Specifications

Publication 1794-SG002D-EN-P - May 2012
About the FLEX Ex I/O Systems 75
Entity-Based Architecture
Entity parameters provide a system of quantifying and matching safe levels for
voltage, current, inductance, and capacitance when connecting intrinsically safe
field devices and system devices together.
Configuration of the FLEX Ex system is based on the entity parameter method.
Using entity parameters allows high system flexibility in matching field and
system devices. This provides maximum utility to the IS system designer and
installer. For more information, refer to the FLEX Ex System Certification
Reference Manual, publication 1797-RM001
.
Hazardous Area
Designation
A hazardous area is designated as any location in which a combustible material is
or may be present in the atmosphere in sufficient concentration to produce an
ignitable mixture.
The North American method identifies these areas by Class, Division, and Group
while the IEC (CENELEC) designates these areas by Zone and Gas Group.
Recently, North America has adopted the Zone method of identifying hazardous
locations as an option to the Division method.
Class Designation
Class identifies the type of hazardous atmosphere.
Division/Zone Designations
Division/Zone identifies the likelihood of a hazardous atmosphere being present.
Gas/Dust Groups
Hazardous locations are grouped according to their ignition properties.
Class I Gas or vapor
Class II Dust
Class III Fiber or flying (no group designation)
Division Method
(North America)
IEC Standard Zone Method
Ignitable mixture present continuously
(long periods)
Division 1 Zone 0 (Zone 20 - Dust)
Ignitable mixture present intermittently Zone 1 (Zone 21 - Dust)
Ignitable mixture is not normally present Division 2 Zone 2 (Zone 22 - Dust)