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MTL7706
Operating Manual
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Dwyer Instruments MTL7706 Operating Manual

Instruction Manual
INM7700
MTL7700 Series Shunt-diode safety barriers
ii
INM7700-6 Jan 2010
1 OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.2 MTL7700 Series – barrier ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.3 MTL7700 Series – accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3 SAFETY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1 General requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2 Safety checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4 INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.2 Mounting/removing barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.3 Installing accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5 WIRING CONNECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2 Barrier connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3 Connections to plant earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.4 Connections to dummy barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6 MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.2 Routine inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.2 Power supply check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.3 Barrier resistance test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8 EQUIPMENT AND BARRIER TESTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1 Thermocouple and RTD tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.2 Barrier tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.3 Tests for Active Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.4 Test tables for passive barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
APPENDIX A: TYPICAL WIRING CONNECTIONS FOR SPECIFIC APPLICATIONS. . . . . . . . . . . . . . . . . . . 17
CONTENTS PAGE
© 2010 MTL Instruments Group plc. All rights reserved.
INM7700-6 Jan 2010
iii
INM7700-6 Jan 2010
iv
1
INM7700-6 Jan 2010
MTL7700 Series Shunt-diode safety barriers
INM7700-6
Jan 2010
Figure 1: MTL7700 Series shunt-diode safety barriers
1 OVERVIEW
This instruction manual contains all information needed to install, maintain, fault-find and test MTL7700 Series shunt-diode safety barriers.
Section 3 includes a checklist of essential safety factors that must be considered when using MTL7700 Series 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 supplied MTL publication:
INA7700 MTL7700 Series
Instructions for Safe Use
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 MTL 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 Series shunt-diode safety barriers
MTL IS catalogue The MTL IS catalogue includes detailed
specifications of all MTL7700 Series barriers and accessories
IS certificates Copies of Baseefa, FM and CSA IS
apparatus and system certificates for MTL7700 Series barriers
If not supplied with the product, these publications are available either from the company website (
www.mtl-inst.com
) or on request
from your local MTL office.
2 DESCRIPTION
2.1 Introduction
MTL7700 Series ‘fourth-generation’ intrinsically safe shunt-diode safety barriers are innovative successors to the MTL700 Series.
MTL7700 Series 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 Series 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 Series – 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 ‘voltage­producing 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.
2
INM7700-6 Jan 2010
2.3 MTL7700 Series – accessories
MTL7700 Series barriers mount directly onto DIN-rail. A comprehensive selection of mounting, tagging, power and earthing accessories is available. Installation details are given in section 4.3.
Essential accessories
The following are usually considered essential for mounting and earthing MTL7700 Series barriers:
DIN-rail (eg, THR2 or THR7000) Insulating spacers (eg, ISP7000) Earth terminal (eg, ETL7000)
The tagging systems for individual modules and columns of barriers are described here. They are shown below under Tagging accessories for columns of barriers.
Mounting accessories (figure 2)
THR2 Standard DIN-rail, 35 x 7.5mm, (in 1m lengths) THR7000 Nickel-plated DIN-rail, 35 x 7.5mm, for use in
potentially corrosive atmospheres (in 1m lengths)
ISP7000 Insulating spacer: attaches to the base of a DIN-
rail to isolate the IS earth from a structural earth
Tagging accessories for individual barriers (figure 2)
TH7700 Tag holder for mounting on the top of an
individual barrier
Tagging accessories for columns of barriers (figure 2)
TAG57 Tagging strips for mounting over a column of
barriers, for marking barrier locations. Supplied (with labels) in 1m lengths for cutting to size.
TGL7700 Spare labels for use with TAG57 tagging strips:
0.5m strips, supplied in sets of 10.
IMB57 Tagging strip supports. Two needed for each
tagging strip. It can also be used as centre support by breaking off the top end tab.
Power accessories (figure 3)
BPL7700 Power link for feeding 24V dc to a maximum of
40 barriers in a single column from an MTL7798 power feed module or MTL7799 Dummy module.
Earthing accessories (figure 3)
ETL7000 Earth terminal providing connections for
routeing the IS earth from the DIN-rail to an appropriate plant earth. Two recommended for each length of DIN-rail.
