For containers stowed on partially weatherproof hatchway covers, constant supervision can be achieved and accessibility is maintained Principles (1) and (2) can, therefore, also be achieved by on deck stowage on container ships with partially weatherproof hatchway covers.
The risk of on deck stowage of containers packed with dangerous goods of class 8 due to unobserved corrosion of such ships is insignificant. Principle (3-3), therefore, is not a matter of on deck stowage of dangerous goods on such ships. Thus, substantial risks of "formation of explosive gas mixtures" and "development of highly toxic vapoues" should be considered for judgement on limitation of stowage of containers packed with dangerous goods on such ships.
Based on the above mentioned principles, (3-1) and (3-2), a container packed with dangerous liquids, for which on deck only stowage is specified, other than class 3 and class 6.1 not having subsidiary risk of class 3 nor class 6.1 can be stowed on a hatchway cover having gaps provided that the cargo hold under the hatchway covers complies with the relevant requirements in regulation II-2/54.
4.2 Stowage of containers packed with dangerous liquids having risks of class 3 or 6.1 for which on deck only stowage is specified
Though the risks of "on hatchway cover stowage" of a container packed with dangerous liquids having risk of class 3 or class 6.1 on a container ship with partially weatherproof hatchway covers are significant the risks are acceptable, for the reasons mentioned in paragraph 3.1. Therefore, a container packed with dangerous liquids having risks of class 3 or class 6.1, for which on deck only stowage is specified, can be stowed on a hatchway cover provided that the cargo hold under the hatchway cover complies with the relevant requirements in regulation II-2/54. In other words, no limitation is necessary in addition to the limitation of on deck stowage described in paragraph 3.3 for container ships with partially weatherproof hatchway covers, in view of on deck only.
5 Segregation requirements on ships with partially weatherproof hatchway covers
5.1 Basic principles for vertical segregation of containers on ships with partially weatherproof hatchway covers
Regarding segregation of containers on board container ships, table 7.2.3.2 in PART 7 of the IMDG Code governs the requirements. In the footnote of the table, it is described that "all bulkheads and decks should be resistant to fire and liquid". Hatchway covers having clear gaps, therefore, cannot be regarded as "a deck" in view of vertical segregation. Additional segregation requirements should, therefore, be considered for such ships where "not in the same vertical line unless segregated by a deck" is required.
When a container packed with dangerous solids or gases was stowed on a hatchway cover having clear gaps, the possibility of ingress of the solids or gases into cargo hold could be insignificant. When a container packed with dangerous liquids is stowed on such a hatchway cover, the dangerous liquids may ingress into the cargo hold through the gap in the event of spillage from the container. In such a case, the dangerous liquids may reach containers in the cargo hold stowed in vertical lines near the gap. Even in such a case, however, it is supposed that the probability of contact of the dangerous liquids on the containers stowed in vertical lines not located near the gap is small. Special care should, therefore, be taken for the stowage of incompatible dangerous goods in vertical lines near the gap between hatchway covers.
