M&C PMA Series Instruction Manual page 39

Safety handbook according to SIL
Contemplated devices
It was contemplated the PMA 50 EX with part no. 05A1000(a) and the following options:
-
Enclosure ventilation and enclosure purging (part no. 05A9005 and 05A9000),
-
Measuring cell solvant resistant or with glass solder (part no. 90A0009 u. 90A0006)
Excluded are the PMA 50 EX/P/PD... with pressure compensation, part no. 05A2500(a) as well as the options
0-20 mA outlet, part no. 05A2505(a) resp. zero suppression, part no. 05A9015.
Device description and safety function
The safety function of the device is the measurement of the oxygen concentration in the measuring cell
which is provided as linear current signal 4-20 mA. The status relay as transmission of a summary fault indi-
cation is element of the safety function. Current signals <3.2 mA and > 20.5 mA as well as an open status
contact have to be evaluated as failure from a downstream device.
The SIL-qualification is valid for all adjustable measuring ranges. It applies for alarm of rising oxygen concen-
tration (dangerous fault: oxygen signal is to small) as well as for alarm of decreasing oxygen concentration
(dangerous fault: oxygen signal is too big).
For one channel and two channel operation of the oxygen analyzer PMA 50 EX the following parameters have been
determined.
Safety function
Dangerous error
Measuring range
Device type
Proof test interval
MTTR
SFF
HFT
SIL–ability

factor
PFD

du

dd

su

sd
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Single channel
Redundant 1oo2
0B
1oo1
Mesurement of the oxygen
concentration
Oxygen signal too low
Depending on the measuring task
B
(but without μP and software)
1 year
24 hr
91,3 %
0
2
—
-4
3.83 × 10
-8
8.44 × 10 (per hr)
-7
4.62 × 10 (per hr)
-7
4.25 × 10 (per hr)
-11
5.70 × 10 (per hr)
Single channel 1oo1
1B
Mesurement of the oxygen
Depending on the measuring task
(but without μP and software)
1
3
5 %
-5
1.93 × 10 1.66 × 10
PMA 50 EX | 1.01.04
Redundant 1oo2
concentration
Oxygen signal too big
B
1 year
24 hr
96,4 %
0 1
3
2
— 5 %
-4
8.34 × 10
-8
3.52 × 10 (per hr)
-7
4.62 × 10 (per hr)
-7
4.74 × 10 (per hr)
-11
5.70 × 10 (per hr)
-6
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