Yokogawa digitalYEWFLO (DY) - Manual (Page 169)

<INSTALLATION AND OPERATING PRECAUTIONS FOR TIIS FLAMEPROOF EQUIPMENT>
3
IM 01F06A00-01EN
6. Maintenance of Flameproof Apparatus
To maintain the fl ameproof apparatus, do the
following. (For details, refer to Chapter 10
“MAINTENANCE OF EXPLOSION-PROTECTED
ELECTRICAL INSTALLATION” in the USER’S
GUIDELINES for Electrical Installations for
Explosive Gas Atmospheres in General Industry.)
(1) Maintenance servicing with the power
on.
Flameproof apparatus shall not be maintenance-
serviced with its power turned on. However, in
cases where maintenance servicing is to be
conducted with the power turned on, with the
equipment cover removed, always use a gas
detector to check that there is no explosive gas
in that location. If it cannot be checked whether
an explosive gas is present or not, maintenance
servicing shall be limited to the following two items:
(a) Visual inspection
Visually inspect the fl ameproof apparatus,
metal conduits, and cables for damage or
corrosion, and other mechanical and structural
defects.
(b) Zero and span adjustments
These adjustments should be made only to
the extent that they can be conducted from the
outside without opening the equipment cover.
In doing this, great care must be taken not to
cause mechanical sparks with tools.
(2) Repair
If the fl ameproof apparatus requires repair, turn
off the power and transport it to a safety (non-
hazardous) location. Observe the following points
before attempting to repair the apparatus.
(a)
Make only such electrical and mechanical
repairs as will restore the apparatus to
its original condition. For the fl ameproof
apparatus, the gaps and path lengths of joints
and mating surfaces, and mechanical strength
of enclosures are critical factors in explosion
protection. Exercise great care not to damage
the joints or shock the enclosure.
(b) If any damage occurs in threads, joints
or mating surfaces, inspection windows,
connections between the sensor and
terminal box, shrouds or clamps, or external
wiring connections which are essential in
fl ameproofness, contact Yokogawa Electric
Corporation.
CAUTION
Do not attempt to re-process threaded
connections or refi nish joints or mating surfaces.
(c) Unless otherwise specifi ed, the electrical
circuitry and internal mechanisms may be
repaired by component replacement, as this
will not directly affect the requirements for
fl ameproof apparatus (however, bear in mind
that the apparatus must always be restored to
its original condition). If you attempt to repair
the fl ameproof apparatus, company-specifi ed
components shall be used.
(d) Before starting to service the apparatus, be
sure to check all parts necessary for retaining
the requirements for fl ameproof apparatus.
For this, check that all screws, bolts, nuts, and
threaded connections have properly been
tightened.
(3) Prohibition of specifi cation changes
and modifi cations
Do not attempt to change specifi cations or make
modifi cations involving addition of or changes in
external wiring connections.
7. Selection of Cable Entry Devices for
Flameproof Type
IMPORTANT
The cable glands (cable entry devices for
fl ameproof type) conforming to IEC Standards
are certifi ed in combination with the fl ameproof
apparatus. So, Yokogawa-specifi ed cable entry
devices for fl ameproof type shall be used to meet
this demand.
References:
(1) Type Certifi cate Guide for Explosion-Protected
Construction Electrical Machinery and
Equipment (relating to Technical Standards
Conforming to International Standards), issued
by the Technical Institution of Industrial Safety,
Japan
(2) USER’S GUIDELINES for Electrical
Installations for Explosive Gas Atmospheres
in General Industry (1994), issued by the
Japanese Ministry of Labour, the Research
Institute of Industrial Safet