The BP Oil Tanker Structural Monitoring System

Abstract

BP Oil Company time-charters a fleet of American-flag tankers for the ocean transportation of crude oil and petroleum products to the East, West and Gulf Coasts of the United States. Commencing in 1991, ship response and structural monitoring instrumentation was installed on the four ships of the Atigun Pass-class. These crude carriers are operated in the Trans-Alaska Pipeline Service, or "TAPS" trade, sailing the waters of the North Pacific Ocean and Gulf of Alaska. The structural monitoring systems were designed to measure the effects of subjecting a ship to the typical loads and forces encountered while at sea: hogging, sagging, slamming, hydrostatic pressure, and hull girder springing. Additionally, BP was interested in developing a system that could provide shiphandling guidance to the master or watch officer so that the detrimental effects of prolonged exposure to such loads and forces could be effectively minimized. The paper describes in detail the physical arrangement of the BP Oil Tanker Structural Monitoring System (BPSMS), including the suite of sensors employed to measure ship responses and hull girder stresses. It explains how the response data collected by the sensors is analyzed by the onboard computer located on the ship's bridge and how ship response data are presented back to the deck officers via a family of display monitor screens. These displays provide the officers with a "tool" that can be used to effectively monitor the physical and structural response of their ship to waves, and to quantify, in terms of lowering the wave bending moment and reducing the risk of slamming, the result of an action or actions taken to minimize the risk of incurring structural damage. Onboard ship response and structural monitoring is now an integral part of BP's tanker fleet structural management program. The units have greatly increased the awareness of the ship's officers regarding their role in helping to control the amount of structural damage done to the ships. Data from the units have also helped management make more informed decisions regarding operational requirements placed on the ships.