O
PERATION
M
ANUAL
VKL
10
/100
V
ERSION
V005-06-2020
16
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.