Section
4 Electrical equipment for use in explosive gas atmospheres or
in the presence of combustible dusts
4.1 General
4.1.1 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.
4.1.2 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.
4.1.3 Spaces and locations are considered as hazardous on 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 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 on board use), 3, 6.1 and 8;
- 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.
4.2 Hazardous areas
4.2.1 For hazardous areas and sources of hazards for naval ships, the following principles
are to apply in general.
4.2.2 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 is likely to occur
periodically or occasionally in normal operation,
- zone 2: an area in which an explosive atmosphere is not
likely to occur in normal operation but, if it does occur, will persist for
a short period only. See IEC 60079-101-1: Explosive atmospheres –
Part 10-1: Classification of areas – Explosive gas atmospheres.
4.2.3 Hazardous areas associated with solid substances or packaged liquids to
which Vol 2, Pt 9, Ch 5, 4.12 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.
4.2.4 The following areas are regarded as hazardous, zone 0:
- the interiors of those spaces, tanks, piping systems and
equipment defined by Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(a) and
Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(b);
and
- enclosed, unventilated spaces containing pipework or equipment
defined by Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(b) and
Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(e).
4.2.5 The following areas are regarded as hazardous, zone 1:
- the interiors of spaces containing
dangerous goods as defined by Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(d);
- unventilated spaces separated by a
single bulkhead or deck from a cargo defined by Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(a);
- ventilated spaces containing
pipework or equipment defined by Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(b) and Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(e)
- zones within a 3 m radius of
ventilation outlets, hatches or doorways or other openings into spaces
defined by Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(a), Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(b) or Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(c)
- zones on open deck within 3 m of
the ventilation outlets of tanks defined in Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(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 Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(b);
- zones within a 1,5 m radius of
flanged joints, or glands or other openings defined by Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(e) and
Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(f);
- zones within a 3 m radius of bunds
or barriers intended to contain spillage of liquids defined by Vol 2, Pt 9, Ch 5, 4.1 General 4.1.3.(a);
- zones on open deck within a 1,5 m
radius of any opening into a space defined by Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(b);
- enclosed or semi-enclosed spaces
with direct opening into a zone 1 hazardous location;
- (zones within a 1,5 m radius of
ventilation inlets or other openings serving spaces defined by Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(c);
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.
4.2.6 The following zones or spaces 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 Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(d), Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(f), Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(g), Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(h) or Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(i);
- zones on open deck extending 2 m
beyond those defined by Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(e);
- zones on open deck extending 4m
beyond those defined by Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.5.(k); and
- enclosed or semi-enclosed spaces
with direct opening into a zone 2 hazardous location.
4.3 Selection of equipment for use in explosive gas atmospheres
4.3.1 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, an agreed
specified standard where applicable, see
Vol 2, Pt 9, Ch 5, 4.3 Selection of equipment for use in explosive gas atmospheres 4.3.4, Vol 2, Pt 9, Ch 5, 4.3 Selection of equipment for use in explosive gas atmospheres 4.3.5 or Vol 2, Pt 9, Ch 5, 4.3 Selection of equipment for use in explosive gas atmospheres 4.3.6.
4.3.2 The equipment protection type permitted depends on the hazardous area where
the equipment is to be located, as defined in Vol 2, Pt 9, Ch 5, 4.5 Installation of electrical equipment. For certain locations on the ship other requirements may
limit installations to specific equipment types and/or particular applications.
4.3.4 In zone
0, the following may be considered:
-
intrinsically
safe, category ‘a’ (Ex ‘ia’); or
-
simple electrical apparatus and components (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.
4.3.5 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’); and
-
Special –
Ex ‘s’, where permitted by the equipment certification.
4.3.6 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"; and
-
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.
4.3.7 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.
4.3.8 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.
4.3.9 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 5.4.1 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 5mW/mm2 or 35mW for constant wave and 0,1mj/mm2
pulsed.
- the optical energy levels in zone 2, including fault conditions, are to be
limited to 10mW/mm2 or 35mW for constant wave and 0,5mj/mm2
pulsed; and
- pulsed sources with a pulse interval less than 5 seconds, are to be considered
constant wave sources.
Table 5.4.1 Zone classification for types of protection associated with optical fibre
transmission systems
Zone
|
Type of protection allowed
|
Associated requirements
|
0
|
‘op is’, Inherently safe optical
radiation,
|
Safe with two faults
|
|
‘op sh’, Protected fibre optic media with ignition
capable beam
|
additional mechanical protection required
|
1
|
‘op is’, Inherently safe optical,
radiation
|
Safe with single fault
|
|
‘op pr’, Protected fibre optic media with ignition
capable beam
|
with additional mechanical protection
required
|
|
‘op sh’, Protected fibre optic media with ignition
capable beam interlocked with fibre breakage
|
additional mechanical protection not necessarily
required
|
2
|
‘op pr’, inherently safe optical radiation, ‘op
is’
|
Safe in normal operation
|
|
‘op pr’, Protected fibre optic media with ignition
capable beam
|
additional mechanical protection not necessarily
required
|
|
‘op sh’, Protected fibre optic media with ignition
capable beam interlocked with fibre breakage
|
additional mechanical protection not necessarily
required
|
4.4 Selection of equipment for use in the presence of combustible
dusts
4.4.1 Where equipment is to be installed in hazardous areas, as defined by
Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.3, 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.
