Palas VKL 10 User manual

PALAS GmbH
Partikel- und Lasermesstechnik
Greschbachstrasse 3b
76229 Karlsruhe
Phone [phone]
Fax [phone]
[email protected]
www.palas.de
Operation Manual
Dilution System
VKL 10 and VKL 100

OPERATION MANUAL VKL 10 /100
VERSION V005-06-2020
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Content
Important Note !!!................................................................................................................................... 4
1. Delivery................................................................................................................................................ 5
1.1. Delivery Check......................................................................................................................... 5
2. Safety conditions / Intended use .................................................................................................... 6
2.1. General safty conditions.......................................................................................................... 6
2.2. Intended use............................................................................................................................ 6
2.3. Responsibility of the operator................................................................................................. 6
3. Initial Operation .............................................................................................................................. 7
3.1 Initial operation and short instruction .......................................................................................... 7
4. Operating Principle.............................................................................................................................. 8
4.1. General Information..................................................................................................................... 8
4.2. The Inlet System and the Mixing Chamber .................................................................................. 9
4.3. The Dilution Factor..................................................................................................................... 10
4.4. The Outlet Nozzle and Isokinetic Conditions ............................................................................. 10
5. Equipment Layout ............................................................................................................................. 11
5.1. The Pneumatic System............................................................................................................... 11
5.2. Components and their Function................................................................................................. 12
5.3. The Calibration Certificate.......................................................................................................... 14
6. Operation .......................................................................................................................................... 15
6.1. Installation.................................................................................................................................. 15
6.1.1. Installation as Single Unit.................................................................................................... 15
6.1.2. Cascading of Two or More Units ......................................................................................... 16
6.2. Selecting Appropriate Outlet Nozzles ........................................................................................ 18
6.3. Setting of Pre-pressure............................................................................................................... 19
6.4. Impact of Pressure and Temperature ........................................................................................ 20
6.4.1. Pressure Impact................................................................................................................... 20
6.4.2. Temperature Impact............................................................................................................ 20
7. Cleaning............................................................................................................................................. 21
7.1 General Information.................................................................................................................... 21
7.1.1 Cleaning of the Inlet Nozzle.................................................................................................. 21
7.1.2. Cleaning of the Outlet Nozzle .............................................................................................. 21
7.1.3. Cleaning of the Mixing Chamber......................................................................................... 22
7.2. Filter Control and Filter Change ................................................................................................. 23

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7.2.1. Filter Control........................................................................................................................ 23
7.2.2 Filter Change......................................................................................................................... 23
8. Maintenance ..................................................................................................................................... 24
9. Troubleshooting ................................................................................................................................ 27
10. Problems –what to do if the dilution system of the series VKL does not work correctly:............. 28
10.1 Pollution of the dilution system ............................................................................................ 28
10.2 FAQs ...................................................................................................................................... 28
10.3 General.................................................................................................................................. 28
11. Technical Data ................................................................................................................................. 29
12. Spare parts list / accessories list...................................................................................................... 30
13 Transport, packaging and storage............................................................................................. 30
13.1 Packaging:.................................................................................................................................. 30
13.2 Storage: ..................................................................................................................................... 30
13.3 Transport:.................................................................................................................................. 30
14. Disposal of the VKL dilution systems............................................................................................... 31
15. Literature......................................................................................................................................... 31
16. Feedback form................................................................................................................................. 32

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Important Note !!!
It is important to read the operating instructions thoroughly before operating the dilution
system !
The manufacturer will not be liable for damages caused by incorrect handling, operating or
cleaning.
Please observe the following points:

Operation of equipment should only take place in dry rooms, under ambient
atmospheric pressure, and at room temperature. If operation under different
conditions becomes necessary, you should contact the manufacturer prior to starting
operation.

The manufacturer will not be liable for defects resulting from improper operation,
if operation takes place under different environmental conditions, such as corrosive
or explosive environment, strong electric or electromagnetic fields, within areas of
ionizing radiation, within areas prone to shock or vibration.

If the dilution system is used with humid and sticky aerosols it needs to be
checked for dirt more frequently (especially for plugging of the inlet nozzle).

Do not suck in any aerosols that react aggressively to brass, to anodized aluminum,
or to stainless steel.

Only use original spare parts.
Attention: Aerosols might be dangerous to your health. That’s why they ought not to be
inhaled. It might also be necessary to wear protective clothes. Please pay attention to the
correspondent standards and safety rules.

