Classified, Hazardous Area Protection Components And Functions - Ametek IPS-4 Essential Health & Safety Requirements

Classified, Hazardous Area Protection Components and Functions

The Division 1/Zone 1 versions of the IPS-4 are designed to be, and comply with requirements
for, electrical equipment in Division 1 and 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, disconnect assembly and enclosure designs assure
that the system will not ignite surrounding gases. For this reason, any repairs must not bypass
these safety considerations and must use only recommended components.
The purge system consists of the electronics enclosure, a purge controller, an overpressure vent,
a bypass switch and power/signal disconnect assembly. It maintains a positive pressure in the
electronics enclosure that prevents flammable and corrosive gases from contacting electrical
components. The oven enclosure and the seals between the enclosures are designed to assure
that the required 5x factor of safety to assure that the sample containment system will not inter-
fere with proper operation of the purge system.
The disconnect assembly receives a pneumatic signal from the purge controller when the enclo-
sure has been adequately purged and the overpressure is maintained. Until these conditions are
met, the relays in the disconnect assembly break all power and signal connections between the
field and the analyzer. When the electronics enclosure is opened or the pressurization gas sup-
ply is lost, the system will shut the analyzer down and transfer a set of contacts that may be used
to provide an alarm.
The bypass switch enables operation of the analyzer by applying air pressure to the disconnect
assembly - bypassing the purge controller. This feature must only be used when the area is
known to be safe and is being continuously monitored (See Combustible Gas Detection protec-
tion techniques in NFPA70 article 500 and 505). Figure 1 is a state diagram showing the opera-
tion of the pressurization system and the pressure settings.
The analyzer must be installed and operated in accordance with this instruction manual. Instru-
ment air or nitrogen may be used as the purge gas.
Once the analyzer has been located in an area contaminated with flammable gases or vapors
!
the IPS-4 purge system must be activated to keep these gasses out of the enclosure. For this
reason, AC power and an instrument air supply must be connected to the IPS-4. See "System
CAUTION
Start- Up" for instructions on how to initialize the purge system. If it is not required that the
IPS-4 be powered on at this time, switching the power off at the power source will shut down
the analyzer while maintaining the protective internal pressure. Switching the power on again
will re-activate the IPS-4 if the purge controller is still in the normal pressurization mode.
!
For the protection system to operate properly, the cover on the disconnect enclosure must be
properly installed and the electronics and oven enclosure doors must be securely shut. All door
CAUTION
latches must be properly tightened with the key.
Essential Health & Safety Requirements | 11