付録3 The 14th International Symposium on the Transportation of Dangerous Goods by Sea and Inland Waterways 発表論文
Evaluation of the Liquefaction Potential of Solid Bulk Cargoes (Japan)
Susumu OTA, National Maritime Research Institute
Tamaki URA, Institute of Industrial Science, University of Tokyo
Masaki MURAYAMA, Research Institute of Marine Engineering
Masato TANAKA, Research Institute of Marine Engineering
Takao TOBINOBU, Nippon Kaiji Kentei Kyokai
Abstract
It is required by SOLAS Convention that cargoes which may liquefy shall only be accepted for loading when the actual moisture content of the cargo is less than its transportable moisture limit. For the proper implementation of the requirement, the scope of application should be clarified. We developed a new test procedure for evaluating liquefaction potential of solid bulk cargoes and proposed it to the DSC subcommittee. We confirmed the effectiveness of the new test procedure by several series of tests, some of which were carried out as an international collaboration program. This paper outlines the results of these tests and some issues related to liquefaction of solid bulk cargoes.
1 Introduction
1.1 Requirement on the carriage of cargoes which may liquefy
Liquefaction of solid bulk cargo in a cargo hold during voyage badly affects the stability of the ship and may result in capsizing. To prevent the accident caused by liquefaction of a solid bulk cargo, moisture content of the cargo should be limited. (The definitions of various technical terms are attached in Appendix 1 , to assist understanding on this paper.) Thus the following requirement is provided in SOLAS Convention (1) and entered into force on January 1, 1994 (Reg. VI/6.2):
"Concentrates or other cargoes which may liquefy shall only be accepted for loading when the actual moisture content of the cargo is less than its transportable moisture limit. However, such concentrates and other cargoes may be accepted for loading even when their moisture content exceeds the above limit, provided that the safety arrangements to the satisfaction of Administration are made to ensure adequate stability in case of cargo shifting and further provided that the ship has adequate structural integrity."
The first sentence is the essential requirement and the second sentence is the provision for the carriage of such cargoes on specially constructed/fitted ships. For the proper implementation of the requirement, the scope of the application should be clarified. In other words, it should be judged whether a cargo may liquefy when it contains much moisture or a cargo is not liable to liquefy regardless of moisture content at shipment.
1.2 Scope of the application of the requirement
In view of safety of carriage, it is appropriate to apply the above requirement for cargoes which are suspected to be possible to liquefy. Such conservative way of implementation of the requirement, however, often causes the problem that moisture content measurement and determination of transportable moisture limit (TML) should be carried out even for cargoes which are not liable to liquefy. According to the Code of Safe Practice for Solid Bulk Cargoes (BC Code) (2), the TML of liquefaction materials should be determined by a competent authority at least once every six months and the actual moisture content of the cargo should be certified at each shipment as near as possible to the time of loading. It can, therefore, be said that conservative application may require unnecessary work and cost for shippers. Actually, the problem of conservative application was emphasized by shippers during the discussion on the amendments to the national regulations of Japan corresponding to the requirement mentioned above.
The problem is caused by the ambiguity of the definition of "cargoes which may liquefy". In general "cargoes which may liquefy" are the cargoes listed in Appendix A of the BC Code (1998 edition). However, the list is not exhaustive as described in the appendix itself. Since many industries continue to produce various new materials, it is necessary to identify materials which may liquefy.
