Classied, Hazardous Area Protection
Components and Functions
The Zone 1 version of the Model 888 is designed to be, and comply with
requirements for, electrical equipment in Zone 1 classified hazardous
areas. The methods of protection used include type “p” (pressurized),
and type “d” (flameproof enclosure). The purge system, redundant heater
control, and enclosure designs assure that the system will not ignite sur-
rounding gases. For this reason, any repairs must not bypass these safety
considerations and must use only recommended components. The purge
system consists of a regulated supply of instrument air, the electronics
enclosure, purge enclosure and purge exhaust vent.
The purge controller monitors the enclosure pressure and interrupts
mains power in the event pressure is lost. A disconnect assembly within a
flameproof enclosure isolates all external signals should mains power be
disconnected.
After the instrument air (or nitrogen) supply has been connected to the
analyzer and turned on, the system is to be purged for approximately 10
minutes to ensure five (5) full exchanges of air within the purged enclo-
sure. The flow is controlled by the purge controller through an exhaust
vent. Once the controller senses that there have been five air exchanges
within the enclosure, mains power is connected to the electronics.
When the electronics enclosure is opened or the pressurization gas supply
is lost, the purge controller will disconnect mains power which, in turn,
will disconnect all signal wiring. The analyzer should not be used without
purge protection unless the area is known to be safe and is being continu-
ously monitored (See Combustible Gas Detection protection techniques in
NFPA70 article 500 and 505).
The analyzer must be installed and operated in accordance with this in-
struction manual.
Working with the purged enclosure in an open position is typically done
only during installation, start-up (and verification), and certain trouble-
shooting and maintenance procedures. In these cases, appropriate safety
conditions must have been met, per company policy.
To Next Page
Loading...
Need help?
General