TAG57
TGL7700
ERB57O
IMB57
ETL7000
ISP7000
TH7700
Figure 2: MTL7700 Series mounting and tagging accessories
Table 1: MTL7700 Series Key barriers
Type Application Key barriers
MTL
Analogue Resistance temperature detectors 7755ac
input Thermocouples, ac sensors 7756ac
(low-level) 7760ac
Analogue Controller outputs, one line earthed 7728+
output Controller outputs, neither line earthed 7787+
dc power supply
26V 20-35V
Analogue Transmitters, 2-wire, 4–20mA 7787+ 7706
input
(high-level)
Digital Switches 7787+ 7707+
(on/off) 7741-44
input
Digital Solenoids, alarms, LEDs 7728+ 7707+
(on/off)
output
3
INM7700-6 Jan 2010
ERB57O
IMB57
ETL7000
ERL7
ETM7
ISP7000
THR2/THR7000
Figure 3: MTL7700 Series earthing accessories
Note: Module earth terminals may be used for cable
screen earth connections. See Figure 17
ERB57S Nickel-plated straight earth-rail bracket,
supplied with two push fasteners, one 14mm earth-rail clamp and one 9mm earth clamp < 16mm2.
ERB57O Nickel-plated offset earth-rail bracket, supplied
with two push fasteners, one 14mm earth-rail clamp and one 9mm earth clamp < 16mm
2
.
ERL7 Nickel-plated 3 x 10mm earth rail supplied in
1m lengths. Provides earthing facilities for cable screens and 0V earth returns, additional to those provided on the module earth foot.
ETM7 Earth terminal (5mm wide) for attachment to an
ERL7 earth rail, for terminating cable screens and spare cable cores.
3 SAFETY CONSIDERATIONS
3.1 General requirements
All installers of shunt-diode barriers should be familiar with the installation instructions provided by nationally accepted codes of practice, eg, BS EN 60079-14 for the UK, or a recommended practice, eg, ANSI/ISA-RP 12.6 for the USA.
Users within the European Community should also refer to the supplied MTL publication:
INA7700 MTL7700 Series
Instructions for Safe Use
3.2 Safety checks
Table 2 itemises the essential checks that should be carried out to ensure the safety of a barrier installation. Use the checklist to prevent important safety considerations being overlooked when installing, commissioning, modifying or servicing an installation of MTL7700 Series barriers. Check the list both before and after a barrier system has been installed, the final check being made by someone other than the person(s) who carried out the installation work. Each item in the list is cross-referenced to the appropriate section of the manual.
For Factory Mutual (FM) based installations see also Appendix B for FM certification information.
4 INSTALLATION
4.1 General
MTL7700 Series barriers clamp directly onto standard T-section DIN­rail (DIN EN 50 022). The simple mounting procedure for barriers is described in section 4.2 and for accessories in section 4.3.
4.1.1 DIN-rail length
BEFORE mounting the barriers, make sure the rail length is sufficient for the proposed number of barriers and for other mounting accessories. As a guide, on a given length of DIN-rail, allow space (length) for:
a) Barrier packing pitch: 12.6mm b) ETL7000 earth terminals: 10mm each (minimum
of two)
c) IMB57 tagging strip support 16.0mm (minimum of
(if specified) two)
d) ISP7000 insulating spacer 14.7mm (minimum of
(if specified) two)*
e) ERB57S or O earth-rail 8 mm (minimum of two)
mounting bracket (if specified)
* See Note in section 4.3.2
Make sure that there is sufficient clearance between the DIN-rail and any possible obstruction (eg, other columns of barriers) to remove barriers and install accessories such as ERB57S/O earth rails.
Provide sufficient height for IMB57 tagging strip supports and ISP7000 insulating spacers when fitted.
As a guide, refer to figure 4 (dimensions of an individual barrier) and figure 5 (clearances needed for accessories).
4.2 Mounting/removing barriers
MTL7700 Series barriers clamp directly onto T-section DIN-rail, earthing the barrier through the rail.
a) Hook the hazardous-area end of the mounting/earthing clamp
over the hazardous-area flange of the DIN-rail (figure 6).
b) Push the safe-area end of the barrier firmly down by hand until
it clicks into place.
c) Check that the barrier is securely clamped into place (see notes
below).
d) To remove a barrier (figure 7), use the tip of a screwdriver (with
a blade width of 4 to 5mm, minimum shaft length 60mm) to ease the metal clip at the base on the safe-area end outwards until the barrier is freed and can be removed easily by unhooking the hazardous-area end.
Notes
1: Make sure the barrier is properly clamped onto the rail to ensure the essential earth connection. In a row of barriers, one end of an improperly mounted barrier will stick up slightly.
2: Once an MTL7700 Series barrier is fitted, its mounting/earthing foot grips the DIN-rail strongly in order to maintain positional stability and create a high-integrity earth bond. The unit should not be forced along the rail. If it is necessary to reposition a barrier, detach it from the DIN-rail and re-attach it in the correct location. Where minor repositioning is needed, relieve the pressure on the spring of the mounting foot with a screwdriver and ease the unit into place.
