Rockwell Automation 1797-IRT8 FLEX Ex Thermocouple/RTD/mV Input Module User Manual - Manual (Page 56)

Publication 1797-6.5.2 - February 2001
6-2 Applying FLEX Ex Thermocouple/RTD/mV Input Modules
Define the Area
Classification Before you can determine what components will make up your FLEX
Ex system, you must define the area in which that system will operate.
You must determine the following:
•
classification method
•
hazard
•
temperature rating
Decide Classification Method
Your application location will usually decide whether the classification
method is Zone or Class/Division, but the system designer may make
this determination. FLEX Ex is presently certified for Zone
method only.
Determine Hazard
Hazard–typically gas, dust, or fibers–is determined by the material
being processed. For example, a coal mine will generally be rated for
dust and methane gas hazards. FLEX Ex is presently certified for
gas hazard method only.
Determine Temperature Rating
The spontaneous ignition temperature of the hazardous in your
application determines the temperature rating. For example, an
application with a hydrogen hazard uses a temperature rating of T1
because hydrogen’s ignition temperature is 450°C. FLEX Ex is
presently certified as a T4 system.