Crouse-Hinds series MTL Megablock™ is a DIN-rail mounted passive hub

designed for use in FOUNDATION™ fieldbus H1 and Profibus PA networks.

Megablocks minimize hand wiring and allow individual devices to be added

to and removed from the segment without disrupting network communication.

The SpurGuard™ option provides short circuit protection for the segment.

Hazardous area approvals permit installation in a variety of configurations in

Zone 1 or 2 and Division 1 or 2. Within Zone 2 or Division 2. Megablocks may

be installed as part of non-sparking (non-arcing) or energy-limited

(non-incendive) circuits.

• F2xx-IS models: Intrinsically Safe Megablocks for Zone 1 applications

• F2xx-XE models: Megablocks for Zone/Div 1 applications

• F300 models: Megablocks for Safe Area and Zone/Div 2 applications

CERTIFICATION

MTL7000 Series barriers protect devices located in all normally

occurring explosive atmospheres, including air/flammable gas

mixtures, dusts and fibres.  MTL7000 Series barriers are certified [EEx

ia] IIC (except MTL7129P+, certified IIB) BY BASEEFA to CENELEC

standards, by FM in the USA, CSA in Canada and also by other

authorities, providing worldwide certification. MTL7000 Series

barriers are designed to the same safety descriptions as MTL700

Series equivalents (in some cases slightly stricter) and can therefore be

used for the same applications.

HOW THEY WORK

All MTL7000 Series barriers are based on the same simple principle.

Each channel contains three stages of Zener or forward-connected

diodes and an ‘infallible’ terminating resistor. In the event of an

electrical fault in the safe area, the diodes limit the voltage that can

reach the hazardous area and the resistor limits the current: active

output-current limiting circuits are not used. An internal fuse protects

the diodes, and the three stages of voltage limitation ensure continued

safety if the first or second stage should fail. MTL7100 barriers have

an additional replaceable fuse which protects the internal fuse.

The MTL7000 Series includes seven key barrier types which cover the

majority of applications, simplifying barrier selection and the

maintenance of spares stocks.

Secondary replaceable fuse versions of

many barriers are available and form the

MTL7100 sub-series. These are useful where there is

a possibility of faults occurring during commissioning

which would otherwise blow the barriers’ internal

safety fuses. One secondary replaceable fuse for

each barrier channel is provided and is lower in

value than the related safety fuse. Fuses are

packaged in small mouldings which can be latched

in a ‘disconnect’ position to break the safe and

hazardous areas during commissioning,

maintenance or fault finding, thus avoiding the need

for additional disconnect terminals.

Where a fuse is less likely to be

necessary, the MTL7200 sub-series uses a latching

out link only, to provide the basic loop disconnection

of the MTL7100 sub-series.

SUB-SERIES

MTL7000 Series barrier circuits are based on the well-proven designs

originally developed for the MTL700 Series. To simplify identification

for those familiar with the latter, part numbers are the same for

equivalent barriers, but with a ‘0’, ‘1’ or ‘2’ inserted after the initial

‘7’ to identify the relevant sub-series:

MTL7000 standard

MTL7100 fuse-disconnect

MTL7200 link-disconnect

◆ Exceptionally high packing densities – only 7mm barrier width

◆ 24V dc supply connections simplified – optional power comb

feeds many barriers

◆ Direct connection of cable screens and 0V lines – third terminal

on both hazardous and safe sides

◆ Patent US 5838547

MTL7000 Series award-winning, intrinsic safety shunt-diode

safety barriers are innovative devices designed to provide

exceptionally high packing densities, straightforward

‘single-operation’ installation and simplified

connection, commissioning and maintenance

facilities. Many of the MTL7000 Series features

duplicate the functions of conventional field terminals

and the barriers can, therefore, ‘double up’ as

terminals for many applications, saving even more space.

A barrier width of only 7mm enables

maximum packing densities due to the use of surface

mount and thick-film hybrid circuit technologies

(subjects of patent applications).

