Section
14 Electrical equipment for use in explosive gas atmospheres or
in the presence of combustible dusts
14.1 General
14.1.1 The installation of electrical equipment in spaces and locations in which
flammable mixtures are liable to collect, e.g. areas containing flammable gas or vapour
and/or combustible dust, is to be minimised.
14.1.2 In order to eliminate potential sources of ignition from spaces and
locations in which flammable mixtures are liable to collect such hazardous areas are to
be identified and electrical equipment within these areas is to be selected and
installed in accordance with the requirements of this Section.
14.1.3 Spaces and locations are considered as hazardous in the presence of any of the
following:
- spaces or tanks containing either:
- flammable liquid having a flashpoint (closed-cup test) not exceeding 60°C
and below;
- flammable liquid having a flashpoint exceeding 60°C, heated or raised by
ambient conditions to a temperature within 15°C of its flashpoint; or
- flammable gas;
- piping systems or equipment containing
fluid defined by (a) and having flanged joints or glands or other openings through
which leakage of fluid may occur under normal operating conditions;
- spaces containing coal, grain or other
solids liable to release flammable gas and/or combustible dust;
- spaces containing dangerous goods in
packaged form, of the following Classes as defined in the IMDG Code: 1(with the
exception of goods in division 1.4, compatibility group S), 2.1 (inclusive of
applicable gas bottles for onboard use), 3 (FP<23ΊC), 6.1 (FP<23ΊC) and 8
(FP<23ΊC);
- piping systems or equipment associated
with processes (such as electro-chlorination) generating flammable gas as a
by-product and having openings from which the gas may escape under normal
operating conditions; or
- piping systems or equivalent
containing flammable liquids not defined by (a), having flanged joints, glands or
other openings through which leakage of fluid in the form of a mist or fine spray
may occur under normal operating conditions.
Note FP means flashpoint (closed-cup
test).
14.2 Hazardous areas
14.2.1 Hazardous areas and sources of hazard for ships intended for the carriage in
bulk of oil cargoes, liquefied gases, other flammable liquid cargoes, the special
requirements for ships with spaces for carrying vehicles with fuel in their tanks for
their own propulsion, the special requirements for ships intended for the carriage of
dangerous goods and materials hazardous only in bulk and the requirements for ships with
spaces for storing paint, are defined (either directly, or by reference to other
documents) in Pt 6, Ch 2, 14.10 Requirements for tankers intended for the carriage in bulk to Pt 6, Ch 2, 14.15 Requirements for ships with spaces for storing paint . A 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 equipment.
14.2.3 Hazardous areas associated with flammable liquids or gases are classified
into zones based upon the frequency of the occurrence and duration of an explosive gas
atmosphere, as follows:
-
zone 0: an area in which an explosive atmosphere is present continuously or
for long periods or frequently
-
zone 1: an area in which an explosive atmosphere consisting of a mixture with
air of flammable substances in the form of gas, vapour or mist is likely to occur in
normal operation occasionally
-
zone 2: an area in which an explosive atmosphere consisting of a mixture with
air of flammable substances in the form of gas, vapour or mist is not likely to occur
in normal operation but, if it does occur, will persist for a short period only.
See IEC 60079-101: Explosive atmospheres Part 10-1: Classification of areas
Explosive gas atmospheres..
14.2.4 Hazardous areas associated with solid substances or packaged liquids to
which Pt 6, Ch 2, 14.14 Special requirements for ships intended for the carriage of dangerous goods and materials hazardous only
in bulk applies are classified into zones based upon the frequency of
the occurrence and duration of an explosive atmosphere due to the presence of gas and/or
combustible dust, as follows:
-
hazardous area: area in which an explosive atmosphere is likely to occur in
normal operation (comparable with zone 1)
-
extended hazardous area: area in which an explosive atmosphere is not likely
to occur in normal operation and, if it does occur, is likely to do so only
infrequently and will exist for a short period only (comparable with zone 2).
