Allen-Bradley expands into
process control with FLEX Ex,
the intrinsically safe FLEX I/O
line extension.
Product Profile
Allen-Bradley’s approach to Class I Division 1 or
Zone 1 applications is to eliminate standalone
IS barriers/isolators and separate control and
process by certifying the entire FLEX Ex™ system
as intrinsically safe. In this way FLEX Ex can
be mounted directly on the controlled equipment
in the hazardous area or distributed throughout
the hazardous area at a significant savings to
the end user. The catalog number for FLEX Ex
is 1797.
Highlights
FLEX Ex can be highly distributed throughout the
hazardous area in field-mounted junction boxes
with a single penetration into the hazardous
area.
Differences in Existing Barriers
Distribution of I/O provides numerous benefits
to control system users, both in terms of lower
costs and more effective maintainability.
However, traditional methods of hazardous
environment protection have made it difficult to
distribute control system I/O in potentially
explosive environments.
Intrinsic safety is one of the most universally
accepted methods of protection in hazardous
environments. Intrinsic safety (IS) prevents
sensors, man-machine interface (MMI),
actuators, and other low-voltage instruments
from releasing enough energy into a hazardous
area of volatile gases to cause ignition. The
fundamental principle of this technique is
energy limitation, in which the inherent energy
of an electrical circuit is restricted to such low
levels that any spark occurring does not contain
A single or redundant-media fiber cable
accommodates communication with the control
system. The advantages of this architecture
include:
■ Elimination of wiring from the
control room to the field
mounted junction boxes
■ Elimination of terminal blocks,
barriers, and fuses
■ Faster system commissioning
■ More simple architecture
Adapter FLEXibility
■ Significant reduction in system
Redundant Media Controlnet
costs
COMM
FLEX Ex
Galvanic Insulation between bus, module and power
DC Input
DC Output
Current Input
TC/RTD Output
Counter Input
Current Input
STATUS
Termination FLEXibility
Screw Termination/Spring Clip Termination
30115-MC
sufficient energy to ignite an explosive mixture.
FLEX Ex incorporates this technology. There is
functional galvanic isolation between the I/O
backplane, input circuitry, and power supply.
■
1797-OE8, Eight-point, 13 bit, single-ended,
non-isolated, analog output module
network cable of communicating to 8 I/O
modules for up to 128 I/O points.
Specialty modules:
■ 1797-IJ2, Two-channel high-resolution
frequency input module with magnetic
contact inputs providing accurate shaft
position information
I/O Choices
Digital modules:
■ 1797-IBN16, Sixteen-point digital modules
provide compatibility with NAMUR proximity
sensors, limit switches, contact closures,
push buttons, and other simple apparatus
■ 1797-OB4D, Four-point source output module
is compatible with several solenoid valves,
audible alarms, pilot lights, LEDs, and other
associated apparatus
■
A ControlNet repeater hub provides the user
with a tremendous degree of flexibility which
conventional systems do not offer. The hub
facilitates the mixing of IS and non-IS systems
via a communications link by incorporating an IS
isolator and fiber optics for effective
communication between hazardous and safe
areas. The medium range fiber repeater extends
communications up to 3 kilometers.
1797-IRT8, Eight-point, 16 bit, single-ended,
non-isolated, 4-wire RTD, thermocouple and
millivolt input module can connect
thermocouples, (2-, 3-, 4-wire) RTDs, strain
gauge bridges, and potentiometers
In the hazardous area, coax cable is used to
connect between multiple ControlNet nodes,
reducing the number of penetrations into the
hazardous area and reducing the requirements
for cable trays and explosion proof piping.
Networking Choices
The diagnostic capabilities and determinism of
the ControlNet™ network make it an ideal choice
for hazardous area applications.
