Improved Inspection of Wooden Vessel Fasteners.
Abstract
The Coast Guard is responsible for the safety of over 2000 wooden vessels which carry passengers. In 1993, a vessel sank in the Chesapeake Bay with the loss of three lives. The investigation concluded that the sinking was caused by faulty fasteners adjacent to the keel. The National Transportation Safety Board recommended that the Coast Guard investigate methods to non-destructively evaluate fasteners. This report documents the evaluation of various nondestructive methods such as sounding methods, specialized drills, ultrasonics, stress wave techniques, a capacitor based system and x-rays. These techniques were tested under field conditions on a hull and in the laboratory. Two x-ray techniques were the only methods which directly measured the condition of the fasteners themselves. Conventional x-rays were effective at identifying the fasteners and their condition. The real time x-ray system used in this study did not perform as well, but it shows potential due to its smaller size and faster processing speed. Other real time systems with stronger sources, currently on the market, are expected to perform as well as conventional x-rays. Neither technique can evaluate the condition of the wood immediately adjacent to the fasteners, although deteriorated wood is not usually found next to a good fastener unless the vessel has been refastened. The results of the x-rays should not be the only piece of information used to assess the condition of the fasteners. information such as the vessel's history and visual clues should be combined for a total assessment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1997
- Accession Number
- ADA338018
Entities
People
- Kurt A. Hansen
Organizations
- United States Coast Guard Research & Development Center