See IEC 60092-506:Electrical Installation in ships Part 506: Special
features Ships carrying specific dangerous goods and materials hazardous only in
bulk. An explosive atmosphere may exist due to gas and/or combustible dust.
14.2.5 The following areas are regarded as hazardous, zone 0:
-
the interiors of those spaces, tanks, piping systems and equipment
defined by Pt 6, Ch 2, 14.1 General 14.1.3.(a) and Pt 6, Ch 2, 14.1 General 14.1.3.(b); and
-
enclosed, unventilated spaces containing pipework or equipment
defined by Pt 6, Ch 2, 14.1 General 14.1.3.(b) and Pt 6, Ch 2, 14.1 General 14.1.3.(e).
14.2.6 The following areas are regarded as hazardous, zone 1:
-
unventilated spaces separated by a single bulkhead or deck from a
cargo defined by Pt 6, Ch 2, 14.1 General 14.1.3.(a);
-
ventilated spaces containing pipework or equipment defined by Pt 6, Ch 2, 14.1 General 14.1.3.(b) and Pt 6, Ch 2, 14.1 General 14.1.3.(e);
-
zones within a 3 m radius of ventilation outlets, hatches or doorways
or other openings into spaces defined by Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(a) or Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(b), vapour having a density relative
to that of air of more than 0,75, the hazardous zone is considered to extend.
-
zones on open deck within 3 m of the ventilation outlets of cargo
tanks defined in Pt 6, Ch 2, 14.1 General 14.1.3.(a), which permit the flow of
small volumes of vapour or gas mixtures caused by thermal variation;
-
zones within a 3 m radius of flanged joints, or glands or other
openings defined by Pt 6, Ch 2, 14.1 General 14.1.3.(b);
-
zones within a 1,5 m radius of flanged joints, or glands or other
openings defined by Pt 6, Ch 2, 14.1 General 14.1.3.(e) and Pt 6, Ch 2, 14.1 General 14.1.3.(f);
-
zones within a 3 m radius of bunds or barriers intended to contain
spillage of liquids defined by Pt 6, Ch 2, 14.1 General 14.1.3.(a);
-
zones on open deck within a 1,5 m radius of any opening into a space
defined by Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(a);
-
enclosed or semi-enclosed spaces with direct opening into a zone
1 hazardous location.
- interiors of chemical lockers, gas cylinder
stores and other such spaces, as defined by Pt 6, Ch 2, 14.1 General 14.1.3.(d), containing dangerous goods for on-board use. This
includes, but is not limited to, paints, gas cylinders, chemicals and small
quantities of fuel.
- zones within a 1,5 m radius of ventilation
inlets or other openings serving spaces defined by Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(b); and
- zones on open deck within a vertical
cylinder of unlimited height and 6 m radius centred upon the centre of the outlet,
and within a hemisphere of 6 m radius below the outlet which permit the flow of large
volumes of vapour or gas mixtures during loading/discharging/ballasting
14.2.7 The following areas are regarded as hazardous, zone 2;
-
ventilated spaces separated by a single bulkhead or deck from a
zone 0 space;
-
zones on open deck extending 1,5 m beyond those defined by Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(c), Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(e), Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(f), Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(g) or Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(h);
-
zones on open deck extending 2 m beyond those defined by Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(d);
-
zones on open deck extending 4 m beyond those defined by Pt 6, Ch 2, 14.2 Hazardous areas 14.2.6.(i); and
-
enclosed or semi-enclosed spaces with direct opening into a zone
2 hazardous location.
14.2.9 Consideration may also be given to hazardous areas and sources of hazard defined in
accordance with IEC 60079-10-1: Explosive atmospheres Part 10-1:
Classification of areas Explosive gas atmospheres and/or IEC 60079-10-2:
Explosive atmospheres Part 10-2: Classification of areas Combustible dust
atmospheres.
