Paik / Melchers Condition Assessment of Aged Structures

1. Auflage 2014
ISBN: 978-1-84569-521-7
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 552 Seiten

Reihe: Woodhead Publishing Series in Civil and Structural Engineering

Any structural system in service is subject to age-related deterioration, leading to potential concerns regarding maintenance, health & safety, environmental and economic implications. Condition assessment of aged structures is an invaluable, single source of information on structural assessment techniques for marine and land-based structures such as ships, offshore installations, industrial plant and buildings. Topics covered include: - - Current practices and standards for structural condition assessment - - Fundamental mechanisms and advanced mathematical methods for predicting structural deterioration - - Residual strength assessment of deteriorated structures - - Inspection and maintenance of aged structures - - Reliability and risk assessment of aged structuresProfessionals from a broad range of disciplines will be able to gain a better understanding of current practices and standards for structural condition assessment or health monitoring, and what future trends might be. - Single source of information on structural assessment techniques for marine and land-based structures - Examines the residual strength and reliability of aged structures - Assesses current practices covering inspection, health monitoring and maintenance

Autoren/Hrsg.

Paik, J K

Melchers, R E

Leseproben

1 Current practices in condition assessment of aged ships and floating offshore structures
G WANG, C SERRATELLA and S KALGHATGI,     American Bureau of Shipping (ABS), USA Abstract
This chapter introduces the background of the inspection regime, including inspections by classification societies, regulatory requirements, and industry voluntary inspections. It also explains the practice of designing and maintaining marine structures, typically ships and offshore floating structures, and nondestructive examination and monitoring techniques. The chapter concludes with challenges and future trends that serve as the starting point for the entire book. Key words inspection corrosion crack nondestructive testing coating 1.1 Introduction
The economic boom that started in Asia created the demands for the shipping of more energy, materials and products. This boom has been driving the shipping industry to build larger and more sophisticated vessels. Oil prices are at a historically high level, which in turn have made development of the oil fields in remote and less accessible locations economically feasible. The shipping and offshore industries are taking a more proactive approach and are embracing innovative and novel concepts. A foreseeable result of these actions is the need for more proactive and intelligent maintenance as well. In response to ever-heightening public concerns over safety at sea, the regulatory agencies are increasingly involved in the design, operation and maintenance of marine structures. The European Union has decided to accelerate phasing out of single-hull tankers. The International Maritime Organization (IMO) has embarked on developing regulations for design and maintenance of ship structures. This goal-based standards (GBS) initiative reflects the demand of the public for explicitly defined safety or risk levels for the marine industry. One of the keys to maintaining and improving safety levels is to more effectively and efficiently manage the structural integrity of ships and offshore installations. The network of maritime safety partners includes the shipowner and shipbuilder, the classification society, the IMO, the flag state, port state, underwriter, financier, marine insurance company, and charterer, among others. Responsible parties are committed to continuous improvement in overall safety and in the reduction of pollution, ‘striving for zero’ –zero fatalities, zero pollution and zero detentions! To achieve these goals, the industry has developed and implemented a series of initiatives and is embarking on others. The accumulated efforts of these partners have led to an improved level of safety. The number of marine incidents clearly demonstrates a declining trend, as illustrated by the tanker industry information shown in Fig. 1.1.
1.1 Number of reported tanker incidents during 1978–2007 and extent of accidental pollution (INTERTANKO 2006). The industry has established a practice of maintaining the life-cycle integrity of hull structures through design, corrosion protection, inspection, monitoring and repair. Periodic inspection and survey play a key role in maintaining lifecycle structural integrity. The primary purpose of hull inspections is to identify the condition of the structures in order for the risks of potential structural failures to be assessed so that appropriate actions can be taken. This chapter introduces the background of the inspection regime, including inspections by classification societies, regulatory requirements, and industry voluntary inspections. It also explains the practice of designing and maintaining marine structures, typically ships and offshore floating structures, and nondestructive examination (NDE) and monitoring techniques. The chapter concludes with challenges and future trends that serve as the starting point for the entire book. 1.2 International Association of Classification Societies (IACS) and vessel inspections by classification societies