4.3 Installing accessories
See section 2.3, figure 2 and figure 3 for brief details of the accessories available for use with MTL7700 Series barriers. More information and installation details (where relevant) for the various accessories are detailed in the following sections:
4
INM7700-6 Jan 2010
90
Hazardous­area terminals
Safe-area terminals
12.6
105
Installation and approval side label
Product top label
Colour-coded top label
Top label background colour codes
Red = positive barrier Black = negative barrier Grey = ac barrier White = dummy barrier Orange = power feed module
Figure 4: Dimensions (mm) of an MTL7700 Series barrier
Mounting accessories Section 4.3.1 to 4.3.
Earthing accessories Section 4.3.3, 4.3.4
Tagging accessories Section 4.3.5, 4.3.6
Power links Section 4.3.7, 4.3.8
4.3.1 DIN-rail (THR2 and THR7000)
MTL can supply both standard (THR2) and plated (THR7000) low­profile T-section DIN-rail. Although standard DIN-rail maintains a high-integrity earth in normal conditions, for aggressive environments MTL provides THR7000 nickel-plated DIN-rail. Both types are supplied in 1m lengths for cutting to size as necessary. Although there is no strict requirement for the DIN-rail to be isolated from earthed surfaces, it is advisable, in order to minimise the possibility of the earth circuit being invaded by fault currents which might interact adversely with other systems. ISP7000 insulating spacers are a convenient method of insulating the DIN-rail. It is much easier to install insulating spacers during the initial build, than to discover later that an equipped and running installation must be modified.
4.3.2 Insulating spacers (ISP7000)
When used, ISP7000 insulating spacers are attached to each end of the DIN-rail and at intervals depending upon the length of the rail. It is recommended that spacers be mounted at 300mm intervals on low­profile (7.5mm) DIN-rail and at 500mm intervals on high-profile (15mm) rails – see figure 8. The spacers are provided with suitable screws for attaching to both the DIN-rail and the mounting surface, which will need to be suitably drilled and tapped for the purpose. Install each spacer as follows (figure 9):
a) On the mounting surface, drill and tap two holes for M4 screws. b) Attach the spacer to the surface with the two M4 x 16 screws
provided.
c) Drill an M6 clearance hole (6.5mm) in the centre of the base of
the DIN-rail (if not already suitably slotted)
d) Attach the DIN-rail to the spacer with the M6 x 16 screw
provided.
Table 2: Safety checklist
Item Refer to no. section: Action
1 3.1 Before beginning installation, check that the
safety documentation confirms that the proposed system is fully certified (if applicable) and complies with the recommendations contained in the relevant sections of IEC 60079-14 for the gas group, temperature classification and area classification required.
2 4.1/6.2 Make sure the barriers are of the correct type
and polarity as specified in the safety documentation.
3 4.1 Make sure all barriers are mounted the right
way round and are properly attached so that the essential earth contact is made securely in accordance with the safety documentation and in compliance with the recommendations of IEC 60079-14.
4 5.3/6.2 Measure the resistance between the barrier
earth DIN-rail and the main power system earth and make sure it does not exceed the maximum permitted resistance specified in the safety documentation.
5 4.1/6.2 Inspect carefully all cables connected between
the barriers and the hazardous-area equipment, making sure the cables are the type specified by the safety documentation and that they are connected to the correct terminals.
6 5/6.2 Make sure all hazardous-area cables are well
secured and are segregated from all other cables.
7 5 Make sure the permitted cable parameters for
hazardous-area circuits are not exceeded (see relevant certificate or INA7700).
8 5 Make sure all hazardous-area apparatus and
cables are either earth-free or correctly bonded with an equipotential conductor.
9 5.3/6.2 Make sure all hazardous-area cables and cable
screens are terminated correctly, the latter preferably via earth foot on the hazardous side of each barrier or via ERL7.
10 5.4 Make sure all unused hazardous-area cables
are terminated by a dummy barrier (MTL7799), earth rail (ERL7) or otherwise safely connected to earth.
11 Make sure all hazardous-area energy-storing
devices are independently and appropriately certified.
12 4.1/ Inspect all tagging or identification labels and
4.3.5/ make sure they relate to the correct barrier
4.3.6 types, polarities and circuit loop numbers.
13 5/6.2 Inspect carefully all cables connected to the
safe-area equipment and make sure they are connected to the safe-area terminals of the barriers.
14 5.3 Make sure that no safe-area equipment is
supplied from (or includes) a source of potential with respect to earth that exceeds 250V rms or 250V dc under normal or fault conditions unless specifically permitted by the safety documentation.
Note: One phase of a 3-phase supply of up to 440V is permitted as its value is equivalent to 250V rms.
15 Make sure all barriers are protected adequately
against moisture, dust, dirt, vibration, excessive temperatures, physical damage and unauthorised modifications.
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