14.3 Selection of equipment for use in explosive gas atmospheres
14.3.1 When equipment is to be installed in areas where an explosive gas
atmosphere may be present, it is generally to be of a type providing protection against
ignition of the gases encountered and compliant with the relevant Parts of IEC 60079:
Explosive atmospheres, or an acceptable and relevant National Standard, unless
permitted otherwise by Pt 6, Ch 2, 14.3 Selection of equipment for use in explosive gas atmospheres 14.3.4, Pt 6, Ch 2, 14.3 Selection of equipment for use in explosive gas atmospheres 14.3.5 or Pt 6, Ch 2, 14.3 Selection of equipment for use in explosive gas atmospheres 14.3.6.
14.3.2 The equipment protection type permitted depends on the hazardous area where
the equipment is to be located, as defined in Pt 6, Ch 2, 14.2 Hazardous areas. For
certain locations on the ship other requirements may limit installations to specific
equipment types and/or particular applications.
14.3.4 In zone 0, the following may be considered:
-
intrinsically safe, category a (Ex ia); or
-
simple apparatus (for example thermocouples, photocells, strain
gauges, junction boxes, switching devices), included in intrinsically safe
circuits of category ia, compliant with IEC 60079-14: Explosive atmospheres
Part 14: Electrical installations design, selection and erection.
14.3.5 In zone 1, the following may be considered:
-
equipment permitted within zone 0;
-
intrinsically safe, category b (Ex ib);
-
simple apparatus as defined above, included in intrinsically safe
circuits of category ib;
-
increased safety (Ex e);
-
flameproof (Ex d);
-
pressurised enclosure (Ex p);
-
powder filled (Ex q); or
-
encapsulated (Ex m).
14.3.6 In zone 2, the following may be considered:
-
equipment permitted within zone 1;
-
type of protection n or N;
-
equipment such as control panels, protected by purging and
pressurisation and capable of being verified by inspection as meeting the
requirements of IEC 60079-2: Explosive atmospheres Part 2: Equipment
protection by pressurized enclosures "p"; or
-
radio aerials having robust construction, meeting the relevant
requirements of IEC 60079-15: Explosive atmospheres Part 15: Equipment
protection by type of protection "n". Additionally, in the case of
transmitter aerials, it is to be shown, by detailed study or measurement, or by
limiting the peak radiated power and field strength to 1 W and 30 V/m,
respectively, that they present negligible risk of inducing incendive sparking in
adjacent structures or equipment.
14.3.7 Equipment having type of protection ia, ib, or d, is to be of a Group
(IIA, IIB or IIC) meeting or exceeding that required for safe operation in the presence
of any gas or vapour that can be present, or is to be certified specifically for such
gases or vapours.
14.3.8 All equipment is to be of a temperature classification (T1 to T6) that
confirms, or is to be assessed so as to confirm, that its maximum surface temperature
will not reach the ignition temperature of any gas or vapour, or mixture of gases or
vapours, which can be present. The surface temperature considered may be that of an
internal or external part, according to the type of protection of the equipment.
14.3.9 Where optical fibre transmission equipment located in a hazardous or non-hazardous area
provides energy to, or passes optical energy through, a hazardous area with an explosive
gas atmosphere, then:
- The protection type to be appropriate to the zone classification, as detailed in
Table 2.14.1 Zone classification for types of
protection associated with optical fibre transmission systems .
- The optical energy levels in zone 0 and 1, including fault conditions,
are to be limited to 5 mW/mm2 or 35 mW for constant wave and 0,1
mJ/mm2 pulsed.
- The optical energy levels in zone 2, including fault conditions, are to be
limited to 10 mW/mm2 or 35 mW for constant wave and 0,5 mJ/mm2 pulsed, and
- Pulsed sources with a pulse interval less than 5 seconds, are to be considered
constant wave sources.