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1. Delivery
1.1. Delivery Check
Please verify immediately after unpacking of equipment, if delivery is complete. Besides the
dilution stage itself, the following items must be part of the delivery:
1 suction nozzle
4 transport covers (yellow plastic parts, installed at the equipment)
1 box spanner, size 14 mm (nut)
1 tube connector for the excess aerosol outlet (black plastic part).
Fig.: 1.1 VKL 10

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2. Safety conditions / Intended use
2.1. General safty conditions
•For safety reasons, under no circumstances may the machine be commissioned if there is
visible damage.
In this event, please contact Palas® (Tel.: [phone]).
•The dilution system has been set by the manufacturer to be used with a maximum pre-
pressure of Pmax 8 bar for the compressed air supply. Please make sure that the
maximum pre-pressure of Pmax 8 bar specified on the type plate agrees with the
provided compressed air line where the machine is to be used.
•Only use original spare parts! Please contact the manufacturer whenever necessary.
•Please only use dry, particle- and oil-free compressed air supply.
2.2. Intended use
•The dilution system of the series VKL was designed to dilute a high concentrated aerosol
by the ejector principle with dry, oil- and particle free compressed air.
•The manufacturer is not responsible for any damage, which arease due to incorrect
operation, cleaning, error in operation or the measurement of aerosols which gas
conditions or compound the instrument is not specified for.
•The machine may only be operated in dry rooms, under atmospheric ambient pressure
and at room temperature.
Operating under other ambient conditions such as in corrosive or explosive
environments, in strong electric or electromagnetic fields, in areas with ionising radiation
as well as in areas subject to impact and vibration is not covered by any functional
guarantee by the manufacturer
2.3. Responsibility of the operator
•The device was designed and built in consideration of the standards to be adhered to. It
therefore represents state-of-the-art technology and allows a high degree of safety in
operation.
•Please only operate the dilution systems of the VKL series after reading carefully the
manual.
•Shall be operated by trained personal only.
•Be sure that the machine shall not be used by unauthorised personnel.
•Caution: Depending on the type, aerosols can pose a health hazard. They should
therefore not be inhaled. When working with or when around hazardous materials, care
must also be taken to wear appropriate protective clothing (respirator mask). Please
follow all applicable guidelines and accident prevention regulations.

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3. Initial Operation
3.1 Initial operation and short instruction
remove all four transport covers; keep them and re-install them after experiment is done.
position dilution system inbetween dust or aerosol take-out and measuring instrument
connect inlet nozzle to sampling probe
connect measuring instrument to outlet nozzle
make sure that excess air is drawn away.
No counterpressure may be produced at the excess air outlet.
toggle switch in position "off"
connect compressed air supply (4 - 8 bar) (fast coupling NG 8)
turn pre-pressure control counterclockwise first, until it arrests (lift locking ring)
switch on dilution stage
set desired pre-pressure by turning pre-pressure control clockwise
start measuring instrument and procedure
WARNING
Escaping aerosols can be toxic and pose a health hazard.
Residual air flows out of the device via the exhaust air outlet.
If hazardous aerosols are used and the exhaust air outlet is open,
these aerosols can get into the environment and harm persons.
►If hazardous aerosols are used: Verify that the exhaust air outlet is
connected to a suitable filter or cleaning system via the exhaust air
tube connector.

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4. Operating Principle
4.1. General Information
The purpose of a dilution system is, first of all, to lower the concentration of a given aerosol
while leaving the particle size distribution of the aerosol unchanged. In using the dilution
system VKL, this aim is reached by homogeneously mixing a definite amount of clean air with
a definite amount of aerosol. The ratio of amount of aerosol and clean air is predetermined
and stable. The external clean air flows through an ejector-nozzle system. This causes an
underpressure which sucks in the aerosol. Consequently, the dilution stage is a self-sucking
system.
One single dilution stage VKL 10 has a dilution factor of 10. If a higher dilution factor is
required, several units may be connected in series. Such a cascade connection permits for
example the dilution of 2 liters of aerosol with only 72 liters of clean air by a factor of
10,000.
The dilution factor of the VKL 100 depends on the volume flow rate of particle-free air and
varies between 150 and 90. A dilution factor of 100 is achieved in one unit with the same
clean air consumption compared to two VKL 10.
However, the application range of the VKL 100 is limited compared to the one of the
VKL 10:
- highly concentrated dusts with mass concentration > 100 mg/m3and
particle size > 2 µm may block the capillary tube
- liquid particles with a diameter > 1 µm may break up due to shear forces in the flow
- the dilution factor depends on the clean air flow

