Yokogawa digitalYEWFLO (DY) - Manual (Page 168)

<INSTALLATION AND OPERATING PRECAUTIONS FOR TIIS FLAMEPROOF EQUIPMENT>
2
IM 01F06A00-01EN
(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 classifi cation of the specifi ed 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 specifi ed gases are
present. Those apparatus shall not be installed in a
hazardous area in Zone 0.
Note: Hazardous areas are classifi ed 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 fl ameproof apparatus is limited to
an ambient temperature range from –20°C to
+40°C (for products certifi ed under Technical
Criteria). However, some fi eld-mounted
instruments may be certifi ed at an ambient
temperature up to +60°C as indicated on the
instrument name plates. If the fl ameproof 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 for
their electrical connections. For cable wiring, cable
glands (cable entry devices for fl ameproof type) to
wiring connections shall be attached. All non-live
metal parts such as the enclosure shall be securely
grounded. For details, refer to 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 fl ameproof type) specifi ed 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
waterproofi ng.
• Specifi c 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 fl exible 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 fi ll the
ducts with sand appropriately.
• When branch connections of cables is made,
a fl ameproof or increased-safety connection
box shall be used. In this case, fl ameproof or
increased-safety cable glands meeting the
type of connection box must be used for cable
connections to the box.