Table 2.14.1 Zone classification for types of
protection associated with optical fibre transmission systems
Zone
|
Type of protection level
|
Associated requirements
|
0
|
op is, Inherently safe optical radiation,
op sh, Protected fibre
optic media with ignition capable beam interlocked with fibre
breakage
|
Safe with two faults
additional mechanical protection
required
|
1
|
op is, Inherently safe optical, radiation
op pr, Protected fibre
optic media with ignition capable beam
op sh, Protected fibre
optic media with ignition capable beam interlocked with fibre breakage
|
Safe with single fault
additional mechanical protection
required
additional mechanical protection not necessarily
required
|
2
|
op is, inherently safe optical radiation,
op pr, Protected fibre
optic media with ignition capable beam
op sh, Protected fibre
optic media with ignition capable beam interlocked with fibre
breakage
|
Safe in normal operation
additional mechanical protection not
necessarily required
additional mechanical protection not
necessarily required
|
14.4 Selection of equipment for use in the presence of combustible
dusts
14.4.1 Where equipment is to be installed in hazardous areas, as defined by
Pt 6, Ch 2, 14.2 Hazardous areas 14.2.4, associated with the presence of combustible dusts,
it is, to be of a type certified by a National or other appropriate authority for the
combustible dusts and, additionally, any explosive gases encountered.
14.4.2 Where optical fibre transmission equipment located in a hazardous area,
extended hazardous area or non-hazardous area provides energy to, or passes
optical energy through, a hazardous area with combustible dusts, then the optical energy
levels are to be:
- restricted in hazardous area to 5 mW/mm2 or 35 mW maximum for
constant wave sources or 0,1 mJ/mm2 for pulsed sources;
- restricted in extended hazardous area to 10 mW/mm2 or 35 mW
maximum, for constant wave sources or 0,5 mJ/mm2 for pulsed sources;
- where a pulsed source has a pulse interval less than 5 seconds, it
is to be considered constant wave source.
14.4.4 Electrical equipment for use in hazardous areas is to be designed
and installed to minimise the accumulation of dust which may interfere with the safe
dissipation of heat from the enclosure.
14.4.5 Where equipment is to be installed in extended hazardous areas, as
defined by Pt 6, Ch 2, 14.2 Hazardous areas 14.2.4, associated with the presence of combustible dust
and, additionally, any explosive gases encountered, the following may be considered:
-
equipment permitted within a hazardous area as defined in Pt 6, Ch 2, 14.4 Selection of equipment for use in the presence of combustible dusts 14.4.1;
-
equipment having degree of protection IP5X, or better, and having a
surface temperature under normal operating conditions, but in the absence of a
combustible dust layer, not exceeding two-thirds of the minimum ignition
temperature in degrees Celsius of the combustible dust/air mixture(s) that can be
present and appropriate for any explosive gases encountered; and
-
equipment of a type which ensures absence of sparks or arcs and hot
spots during normal operation.
14.4.6 Where equipment certified for combustible dusts is not available,
consideration will be given to the use of equipment complying as a minimum, with the
following requirements provided no explosive gases will be present:
-
the enclosure is to be at least dust protected (IP5X) having, when
tested in accordance with IEC 60529, an ingress of fine dust within the enclosure
not exceeding 10 g per m3 of free air space, and
-
the surface temperature of the equipment, under normal operating
conditions, but in the absence of a combustible dust layer, is not to exceed
two-thirds of the minimum ignition temperature in degrees Celsius of the
combustible dust/air mixture(s) that can be present, or
-
the equipment is to be certified intrinsically safe ia or ib
having a temperature classification ensuring compliance with Pt 6, Ch 2, 14.3 Selection of equipment for use in explosive gas atmospheres 14.3.5.(b), or
-
pressurised and operated in accordance with procedures ensuring,
prior to its re-energisation, the absence of combustible dust within the enclosure
following loss of pressurisation and consequent shutdown, and having surface
temperature complying with (b), or
-
simple apparatus
included in intrinsically safe circuits or radio aerials, complying
with Pt 6, Ch 2, 14.3 Selection of equipment for use in explosive gas atmospheres 14.3.5 or Pt 6, Ch 2, 14.3 Selection of equipment for use in explosive gas atmospheres 14.3.6 respectively.
14.4.7 Consideration may also be given to other types of protection, selected in
accordance with the requirements of:
- IEC 60079-14: Explosive atmospheres Part 14: Electrical installations
design, selection and erection; or
- arrangements complying with IEC 60092-506: Electrical Installation in ships
Part 506: Special features Ships carrying specific dangerous goods and
materials hazardous only in bulk.