Barrier identification is provided by one or both

of two methods. The first consists of tagging strips

mounted on posts located at each end of a row of

barriers while the other consists of separate

identifiers attached to the tops of individual barriers.

Of these, the first can be used to tag locations as well

as barriers and is recommended for large

installations while the second is better suited to

installations of a few barriers only.

An optional power comb simplifies

installations where multiple barriers are powered

from a common 24V dc source (via a power feed

module or a dummy barrier). The comb replaces

individual power supply connections to each barrier,

yet allows single barriers to be removed without

affecting the others. The power feed module powers

up to 40 barriers and incorporates a trip which

switches off the supply to the barriers if a fault (such

as an overvoltage) occurs in the power source

circuit.

Connections to the Megablock are made using pluggable, screw

terminal type connectors. This allows wire terminations to be made to

the individual connectors which are then plugged into the Megablock.

Devices can then be connected and disconnected easily during

commissioning. After commissioning, retaining screws are tightened

to secure each connector to the Megablock.

Trunk connections for the fieldbus home-run/trunk cable are easily

identified by their black connectors. Separate numbered connections

are provided for each spur drop.

SpurGuard™ is a device-port, short circuit protection technique

that minimizes susceptibility to single points of failure. The FCS-MBx

SG Megablocks range has built-in SpurGuard™ protectors that prevent

a short circuit in any of the individual transmitters or spur cable runs,

from bringing down the entire fieldbus segment. A red LED near each

spur connection indicates when a spur is shorted and hence in “over

current” mode.

FCS-MBx-SG Megablock range*

Passive hubs for general purpose, Zone 2 & Division 2 fieldbus networks

Megablocks are DIN-rail mounted passive hubs for Foundation™

fieldbus networks. They connect several field devices to the network

trunk cable and provide short circuit protection to the segment.

Megablocks minimize hand wiring and allow individual devices to be

added to and removed from the segment without disrupting network

communication.

A green power LED on each unit indicates whether at least 9V dc is

present. Megablocks are available in four, eight, ten and twelve drop

versions. Multiple Megablocks are easily wired to one another to allow

larger segments to be constructed.

Megablocks are available with an integral terminator making

them ideal for a star or “chickenfoot” topology, where several devices

are connected at a single field junction box. Separate Megablock

Terminators are also available, which may be wired easily to any

Megablock. Megablocks having a built-in terminator are clearly marked

(‘T’) for easy identification by field personnel.

For Zone 1 hazardous area mounting the fieldbus barrier must be

mounted in a suitable, increased safety, (Ex e) enclosure that will

segregate spur and trunk cabling in accordance with hazardous

area requirements. Complete, pre-assembled enclosure systems

are also available -consult Eaton. The barrier module has a separate

compartment, which contains increased safety (Ex e) trunk wiring

terminals where the incoming trunk wiring terminates. This

compartment has a protective cover to deter interference, and

carries a warning to the user not to work on trunk wiring without

first isolating the power. A fieldbus terminator is included; this

can be disabled where the fieldbus trunk is extended to a second

Fieldbus Barrier Module.

A single barrier module provides 12 spur connections. Each spur is

short circuit protected, so that other devices continue to operate in

the presence of field wiring faults.

Surge protection can also be added on the spur connections by the

use of individual Spur Surge protection modules (part no. FS32).

Surge protection of the fieldbus trunk connection can be provided

using protector type TP32-I-NDI; consult Eaton MTL for pre

engineered enclosure systems containing appropriate electrical

and mechanical hardware.

The 9377-FB3-Px fieldbus barrier module is bus-powered and

requires no additional power supply in the field. When used with a

fieldbus host control system, power for the trunk must be provided

only by a supply conforming to IEC 61158-2. e.g. MTL F800 or MTL

918x-x2 range of redundant power supplies.

The module has four mounting lugs with holes, enabling it to be

mounted to a suitable mounting plate inside an enclosure using

either bolts or fixed studs. Alternatively, it has built-in mounting

clips to permit it to be mounted onto ‘top-hat’ DIN rail, 35mm x

7.5mm, complying with EN60715 or similar local standards.

