MSA PRIMAX IR Mode D'emploi page 6

Possible structures and acquirable SILs
The following table shows which structure has to be selected to fulfill the requirements of a
specific SIL.
LDM = Low Demand Mode
HDM = High Demand or Continuous Mode
LDM
Structure 1oo1
Structure 1oo2
Depending on the selected configuration and the sensor version, the following safety-
relevant parameters have to be considered while implementing the safety loop:
General conditions for safe use:
- The application advice and the limitations of the manual have to be considered.
For calibration and maintenance, the regional and national regulations have to be
considered.
- A defective device has to be repaired within 72 hours.
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- The HART interface cannot be used for the transmission of safety related data.
- The connected controller has to monitor the 4-20 mA signal current for values below
4 mA and above 20 mA.
- A functional check/calibration check has to be done for the complete system.
- A visual check has to be done together with the calibration.
- A system check has to be done every year.
- Calibration and adjustment are part of the function/calibration check.
- The test gas must be the gas to be monitored. The concentration of the test gas has to
be in the middle of the measurement range.
- For zero gas, clean air free of hydrocarbon combustible gas or synthetic air has to be
used.
- An adjustment has to be done under the following conditions:

difference at zero > +/- 5 % LEL

difference at sensitivity > +/- 20 % of the rated value
- If the calibration is inside of the valid tolerance, the calibration interval can be doubled.
- The maximum of the calibration interval is 52 weeks.
- The gas monitor has to be replaced if the sensor sensitivity during the operation is
reduced to less than 50% of the initial sensitivity.
Special conditions for SIL 2
- The use of the device in a High Demand or Continuous Mode is allowed only in a
1oo2 - structure.
- The 4-20 mA output of the device must be monitored regarding deviations.
Special conditions for SIL 3
- The use of the device is allowed only in a 1oo2 - structure.
- The 4-20 mA output of the device must be monitored regarding deviations.
SIL 1
HDM LDM
X X X
X X X
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SIL 2 SIL 3
HDM LDM
X X
SIL SAFETY MANUAL
HDM
X