14.5 Installation of electrical equipment
14.5.1 The method of installation and application of electrical equipment suitable for use in
explosive gas atmospheres or in the presence of combustible dusts is to be in accordance
with:
- IEC 60079-14: Explosive atmospheres Part 14: Electrical installations
design, selection and erection; or
- the National code of practice relevant to the standard with which the equipment
complies.
14.5.2 The ambient temperature range for which the equipment is certified is to be
taken to be 20°C to 40°C, unless otherwise stated, and account is to be taken of this
when assessing the suitability of the equipment for the auto-ignition temperature of the
gases and combustible dusts encountered.
14.5.3 Any special requirements laid down by the equipment certification
documentation are also to be observed.
14.5.4 All switches and protective devices from which electrical equipment located
in hazardous areas is supplied are to be located in non-hazardous areas. Where it is not
practicable to locate the switches and protective devices in non- hazardous area, then
the applicable requirements of this section are to be applied to that equipment.
14.5.5 All switches and protective devices from which electrical equipment located
in hazardous areas is supplied are to interrupt all poles or phases.
14.5.6 Electrical equipment in hazardous areas, switches and protective devices are
to be clearly labelled for identification purposes.
14.6 Semi-enclosed spaces
14.6.1 Semi-enclosed spaces are considered to be spaces limited by decks and/or
bulkheads in such a manner that the natural conditions of ventilation are different from
those obtained on open deck.
14.7 Ventilation
14.7.1 Natural or mechanical ventilation is to be provided for hazardous enclosed or
semi-enclosed areas in order to prevent accumulation of explosive gas atmosphere,
leaving no areas of stagnant air. Ventilation rates are to be calculated based on IEC
60079-10-1: Explosive atmospheres Part 10-1: Classification of areas Explosive
gas atmospheres.
14.7.2 Where
the rate of ventilation air flow, in relation to the maximum rate
of release of flammable substances reasonably to be expected under
normal conditions, is sufficient to prevent the concentration of flammable
substances approaching their lower explosive limit, consideration
may be given to regarding as non-hazardous, the space, ventilation
and other openings into it, and the zone around the equipment contained
within.
14.7.3 An
alarm is to be provided on the navigating bridge, engine control room,
and where applicable, cargo control room to indicate any loss of the
required ventilation capacity.
14.8 Pressurisation
14.8.1 A space having access to a hazardous area defined as zone 1 or
zone 2 may be regarded as non-hazardous if all following requirements are met:
-
access is by
means of an air-lock, having gastight steel doors, the inner of which
as a minimum, is self-closing without any hold-back arrangement;
-
it is maintained at an overpressure (minimum 0,25 mbar) relative to
the external hazardous area by ventilation from a non-hazardous area;
- the relative air pressure within the space is
continuously monitored and so arranged that:
- in the event of loss of overpressure, an alarm is given;
- the electrical supply to all equipment not of a type suitable for zone 1
is automatically disconnected;
- where the disconnection of equipment could introduce a hazard, an alarm may be
given, in lieu of automatic disconnection, upon loss of overpressure; and
- a means of manual disconnection of electrical equipment not of a type suitable
for zone 1, capable of being controlled from an attended station, is to
be provided in conjunction with an agreed operational procedure; and
- where the means of disconnection, capable of being controlled from an attended
station, is located within the space then it is to be of a type suitable for
zone 1;
-
any electrical
equipment required to operate upon loss of overpressure, lighting
fittings (see
Pt 6, Ch 2, 5.7 Lighting circuits 5.7.3)
and equipment within the air-lock, is to be of a type suitable for zone 1; and
-
means are to be provided to prevent electrical equipment, other than
of a type suitable for zone 1, being energised until the atmosphere within
the space is made safe, by air changes of at least 10 times the capacity of the
space.
