3500/04-01-R0 136719-01  Internal Barriers

Each component complies both individually and as part of a system with the safety requirements of North American and
international standards. Hence, you don’t have to reference individual certificates to verify the compatibility between
components.
Standard and internal barrier monitors can reside within the same 3500 rack. You can upgrade standard monitors by
replacing existing I/O modules with those that contain internal barriers.

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

350004-01

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.