Yokogawa EJA118 - Manual (Page 66)

EX-A03E 3
INSTALLATION AND OPERATING PRECAUTIONS FOR JIS INTRINSICALLY SAFE EQUIPMENT
intrinsically safe apparatus may be used at an ambient
temperature up to 60
°
C. So, specifications should be checked
before installing intrinsically safe apparatus.
If the intrinsically safe apparatus are exposed to direct
sunshine or radiant heat from plant facilities, appropriate
thermal protection measures shall be taken.
6. Wiring for Intrinsically Safe
Circuits
In intrinsically safe construction, safety shall be maintained
as an intrinsically safe system involving intrinsically safe
apparatus and safety barriers connected thereto, and electrical
wiring (through intrinsically safe circuits) interconnected
between them. In other words, even when safety
requirements are maintained individually by intrinsically safe
apparatus and safety barriers, they shall not be affected by
electrical or magnetic energy caused by electrical wiring.
To make electrical wiring for intrinsically safe circuits, you
must:
(a) refer to the equipment configuration diagram and make
electrical wiring properly;
(b) prevent intrinsically safe wiring from being contacted
with non-intrinsically safe wiring, and separate the
intrinsically safe circuit from other electrical circuits;
(c) prevent intrinsically safe wiring from being
electrostatically and magnetically affected by non-
intrinsically safe wiring;
(d) reduce wiring inductance and capacitance produced
between the intrinsically safe apparatus and safety
barrier where possible, and use a shorter cable between
the intrinsically safe apparatus and safety barrier than
specified if the maximum permissible inductance of the
cable is specified as operating conditions;
(e) conform to conditions of installation such as wiring
method, earthing or the like, if any; and
(f) protect the outer sheath of cables from damage with
appropriate measures.
7. Maintenance and Inspection of
Intrinsically Safe Apparatus
and Safety Barriers
Maintenance and inspection of intrinsically safe apparatus
and safety barriers shall be limited to within the instructions
described in applicable instruction manuals. If other than this
is required, contact the manufacturers. For more information,
refer to the “USER’S GUIDELINES for Electrical
Installations for Explosive Gas Atmospheres in General
Industry” issued in 1994 by the Japanese Ministry of Labour,
the Research Institute of Industrial Safety.
(1) Requirements for maintenance personnel
Maintenance and inspection of intrinsically safe apparatus
and safety barriers shall be conducted by maintenance
personnel skilled in intrinsically safe construction and
installation of electrical devices as well as capable of
applying associated rules.
(2) Maintenance and Inspection
(a) Visual inspection
Visually inspect the external connections of intrinsically
safe apparatus and safety barriers, and cables for damage
or corrosion as well as other mechanical and structural
defects.
(b) Adjustments
Zero, span and sensitivity adjustments shall be made
with applicable adjusting potentiometers and mechanical
adjustment screws.
These maintenance adjustments shall be made in a non-
hazardous location.
CAUTION
If intrinsically safe apparatus and safety barriers
require maintenance service and checking, a
gas detector shall be used to ensure that there
is no explosive gas in the location (mainte-
nance servicing shall be conducted in a non-
hazardous location).
(3) Repair
Intrinsically safe apparatus and safety barriers shall be
repaired by manufacturers.
(4) Prohibition of modifications and specifica-
tion changes
Do not attempt to make modifications or change specifica-
tions which may affect safety.