13.6 Gas detection
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Statutory Documents - IMO Publications and Documents - Resolutions - Maritime Safety Committee - Resolution MSC.370(93) – Amendments to The International Code for The Construction and Equipment of Ships Carrying Liquefied Gases In Bulk (IGC Code) – (Adopted on 22 May 2014) - Annex - Amendments to The International Code for The Construction and Equipment of Ships Carrying Liquefied Gases In Bulk (IGC Code) - Chapter 13 — Instrumentation and Automation Systems - 13.6 Gas detection

13.6 Gas detection

  13.6.1 Gas detection equipment shall be installed to monitor the integrity of the cargo containment, cargo handling and ancillary systems, in accordance with this section.

  13.6.2 A permanently installed system of gas detection and audible and visual alarms shall be fitted in:

  • .1 all enclosed cargo and cargo machinery spaces (including turrets compartments) containing gas piping, gas equipment or gas consumers;

  • .2 other enclosed or semi-enclosed spaces where cargo vapours may accumulate, including interbarrier spaces and hold spaces for independent tanks other than type C tanks;

  • .3 airlocks;

  • .4 spaces in gas-fired internal combustion engines, referred to in 16.7.3.3;

  • .5 ventilation hoods and gas ducts required by chapter 16;

  • .6 cooling/heating circuits, as required by 7.8.4;

  • .7 inert gas generator supply headers; and

  • .8 motor rooms for cargo handling machinery.

  13.6.3 Gas detection equipment shall be designed, installed and tested in accordance with recognized standardsfootnote and shall be suitable for the cargoes to be carried in accordance with column "f" in table of chapter 19.

  13.6.4 Where indicated by an "A" in column "f" in the table of chapter 19 ships certified for carriage of non-flammable products, oxygen deficiency monitoring shall be fitted in cargo machinery spaces and hold spaces for independent tanks other than type C tanks. Furthermore, oxygen deficiency monitoring equipment shall be installed in enclosed or semi-enclosed spaces containing equipment that may cause an oxygen-deficient environment such as nitrogen generators, inert gas generators or nitrogen cycle refrigerant systems.

  13.6.5 In the case of toxic products or both toxic and flammable products, except when column "i" in the table of chapter 19 refers to 17.5.3, portable equipment can be used for the detection of toxic products as an alternative to a permanently installed system. This equipment shall be used prior to personnel entering the spaces listed in 13.6.2 and at 30-minute intervals while they remain in the space.

  13.6.6 In the case of gases classified as toxic products, hold spaces and interbarrier spaces shall be provided with a permanently installed piping system for obtaining gas samples from the spaces. Gas from these spaces shall be sampled and analysed from each sampling head location.

  13.6.7 Permanently installed gas detection shall be of the continuous detection type, capable of immediate response. Where not used to activate safety shutdown functions required by 13.6.9 and chapter 16, sampling type detection may be accepted.

  13.6.8 When sampling type gas detection equipment is used, the following requirements shall be met:

  • .1 the gas detection equipment shall be capable of sampling and analysing for each sampling head location sequentially at intervals not exceeding 30 min;

  • .2 individual sampling lines from sampling heads to the detection equipment shall be fitted; and

  • .3 pipe runs from sampling heads shall not be led through non-hazardous spaces except as permitted by 13.6.9.

  13.6.9 The gas detection equipment may be located in a non-hazardous space, provided that the detection equipment such as sample piping, sample pumps, solenoids and analysing units are located in a fully enclosed steel cabinet with the door sealed by a gasket. The atmosphere within the enclosure shall be continuously monitored. At gas concentrations above 30% lower flammable limit (LFL) inside the enclosure, the gas detection equipment shall be automatically shut down.

  13.6.10 Where the enclosure cannot be arranged directly on the forward bulkhead, sample pipes shall be of steel or equivalent material and be routed on their shortest way. Detachable connections, except for the connection points for isolating valves required in 13.6.11 and analysing units, are not permitted.

  13.6.11 When gas sampling equipment is located in a non-hazardous space, a flame arrester and a manual isolating valve shall be fitted in each of the gas sampling lines. The isolating valve shall be fitted on the non-hazardous side. Bulkhead penetrations of sample pipes between hazardous and non-hazardous areas shall maintain the integrity of the division penetrated. The exhaust gas shall be discharged to the open air in a non-hazardous area.

  13.6.12 In every installation, the number and the positions of detection heads shall be determined with due regard to the size and layout of the compartment, the compositions and densities of the products intended to be carried and the dilution from compartment purging or ventilation and stagnant areas.

  13.6.13 Any alarms status within a gas detection system required by this section shall initiate an audible and visible alarm:

  • .1 on the navigation bridge;

  • .2 at the relevant control station(s) where continuous monitoring of the gas levels is recorded; and

  • .3 at the gas detector readout location.

  13.6.14 In the case of flammable products, the gas detection equipment provided for hold spaces and interbarrier spaces that are required to be inerted shall be capable of measuring gas concentrations of 0% to 100% by volume.

  13.6.15 Alarms shall be activated when the vapour concentration by volume reaches the equivalent of 30% LFL in air.

  13.6.16 For membrane containment systems, the primary and secondary insulation spaces shall be able to be inerted and their gas content analysed individuallyfootnote. The alarm in the secondary insulation space shall be set in accordance with 13.6.15, that in the primary space is set at a value approved by the Administration or recognized organization acting on its behalf.

  13.6.17 For other spaces described by 13.6.2, alarms shall be activated when the vapour concentration reaches 30% LFL and safety functions required by chapter 16 shall be activated before the vapour concentration reaches 60% LFL. The crankcases of internal combustion engines that can run on gas shall be arranged to alarm before 100% LFL.

  13.6.18 Gas detection equipment shall be so designed that it may readily be tested. Testing and calibration shall be carried out at regular intervals. Suitable equipment for this purpose shall be carried on board and be used in accordance with the manufacturer's recommendations. Permanent connections for such test equipment shall be fitted.

  13.6.19 Every ship shall be provided with at least two sets of portable gas detection equipment that meet the requirement of 13.6.3 or an acceptable national or international standard.

  13.6.20 A suitable instrument for the measurement of oxygen levels in inert atmospheres shall be provided.

Parent topic: Chapter 13 — Instrumentation and Automation Systems
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