MSC.1/Circ.

MSC.1-Circ.1558 - Unified Interpretations Of The Igf Code (Secretariat)

MSC.1/Circ.1558 28 November 2016

UNIFIED INTERPRETATIONS OF THE IGF CODE
1 The Maritime Safety Committee, at its ninety-seventh session (21 to 25 November 2016), with a view to providing more specific guidance for the application of the relevant requirements of the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code), approved unified interpretations of the IGF Code prepared by the Sub-Committee on Carriage of Cargoes and Containers, at its third session, as set out in the annex.
2 Member States are invited to use the annexed unified interpretations as guidance when applying relevant provisions of the IGF Code and to bring them to the attention of all parties concerned.
***

MSC.1/Circ.1558 Annex, page 1
https://edocs.imo.org/Final Documents/English/MSC.1-CIRC.1558 (E).docx
ANNEX
UNIFIED INTERPRETATIONS OF THE IGF CODE
1 Tank connection space for tanks on open deck and tank connection space equipment (paragraph 2.2.15.3)
1.1 A tank connection space may be required also for tanks on open deck. This may apply for ships where restriction of hazardous areas is safety critical. A tank connection space may also be necessary in order to provide environmental protection for essential safety equipment related to the gas fuel system like tank valves, safety valves and instrumentation.
1.2 A tank connection space may also contain equipment such as vaporizers or heat exchangers. Such equipment is considered to only contain potential sources of release, but not sources of ignition.
2 Fuel preparation room (paragraph 2.2.17)
A tank connection space which has equipment such as vaporizers or heat exchangers installed inside is not regarded as a fuel preparation room. Such equipment is considered to only contain potential sources of release, but not sources of ignition.
3 Appropriate location of premixed engines using fuel gas mixed with air before the turbocharger (paragraph 5.4.1)
Premixed engines using fuel gas mixed with air before the turbocharger should be located in ESD-protected machinery spaces.
4 Protection against cryogenic leakage and control of hazardous zones in fuel preparation rooms on open deck (paragraphs 5.8 and 6.2.1.1)
4.1 Fuel preparation rooms, regardless of location, should be arranged to safely contain cryogenic leakages.
4.2 The material of the boundaries of the fuel preparation room should have a design temperature corresponding with the lowest temperature it can be subjected to in a probable maximum leakage scenario unless the boundaries of the space, i.e. bulkheads and decks, are provided with suitable thermal protection.
4.3 The fuel preparation room should be arranged to prevent surrounding hull structure from being exposed to unacceptable cooling, in case of leakage of cryogenic liquids.
4.4 The fuel preparation room should be designed to withstand the maximum pressure build up during such a leakage. Alternatively, pressure relief venting to a safe location (mast) can be provided.
5 External surface area of the tank for determining sizing of pressure relief valve (paragraph 6.7.3.1.1.2 and figure 6.7.1)
For prismatic tanks
5.1 Lmin, for non-tapered tanks, is the smaller of the horizontal dimensions of the flat bottom of the tank. For tapered tanks, as would be used for the forward tank, Lmin is the smaller of the length and the average width.
MSC.1/Circ.1558 Annex, page 2
https://edocs.imo.org/Final Documents/English/MSC.1-CIRC.1558 (E).docx
5.2 For prismatic tanks whose distance between the flat bottom of the tank and bottom of the hold space is equal to or less than Lmin/10:
A = external surface area minus flat bottom surface area.
5.3 For prismatic tanks whose distance between the flat bottom of the tank and bottom of the hold space is greater than Lmin/10:
A = external surface area.
6 Control and maintenance of pressure and temperature of liquefied gas fuel tanks after the activation of the safety system (paragraphs 6.9.1.1 and 6.9.1.2)
Liquefied gas fuel tanks' pressure and temperature should be controlled and maintained within the design range at all times including after activation of the safety system required in 15.2.2 for a period of minimum 15 days. The activation of the safety system alone is not deemed as an emergency situation.
7 Special consideration within the risk assessment of closed or semi-enclosed bunkering stations (paragraph 8.3.1.1)
The special consideration should as a minimum include, but not be restricted to, the following design features:
 segregation towards other areas on the ship  hazardous area plans for the ship  requirements for forced ventilation  requirements for leakage detection (e.g. gas detection and low temperature detection)  safety actions related to leakage detection (e.g. gas detection and low temperature detection)  access to bunkering station from non-hazardous areas through airlocks  monitoring of bunkering station by direct line of sight or by CCTV.
8 Ventilation of machinery spaces (paragraph 13.5.1)
Spaces enclosed in the boundaries of machinery spaces (such as purifier's room, engine-room workshops and stores) are considered an integral part of machinery spaces containing gas-fuelled consumers and, therefore, their ventilation system does not need to be independent of the one of machinery spaces.
9 Ventilation of double piping and gas valve unit spaces in gas safe engine-rooms (paragraph 13.8.2)
Double piping and gas valve unit spaces in gas safe engine-rooms are considered an integral part of the fuel supply systems and, therefore, their ventilation system does not need to be independent of other fuel supply ventilation systems provided such fuel supply systems contain only gaseous fuel.
10 Ventilation inlet for double wall piping or duct (paragraph 13.8.3)
The ventilation inlet for the double wall piping or duct should always be located in a non-hazardous area in open air away from ignition sources.
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