14.8.2 A space having access to a hazardous area defined as zone 2 may be
regarded as non-hazardous if all following requirements are met:
-
access is by
means of a self-closing gastight steel door without any hold-back
arrangement;
-
it is maintained at an overpressure (minimum 0,25 mbar) relative to
the external hazardous area by ventilation from a non-hazardous area;
- the relative air pressure within the space is
continuously monitored and so arranged that:
- in the event of loss of overpressure, an alarm is given; and
- a means of manual disconnection of electrical equipment not of a type suitable
for zone 2, capable of being controlled from an attended station, is
to be provided; where the means of disconnection, capable of being controlled
from an attended station, is located within the space then it is to be of a
type suitable for zone 2;
-
any electrical equipment required to operate upon loss of
overpressure (e.g. lighting fittings, see
Pt 6, Ch 2, 5.7 Lighting circuits 5.7.3), is to be of a type suitable for zone
2; and
- means are to be provided to prevent electrical equipment, other than of a type
suitable for zone 2, being energised until the atmosphere within the space is
made safe, by air changes of at least 10 times the capacity of the space.
14.9 Cable and cable installation
14.9.1 Electric cables are not, as far as is practicable, to be installed in
hazardous areas, except where serving equipment installed within the area. Through runs
of cable may be accepted in locations classified as Zone 1 or Zone 2,
where alternative routes are impracticable.
14.9.2 In addition to the requirements of Pt 6, Ch 2, 11 Electric cables, optical fibre cables and busbar trunking systems (busways), cables for circuits that are not intrinsically safe, which
are located in hazardous areas, or which may be exposed to cargo oil, oil vapour or gas,
are to be either:
-
armoured or braided for earth detection, or
-
otherwise adequately protected against mechanical or chemical damage,
within Zone 2 or non-hazardous locations only, or
-
as otherwise specifically permitted elsewhere within this Section,
or
-
mineral insulated with copper sheath.
14.9.3 Armouring, braiding and other metal coverings of cables installed in
hazardous areas are to be effectively earthed at least at both ends.
14.9.4 Where
there is risk of intermittent contact between armour and exposed metalwork,
non-metallic impervious sheath is to be applied over metallic armour
of cables.
14.9.5 Cables
associated with intrinsically safe circuits are to be used only for
such circuits. They are to be physically separated from cables associated
with non-intrinsically safe circuits, e.g. neither installed in the
same protective casing nor secured by the same fixing clip. Consideration
may be given to other arrangements complying with IEC 60079-14: Explosive
atmospheres Part 14: Electrical installations design, selection
and erection.
14.9.6 In Zone 0, cable joints may only be used in intrinsically safe
circuits.
14.9.7 Cable runs in Zone 1 or Zone 2 are, where practicable, to be
uninterrupted. Where discontinuities cannot be avoided, cable joints are to:
- be made in an enclosure with a type of protection appropriate
to the location; or
- provided the joint is not subject to mechanical stress, be epoxy
filled, compound-filled or sleeved with heat-shrunk tubing, in accordance
with the manufacturers instructions.
14.9.8 Cable penetrations of decks and bulkheads are to be sealed when a pressure difference
between the areas is to be maintained.
14.10 Requirements for tankers intended for the
carriage in bulk
14.10.1 See IEC 60092: Electrical installations in ships Part 502:
Tankers Special features.
14.11 Requirements for ships for the carriage of liquefied gases in
bulk
14.12 Requirements for ships intended for the
carriage of other flammable liquid cargoes in bulk
14.13 Special requirements for ships with spaces for carrying vehicles
with fuel in their tanks, for their own propulsion
14.13.1
Passenger ships with special category spaces below the bulkhead deck for carrying
vehicles: electrical equipment fitted within the space and within the exhaust
ventilation trunking for the space, is to be of a type acceptable for zone 1.
14.13.2
Passenger ships with special category spaces above the bulkhead deck for carrying
vehicles:
-
electrical equipment fitted within a height of 45 cm above the
vehicle deck, or any platform on which vehicles are carried, or within the exhaust
ventilation trunking for the space, is to be of a type acceptable for zone
1;
-
electrical equipment situated elsewhere within the space is to be of
a type acceptable for zone 2, or is to have an enclosure of ingress
protection rating of at least IP55, see IEC 60529: Degrees of protection
provided by enclosures (IP Code). Smoke and gas detector heads are exempt
from this requirement.