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4.2. The Inlet System and the Mixing Chamber
The details given in the following chapter only apply to VKL 10!
Figure 4.1. shows a cross-section of the dilution stage. Particle-free air with a volume flow
rate Vrdetermined by the pre-pressure P, flows through an annular slit around the inlet
nozzle. The resulting under-pressure dP0causes the aerosol which is to be diluted, to be
sucked in and to be mixed homogeneously with clean air in the mixing chamber. If the clean
air flow rate is increased, the flow speed within the annular nozzle increases
correspondingly. This causes according to Bernoulli (s. below) the under-pressure dP0at the
inlet nozzle to increase, and the flow rate Van increases, too. Both flow rates are connected
through the underpressure, and equally depend on it. Consequently, the ratio of the flow
rates remains constant for different pre-pressures, P.
Bernoulli formula:
dP = 1/2 * rho * v²
dP: pressure drop at a nozzle (here: under-pressure)
rho: gas density
v: gas velocity through the nozzle
excess airoutlet excessair
tubeconnector
outlet nozzle
dP 0
mixingchamber
annularnozzle
inlet nozzle
Vin Vout
Vrcompressed air
with pre-pressure P
Fig. 4.1.: Cross section of dilution stage

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4.3. The Dilution Factor
The dilution factor W describes the ratio between the total volume flow rate Vges and the
inlet volume flow rate Van:
W = Vges / Van
with:
Vges = Vr+ Van
(Vr: clean air flow rate)
The enclosed publication describes this equation in more detail. It demonstrates in theory
and practice that the dilution ratio remains constant, independently of the pre-pressure,
within a large range. The equations 1 - 4 and diagram 4 describe the correlations.
4.4. The Outlet Nozzle and Isokinetic Conditions
Since most particle measuring instruments have a sampling flow rate that is lower than the
flow rate of the diluted aerosol, a portion Vab of this flow has to be taken out of the mixing
chamber for the measurement. This is done via the outlet nozzle. When taking a portion of
the flow you must see to it that isokinetic conditions prevail. Isokinetic conditions are given,
if, at the suction location, the flow velocity inside the nozzle corresponds to the velocity
inside the flow channel. Different nozzle diameters permit the adaptation of different outlet
flow rates to different total flow rates. Following the isokinetic sampling of a part of the
flow, the remaining air flows to the outside via the excess air outlet. For aerosols, for
example, which constitute a danger to health, the excess air has to be led away via a tube. It
is absolutely necessary not to produce any counter-pressure during this process, because an
increase of the pressure POinside the mixing chamber would influence the inlet flow rate
and thus the dilution ratio. See also equations 5 - 6 and diagram 5 of the publication.

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5. Equipment Layout
5.1. The Pneumatic System
Figure 5.1. shows the pneumatic system. Pre-cleaned compressed air is conducted via a
toggle switch to a pressure reduction valve. Via a permanently adjusted throttle and the pre-
pressure indicated at the pressure gauge, the volume flow rate may be adjusted
reproducibly. A filter guarantees sufficiently particle-free air. This particle-free air flows
through the annular nozzle and causes the sucking-in of the aerosol to be diluted. Via the
outlet nozzle, a portion of the diluted aerosol is isokinetically sucked out for further
treatment. The excess aerosol is conducted outside through the excess air outlet.
throttle filter
pressurized air
toggle switchreduction valvepressure gauge
excess air outletmixing chamber
inlet nozzle
excess air tube connector
outlet nozzle
Fig. 5.1: Pneumatic control panel

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5.2. Components and their Function
The figure on the next page shows a dilution system partially disassembled. One can see the
compressed air connection, marked Pmax 8 bar. Below, the toggle switch "On-Off" can be
seen. To the right, the adjustment knob for the pressure control, and right above, the
pressure gauge for indication of the adjusted pre-pressure is located. To the right of the
pressure gauge, the intake opening for the clean air filter can be recognized.
The above-mentioned components, as well as the throttle screw integrated into the cover,
serve the reproducible adjustment and the processing of the clean air which is used for the
dilution of the aerosol.
The inlet nozzle, through which the aerosol to be diluted is sucked in, can be seen on the left
of the picture; the outlet nozzle to which for example the particle measuring instrument is
connected, is shown on the right. Finally, the excess air outlet and the excess air tube
connector can be seen; tubes of 28 mm inner diameter can be connected.

