6.6 Electrical installations in hazardous areas
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Statutory Documents - IMO Publications and Documents - International Codes - 2009 MODU Code - Code for the Construction and Equipment of Mobile Offshore Drilling Units, 2009 – Resolution A.1023(26) - Chapter 6 - Machinery and Electrical Installations in Hazardous Areas for All Types of Units - 6.6 Electrical installations in hazardous areas

6.6 Electrical installations in hazardous areas

  6.6.1 Electrical equipment and wiring installed in hazardous areas should be limited to that necessary for operational purposes. Only the cables and types of equipment described in this chapter may be installed. Selection and installation of equipment and cables in hazardous areas should be in accordance with international standards.footnote

  6.6.2 In selection of electrical apparatus for use in hazardous areas, consideration should be given to:

  • .1 the zone in which the apparatus will be used;

  • .2 the sensitivity to ignition of the gases or vapours likely to be present, expressed as a gas group; and

  • .3 the sensitivity of the gases or vapours likely to be present to ignition by hot surfaces, expressed as a temperature classification.

  6.6.3 Electrical apparatus used in hazardous areas should be manufactured, tested, marked and installed in accordance with international standardsfootnote and certified by an independent testing laboratory recognized by the Administration. Equipment classified in accordance with the following protection classes may be used:

Table 6-1 Electrical protection type

Type Protection method
ia and ib Intrinsic safety
d Flameproof enclosures
e Increased safety
m Encapsulation
n Non incendive
o Oil immersion
p Pressurized enclosures
q Powder filling
s Specialfootnote

Repairs, maintenance and overhaul of hazardous area certified equipment should be performed by suitably qualified personnel in accordance with appropriate international standards.footnote

There should be maintained a register of electrical equipment installed in the designated hazardous areas, including a description of the equipment, applicable degree of protection and ratings.

  6.6.4 Types of electrical equipment permitted should be determined according to the electrical hazardous area classification of the location in which the equipment is to be installed. Permissible equipment is shown by an “x” in table 6-2. The use of type “o” (oil immersion) should be limited. For transportable apparatus, protection type “o” should not be used.

Table 6-2 Type of electrical apparatus used in hazardous zones

Protection Type ia ib d e m n o p q s
Zone 0 x                  
Zone 1 x x x x x   x x x  
Zone 2 x x x x x x x x x x

  6.6.5 Group selection for electrical equipment should be as follows:

  • .1 Group II should be selected for types “e”, “m”, “n”, “o”, “p”, “q” and “s” apparatus.

  • .2 Group IIA, IIB or IIC should be selected for types “i”, “d”, and certain types of “n” apparatus according to table 6-3.

Table 6-3 Relationship between gas/vapour group and permitted equipment group

Gas/vapour group Electrical equipment group
IIC IIC
IIB IIB or IIC
IIA IIA, IIB or IIC

  6.6.6 Electrical apparatus should be so selected that its maximum surface temperature will not reach ignition temperature of any gas/vapour possibly presenting in the hazardous areas in which the electrical apparatus is located. The relationship among equipment temperature class, equipment maximum surface temperature, gas/vapour ignition temperature is shown in table 6-4.

Table 6-4 Relationship among temperature class, maximum surface temperature and ignition temperature

Electrical apparatus Temperature class Electrical apparatus maximum surface temperature (°C) Gas/vapour ignition temperature (°C)
T1 450 >450
T2 300 >300
T3 200 >200
T4 135 >135
T5 100 >100
T6 85 >85

  6.6.7 Electrical apparatus located in hazardous drilling well and mud processing areas should meet at least Group IIA and temperature class T3.

  6.6.8 Electrical cables should meet the following:

  • .1 Only cables associated with type “ia” equipment should be permitted in zone 0 areas.

  • .2 Thermoplastic sheathed cables, thermosetting sheathed cables or elastomeric sheathed cables should be used for fixed wiring in zone 2 areas.

  • .3 Flexible and portable cables, where necessary, used in zone 1 and zone 2 areas should be to the satisfaction of the Administration.

  • .4 Permanently installed, fixed cable passing through zone 1 hazardous areas should be fitted with conductive covering, braiding or sheathed for earth detection.

Parent topic: Chapter 6 - Machinery and Electrical Installations in Hazardous Areas for All Types of Units
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