ABB Zone 2 certification by design
Introduction
For a classified Ex zone 1 area, the rationale behind
this “Zone 2 by design” analyzer is that the analyzer
must remain safe when operated in an abnormal
condition. In the event of a fault, the PGC5000
provides continual protection:
• Should a failed component become ignition
capable, the pressurization system prevents the
components from being exposed to flammable
gases or vapors.
• Should a failed pressurization system expose the
internal components to flammable gases or
vapors, the analyzer’s alarm provision will alert the
user of the failure.
Neither of these single faults would present a
hazard to the potentially explosive atmosphere;
therefore, electrical power interlock is not required
for this type of pressurization protection. Enclosure
doors are not required to be interlocked so that the
electrical supply is disconnected automatically
when doors are opened. The requirement is simply
an alarm provision since there are no hazards inside
the enclosure when in normal operation.
The zone 1 certified PGC5000 analyzer offers simple
pressurization protection, commonly referred to as
Ex ‘py’ or “Y-purge”. This enclosure pressurizing
technique is made possible by ensuring that the
internal components within the analyzer are not
capable of causing an ignition in normal operation,
thus allowing for a reduction in classification within
the protected enclosures from zone 1 to zone 2.