Yokogawa EJA115 - Manual (Page 34)

<Installation and Operating Precautions for TIIS Intrinsically Safe Equipment>
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EX-A03E
Installation and Operating Precautions for TIIS Intrinsically Safe Equipment
Apparatus Certifi ed Under Technical Criteria (IEC-compatible Standards) and from
“RECOMMENDED PRACTICES for Explosion-Protected Electrical Installations in General
Industries,” published in 1979
1. General
The following describes precautions on electrical apparatus
of intrinsically safe construction (hereinafter referred to as
intrinsically safe apparatus).
Following the Labor Safety and Health Laws of Japan, an
intrinsically safe apparatus must undergo type tests in order
to be certifi ed by the Technical Institute of Industrial Safety,
Inc. These tests are required to satisfy either the technical
criteria for electrical machinery and equipment in compliance
with explosionproof standards involving infl ammable gases or
vapors and for machinery and equipment having explosionproof
performance (standards notifi cation no. 556 from the Japanese
Ministry of Labor) (hereinafter referred to as technical criteria), in
conformity with IEC Standards, or the “Recommended Practice
for Explosion-Protected Electrical Installations in General
Industries,” published in 1979. Such a certifi ed apparatus can be
used in hazardous locations where infl ammable gases or vapors
may be present.
Certifi ed apparatus includes a certifi cation label and an
equipment nameplate with the specifi cations necessary for
explosion requirements as well as precautions on explosion
protection. Please confi rm these precautionary items and use
them to meet specifi cation requirements.
For electrical wiring and maintenance servicing, please refer
to “Internal Wiring Rules” in the Electrical Installation Technical
Standards as well as “USER’S GUIDELINES for Electrical
Installations for Explosive Gas Atmospheres in General
Industry,” published in 1994.
To meet intrinsically safe requirements, equipment that can be
termed an “intrinsically safe apparatus” must:
(1) be certifi ed by the Technical Institute of Industrial Safety,
Inc. in accordance with the Labor Safety and Health Laws of
Japan and have the appropriate mark of certifi cation labeled
on its case, and
(2) be used in compliance with the specifi cations marked on its
certifi cation label, equipment nameplate and precautionary
information furnished.
Note: Intrinsically safe apparatus satisfy their performance under
specifi c conditions. They are not always absolutely safe under
every operational and environmental condition. In other words,
they are not safe products involved with factors such as chemical
reactions, geographical changes or the like other than affected by
electric energy from the equipment itself.
2. Electrical Apparatus of Intrinsic Safety Type of
Explosion-Protected Construction
The intrinsic safety type of explosion-protected construction is
a method of protection applicable to a circuit or part of a circuit
in which, under prescribed test conditions, no spark or thermal
effect, whether produced normally or accidentally, is capable
of causing a prescribed explosive gas to ignite. In other words,
electrical apparatus of this construction is intended to suppress
electrical energy thereby preventing ignition of a given explosive
gas atmosphere even though spark or high thermal effect occurs
in the electric circuitry.
Intrinsically safe electrical apparatus generally comprise
intrinsically safe apparatus installed in a hazardous location
and a safety barrier (associated apparatus), installed in a non-
hazardous location, aimed at preventing electrical energy from
fl
owing into the electric circuitry of intrinsically safe apparatus.
However, battery-operated, portable intrinsically safe apparatus
or the like may be used alone.
3. Terminology
(1) Intrinsically safe apparatus: Electrical apparatus in which all
the circuits are intrinsically safe circuits.
(2) Associated apparatus: Electrical apparatus in which there
are both intrinsically safe circuits and non-intrinsically safe
circuits that can affect the safety of intrinsically safe circuits.
(3) Safety barrier: A specifi c type of associated apparatus, which
consists mainly of safety barrier elements, and serves to
limit the fl ow of excessive electrical energy, which is capable
of causing ignition of a given explosive gas or vapour of a
non-intrinsically safe circuit into concerned intrinsically safe
circuits.
(4) Apparatus of category “ia”: Intrinsically safe electrical
apparatus and associated apparatus which are incapable of
causing ignition of a given explosive gas or vapour with the
appropriate safety factors such as:
- when up to two countable faults are applied and, in
addition,
- when non-countable faults produce an onerous condition.
(5) Apparatus of category “ib”: Intrinsically safe electrical
apparatus and associated apparatus which are incapable of
causing ignition of a given explosive gas or vapour, with the
appropriate safety factors such as:
- when up to one countable fault is applied and, in addition,
- when non-countable faults produce an onerous condition.
(6) Safety rating: A rating to be designated to intrinsically safe
apparatus as well as associated apparatus and is the
maximum rating allowable for maintaining intrinsic safety of
concerned intrinsically safe circuits.
4. Caution on Combining Intrinsically Safe
Apparatus and Safety Barriers
(1) A combination of certifi ed intrinsically safe apparatus and
safety barriers needs to satisfy combination requirements.
If intrinsically safe apparatus specify safety barriers for
combination, safety barriers other than specifi ed cannot be
used (see Note 1 for more details).
(2) Certifi ed intrinsically safe systems specify specifi c safety
barriers in combination with intrinsically safe apparatus. So
safety barriers other than specifi ed cannot be used (see
Note 2 for more details).
(3) Other than limitations of combining intrinsically safe
apparatus and safety barriers as given in (1) and (2) above,
two or more pieces of apparatus certifi ed under different
standards cannot be combined with each other (see Note 3
for more details). In addition, bear in mind that classifi cations
of explosion protection such as “IIA,” “IIB” and “IIC” and
category “ia” and “ib” limit a combination of intrinsically safe
apparatus and safety barriers.
For more details, see the “Type Certifi cate Guide for
Explosion-Protected Construction for Electrical Machinery
and Equipment,” issued by the Japanese Ministry of Labour,
the Research Institute of Industrial Safety.
Note 1: Testing Apparatus
Intrinsically safe apparatus and safety barriers are assessed
individually to ensure that their safety requirements are satisfi ed.
Tested and certifi ed intrinsically safe apparatus and safety
barriers incorporate individual certifi cation numbers.
A combination of intrinsically safe apparatus and safety barriers
involves the following two limitations: