Ad Hoc Panel #7

The newly formed SNAME panel, Safety Assessment of Double Hull Tanker Design and Operation, is the seventh in a series of successful ad hoc panels tasked with providing timely responses to critical issues facing the marine industry. The panel will serve under the direction of the SNAME Technical & Research organization, with sponsorship provided by the Ship Structure Committee. The principal objective of the Oil Pollution Act of 1990 (OPA 90) provisions and MARPOL amendments mandating double hull construction for tankers is to mitigate oil spillage from collisions, allisions, and groundings. Theoretical analysis and anecdotal information indicate that double hull tankers perform well in this regard, although an evaluation of recent casualty statistics is needed to substantiate this view.

Double hull tankers also present different design, construction, maintenance, and operational considerations as compared to single hull tankers. For example, there is a risk of explosion whenever vapors escape into the outer hulls; the large surface areas of the ballast tanks introduce challenges regarding corrosion control and inspection; and single hull and double hull vessels have different behaviors when breached during groundings. The Ad Hoc Panel will take a retrospective look at tanker design and operations during the 1990’s. Current practices will be reviewed, and the advantages and disadvantages of double hull tankers assessed.

An overview of the panel’s anticipated effort is described below. The first meeting of the Ad Hoc Panel will be held on April 27^th in Houston, at which time the complete work scope will be defined.

• The Ad Hoc Panel will identify critical issues related to safety and pollution.
• A letter will be sent to double hull tanker operators requesting their input on the advantages and disadvantages of double hull tankers relative to single hull tankers, and their experience and opinions related to the critical issues identified by the Ad Hoc Panel. The responses will be compiled and included in the panel’s report.
• The panel will summarize current practices related to double hull tanker design, including tankage arrangements, coatings for ballast and cargo tanks, structural design (e.g. design standards for fatigue life), etc.
• The panel will compile and evaluate casualty and oil spill data on double hull tanker collision, allision, grounding, structural failure and fire/explosion incidents which have occurred since 1990.
• An investigation into the magnitude of risk from fire and explosion associated with vapors in double hull spaces will be conducted. The historical performance of the growing double hull tanker fleet together with other types of double-hulled vessels (chemical carriers, OBO’s) etc. will be reviewed. The effectiveness of design features and operational measures intended to reduce the risk of explosion will also be assessed.
• A workshop will be held with invitations sent to tanker owners and operators, shipyards, designers, environmental representatives, and other industry, regulatory and legislative representatives. The findings from the panel’s studies will be reviewed, and further input solicited.
• The validity of each perceived advantage and disadvantage of double hull tankers will be assessed on the basis of statistical analysis and, where appropriate, expert opinion. Issues requiring further research will be identified.
• The panel’s findings will be summarized in a paper presented at SNAME’s 1999 Annual Meeting in Baltimore.

If you would like to contribute to this effort, either as an active member of the Ad Hoc Panel or as a corresponding member, please contact:

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