12
d)
semiconductor sensors:
Short-term exposure to gases or vapors of organic solvents, which greatly exceed the maximum
range of the sensor, may damage the sensor and a recalibration or replacement may be required. In case of an atmosphere
with an oxygen content of less than 18 %, the measured value will be undervalued.
e)
photoionization sensors:
the UV lamp or sensor must be replaced regularly, as its clogging of can cause loss of signal.
2.
Operation
To maintain proper operation of the detector it is necessary to respect the fact that the presence of certain concentrations of
gases or vapors, other than those for which the sensor is set, can cause an alarm, even if the concentration of the gas does not
exceed the set level. Given the range of disturbing gases or vapors (diluents, exhaust gases, vapors of organic substances,
disinfectants, etc.) a generally allowable concentration of interfering gases can not be determined. Data on cross-sensitivity to
certain gases are listed at the appropriate sensors. Therefore we recommend to have the air in the deployment area of the
detection system analyzed before processing project documentation.
3.
Operation/Maintenance
In case of contamination, the surface can be cleaned with a slightly moistened cloth.
The sensors have a different lifetime depending on the sensing technology used and on environmental conditions.
Characteristics of the sensors vary over time. Therefore it is required to perform regular checks and calibrations, which can
commence in two ways:
a)
1 x per 6 months
carry out a „
calibration“ and functional control -
adjust the sensitivity of the sensor using calibration
gas and check the functionality of the system. The exact interval depends on the purity of the environment, required
accuracy and the occurrence of disturbing gases in the atmosphere.
b)
1 x per 12 months
carry out a „
calibration“ -
adjust the sensitivity of the sensor using calibration gas and check the
functionality of the system. The exact interval depends on the purity of the environment, required accuracy and the
occurrence of disturbing gases in the atmosphere. Also carry out a
„functional control" 1 x per three months -
checking
the function of the entire detection system using a test gas, which does not exceed the range of the sensor. We
recommend using gas intended for laboratory use.
Perform calibration only at certified service centers with a valid certificate of competence or at the manufacturer.
For the Czech Republic only DEGA CZ s.r.o.
Accessories
1.
Additional bushing DEGA BUSHING for NBx III
PG9
Basic type of detectors
1.
Detectors with a catalytic sensor NBx-CL III LCD
Product code
Detector type
Detected gas
Measurement
range
Measurement of
current loop
(4-20 mA)
Resolution
Calibration gas
20100169
DEGA NBM-CL 100 III LCD
Methane (CH
4
)
Natural gas
CNG
0–100 % LEL
0-20 % LEL
0,1 % LEL
Methane 0,88 %
20100170
DEGA NBP-CL 100 III LCD
Butane (C
4
H
10
)
Propan-Butane
LPG
0–100 % LEL
0-20 % LEL
0,1 % LEL
Butane 0,32 %
20100171
DEGA NBH-CL 100 III LCD
Hydrogen (H
2
)
0–100 % LEL
0-20 % LEL
0,1 % LEL
Hydrogen 0,8 %
20100168
DEGA NBHC-CL 100 III LCD
Other
flammable and
combustible
gases and
vapors
according to
the selectivity
of the sensor
0–100 % LEL
0-20 % LEL
0,1 % LEL
According to the selectivity of the
sensor
