Circular Letter
MSC/Circ.1116

UNIFIED INTERPRETATIONS OF THE IBC AND IGC CODES

(2 June 2004)

 

1.  The Maritime Safety Committee, at its seventy-eighth session (12 to 21 May 2004), with a view to ensuring uniform application of the provisions of the IBC and IGC Codes, containing vague wording which is open to diverging interpretations, approved the unified interpretations relating to cargo tank venting systems set out in the annex.

 

2.  Member Governments are invited to use the annexed unified interpretations as guidance when applying relevant provisions of the IBC and IGC Codes for ships constructed on or after 1 July 2004 and to bring them to the attention of all parties concerned.

 

ANNEX.

UNIFIED INTERPRETATIONS OF THE IBC AND IGC CODES

 

INTERNATIONAL CODE FOR THE CONSTRUCTION AND EQUIPMENT OF SHIPS
CARRYING DANGEROUS CHEMICALS IN BULK (IBC CODE)

 

Chapter 8.
Cargo tank venting and gas freeing arrangements

 

Paragraph 8.3.2
By-passing of P/V valves

 

By-passing of P/V valves is allowed during cargo operations for cargoes which do not require a vapour return system, provided that the vent-line outlet is fitted with flame arresters and is located at the required height above the deck level. However, by-passing of high-velocity valves is not permitted.

 

Paragraph 8.3.3.2
Area classification and selection of electrical equipment

 

1. Areas on an open deck, or semi-enclosed spaces on an 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, air or inert gas mixtures during loading/discharging/ballasting are defined as Zone 1.

 

Permitted electrical equipment: Certified safe type equipment for Zone 1.

 

2. Areas within 4 m beyond the zone specified in paragraph 1 above are defined as Zone 2. Permitted electrical equipment:

 

.1 certified safe type equipment for Zone 1;

 

.2 equipment of a type which ensures the absence of sparks, arcs and of hot spots during its normal operation;

 

.3 equipment having an enclosure filled with a liquid dielectric, when required by the application, or encapsulated;

 

.4 pressured equipment; and

 

.5 equipment specifically designed for Zone 2 (for example type n protection in accordance with IEC 60079-15).

 

INTERNATIONAL CODE FOR THE CONSTRUCTION AND EQUIPMENT OF SHIPS
CARRYING LIQUEFIED GASES IN BULK (IGC CODE)

 

Chapter 8.
Cargo tank vent systems

 

Paragraph 8.2.10
Area classification and selection of electrical equipment

 

1. Areas on an open deck, or semi-enclosed spaces on an 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, air or inert gas mixtures during loading/discharging/ballasting are defined as Zone 1.

 

Permitted electrical equipment: Certified safe type equipment for Zone 1.

 

2. Areas within 4 m beyond the zone specified in paragraph 1 above are defined as Zone 2. Permitted electrical equipment:

 

.1 certified safe type equipment for Zone 1;