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5.3. The Calibration Certificate
For manufacturing reasons it is not possible to exactly trim the dilution factor to its
theoretical value of 10. Therefore, every single stage is calibrated and the data values are
recorded in a calibration certificate.
You will find the calibration certificate for the delivered dilution stage on the appendix of
this manual. Essentially, it consists of a table and a diagram.
The inlet flow rate Van, the clean air flow rate Vr, and the dilution factor W as a function of
the pre-pressure P, are recorded in the table. The diagram shows the dilution factor (circles)
and the inlet flow rate (dots) as a function of the pre-pressure. The left ordinate gives the
dilution factor while the right ordinate gives the inlet flow rate. As already mentioned in
section 4.1. the dilution system is a self-sucking system. In using table and diagram, the
sample flow rate can now be adjusted to the desired value via the pre-pressure.
Important!
The pre-pressure not only determines the inlet flow rate, but influences also the isokinetic
conditions when sampling the outlet flow out of the mixing chamber. See also point 4.2.
"Selecting appropriate Outlet Nozzles" of this manual.

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6. Operation
6.1. Installation
When installing the dilution system, various tubes need to be connected to transport the
aerosol. In order to minimize the transportation loss, these tubes should be as short and
straight as possible. When diluting aerosols with a particle size bigger than 5 µm or 10 µm,
vertical operation of the dilution stages is recommended to minimize sedimentation loss.
6.1.1. Installation as Single Unit
Figure 6.1. shows the installation of a single dilution stage, showing the coupling of an
optical particle counter (OPC) to an aerosol duct.
The dilution stage must be sturdily placed inbetween the OPC and the aerosol duct. If
necessary, the M5 winding at the bottom side can be used for fixing. Via tube the inlet
nozzle of the VKL is connected to the sampling probe at the duct. In the same manner,
the inlet nozzle of the OPC is connected to the outlet nozzle of the VKL. The excess air is
disposed of (if necessary) by pushing a tube of 28 mm inner diameter onto the excess air
tube connector and then inserting it into the excess air outlet of the VKL. The compressed air
supply is connected to the dilution stage by means of a fast coupling device. After turning on
the VKL with the toggle switch, the pre-pressure is set to the desired value via the pressure
gauge. (see point 6.3).
Now, the measuring instrument can be turned on, and the measurement can be started.
After the measurements are done, it is advisable to turn off the OPC first, and then the VKL.
In case of prolonged non-use, it is recommended to put the four yellow covers on for dust
protection.

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6.1.2. Cascading of Two or More Units
Figure 6.2. shows the the installation of three dilution systems as a cascade. For cascading of
the systems, the outlet nozzles of two out of the three stages need to be taken out. Then,
the respective inlet nozzles are inserted into the now empty outlet openings and the VKLs
are pressed together until they arrest.
The compressed air is connected via suitable distributor pieces to the 3 VKLs. The excess air
outlets can also be combined. The mounting of the respective connecting pieces is done
exactly as in point 6.1.1. For operation, the same pre-pressure is to be set with all VKLs.
There are two ways how to cascade the dilution systems VKL 10 and VKL 100:
1st version: The VKL 100 is positioned upstream of the VKL 10.
Advantage: By taking the sample from the VKL 100 by the VKL 10 only a small error is
caused due to the non-isokinetic sampling conditions. The flow velocity in the inlet nozzle of
the VKL 10 is too high by only 10 %.
Disadvantage: Due to the very low inlet volume flow rate of the VKL 100 high particle losses
may occur because of diffusion and sedimentation in long tubes.
2nd version: The VKL 10 is positioned upstream of the VKL 100.
Advantage: Negligible losses in inlet tubes.
Disadvandage: The velocity at the inlet of the VKL 100 is too slow by a factor of 10 compared
to isokinetic conditions. For particles < 2 µm the error is however below 5 % due to this fact.

