Dust-Measurement - Paul Gothe GmbH

Isokinetic rate
If the mean actual isokinetic rate during the sampling at the sampling plane differs for more than –5 % to +15 %, the
measurement is not valid.
If this criterion is not fulfilled due to frequent variation of the flow rate in the duct, see 10.2. 10.5
Deposits of dust on non-weighed parts upstream the filter
Experimental work carried out when preparing this Standard proved that dust deposits upstream of the
filter are often in the range of 10 % to 30 % of the total dust when sampling gases from waste incinerators at
concentration around 5 mg/m 3 .
These deposits depend probably on the design of the sampling equipment, and on the kind of dust to be sampled, but no
efficient means was found to keep them at a negligible level. For this reason all non weighed parts of the sampling
equipment prior to the filter shall be rinsed. The mass of dust on non-weighed parts upstream of the filter shall be
indicated in the test report, besides the mass on the filters used during the same measurement series.
When sampling with in-stack filtration devices with no bends between the nozzle and filter holder on non saturated gases, with
a temperature well above the stack gas dew point, the upstream deposits do not have to be quantified provided that
validation has been carried out at similar conditions as the process to prove that the deposits, expressed in the same
units as the measurement results (e.g. in milligrams per cubic metre) do not exceed 10 % of the daily average limit value
set for the process.
Calculation
See our formula sheet or ask for our excel file.
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