Siemens ULTRAMAT 23 Product Information page 13

Protection and purging function of H
Hydrogen sulfide (H S) is a corrosive gas, especially in wet condition and in combination with other gases. A protection and
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purging function has been implemented since H
functionality and service life of the H
for the 50 vpm probe, enabling a discontinuous measurement above its permissible continuous concentration.
Probe protection function
Definition of protection function of the two probes
A value 1.1 times the specified range can be considered as the maximum continuous concentration. Although a
measurement above such a concentration is still correct, the probe is damaged by longer exposure (several hours). The
maximum continuous concentration remains constant even when changing the large measuring range.
The function test is set during execution of the protection function in order to signal that the displayed value is incorrect. The
protection function is also implemented with the 50 vpm probe for compatibility reasons even though its maximum
continuous concentration is below its largest measuring range. Execution is the same as with the 5 000 vpm probe.
How the protection function works
The protection function is triggered if the continuous measured value of H
concentration (110 % of full scale) in measuring mode for a period equal to the sample gas purge time.
The following occurs when the protection function starts:
● The H S measured value display is set to "*****"
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● A "H" (H S protection function running) is displayed in the measurement screen at the right edge where the test letter "!"
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appears (fault no longer pending logged).
● The zero gas value is opened
● The "Function test" status is set.
As long as the protection function is active, the zero gas valve remains open during the zero gas purge time. The device
then switches to the sample gas path. This process is repeated if the maximum continuous concentration is exceeded within
the sample gas purge time.
if the maximum continuous concentration is not exceeded again, the protection state is ended and the H
is displayed again, the function test and the test letter "H" are deleted.
This process is repeated up to 6 times. If the sample gas concentration is too high after the 6th occurrence, the zero gas
valve remains continually open and the fault message 28 (measured value channel 3 beyond tolerances).
Return to measuring mode
An active protection function can be interrupted as follows:
● A value is reached below the maximum continuous concentration during the purge time prior to completion of the 6th
cycle
● Set the protection function to 'OFF' by changing the parameter in the limit display or via ELAN
● Start a different state such as calibrate, AUTOCAL, etc.
● Acknowledge fault 28 (measured value of channel 3 outside tolerance) in the logbook
Note
The analyzer continues to measure the gas concentration during execution of the sensor protection function. You can
read via ELAN (k3, k19) or PROFIBUS whether the analyzer is being processed, and in which step.
Supplement 1 for Operating Instructions C79000-G52xx-C216-03
A5E02769382-03, 03/2012
S probes (display in the operating screen: 'Protection Probe H2S')
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S concentrations above the specified continuous concentration impair the
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S probes (50 vpm and 5 000 vpm). A purging function has additionally been integrated
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S is greater than the maximum continuous
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S measured value
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