1,7 MB - UAS - United Air Specialists Inc.

United Air Specialists (UAS) push
developments in the range of oil mist
and emulsion separation
Commissioning of ultra-modern test bench
for electrostatic air filters
I N D U S T R I A L A I R M O N I T O R I N G
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United Air Specialists (UAS) push developments in the range of oil mist
and emulsion separation
Commissioning of ultra-modern test bench for electrostatic air filters
1st issue 05-2009
Imprint
Authors:
Carlo Saling, product manager, UAS United Air Specialists Inc.
Gerd Munder, head of production department, UAS United Air Specialists Inc.
Editor:
UAS United Air Specialists Inc., Branch Office Germany
Otto-Hahn-Str. 6 | DE-65520 Bad Camberg
Phone +49 (0) 64 34 / 94 22-0 | Fax -99
www.uas-inc.de
Layout:
IHW Jörn Jacobs & Co.
Otto-Hahn-Str. 15 | DE-65520 Bad Camberg
www.ihw-marketing.eu
Copy, also in extracts, only permitted if consented by the editor.
2

United Air Specialists (UAS) push developments
in the range of oil mist and emulsion separation
Commissioning of ultra-modern test bench for electrostatic
air filters
In Germany, coolants are used [1]
in about 200,000 metal-working
shops in the scope of chipping
and chipless production processes.
They are indispensable in metal
working and processing. On the
other hand, coolants bear health
hazards for the people involved in
the process when handled carelessly.
Coolants (KSS) are deemed liquids
which are used in the production
processes of chipless processing,
cutting and machining of materials.
In the production processes,
they cool the tool, reduce friction
between workpiece and tool and
wear of the tool, and/or remove
chips among others.
The variety of applications results
in many types and different
compositions of the coolants.
Coolants can be classified as
shown in the following figure: The
coolants in their original state are
defined as primary substance; the
secondary substances are developed
unintentionally during use
and/or are added.
[1] VDMA “Cooling lubricants - Fresh air at the
workplace“, trade association “General ventilation“,
team ”Aerosols“
Coolants
Non-water-miscible coolants
(in the past also: cutting oil, grinding oil,
drilling oil)
Water-miscible coolants
e.g. oil-water emulsion
(in the past also: diluted soluble oil,
drilling milk)
Basic materials
Attendant materials
Additives
Reaction products
Foreign matters
Microorganisms
Primary substances
Secondary substances
Coolants
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United Air Specialists (UAS) force development work
Hazards involved with coolants [2]
In addition to the general impurities
at the workplace, vapour,
smoke, and aerosols are formed in
the ambient air of liquid coolants. [2]
This involves the hazard that particles
may affect the operator while
the following mechanisms occur:
Absorption through respiratory
system:
Only a small par t of drops
contained in aerosols with a
diameter of more than 100 µm is
normally inhaled. Whereas particles
with a diameter of less than
5 µm reach the lower respiratory
tracts. Drops with a diameter of
2 to 2.5 µm even penetrate the
alveoli.
Absorption via digestive tract:
Bigger drops deposit in the nose,
windpipe, and bronchial tubes and
can thus also be swallowed
Skin contact:
The natural protective function of
the skin is impaired
As a consequence of the above
described mechanisms, the following
effects on the human body
may occur:
[2] VDMA “Cooling lubricants - Fresh air at the
workplace“, trade association “General ventilation“,
team “Aerosols“
Irritant effects:
Irritation of skin, respiratory tracts,
and mucous membranes, conjunctivitis,
vertigo, stimulation, possibly
euphoria
Allergenic effects:
Toxic-degenerative contact eczema,
allergic contact eczema, rarely
bronchial asthma
Toxic effects:
Alterations of organs, impairment
of nerves by absorption of
substances through skin
Carcinogenic effects:
Formation of different types of
cancer as well as tumours of brain
and respiratory system
Mutagenic effects:
Gene mutation by mist of nonwater-miscible
coolants and nitrosamines
Further health hazards may be
involved by microorganisms which
preferably settle in water-mixed
coolants. These microorganisms
are mainly connected to aerosols
and this is why an efficient separation
of aerosols is compulsory.
Germs and funguses may result
in weakening of the body‘s own
immune system and cause general
diseases.
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Continuous further development and research for
improved separation of coolants – why?
For some years, modern machining
centres and machine tools have
been showing a tendency towards
ever increasing shaft power and
chipping speeds resulting in higher
emissions of pollutants and smaller
particles.
Due to the fact of progressing
development in machining, further
research is also required in the
separation of coolants in order
to ensure work protection under
changing technical framework
conditions also in future.
Seen from this angle, the Company
United Air Specialists Inc. successfully
commissioned an ultramodern
test bench at their site in Bad
Camberg in Germany in spring
2009 in order to boost its research
activities in the range of electrostatic
and mechanic oil mist and
emulsion filters for the separation
of coolants.
Figure 1: Picture of test bench
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United Air Specialists (UAS) force development work
Design of test area
The constructional drawing illustrates the design of the test bench.
7
6
2
3
1
1 Aerosol generator
2 Isokinetic sampling
3 Aerosol spectrometer
5
4
4 Filter (here: two-step electrostatic filter)
5 Fan
6 Control cabinet with frequency converter
7 Flow meter
Figure 2: 3D constructional drawing of test bench
The aerosol generator (type PLG
2300 by Palas), which complies
with the requirements of VDI
directive 3491, produces finest
mist of liquids (coolants) which is
introduced in the air flow of the
test bench. The generator uses
the Laskin principle: One nozzle
atomises a test medium (e.g. coolant
diethylhexyl Sebacat (DEHS)
or dioctylphthalate (DOP)) by
means of compressed air from the
in-house mains.
To be able to produce high
concentrations of aerosol of up to
100 mg/m³ in the test bench, the
primary pressure of compressed
air can be set by means of a needle
valve (1-8 bar ü) and the temperature
of the test medium can be set
in the liquid container inside the
generator (20-80 °C).
The nominal temperature of the
test medium is set to the desired
temperature using a temperature
probe. Furthermore, a sensor
monitors the liquid level in the
container activating a hose pump
to fill the container automatically if
the limit is fallen short of for being
able to perform long-term measurements
of the filter in the test
bench as well.
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Figure 3 shows a typical emission
spectrum of the aerosol generator.
The particle spectrum - measured
with the lubricant DEHS
- is subject to the Gaussian normal
distribution curve; the median of
the number of particles amounts
to 0,3 – 0,4 µm. When commissioning
the plant, it was demonstrated
that the number as well
as the distribution of particles
are constant regarding time and
are reproducible under equal
test conditions. This particle spectrum
corresponds to the results
obtained with modern machine
tools (lathes, milling machines, and
grinding machines) with high shaft
power and thus reflects actual
operating conditions [3] .
[3] “Exhaust and filtration of metal working
fluids emissions on machine tools“ by German
Federation of institutions for statutory accident
insurance and prevention (HVBG), ISBN 3-88383-
714-8, November 2006
The samples are taken from the
piping in an isokinetic way, i.e. a
part of the air flow is soaked up
by a nozzle and conveyed to the
particle sensor at the same speed.
The nozzles are made of stainless
steel and comply with the European
Standard EN 13284-1 [4] .
In addition, samples are taken
using electrically conductive plastic
hoses in order to prevent separation
by electrostatic charge in the
hoses. Furthermore, it was seen
to it that the track where samples
were taken was vertical and short
in order to prevent coarser particles
from depositing or segregating.
[4] VDI directive 2066: “Particulate matter measurement
- Dust measurement in flowing gases
- Gravimetric determination of dust load“, Beuth
Verlag, November 2006
Figure 3: Particle spectrum of aerosol generator (DEHS)
Note: Distribution, absolute number of particles and time constancy
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United Air Specialists (UAS) force development work
Figure 4: Isokinetic nozzles
The sample gas volume is controlled
and monitored by the control
electronics (type welas 3000 by
Palas). The particles are measured
by optical white light aerosol
spectrometers (type welas 3000
by Palas). The particle diameter
is defined using the intensity of
scattered light and the pulses are
counted over a specified period for
the purpose of obtaining a statistic
confidence level of the results.
We obtain a distribution histogram
with high resolution (cf. figure 3)
which illustrates the number of
particles of the samples as a function
of the diameter. This histogram
permits the measurement
of fractional filtration efficiencies
when a sensor is used on both the
crude gas and the clean gas side.
When measuring the particles,
typical sources of error such as
border-zone or coincidence errors
are eliminated thanks to the white
light source, 90° scattered light
detection, and T-stop technology.
White light aerosol spectrometers
measure concentrations of up to
100,000 particles per cm³. As the
filter elements in the test field
can also be subjected to extremely
high pollutant concentrations
Important for sampling:
Isokinetics
Suction from the gas flow in the
pipe is effected at equal speed
(isokinetic). Thus, a precise concentration
can be measured. In case of
suction at higher speed (hyperkinetic)
the measured concentration
would be lower than the actual
concentration due to inertness of
particles. On the other hand, the
measured concentration would
be higher than the actual concentration
in case of suction at lower
speed (hypokinetic).