1.2.1 Classification societies and the International Association of Classification Societies
Classification societies were established to act as neutral third parties, undertaking ship surveys in support of insurers. Classification societies establish standards, usually called classification rules, regulating design and maintenance of ships, and conduct periodic surveys to implement these standards (IACS 2004a). Classification societies have their own individual histories, some having been in business for more than 100 years. Their primary purpose is to perform inspections and surveys of vessels to verify that they are maintained to the requirements of classification societies’ rules and standards. These inspections and surveys are performed at periodic intervals to ensure compliance with the respective rules. The International Association of Classification Societies (IACS) was formed by seven leading societies on 11 September 1968. IACS presently consists of 10 member societies and one associate member. With 90% of world cargo-carrying tonnage covered by the rules of IACS members, IACS plays a vital role in improving the standards of the maritime industry. The value of their combined and unique levels of knowledge and experience has been widely recognized. In 1969, IACS was given consultative status with the IMO with the first permanent representative appointed in 1976. 1.2.2 Hull inspections by classification societies
Fundamentally, there are three reasons for ships to be inspected – to verify the condition of the vessel, to check for compliance with statutory requirements for the ship and its manning, and to confirm the suitability of the ship for its intended commercial operation. It has been a challenge to inspect hull structures due to the sheer size of ships and offshore structures (see Fig. 1.2). Classification societies carry out hull classification surveys to confirm the condition of a vessel through a process of overall visual examinations, close-up visual examinations, NDE and thickness measurements. Surveys are typically made up of Annual Surveys, Intermediate Surveys and Special Surveys (ABS 2007).
1.2 Inspection of marine structures is very challenging because of their sheer size – the two diagrams are to the same scale (EMSA 2005). Annual Surveys (AS) are carried out each year to ensure that the hull structure and piping are maintained in satisfactory condition. An Annual Survey typically takes one to two days. Usually, the survey includes the externally accessible hull and piping surfaces. Intermediate Surveys (IS) are carried out at the mid-point of the five-year special survey/certificate cycle. The Intermediate Survey is comprised of the same inspection of external hull and piping surfaces as in the Annual Surveys plus an examination of ballast tanks and cargo tanks. The aim of the Intermediate Survey is to verify that conditions have not deteriorated at a rate greater than that assumed during the preceding Special Survey (see below). For vessels that are older than 10 years, the extent of the survey is increased. More extensive thickness measurements may be required. Intermediate Surveys take approximately three to four days for completion. Special Surveys (SS) are carried out every five years in order to provide an in-depth examination of the structural condition of the vessel. All compartments are subjected to survey while the vessel is dry-docked. Special Surveys take about one to two weeks, and the extent of time increases with the age of the ship. General Visual Inspection (GVI) is carried out as part of an SS. GVI is an overall visual examination of the structure to decide upon its general condition and to narrow down the areas that need to be examined in close proximity. Close Visual Inspection (CVI) is the visual examination in close proximity. CVI provides the best representative samplings of areas likely to be most exposed to the effects of corrosion, sloshing and stress concentration. The special value of CVI is that it provides the best representative samplings of those areas most likely experiencing the greatest exposure from the effects of corrosion, sloshing and stress concentration. The close proximity of the inspection is usually considered to be within hands’ reach or less than three feet of distance between the structure and the inspector’s eyes. CVI provides an assessment to the inspector as to the quality of coating protection, the rate of material degradation, and the ability of the structure to serve its intended or design purpose. Both GVI and CVI may be supplemented by thickness measurement, with requirements based on age and type of vessel. 1.2.3 Thickness measurement
Thickness measurement is also called gauging. Its purpose is to establish, in conjunction with a visual examination, that the condition of the existing structure is fit for continued service during the subsequent survey...