ABS Group Programs for Technical Evaluation and Longevity Assessments of Ageing Gas Carriers (eBook)

Published Date

January 2000

ABS Group Programs for Technical Evaluation and Longevity Assessments of Ageing Gas Carriers (eBook)

(Excludes any applicable taxes)

This paper will discuss the ABS Condition Assessment Program as applied to 15 existing LPG Carriers and 2 LNG Carriers. (12pp)

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In 1987 the American Bureau of Shipping, at the request of Marathon Oil Company performed hull-girder bending moment analysis and hull- girder strength analysis to estimate the service life of the ARCTIC TOKYO and the POLAR ALASKA LNG Carriers. The study was requested as the vessels approached their twentieth anniversary which is the nominal service life assumed in the IMO Gas Code. Today, over 37 % of the worlds fleet of LPG and LNG carriers are operating beyond this age as owners and operators are confident that their vessels can continue to provide safe and reliable service. However, in view of the risks inherent in the gas tanker trade, prudence dictates that this confidence be somehow substantiated on a technical basis.

In 1994 ABS Group, the wholly owned subsidiary of the American Bureau of Shipping developed a Condition Assessment Program (CAP) for oil tankers and bulk carriers. This service has now been extended to gas carriers and containerships. This service provides a formalized means of evaluating the condition of a vessel at a point in time. It also provides the owner with useful information as to the expected condition of the vessel based on the observed rates of corrosion. For oil tankers, bulk carriers and container vessels, the tool used for the structural evaluation is SafeHull the ABS dynamic based load and response criteria for design and evaluation of hull structure first introduced in 1994. This criteria is based on an engineering first principles approach that establishes the dynamic loads and the combination of these loads, and corresponding strength formulation to judge the adequacy of the structure to resist the dominant failure modes of yielding, buckling and fatigue.

The ABS paper presented at GASTECH 1994 in Kuala Lumpur discussed how this SafeHull technology could be applied to existing LNG Carriers. Since that time ABS had developed additional tools for strength and fatigue assessment of designs. This methodology, which is currently being applied to site specific FPSO vessels, evaluates the structure of an existing vessel taking into consideration the fatigue damage accumulated during trading history, the route and / or site-specific wave environment and strength and fatigue demand at the intended site.

This paper will discuss the ABS Condition Assessment Program as it has been applied to 15 existing LPG Carriers and 2 LNG Carriers and what has been observed. It will also discuss how the ABS SafeHull technology, particularly with the latest developments, can be used for much more detailed longevity assessments including fatigue considerations to fully refrigerated LPG carriers. In addition recent developments of an approach proven very effective on some existing oil carriers for minimizing further fatigue damage with potential immediate application to gas carriers will be presented.

Paper Delivered by:
James J. Gaughan
Peter G. Noble
Prepared for:
Gastech Houston 2000

For over 45 years, the Gastech Exhibition & Conference has been at the forefront of the international gas and LNG market. This world-renowned event is regarded as the most significant meeting place for gas and LNG professionals, where the global industry gathers to do business.

Gastech hosts major IOCs, NOC’s, global utility companies, EPC contractors, shipbuilders, pipeline companies, manufacturers, distributors, technology and service providers, all who play an active role in the global energy value chain.

Title: ABS Group Programs for Technical Evaluation and Longevity Assessments of Ageing Gas Carriers (eBook)
Product Code: 4433g098
Published Date: January 2000

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