Dwyer MTL7787 - Manual (Page 7)

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 <
16mm
2 .
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 DIN-
rail (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: