User manual

Publication 1797-6.5.1 - April 1999
6-2 Applying FLEX Ex Analog I/O 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 certified for Zone method only. Certification
is pending for Division method.
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 certified for gas hazard only.
Certification is pending for attaching wiring to FLEX Ex I/O modules from
a dust and fiber hazardous area.
Determine Temperature Rating
The spontaneous ignition temperature of the hazard in your application
determines the temperature rating. For example, an application with a
hydrogen hazard may use equipment with a temperature rating of T1
because hydrogen’s ignition temperature is 550°C. FLEX Ex is certified as
a T4 system.
Select Protection Method(s)
Although the FLEX Ex system primarily uses the Intrinsic Safety protection
method, the system uses all methods listed below.
Table 6.A
Protection Methods for Hazardous Applications
Protection Method
Designation
1
Method of Achieving
Protection
Intrinsic Safety EEx
ia
/EEx
ib
Energy Limiting
Encapsulation EEx
m
Segregation
Increased Safety EEx
e
Refined Mechanical Design
Flameproof EEx
d
Containment
1 In the Non-Incendive protection method, n: used locally in the United States and United Kingdom.
In the Intrinsic Safety method, ia: Zone 0, 1, 2 & ib: Zone 1, 2