Goal
To ensure that electrical installations are designed such as to minimize the risk
of fire and explosion from flammable products, and that electrical generation
and distribution systems relating to the safe carriage, handling and
conditioning of cargo liquid and vapour are available.
10.1 Definitions
For the purpose of this chapter, unless expressly provided otherwise,
the definitions below shall apply.
10.1.1
Hazardous area is an area in which an explosive gas atmosphere is or may be
expected to be present, in quantities such as to require special precautions for the
construction, installation and use of electrical apparatusfootnote.
10.1.1.1
Zone 0 hazardous area is an area in which an explosive gas atmosphere is
present continuously or is present for long periods.
10.1.1.2
Zone 1 hazardous area is an area in which an explosive gas atmosphere is
likely to occur in normal operation.
10.1.1.3
Zone 2 hazardous area is an area in which an explosive gas atmosphere is not
likely to occur in normal operation and, if it does occur, is likely to do so
infrequently and for a short period only.
10.1.2
Non-hazardous area is an area in which an explosive gas atmosphere is not
expected to be present in quantities such as to require special precautions for the
construction, installation and use of electrical apparatus.
10.2
General requirements
10.2.1 Electrical installations shall be such as to
minimize the risk of fire and explosion from flammable products.
10.2.2 Electrical installations shall be in accordance
with recognized standards.footnote
10.2.3 Electrical equipment or wiring shall not be
installed in hazardous areas, unless essential for operational purposes or safety
enhancement.
10.2.4 Where electrical equipment is installed in
hazardous areas as provided in 10.2.3, it shall be selected, installed and
maintained in accordance with standards not inferior to those acceptable to the
Organization. Equipment for hazardous areas shall be evaluated and certified or
listed by an accredited testing authority or notified body recognized by the
Administration. Automatic isolation of non-certified equipment on detection of a
flammable gas shall not be accepted as an alternative to the use of certified
equipment.
10.2.5 To facilitate the selection of appropriate
electrical apparatus and the design of suitable electrical installations, hazardous
areas are divided into zones in accordance with recognized standards.
10.2.6 Electrical generation and distribution systems,
and associated control systems shall be designed such that a single fault will not
result in the loss of ability to maintain cargo tank pressures, as required by
7.8.1, and hull structure temperature, as required by 4.19.1.6, within normal
operating limits. Failure modes and effects shall be analysed and documented to a
standard not inferior to those acceptable to the Administration.footnote
10.2.7 The lighting system in hazardous areas shall be
divided between at least two branch circuits. All switches and protective devices
shall interrupt all poles or phases and shall be located in a non-hazardous
area.
10.2.8 Electrical depth sounding or log devices and
impressed current cathodic protection system anodes or electrodes shall be housed in
gastight enclosures.
10.2.9 Submerged cargo pump motors and their supply
cables may be fitted in cargo containment systems. Arrangements shall be made to
automatically shut down the motors in the event of low-liquid level. This may be
accomplished by sensing low pump discharge pressure, low motor current or low liquid
level. This shutdown shall be alarmed at the cargo control station. Cargo pump
motors shall be capable of being isolated from their electrical supply during
gas-freeing operations.