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8009441/YN36/V3-0/2015-08| SICK OPERATING INSTRUCTIONS|GM35
Subject to change without notice
TROUBLESHOOTING AND CLEARING MALFUNCTIONS
9.2 Purge air failure
Failure of the purge air supply demands measures to be taken immediately or within a
short time, depending on the installation conditions, to protect the measuring system. A
purge air failure, however, rarely occurs in practice. It is still however wise to be prepared
for such an occurrence to prevent damage to the measuring system.
Indications of a potential purge air failure
• Error message on systems that are equipped with a pressure difference sensor
• Purge air unit power supply failure
• Increase in the enclosure temperature of the GM35 SR-unit
• Rapid increase in contamination on the optical interface of the SR-unit
• Hose for the purge air supply to the purge air fixture is visibly loose or damaged.
Fig. 75: Possible consequences of a purge air failure
Tools for troubleshooting
• Suitable protective equipment (protective clothing, protective gloves, etc.) that enable
the gas duct to be opened safely and the SR-unit and reflector removed under the given
installation conditions (hot/corrosive/noxious/dusty sample gases, overpressure in the
duct).
• 2 wrenches to remove the SR-unit and reflector and, possibly, other tools required to
restore the power supply.
• Flange cover to seal off the flange opening when the measuring system is removed.
Sample gas penetrating through
the purge air fixtures
Contamination and/or thermal
damage of the reflector
Contamination of the optical
interface, SR-unit overheats
Sample gas escapes if the
purge air supply hose is
damaged or disconnected
Purge air unit possibly overheats or is
damaged by inflowing sample gas.
Sample gas possibly escapes through the
failed purge air unit
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