Foxboro DCS Compact FBM241/c/d, Redundant, Discrete I/O Modules

Foxboro  DCS Compact FBM241/c/d, Redundant, Discrete I/O

Modules

The Compact FBM241. FBM241c, and FBM241deach have eight discrete inputs and

eight discrete outputs available as a single or redundant module. A redundant pair of

the modules combine to provide redundancy at the FBM level with field I/O wired to

one commontermination assembly.

The Compact Channel Isolated, Discrete I/O Interface Modules (Compact FBM241/c/

d) have eight discrete input channels and eight discrete output channels. Associated

termination assemblies (TAs) support discrete input or output signals at voltages of

under 60 VDC, 120 VAC/125 VDC, or 240 VAC.

Depending on the type of I/O signal required, the TAs contain current limiting devices,

fuses, relays, or relay outputs with internal or external power source and fusing.

The module is available in three distinct types and each type with its associated TA

supports the following discrete inputs and outputs:

Each type of Fieldbus Module (FBM), without signal conditioning, uses a 15 to 60

VDCinput or output signal. Each discrete input and output is galvanically isolated

from other channels and ground. When used with external excitation, each discrete

input and output is group isolated.

The module performs signal conversion required to interface electrical input signals

from field sensors to the optionally redundant fieldbus. It executes the Discrete I/O or

Ladder Logic program, with the following configurable options: Input Filter Time, Fail

Safe Configuration, Fail-Safe Fall-Back, and Sustained or Momentary Outputs. If the

Momentary Output configuration is selected, then Pulse Output Interval is also

configurable

Features

• 8discrete inputs

• 8discrete outputs

• Single or Redundant Module

• Supports discrete inputs/output signals at voltages of:

◦ 15to60VDC

◦ 120VAC/125VDC

◦ 240VAC

• Eachinput and output is galvanically isolated: group isolated when used with

external excitation

• Compact,rugged design suitable for enclosure in Class G3 (harsh) environments

• Executes the Discrete I/O or Ladder Logic program, with the following

configurable options: Input Filter Time, Fail Safe Configuration, Fail-Safe Fall

Back, and Sustained or Momentary Outputs

• Various Termination Assemblies (TAs) that contain:

◦ Current limiting devices

◦ Fuses

◦ Relayoutputs

◦ Relayoutputs with internal or external power source and fusing

◦ Solid state outputs

Redundant Outputs

Aredundant contact output function block, COUTR, is used for each redundant pair of

outputs. The COUTR block handles output writes and initialization logic for the

redundant channels. On each write of the COUTR block, identical output writes are

sent to both modules, fully exercising the Fieldbus and the logic circuitry of each

module. You can select a sustained output that follows the block input or a pulsed

output with a selectable pulse width.

Whenafailure is detected in the modules, its output is marked as BAD and the

corresponding channel in the good module automatically continues to drive the

discrete outputs. Each output channel drives an externally powered load. Power for

each Compact FBM241 module is diode OR’d together in the redundant adapter to

help assure redundant power. The microprocessor of each module executes the

digital output application program, plus diagnostic routines that validate the health of

the FBM.

Compact Design

The Compact FBM241’s design is narrower than the standard 200 Series FBMs. It

has a rugged Acrylonitrile Butadiene Styrene (ABS) exterior for physical protection of

the circuits. Enclosures specially designed for mounting the FBMs provide various

levels of environmental protection, up to harsh environments, per ISA Standard

S71.04

Visual Indicators

Light-emitting diodes (LEDs) incorporated into the front of the module provide visual

indication of the Fieldbus Module operational status, as well as the discrete states of

the individual input and output points.

Easy Removal/Replacement

The module mounts on a Compact 200 Series baseplate. Two screws on the FBM

help secure the module to the baseplate.

The module can be removed or replaced without removing field device termination

cabling, power, or communication cabling.

Redundant modules must be located in adjacent positions on the baseplate, with the

first module located in an odd-numbered position (for example, the positions labelled

3 and 4). To achieve redundancy, a redundant adapter module is placed on the two

adjacent baseplate termination cable connectors to provide termination for a single

cable. A single termination cable connects from the redundant adapter to the

associated termination assembly (TA).

