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The internal barriers for a 3500 rack are
incorporated in special Monitor I/O Modules.
These barriers provide explosion protection for
transducer systems that are connected to the
3500 system. An intrinsically safe (IS) earthing
module provides the IS earth connection
through the 3500 system backplane.
The IS Earth Module requires a dedicated I/O
module position and precludes the use of this
monitor position for other 3500 System
modules. This limits a standard 19-inch rack to
13 monitor positions. Furthermore, a number of
installation options are not available when
internal barriers are installed in a 3500 rack.
New Rack Installations
The same rack can contain both internal
barrier and standard I/O module types without
compromising the separation between
hazardous and safe area field wiring.
The External Termination option is not available
for I/O modules with internal barriers because
hazardous area approvals do not allow the use
of intrinsically safe wiring within a multi-cored
cable assembly.
Monitors that contain Triple Modular Redundant
(TMR) rack options cannot use internal barrier
I/O modules since connecting a transducer to
multiple I/O module inputs will compromise the
integrity of the IS system.
A rack that contains any internal barrier
module must have a 3500/04-01 IS Earthing
Module to provide the Barrier Module IS earth
connection.
I/O Module Positioning
Internal barrier I/O modules have an increased
depth over that of standard barrier I/O
modules. Consider the rack position with
respect to adjacent modules to ensure that you
can easily access the I/O modules during
maintenance.
Internal barrier I/O and IS Earthing modules can
occupy any general-purpose rack position and
can be adjacent to standard I/O module types
without compromising the 50 mm (2 in)
physical separation requirement between safe
and hazardous area field wiring.
Follow these guidelines when positioning I/O
modules:
l Group all internal barrier I/O modules in
adjacent rack positions to simplify the
installation.
l Place the IS Earthing Module in a rack
position that provides easy access for
routine online maintenance.
l Consider the IS Earthing Module's
positioning relative to adjacent internal
barrier I/O modules and cabinet
bulkheads.
If you plan to install standard I/O modules or
the IS Earthing Module between a pair of
internal barrier I/O modules, allow a minimum
of two rack positions so that you can easily
access the standard I/O or IS Earthing Module
online without disturbing the adjacent I/O
modules.