Tankers and Bulk Carriers

V enting and Inerting Double Hull Spaces

The MSC issued as a Guideline the IACS recommendations for venting and inerting double hull spaces. The guidelines illustrate various arrangements and describe methods with associated precautions for carrying out this task. Due regard is given to the tank configurations of double hull tankers and to the characteristics of the heavier hydrocarbon gasses.

Ships Carrying Benzene Mixtures

Special provisions to protect the health of seafarers on ships carrying mixtures which contain > 0.5% of benzene were adopted and issued as a recommendation. The guidelines include the maximum permissible operational exposure limit of 1 ppm of air (Time Weighted Average) per an 8 hour period and 5 ppm of air (Short Term Exposure Limit) per any 15 minute period. Specifics of the appropriate respiratory equipment to be worn by trained personnel for cargo operations and tank entry are also provided for different concentrations of benzene.

Double Hull Tanker Stability

At MSC-65, in November 1995, intact stability criteria for loading/unloading of double hull tankers was accepted. This included requirements to maintain an initial GM > 0.15m together with criteria governing the magnitude, area and range of the righting arm curve. However, during discussions at this meeting a question was raised concerning the means by which the ship is to comply with the criteria; i.e., by design alone or by design with consideration being given to operating restrictions on tank sequencing. During this session, the MSC was equally divided on this matter and therefore tasked its technical Sub-committee to further evaluate the two proposals with the view to developing a compromise while maintaining the “design only” principle.

Revisions to the Enhanced Survey Program

The Enhanced Survey Program contained in IMO Resolution A.744(18) and required via SOLAS Regulation XI/2 was amended to require that renewal surveys for tankers and bulk carriers carried out on or after 1 July 1998 are to be based on a written survey program. The submitted program is to show compliance with the close-up, thickness measurement and tank testing requirements of A.744(18) and incorporate relevant information including scantling drawings; plans of holds and tanks with coating information; provisions for tank cleaning, safe access and survey; and nominated tanks and structural sections for survey and testing.

These amendments are in line with the class requirements already implemented by IACS Member Societies. IACS proposals with respect to the accelerated and more rigorous surveys for bulk carriers and the survey of structures protected with soft coatings will be discussed at MSC-67 (November 1996) and MSC-68 (May 1997).

Ballast Tank Coatings

All dedicated seawater ballast tanks on tankers and bulk carriers constructed on or after 1 July 1998 shall have an efficient corrosion prevention system, such as hard protective coatings or an equivalent system. Where coatings are used they are preferably to be of a light color. The scheme for selection, application and maintenance of the system shall be approved by the Administration based on IMO Resolution A.798(19), which provides qualitative guidance to the owner.