Category: Industry Trends

DESCRIPTION

The Ex ic concept

In May 2013 the Ex nL certification method was removed from the IEC60079-15

standard, and replaced by intrinsic safety method Ex ic in IEC60079-11.  Although Ex

ic and Ex nL are broadly similar, Ex ic brings with it additional requirements that are

associated with the wider intrinsic safety approach.

Ex ic is a new level of protection under the intrinsic safety protection method,

suitable for use in Zone 2 only, where Ex ic circuits may be ‘live-worked’ in the

presence of a flammable atmosphere.  It follows the same energy-limitation principles

as all intrinsically safe circuits, but safety is maintained only in ‘normal operation’.

Host H1 control system

In a typical network installation using the F30 Ex ic Adaptor, F300 Megablock and

9192-FP power supply module, the H1 interface of the host control system is

electrically connected in parallel with the fieldbus trunk circuit. The H1 interface

and host control system are not required to carry hazardous area certification in

this application, but they must comply with electrical safety standards IEC61010 or

IEC60950.  Apparatus carrying a CE mark will comply with this requirement. This

requirement also applies to any other apparatus that is connected electrically in

parallel with the fieldbus trunk circuit.

OVERVIEW

This manual explains the installation and maintenance procedures for the F30 Ex ic

Adaptor and should be read in conjunction with the product datasheet that contains

the electrical data.

The F30 Ex ic Adaptor is an accessory that works with MTL F300 range of DIN-rail

mounted, passive device couplers and extends their usage by enabling them to

provide Ex ic spur connections in Zone 2 hazardous areas. The F300 device couplers

provide a simple means of connecting a group of local field devices to the network

trunk cable that carries the signal and provides the necessary power supply.

This manual also introduces the concept of the Ex ic intrinsic safety method of

protection and explains how it applies to the F300 device couplers and the F30 Ex ic

adaptor.  Other topics will include the trunk power supply and suggested enclosures

for housing the adaptor and hubs in the hazardous area.

NOTE

The user/installer should also refer to the following datasheets and installation manuals:

• F300 range of Megablocks data sheet, EPS F300

• F300 range of Megablocks installation manual, INM F300

• 918x  Redundant Power Supply data sheets, EPS 918x

• Redundant Power Supply installation manuals, INM 918x in order to obtain

details of their installation, operating parameters and usage.

Overview

Certifications and compliances

• For a complete listing of certification and approvals across our MTL Megablock range,

download the product datasheets in the resources section of this family page.

Design features

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

• Available in two, four, eight, ten and twelve drop versions

• Multiple Megablocks are easily wired to one another to allow larger segments to be

constructed

• Choice of rising cage-clamp screw terminal or spring clamp type connections simplifies

commissioning and maintenance

• Available with built-in SpurGuard™ protectors that prevent a short circuit in any of the

individual transmitters or spur

cable runs from bringing the entire fieldbus segment down

• A red LED near each spur connection indicates that a spur is shorted and is in

“over-current” mode

Standard materials

• Housing:  Polycarbonate

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.