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aerosol duct
excess air
pressurized air
OPC
Fig 6.1 : Installation with dilution factor 10
OPC
e x p r e s s a i r
a e r o s o l d u c t
pressurized air
Fig 6.2 : Installation with dilution factor 1000

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6.2. Selecting Appropriate Outlet Nozzles
A partial flow rate Vab is taken from the total flow rate of the diluted aerosol by means of the
outlet nozzle. The take-out must be done isokinetically. Since the measuring instrument
used determines the partial flow rate, the isokinetic adaptation must ensue from
appropriate measures inside the dilution stage. There are two possibilities for the
adaptation. The modification of the total volume flow is one possibility (this is done by
changing the pre-pressure), or the change of the diameter of the outlet nozzle, as the second
possibility. The total volume flow can be modified within the range of 20 and 50 l/min, with
a stable dilution factor (see calibration certificate in the appendix of this manual).
Consequently, by changing the pre-pressure, we have the possibility, given a certain outlet
nozzle diameter, to adapt isokinetically such partial volume flows that differ up to the factor
of 2.5.
There are various measuring instruments on the market, with volume flows that vary from
0.3 l/min. to 28 l/min. In order to guarantee the isokinetic adaption within this wide range,
outlet nozzles with different diameters are available. The standard jet has a diameter that
guarantees isokinetic conditions when both, outlet and inlet flow rate, are the same, i.e.: the
standard dilution stage is suitable for measuring instruments with a flow rate from 1 to 5
l/min.
For measuring instruments with 28 l/min a bigger nozzle instead of the standard nozzle is
used, for measuring instruments with 0.3 l/min a smaller nozzle is installed. The respective
flow rate of the equipment must be indicated when ordering.
For VKL 100, the same outlet nozzles can be used as for VKL 10. In order to achieve exact
isokinetic conditions, the clean air volume flow rate has to be lower by 10 % than for the VKL
10. When changing the nozzle, the old nozzle is pulled out of the outlet opening, and the
new nozzle is pushed in until it arrests.

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6.3. Setting of Pre-pressure
The pre-pressure is set by turning the knob of the pressure reduction valve and can be seen
on the pressure gauge. With the regulator adjustment completely backed-off the air supply
can be turned on. The adjusting knob can be rotated clockwise to increase the spring load
and the pressure increase observed on the gauge. Minor adjustments after setting changes
can be avoided by always approaching the desired setting from a lower level. When a lower
setting is required, firstly reduce to a lower lever and then increase to the desired setting.
The non rising adjusting knob includes a locking feature; push knob in after setting to lock
and prevent adjustment. To release pull knob out.
IMPORTANT:
In order to avoid overloading of the pressure gauge (zero shifting), the following must be
observed:
If you are not sure whether the pre-pressure control is set to a value smaller than 2.5 bar,
turn the control counterclockwise until it arrests, before starting the VKL. After starting the
VKL, set the desired pre-pressure.
As mentioned under point 6.2, the isokinetic adaptation may be done, within a given range,
by adjusting the prepressure. Figure 6.3 graphically shows the relation between outlet flow
rate and pre-pressure for the delivered outlet nozzles. The outlet flow rate is represented on
the ordinate, and the pre-pressure on the abscissa. To find the correct pre-pressure setting,
proceed as follows:
Take the particle counter flow rate because this is the given, pre-determined outlet flow rate
and find this value on the ordinate.
Starting at this value, draw a line parallel to the abscissa, until the line crosses the curve for
one nozzle. Starting at this point of intersection, draw a line parallel to the ordinate until you
reach the abscissa, and write down the indicated pre-pressure. Install the nozzle belonging
to the cut curve and set to indicated pre-pressure. If the horizontal line does not meet a
curve for a nozzle, order a suitable outlet nozzle with the manufacturer, and indicate the
outlet flow rate.

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6.4. Impact of Pressure and Temperature
The dilution stages are constructed at the plant in such a way that the dilution factors
indicated in the calibration certificate are only reached, if:
- the pressure inside the mixing chamber is equal to the
pressure at the place of sampling,
- these two pressures are about 1013 hPa,
- the temperature of the dilution air is equal to the temperature of the aerosol to be
diluted,
- these two temperatures are about 20 C.
The previously described operating condition is, according to experience, the most frequent.
6.4.1. Pressure Impact
The impact of the pressure at the sampling point is described in detail in the publication (see
figure 1 with pressure P1, equations 5 and 6, figure 5).
Equation 5 demonstrates that, with increasing underpressure dP0, the impact of the
pressure difference (P1 - P0) decreases. Consequently, higher pre-pressures should possibly
be used, if the pressure conditions at the sampling point are unstable (but: remember the
isokinetic conditions).
6.4.2. Temperature Impact
The temperature of a gas influences its density. It follows that with a stable operating
volume flow rate, the mass flow rate of a gas changes with the temperature. In addition,
according to the Bernoulli equation (dP = 1/2 * rho * v²), the inlet flow rate depends directly
on the gas density. Therefore, the gas temperature influences the dilution factor in two
ways. An estimation of this influence under different operating conditions can be given by
the manufacturer upon demand.