18 User Manual QuickTOC
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purity
ATEX 2 04E3920
2 Operating Principle of the Analyser
2.2 Explosion Protection LAR | PROCESS ANALYSERS AG
2.2 Explosion Protection
The Instruction Manual at hand describes the use of the analyser in areas with high risks of explosions.
According to DIN EN 60079-14 the pressurisation type „pz“ defines devices for ATEX zone 2. The pres-
surization according to ATEX zone 2 prevents potentially explosive atmospheres from entering the ana-
lyser. Thanks to the pressurization, the atmosphere rating in the analyser is downgraded from
„dangerous“ to „inert“.
The analyser has been built in accordance with the European Safety Guidelines for Explosion Protection
for ATEX Zone 2. Please see the relevant certifications in Chapter Certificates from page 1.
ATEX Zone 2 defines the explosive atmosphere as follows:
„During normal operation it is unlikely that a potentially explosive atmosphere may arise (mix of air and
inflammable gas, vapour or mist), or, if it arises, then only seldom and for very short periods of time.“
During operation of the analyser the casing is overpressurised, thus preventing potentially explosive at-
mosphere from getting inside the casing.
The overpressure is regulated by a control unit and a magnetic valve. At startup, the control unit finitiates
a flushing procedure to remove all potentially explosive atmosphere from inside the analyser. During the
flushing procedure at 7 to 10 mbar, the casing is simultaneously checked for pressurisation.
After the flushing procedure, the overpressure in the casing is reduced and maintained at 2 to 3 mbar.
The flushing procedure is ensured by a separate compressed air supply. All dead spots in the casing
(ceramic furnace, pump engines and the transformer) are being reached by the flushing air. The pump
engines and the transformer are equipped with aeration holes. The furnace is flushed through a separate
conduct.
From the flushing air conduct, a separate conduct is diverted for the carrier gas. The carrier gas flows
through filter cartridges with activated carbon and natron lime. The processed carrier gas then enters the
casing of the analyser.
In case of automatic shutdown due to loss of pressure or power outage, an emergency flushing proce-
dure is initiated. The emergency flushing cools hot surfaces (especially in the area around and on the
furnace) within a predetermined time. The backup air for the furnace emergency cooling must come from
a separate source.
Temperature classes
Devices and utilities may be operated in explosive atmospheres only if their surface temperature is below
the ignition point of the potentially explosive air mix. The air mix is subdivided in temperature classes
from T1 to T6. For the determination of the temperature classes the maximum operating temperature
has to be taken into account.
Depending on the temperature class, the ventilator must ensure cooling down within 45 mins. to the ma-
ximum temperature for the selected temperature class:
• for temperature class T3 max. 200° C
• for temperature class T4 max. 135° C
Depending on the temperature class, your analyser is equipped with an accordingly suitable ventilator
for cooling.
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