Sampling - Wohler DTEST Notice D'utilisation

Dust surface density / level of cleanliness in air ducts and air-guiding surfaces
4.1.2

Sampling

Generally, the sample has to be taken at repre-
sentatives points of the air-guiding surfaces. Take
the sample as follows:
To achieve a meaningful determination of the dust
surface density we recommended a three-fold
determination in accordance with VDI 6022 1.3.
Please note that samples should be taken from
the duct floor at the beginning of the ductwork;
however, this should be at a distance of at least
five times the hydraulic diameter to fitted compo-
nents and obstructions to flow. Alternatively, it is
acceptable to take four samples and calculate the
arithmetic average of the measurement results.
Take samples in the middle of the ductwork width
or as close as possible to the middle if it is not
accessible. The following information is provided
for determining the level of cleanliness to DIN EN
15780:2012: A representative number of samples
from representative parts of and positions in the
ventilation system are required. Take samples in
areas where dust accumulations are obvious.
Before taking samples, choose appropriate points
to take samples on a random basis with the aid of
design and layout documentation.
The sampling points chosen should be in the main
air ducts of the ductwork beginning at the central
VAC handling unit, main ducts, riser ducts and
branch ducts. The points where samples are tak-
en should be in straight sections of ductwork as
well in ductwork with changes in direction and at
joints.
For further details please refer to currently valid
VDI 6022 and DIN EN 15780 standards. We rec-
ommend you determine together with the client, or
at least discuss with the client, the points where
samples are to be taken.
NOTE!
Choosing the right sampling points has a far
greater effect on the accuracy of the measur-
ing process than the method of measurement.
As a consequence, VDI 6022 1.3 2015 requires
personnel who carry out measurements re-
ceive training in accordance with VDI guide-
line 6022 Part 4, Category A.
EN
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