1
INM 7700 Rev 12
MTL7700 range
Shunt-diode safety barriers
Figure 1:
MTL7700 range of shunt-diode safety barriers
1 OVERVIEW
This instruction manual contains all information needed to install,
maintain, fault-find and test MTL7700 range of shunt-diode safety
barriers.
Section 3 includes a checklist of essential safety factors that
must be considered when using MTL7700 range of barriers as
intrinsically safe (IS) interfaces between safe and hazardous areas.
Read section 3 before beginning installation. Users within the
European Community should also refer to the website for multiple
language safety instructions.
It is assumed that all necessary system design, specification
and engineering factors have been taken into account BEFORE
installation work begins. To assist pre-planning, the following
publications covering the theory, design, application, specifications
and certification of shunt-diode safety barriers are available:
AN9003
Application Note: A user’s guide to
intrinsic safety
AN9007
Application Note:
A user’s guide to
MTL700 range of shunt-diode safety
barriers
IS catalogue
The IS catalogue includes detailed
specifications of all MTL7700 range of
barriers and accessories
IS certificates
Copies of Baseefa, FM and CSA IS
apparatus and system certificates for
MTL7700 range of barriers
If not supplied with the product, these publications are available
either from our website (www.mtl-inst.com) or on request from
your local office.
2 DESCRIPTION
2 .1 Introduction
MTL7700 range of ‘fourth-generation’ intrinsically safe shunt-diode
safety barriers are innovative successors to the MTL700 range.
MTL7700 range of barriers are 1-, 2- or 3-channel devices that
use intrinsically safe explosion-protection techniques to pass
electrical signals between safe and hazardous areas, whilst
limiting transferred energy to a level that cannot ignite flammable
atmospheres.
Connected in series with wiring entering any hazardous area on
process plant, MTL7700 range of barriers prevent explosions in all
normally occurring explosive atmospheres – including mixtures of
air with flammable gases, vapours, dusts and fibres – if a fault or
faults develop in the safe area.
2 .2
MTL7700 range – barrier ranges
The range is based on a choice of models which, between
them, cover virtually all applications – including the protection of
installations incorporating uncertified devices known as ‘simple
apparatus’ (eg, switches, thermocouples, resistive sensors,
photocells and LEDs) or separately certified ‘energy-storing’ or
‘voltage-producing apparatus’ (eg, ac sensors, proximity detectors,
transmitters and current-to pneumatic (I/P) converters. Being
intrinsically safe, shunt-diode barriers enable maintenance work or
calibration to be carried out ‘live’ without additional precautions. To
simplify selection, several ‘key’ barriers (see table 1) are highlighted
as meeting the majority of process control requirements.