• For Foundation™ fieldbus networks inhazardous areas

• Mount in Zone 1 (gas) with spurs connected into Zone 0

• Easy mounting via DIN-rail or panel fixing

• Compatible with FISCO and Entity-certified fieldbus instruments

• Compact, modular construction

• Optional, integrated surge protection for trunk and spurs

The 9377-FB3-Px Fieldbus Barrier module is a further enhancement

of the established 937x product range, and provides a compact

and economic solution for Foundation fieldbus networks in

hazardous area applications. The field-mounted barrier receives

power and FOUNDATIONTM fieldbus H1 communications via

a non-intrinsically safe trunk and converts this to a number of

galvanically isolated, intrinsically safe, spur connections.

The trunk terminals are implemented as increased safety (Ex e)

and the spur terminals as intrinsically safe (Ex ia) for connection

to IS fieldbus instruments in IIC, Zone 0 hazardous areas.  The spur

connections are compatible with both FISCO and Entity-certified

field instruments.

Unlike conventional Fieldbus Barrier products that are

based on stand-alone modules, the 937x-FB2-PC-PP range

are supplied as a complete, factory-assembled systems in a

glass reinforced plastic (GRP) enclosures that does not require

additional wiring, customised housing or complex ancillary

components. Electrical and mechanical aspects of the design

are integrated, providing the industry’s first complete,

ergonomic solution for ‘High Energy Trunk’ applications in

hazardous areas.

The key modular components of the system (Fieldbus

Barriers and Surge Protectors) may be ‘hot-plugged’ by

design and without gas-clearance procedures or separate

isolating switches. This virtually eliminates the risk

associated with hazardous area maintenance activities,

speeds module replacement and avoids the need for

specialist operator training.

Optional features include pluggable surge protection

components for the fieldbus trunk and individual spurs.

Connection facilities with generous room for cable

management are provided within the Fieldbus Barrier

enclosure for the trunk and spur wiring. Where appropriate,

the trunk wiring may be extended from one Fieldbus Barrier

enclosure to another.

Enclosure systems for 6 or 12 spurs are supported. For

added flexibility, the 12-spur enclosure can be specified part

populated with one 6-spur barrier module installed (model no.

9374-FB2-PC-PP-001). This permits future expansion from six

to twelve spurs simply by plugging in an additional module.

The 937x-FB2-PC-PP range of Fieldbus Barriers are bus

powered and requires no additional power supply in the field.

When used with a fieldbus host control system, power for the

trunk may be provided by MTL F800 or 9180 range of fieldbus

power supplies in redundant or non-redundant format.

• For FOUNDATION™ fieldbus networks in hazardous areas

• Complete enclosure system for 6 or 12 intrinsically safe spur connections

• Mount in Zone 1 (gas) or 21 (dust) with spurs connected into Zone 0

• Compatible with FISCO and Entity certified fieldbus instruments

• Compact, modular construction

• Ergonomic mechanical design

• Pluggable system components, without ‘gas free’ constraints

• Optional, integrated surge protection for trunk and spurs

The 937x-FB2-Px-PP range of Fieldbus Barriers are field

mounted wiring hubs that create up to twelve intrinsically safe

spur connections from a high-energy trunk, for connection

to suitably certified FOUNDATION™ fieldbus H1 instruments.

Capable of supporting heavily loaded fieldbus segments

and long trunk cable lengths, the Fieldbus Barriers may be

installed in Zone 1 (gas) or Zone 21 (dust) hazardous areas,

with the trunk wiring implemented using suitably protected

cable and increased safety (Ex e) connection facilities.

Each intrinsically safe spur is capable of supporting a FISCO

or ‘Entity’ certified fieldbus device located in a Zone 0 or

1 hazardous area. The short-circuit protected spurs are

galvanically isolated from the trunk and require no protective

ground connection in the field.