Oldham olct ir, Техническое руководство

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7
–
Special instructions for use in
ATEX explosive atmospheres
21
Voltage at detector terminals = 30 VDC max, 16 VDC min.
Max power = 5.8 Watts
- Replacing screws:
If you need to replace a screw from the “Ex d” flameproof housing, use an A4.70 or a screw of higher quality.
- Dusty atmospheres:
When using the equipment in dust explosive atmospheres, the equipment should be thoroughly cleaned on a
regular basis to prevent dust buildup. The dust layer shall be less than 5 mm thick. The joints between the
housing and the sensor part or between the housing and the terminal block cover will be coated with paraffinic
grease.
- Transfer curve and power supply parameters
The following curve shows the OLCT IR current output value depending on the gas concentration, special
maintenance and fault states. In the event the user connects the transmitter to a non-OLDHAM controller, the
user must ensure that the OLTC IR transfer curve is compatible with the controller input characteristics in
order to read properly the signal from the transmitter.
In addition, the controller should provide a power supply of 16 to 32 VDC at detector terminals, with
intermittent peaks at 500 mA.
7.2 Functional Safety
The detector OLCTIR (CH4 and HC versions) has been certified by INERIS as SIL 2 capable according to EN 50402
(Certificate INERIS 03ATEX0141X/02). This standard applies since 2005 and defines the requirements on the
functional safety of fixed gas systems (electrical apparatus for the detection and measurement of combustible or toxic
gases or vapours or of oxygen).
The detector OLCT IR was designed in conformity with IEC 61508 standard.
The safety function of the OLCT IR is to detect combustible gases with infrared absorption technology and to deliver a
4-20mA current output proportionally to the gas concentration as a percentage of the LEL, respectively from 0 to 100%
LEL. In fault mode, the output will be less than or equal to 1 mA or greater than or equal to 23mA.
Maintenance Interval Test
λ
DU
PFD
avg
SFF DC SIL capability
1 year 3.5 10
-7
1.6 10
-3
90% 72.3% 2
λ
DU :
Failure Rate per hour (dangerous undetected)
PFD
avg :
Probability of Failure on Demand
SFF: Safety Failure Fraction
DC: Diagnostic Coverage (fraction between dangerous failures rate and total failures rate).
0
%
100
%
20,0
mA
4,0
mA
2.4
mA
Concentration
En % LIE
Sortie Courant en mA
Défaut
23,2
mA
Défaut
1.2
mA
Mode
Maintenance
120
%
-10 %
Hors
gamme
Défaut
2.0
mA
Concentration
in % LEL
Output Current in
mA
Fault
Fault
Fault
Out of
range
Maintenance
mode