4
INM7700-6
Jan 2010
90
Hazardous-
area
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) low-
profile 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 low-
profile (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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