labels (i.e., metallic
vs. non-metallic).
• Report Creation: A technical cleanliness inspection
report may include the description of certain particle
acquisition parameters, particle classification tables,
particle area coverage details, and images of the
largest particles.
6. Data Presentation and Reporting
There are major differences in the way that data is reported
in the various standards, thus:
• ISO16232 reports interval counts (differential counts).
• ISO18413 reports cumulative counts.
All three ISO standards abbreviate the particle count data
into component cleanliness coding systems as described
below. These systems are based on a geometric power
series with a constant to describe the range in number from
very clean to very dirty in a convenient way. Note that the
numbers of particles quoted are rounded up or down to two
significant figures. Also, the codes can only be compared if
the particle count data is presented in exactly the same way.
7. Conclusions and Recommendations
These standards are used for auditing the cleanliness of
components before their assembly into a system. The
cleanliness level of components shall be managed by the
specification established by two parties who are the supplier
and end-user.
• The following are recommended to ensure efficacy
of the cleanliness evaluation process:
• When implementing a cleanliness audit of
components, the contaminant extraction method
should be reviewed to ensure their efficacy and
compliance to ISO16232.
• Blank tests should be performed on all equipment
used for extracting and analysing particles from
components to verify or to validate the cleanliness
of the equipment and environment.
• If the blank level exceeds 10% of the measured or
presumed component value, it is necessary to
either investigate the cleanliness of the various
procedures or if it is acceptable, to increase the
number of test components analysed in order to
collect more particles and thus fulfil the 10% limit
• The extraction method should be selected for the
geometry component and be validated. The
pressure of test liquid should be adjusted to obtain
a jet of sufficient power to remove and transport the
particles from the controlled surface without
degrading or dissolving the surface material of the
component. The selection of the nozzle is equally
important and may have to be changed to suit the
location e.g. a needle- shaped jet is used for
drillings and narrow passages and a fan-shaped
nozzle is used for flat surfaces.
8. Reference
[1] ISO16232, Road Vehicles - Cleanliness of
components of fluid circuits.
[2] ISO18413, Hydraulic Fluid Power - Cleanliness of
parts and components - Inspection document and
principles related to contaminant collection analysis
[3] ISO4405, Hydraulic Fluid Power - Fluid
Contamination - Determination of particulate contamination
by the counting method using an optical microscope.
[4] ISO11500: 2008, Hydraulic Fluid Power -
Determination of the particulate contamination level of a
liquid sample by automatic particle counting using the light-
extinction principle.
9.Contact
For more information
Please contact-Suraj Jathar.
Phone Number :9595205868.