14.13.3 Passenger ships with cargo spaces, other than special category spaces,
for carrying vehicles and cargo ships with closed ro-ro cargo spaces for carrying
vehicles:
- except where exempted by (b) electrical equipment fitted within the space and within
the exhaust ventilation trunking for the space is to be of a type acceptable for
zone 1;
- where the ventilation system required by SOLAS - International Convention for the
Safety of Life at Sea as amended, Chapter II-2, Regulation 20 - Protection of
vehicle, special category and ro-ro spaces, 20.3.1.1 is arranged to operate
continuously and is sufficient to provide at least ten air changes per hour, whenever
vehicles are on board, electrical equipment above a height of 45 cm from the vehicle
deck, or any platform on which vehicles are carried, is to be of a type acceptable
for zone 2, or is to have an enclosure of ingress protection rating of at
least IP 55.
14.14 Special requirements for ships intended for the carriage of dangerous
goods and materials hazardous only in bulk
14.14.1 Electrical
equipment essential for the safety and operation of the ship is to
be of a type providing protection against ignition of the gases and/or
dusts that can be present, selected in accordance with IEC 60092-506: Electrical installations in ships Part 506: Special features
Ships carrying specific dangerous goods and materials hazardous
only in bulk.
14.14.2 In addition to the requirements of IEC 60092- 506: Electrical
installations in ships Part 506: Special features Ships carrying specific
dangerous goods and materials hazardous only in bulk, pipes such as ventilation
and bilge pipes, having ends opening into a hazardous area are to be considered a
hazardous area. Enclosed spaces such as pipe tunnels and bilge pump-rooms
containing such pipes and with equipment and components such as pumps, valves and
flanges are to be considered as extended hazardous areas unless protected by
overpressure.
14.14.3 Electrical
equipment not essential for the safety or operation of the ship and
which is not of a type providing protection against ignition of the
gases and/or dusts that can be present is to be completely disconnected
and protected against unauthorised re-connection. Disconnection is
to be made outside the hazardous areas and be effected with isolating
links or lockable switches.
14.14.4 Electrical
equipment and all cables, including through runs and terminating cables,
are to be protected against mechanical damage. Cables are to be either
enclosed in screwed heavy gauge steel drawn or seam-welded and galvanised
conduit, or protected by electrically continuous metal sheathing or
metallic wire armour braid or tape.
14.14.5 Cable
penetrations of decks and bulkheads are to be sealed against the passage
of gas or vapour.
14.15 Requirements for ships with spaces for storing paint
14.15.1 In
order to eliminate potential sources of ignition in paint stores,
electrical equipment is to be selected as follows:
-
electrical equipment
fitted within the space and within the exhaust ventilation trunking
for the space is to be of a type acceptable for zone 1;
-
electrical equipment situated within 1 m of inlet and exhaust
ventilation openings or within 3 m of exhaust mechanical ventilation outlets is to
be of a type acceptable for zone 2, or is to have an enclosure of ingress
protection rating of at least IP55 and maximum surface temperature equivalent to
temperature class T3, see IEC 60529, Classification of Degrees of
Protection Provided by Enclosures. See
Pt 6, Ch 2, 1.11 Location and construction 1.11.1 for degrees of protection required for
equipment on open deck.
14.15.2 A
space having access to a paint store may be regarded as non-hazardous
if fulfilling all of the following conditions:
-
access is by
means of a self-closing gastight steel door without any hold-back
arrangement;
-
the paint store
is ventilated from a non-hazardous area and;
-
warning notices
are fitted adjacent to the paint store entrance warning of flammable
liquids contained in paint store.
Note A watertight door may be considered as being gastight.
14.15.3 The
relevant group and temperature class for electrical equipment in hazardous
zones are, respectively, IIB and T3.
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