4.4.2 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 5mW/mm2 or 35mW maximum for constant
wave sources or 0,1mj/mm2 for pulsed sources;
- restricted in extended hazardous area to 10mW/mm2 or 35mW maximum, for
constant wave sources or 0,5mj/mm2 for pulsed sources.
- where pulsed source has a pulse interval less than 5 seconds, it is to be
considered constant wave source.
4.4.3 Electrical equipment for use in hazardous areas is to be so
designed and installed as to minimise the accumulation of combustible dust which may
interfere with the safe dissipation of heat from the enclosure.
4.4.4 Where equipment is to be installed in extended hazardous areas, as
defined by Vol 2, Pt 9, Ch 5, 4.2 Hazardous areas 4.2.3, associated with the presence of combustible dust, the
following may be considered:
-
equipment permitted within a hazardous area as defined by Vol 2, Pt 9, Ch 5, 4.4 Selection of equipment for use in the presence of combustible dusts 4.4.1;
-
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.
4.4.5 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 (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); and
-
simple apparatus
included in intrinsically safe circuits or radio aerials, complying
with Vol 2, Pt 9, Ch 5, 4.3 Selection of equipment for use in explosive gas atmospheres 4.3.4, Vol 2, Pt 9, Ch 5, 4.3 Selection of equipment for use in explosive gas atmospheres 4.3.5 or Vol 2, Pt 9, Ch 5, 4.3 Selection of equipment for use in explosive gas atmospheres 4.3.6 respectively.
4.4.6 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.
4.5 Installation of electrical equipment
4.5.1 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.
4.5.2 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.
4.5.3 Any special requirements laid down by the equipment certification documentation are also
to be observed.
4.5.4 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.
4.5.5 All switches and protective devices from which electrical equipment located in hazardous
areas is supplied are to interrupt all poles or phases and protected against
unauthorised re-connection.
4.5.6 Electrical equipment in hazardous areas, switches and protective devices are to be
clearly labelled for identification purposes.
4.6 Semi-enclosed spaces
4.6.1 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.
4.7 Ventilation
4.7.1 Natural or mechanical ventilation is to be provided for hazardous enclosed or
semi-enclosed spaces 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.
4.7.2 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.
4.7.3 An alarm
is to be provided on the navigating bridge and the engine control
room to indicate any loss of the required ventilation capacity. Initiation
of an alarm by a fan motor running or fan rotation monitoring device
will not normally satisfy this requirement.
4.8 Pressurisation
4.8.1 A space having access to a hazardous area defined as zone 1 or
zone 2 may be regarded as non-hazardous if all the 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;
-
a space and an air-lock are 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 shutdown, 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
Vol 2, Pt 9, Ch 6, 4.3 Lighting circuits 4.3.3) 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.
4.8.2 A space having access to a hazardous space or zone 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
Vol 2, Pt 9, Ch 7, 4.7 Valve control and indication systems 4.7.3), 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.
4.9 Cable and cable installation
4.9.1 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. Electric cables in hazardous areas are to be
clearly labelled for identification purposes.
4.9.2 In addition to the requirements of Vol 2, Pt 9, Ch 3, 8 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 areas only; or
-
as otherwise specifically permitted elsewhere within this Section;
or
- mineral insulated with copper sheath.
4.9.4 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.
4.9.5 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.
4.9.6 In zone
0, cable joints may only be used in intrinsically safe circuits.
4.9.7 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 heatshrunk tubing, in accordance
with the manufacturer’s instructions.
4.10 Requirements for oil supply ships intended
for the carriage of oil cargoes in bulk
4.10.1 See IEC 60092: Electrical installations in ships – Part 502:
Tankers – Special features.
4.11 Special requirements for ships with spaces for carrying vehicles,
helicopters and aircraft, with fuel in their tanks
4.11.1 Ships
with closed spaces carrying vehicles, helicopter and aircraft with
fuel having a flashpoint not exceeding 60ºC:
-
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 the Naval Administration is
arranged to operate continuously and is sufficient to provide at least ten air
changes per hour, whenever vehicles are on board, above a height of 45 cm from the
vehicle deck, or any platform on which vehicles are carried, electrical equipment
having an enclosure of ingress protection rating of at least IP 55 may be accepted
as an alternative to that of a safe type.
4.12 Special requirements for ships intended for the carriage of dangerous goods and materials hazardous only in bulk
4.12.1 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
combustible 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.
4.12.2 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.
4.12.3 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
combustible 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.
4.12.4 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.
4.12.5 Cable penetrations of decks and bulkheads are to be sealed against the passage of gas
or vapour.
4.13 Requirements for ships with spaces for storing paint
4.13.1 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.
4.13.2 A space having access to a paint store 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;
- 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.
4.13.3 The relevant group and temperature class for electrical equipment in hazardous zones
are, respectively, IIB and T3.
|