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of up to 100 mg/m³ which may
be produced by modern machine
tools with high shaft power, the
sample gas on the crude gas side
is to be diluted correspondingly
using a dilution system (type DC
10000 iP by Palas) and a side channel
blower (type SE3 by Elektror).
The dilution factor is considered
automatically in the calculation of
the crude gas concentration. The
error of measurement caused by
the dilution system is < 5 %.
The test bench serves the testing
of filters with electrostatic and
mechanic filter elements. They can
be tested optionally either with or
without pre-filter.
The directly driven fan controls
the volume flow by means of a
frequency converter (type Varispeed
E7 by Omron) and maintains
the desired nominal value
(frequency). The latter is matched
with the actual value through a
Vortex flow meter (type VA40 by
Höntzsch) which is factory-calibrated.
This calibration was checked
using a Prandtl flow pipe (type
ManoAir by Schiltknecht). The
square coefficient of correlation
of the characteristic curve amounts
to R² = 0.999. To provide reliability,
calibration is verified at regular
intervals.
The pressure loss of the filter
elements – in particular essential
for mechanic filter systems –
can be recorded and monitored
by a differential pressure sensor.
A digital meteorological station
(temperature, relative humidity of
air) records the climatic conditions
in the laboratory.
In a next step, the test bench will
be provided with a digital oscilloscope
to effect high-frequency
measurements (current and voltage)
of the ioniser and collector
in the electrostatic separator.
Valuable conclusions can then be
drawn regarding long-term tests of
prototypes. Furthermore, emulsion
measurements are planned. This
requires an insulation/temperature
setting of the test bench.
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Collecting efficiency (%)
United Air Specialists (UAS) force development work
Summary
100
The test bench allows testing and
further development of electrostatic
and mechanic filter cells
according to pertinent directives.
Original cells can be tested
whilst excluding errors of measurement
as a consequence of
down-scaling of test filters.[5]
When designing the test bench it
was taken into consideration that
even extreme pollution loads of
up to 100 mg/m³ can be measured
and fractional filtration efficiencies
in the lower sub-micrometer range
(0.3 to 10 µm) can be determined.
By indicating the total gravimetric
filtration efficiency – as usual in
Figure: Alveolar fraction (A fraction)
Mass fraction of inhaled particles which penetrates the respiratory tracts (alveoli)
practice – the quality of a filter
cannot be evaluated sufficiently
and misinterpretations may result
therefrom.
Thus the test bench also satisfies
the requirements of modern
machine tools regarding pollutant
concentrations and particle spectrums
with which work pieces are
machined at high shaft power [6] .
In particular, aerosols which are
smaller than 1-2 µm and cannot be
seen with the naked eye present
the highest hazards for employees
for these particles penetrate
the alveoli and thus get into the
DIN EN 481
not respirable
50
Tracheo
bronchial
dust
Nose, throat,
larynx dust
alveolar
penetrating the thorax
respirable
10
1
2 5 10 20 50 100
Aerodynamic particle diameter (µm)
Figure 5:
Total efficiency (hazard) as a function of particle diameter [6]
[5] “DIN EN 481 – Directive: Workplaces atmospheres;
size fraction definitions for measurement
of airborne particles“, Beuth Verlag, 1993
[6] “Exhaust and filtration of metal working fluids
emissions on machine tools“ by German Federation
of institutions for statutory accident insurance
and prevention (HVBG), ISBN 3-88383-714-8,
November 2006
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loodstream. A precise size cannot
be indicated for these particles but
only a size distribution.
This range is described in DIN
EN 481 (cf. figure 5). The shown
curve for the A fraction thus illustrates
the probability of a particle
of a certain aerodynamic diameter
depositing in the alveoli [7] . Thanks
to the test bench we are able to
focus on the separation of these
fine and hazardous particles which
cannot be measured with conventional
portable meters.
Last but not least, the test bench
permits the in-house development
of tailored solutions for machine
tool manufacturers in order to
present effective and efficient
filter systems.
[7] “Was ist Staub“, informative page under
http://www.bgglaskeramik.de/d/staub-info/
definition/index.html by BG Glas und Keramik
(German trade association for glass and ceramics)
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United Air Specialists (UAS) force development work
Notes
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Notes
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