Analog modules:
■ 1797-IE8, Eight-point, 16 bit, single-ended,
non-isolated, analog input module captures
signals from differential pressure and
temperature transmitters, level detectors,
flow meters, and other associated apparatus,
designed to interface to positioners current
to pneumatic converters and control valves
A special bus isolator (1797-CEC & BIC) allows
configuration of FLEX Ex and FLEX I/O modules,
all attached to the same adapter and grouped
A redundant media ControlNet Ex™
communications adapter features a high speed,
intrinsically safe, control level communications
Hazar
1794 = FLEX I/O
ACNR
IF4I
OF4I
IV16
OV16
OB8EP
1786-RPA 1786-RPFM
REPEATER ADAPTER
1786-RPA
TB3
ControlNet
Communication Choices
ADN
IE8
TB3
TB3S
TB3S
Analog I/O Choices
IT8
IR8
IE4XOE2
TB3
FIBER MODULE
1786-RPFM
Fiber
Hub
OE4
OE8
OR 1797-CEC
TB3
DeviceNet
ASB/C
IA8
TBN
TB3T
TB3T
TB3S
Discrete I/O Choices
OA8
IB10X0B6 OB16
TBNF
Remote I/O
TB3
TB2
TB3
OR
OR
IE8
1797-BIC
OW8
IT8
TBN
Termination Choices
IB16
1203 FM1
Smart
Motor
Controller
ASB/2
TB3S
1203 FB1
Strain-Gau
Bridges
together on appropriate sides of the bus isolator
so as to configure combination IS and non-IS
systems. This provides for a cost-effective
means to intermix non-IS and IS equipment and
allows for connection to 1794 FLEX I/O adapters.
This scenario is common in many IS
applications.
Termination Choices
Two types of terminal bases are available:
■ 1797-TB3, Terminal base with screw clamps
■ 1797-TB3S, Terminal base with spring clamps
Applications
Some industrial applications of explosion
protection/prevention include:
Infrastructure
Infrastructure may be divided into utilities and
wastewater.
Petrochemicals
Petrochemical applications include
offshore platforms, pipelines, tank farms
and refineries.
Semiconductor /Electronics
■ Applications include doping stations,
chemical dispensing, and gas handling.
■
Fine Chemicals and Pharmaceuticals
■ Solvent-based paint manufacturing includes
several hazardous areas. FLEX Ex may be
applied to mixing/blending, filling containers,
and palletizing.
■ Paint-spray booth manufacturers require
intrinsic safety on I/O points located in
the paint zone.
■ Manufacturing munitions, cosmetics, and
solvent-based inks require intrinsically
safe I/O points.
Pulp and Paper
■ Pulp and paper applications include
bleaching, digestion, and make-up
water/liquor recovery.
■
rdous Area
uge
Food & Beverage
Food & Beverage applications deal primarily
with alcohol manufacturing and grain mills.
Applications include raw material handling,
grain feeders and elevators, brewing,
distillation, and bottling.
■
1797 = FLEX Ex
Zone 1 or
Class I, Div. 1
1797-RPA 1797-RPFM
Up to 3 km
1797-RPFM
FIBER MODULE
MEDIUM RANGE
ACNR15
1797-RPA
COMM MODULE
STATUS STATUS
REPEATER
ADAPTER
PWR
Fiber
Hub
COMM
IE8
IRT8
OE8
IBN16
STATUS
TB3S
ControlNet Ex
Explosion Proof Enclosure
• Motors
• Drives
• Smart Motor
Controllers
Standard 1794 FLEX I/O
OB16
1797-BIC
1794-ADN
TB3 1797-CEC
IJ2
IBN16
OB4D
OB4D
TB3
Zone 0
RTDs
Thermocouples Transmitter
I/P Converters
Position Controllers
Magnetic
Pickup
Flow
Pickup
Sensors/
Proximity switch
Pushbuttons,
Limit Switches
Solenoid Valves/
Audible Alarms
Pilot Light
LED Clusters
30116-MC
Power Supply Choices
A number of field power supplies are available:
Catalog Number
1797-PS1N
1797-PS1E
1797-PS2N
1797-PS2E
Description
85-264V ac In Quad-Ex dc Out Power Supply-Conduit Pipe Thread
85-264V ac In Quad-Ex dc Out Power Supply-Increased Safety
24V dc In Quad-Ex dc Out Power Supply-Conduit Pipe Thread
24V dc In Quad-Ex dc Out Power Supply-Increased Safety
Today's Control Panel/Marshalling Cabinet
Conduit to Junction Box in Hazardous Area
To Controllers
Terminal
Blocks
Rack Based I/O
Terminal Blocks
Intrinsic Safety
Barriers
Junction Box
I/O Systems web page:
www.ab.com/io_systems
Copyright 1999 Rockwell International Corporation
FLEX Ex is a trademark of Rockwell Automation
ControlNet is a trademark of ControlNet International, Ltd.
ControlNet Ex is a trademark of ControlNet International. Ltd.
Tomorrow's FLEX Ex in Class I Division 1 Location
To Controllers
COMM
FLEX Ex
Intrinsically Safe I/O
STATUS
Junction Box
30114-M
Publication 1797-PP001C-EN-P — February 2001
Supersedes Publication 1797-1.1 — May 1999
Copyright 2001 Rockwell International Corporation