Effects of Double-Hull Requirements on Oil Spill Prevention: Interim Report (1996)

Operation of double-hull tankers

1. What is your experience with operational safety of double hull tankers in regard to:

   • stability during loading and discharging

   • safe access to ballast spaces

   • ventilation of ballast spaces

   • any other safety issues that need to be addressed.

Are there significant differences in cargo operations between double-hull and single-hull tankers?

Have you established operational procedures specifically for double-hull tankers?

Inspection and maintenance of double-hull tankers

1. Please provide information on structural and tank coating inspection frequencies and practices on double-hull tankers.

2. What is your experience with different types of coating in ballast spaces? Have you encountered significant corrosion problems? If so, please describe.

3. What are your current practices with regard to ballast tank coatings (include type, number of coats, thicknesses)? From your experience, what is the expected life of the coatings?

4. Do any of your maintenance and inspection practices for single-hull tankers differ from those used on double-hull tankers?

Design of double-hull tankers

1. Have you had any structural problems on double-hull tankers? Please provide information on the type of problems.

2. What is your experience with high strength steel construction?

3. What design changes would you suggest in future double-hull tankers?

Fleet information

1. Please provide the number and size characteristics of double-hull tankers in your fleet.

2. Please note if any of your operation experiences are specific to certain sizes of double-hull tankers.

General

1. Based on your experience, what are the advantages and disadvantages of double hull tankers as compared to single-hull tankers?

Design Characteristics

1. See the attached ship characteristics form for double-hull tankers. Kindly complete the form for double-hull tankers that have been built, or are under construction, or on order in your yard. An example of a completed form is provided for your guidance in completing the form.

2. Additionally, what is the percentage of high strength steel used in each design?

3. What design changes do you foresee in future double-hull tankers?

Producibility

1. In comparing the producibility of single-hull and double-hull designs of 90,000, 150,000, and 280,000 DWT sizes, please provide an estimate of the differences (in absolute terms or on a percentage basis) of labor hours or cost between single-hull and double-hull construction for:

   1. steel fabrication

   2. machinery/outfitting

   3. coatings (include type and extent)

   4. total construction time (keel laying to delivery)

   5. any other comparative data related to construction or producibility

Please describe any particular problems in double-hull construction versus single-hull construction.

Maintenance

1. Accessibility of spaces: what has been your experience relative to ease of access of spaces in double-hull tankers versus single-hull tankers?

2. Ability to gas-free spaces: what has been your experience in the ability to gas-free spaces in double-hull designs for the safe entry of personnel?

3. Maintenance related problems: please describe any maintenance-related problems experienced with double-hull tankers.