Whenredundant, either module can be replaced without upsetting field input signals

to the good module. Each module can be removed or replaced without removing field

termination cabling, power, or communications cabling

Fieldbus Communication

AFieldbus Communications Module or a Control Processor interfaces to the

redundant 2 Mbps module Fieldbus used by the FBMs. The Compact FBM241/c/d

accepts communication from either path (A or B) of the redundant 2 Mbps Fieldbus. If

one path is unsuccessful or is switched at the system level, the module continues

communication over the active path.

Modular Baseplate Mounting

The modules mount on a DIN rail mounted modular baseplate, which accommodates

up to 16 compact FBMs. The baseplate is either DIN rail mounted or rack mounted,

and includes signal connectors for redundant fieldbus, redundant independent DC

power, and termination cables.

Security

Field power for contacts or solid state switches is current limited.

Termination Assemblies

Field I/O signals connect to the FBM subsystem via DIN rail mounted TAs. The TAs

used with the Compact FBM241/c/d are described in Termination Assemblies And

Cables, page 14.

The redundant adapter connects the redundant FBM’s baseplate connectors together.

The redundant adapter provides a single termination connection to a single TA.

Termination Assemblies and Cables

Field I/O signals connect to the FBM subsystem via DIN rail mounted termination

assemblies (TAs). Multiple types of TAs are available with FBMs to provide I/O signal

connections, signal conditioning, optical isolation from signal surges, external power

connections, and/or fusing for protection of the FBM and/or field device as required by

the particular FBM. Since these features are built into the termination assemblies

(where required), in most applications there is no need for additional termination

equipment for field circuit functions such as circuit protection or signal conditioning

(including fusing and power distribution).

The DIN rail mounted termination assemblies connect to the Compact FBM baseplate

by means of removable termination cables. The cables are available in a variety of

lengths, up to 30 meters (98 feet), allowing the termination assemblies to be mounted

as needed by plant design. See Functional Specifications- Termination Assemblies,

page 16 for termination cable part numbers and specifications.

Discrete Inputs

Termination assemblies with discrete inputs support eight 2-wire discrete input signals

at passive low voltage levels of less than 60 VDC and active high voltage levels of

125 VDC, 120 VAC, or 240 VAC. Active termination assemblies support input signal

conditioning for FBMs. To condition signals, these termination assemblies can provide

optical isolation, current limiting, noise reduction, voltage attenuation, or optional

terminal blocks to connect externally supplied excitation voltage.

LowVoltage Discrete Inputs

The low voltage inputs (less than 60 VDC) use passive termination assemblies. Inputs

can either be voltage monitor, switched or contact sense types. Voltage monitor inputs

require an external field voltage source. Contact sense input use the FBM auxiliary

+24 VDCpowersupply to wet field contacts.

Aload may not be required for proper operation of the input channels. A diode may be

required for a DC inductive load only.

High Voltage Discrete Inputs

The high voltage input circuits support 125 VDC, 120 VAC, or 240 VAC. Inputs can be

either voltage monitor or switched types. Voltage monitor inputs require a field voltage

source. Switch inputs use customer supplied excitation voltage applied to dedicated

terminals on the termination assembly and distributed on the termination assembly to

each of the input channels.

These circuits are located on daughter boards that are mounted under the component

covers of the termination assemblies

Discrete Outputs

Termination assemblies with discrete outputs support eight 2-wire discrete output

signals at passive low voltages of less than 60 VDC and active high voltage levels of

120 VACor240VAC.Active termination assemblies support output signal

conditioning for FBMs. To condition signals, these termination assemblies provide

fuse protection, relays, solid-state devices, and terminal blocks to connect externally

supplied optional power distribution.

LowVoltage Discrete Outputs

The low voltage outputs (less than 60 VDC) use passive termination assemblies.

These assemblies are available with and without output protection (fusing).

Termination assemblies with protection have individual user serviceable fuses that are

designed to limit the output current to 2 A. Eight vertically mounted, one per channel,

3.15 A sand filled fuses (temperature derated) allow a maximum of 2 A current per

output channel. Termination assemblies without fusing (unprotected) are intended for

use by Foxboro engineers or customers who are using interposing relays or fuse

terminal blocks between the termination assembly and the field devices.

Power for the low voltage outputs can be supplied by the FBM +24 VDC auxiliary

power supply (internally (FBM) sourced) or by a field voltage