Yokogawa ADMAG AXR - Manual (Page 191)

IM 01E30D01-01EN
2
IM 01E30D01-01EN
(4) Path length of joint surface
On a joint surface, the length of the shortest path
through which flame flows from the inside to outside
of the flameproof enclosure. This definition cannot
be applied to threaded joints.
(5) Gaps between joint surfaces
The physical distance between two mating surfaces,
or differences in diameters if the mating surfaces
are cylindrical.
Note: The permissible sizes of gaps between joint surfaces,
the path length of a joint surface and the number of joint
threads are determined by such factors as the enclosure’
s internal volume, joint and mating surface construction,
and the explosion classification of the specified gases and
vapours.
4. Installation of Flameproof
Apparatus
(1) Installation Area
Flameproof apparatus may be installed, in
accordance with applicable gases, in a hazardous
area in Zone 1 or 2, where the specified gases are
present. Those apparatus shall not be installed in a
hazardous area in Zone 0.
Note: Hazardous areas are classified in zones based upon
the frequency of the appearance and the duration of an
explosive gas atmosphere as follows:
Zone 0: An area in which an explosive gas atmosphere
is present continuously or is present for long
periods.
Zone 1: An area in which an explosive gas atmosphere is
likely to occur in normal operation.
Zone 2: An area in which an explosive gas atmosphere
is not likely to occur in normal operation and if it
does occur it will exist for a short period only.
(2) Environmental Conditions
The standard environmental condition for the
installation of flameproof apparatus is limited to an
ambient temperature range from –20°C to +40°C
(for products certified under Technical Criteria).
However, some field-mounted instruments may
be certified at an ambient temperature up to +60
°C as indicated on the instrument nameplates. If
the flameproof apparatus are exposed to direct
sunshine or radiant heat from plant facilities,
appropriate thermal protection measures shall be
taken.
5. External Wiring for
Flameproof Apparatus
Flameproof apparatus require cable wiring or
flameproof metal conduits for their electrical
connections. For cable wiring, cable glands
(cable entry devices for flameproof type) to wiring
connections shall be attached. For metal conduits,
attach sealing fittings as close to wiring connections
as possible and completely seal the apparatus. All
non-live metal parts such as the enclosure shall be
securely grounded. For details, see the “USER’S
GUIDELINES for Electrical Installations for
Explosive Gas Atmospheres in General Industry,”
published in 1994.
(1) Cable Wiring
• For cable wiring, cable glands (cable entry
devices for flameproof type) specified or
supplied with the apparatus shall be directly
attached to the wiring connections to complete
sealing of the apparatus.
• Screws that connect cable glands to the
apparatus are those for G-type parallel pipe
threads (JIS B 0202) with no sealing property.
To protect the apparatus from corrosive gases
or moisture, apply nonhardening sealant
such as liquid gaskets to those threads for
waterproofing.
• Specific cables shall be used as recommended
by the “USER’S GUIDELINES for Electrical
Installations for Explosive Gas Atmospheres in
General Industry,” published in 1994.
• In necessary, appropriate protective pipes
(conduit or flexible pipes), ducts or trays shall
be used for preventing the cable run (outside
the cable glands) from damage.
• To prevent explosive atmosphere from being
propagated form Zone 1 or 2 hazardous
location to any different location or non-
hazardous location through the protective pipe
or duct, apply sealing of the protective pipes in
the vicinity of individual boundaries, or fill the
ducts with sand appropriately.
• When branch connections of cables, or cable
connections with insulated cables inside
the conduit pipes are made, a flameproof or
increased-safety connection box shall be used.
In this case, flameproof or increased-safety
cable glands meeting the type of connection
box must be used for cable connections to the
box.