286 AO2000 CONTINUOUS GAS ANALYZERS | OI/AO2000-EN REV. B
Fidas24 NMHC: Converter effectiveness testing
Converter service life
The catalyst is a consumable material. Its service life depends on the con-
centration of the converted hydrocarbons. Catalyst poisons (e.g. SO
2
, HCl,
H
2
S, halogenated hydrocarbons, heavy metals) will shorten the converter
service life. Their respective concentration should always be < 20 mg/m
3
.
Effectiveness test
The effectiveness test verifies the degree of converter activity by measuring
the passage of methane (methane loss) and ethane (ethane slip).
The effectiveness test does not need to be performed in normal operation.
We recommend performing an effectiveness test once a year.
Test gases for effectiveness testing
Components Methane in air and ethane in air (separate test gas con-
tainers), connection via bypass
Inlet pressure p
e
= 1000 ± 100 hPa
Flow rate 130 to 250 l/h
Calibration prior to effectiveness testing
Before the effectiveness test the zero and span points of the sample com-
ponents CH
4
and THC must be calibrated.
Perform effectiveness testing
Determine methane loss
1 Connect test gas methane.
2 Press key Conv. Test. Test gas flows through the converter.
3 Write down THC (converter) reading.
4 Press key THC. Test gas flows through the bypass.
5 Write down THC (bypass) reading.
6 Determine the methane loss according to the following formula:
reading Bypass
100 reading) Converter -reading (Bypass
% / loss Methane
×
=
Methane loss is typically approx. 5 to 15 %.
7 Connect sample gas and press key AUTO to return to measuring mode.
Determine ethane slip
1 Connect test gas ethane.
2 Press key Conv. Test. Test gas flows through the converter.
3 Write down THC (converter) reading.
4 Press key THC. Test gas flows through the bypass.
5 Write down THC (bypass) reading.
6 Determine the ethane slip according to the following formula:
reading Bypass
100 reading Converter
% / slip Ethane
×
=
Replace converter if ethane slip exceeds 2 %.
7 Connect sample gas and press key AUTO to return to measuring mode.
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