Structural Integrity Monitoring: Review and Appraisal of Current Technologies for Offshore Applications

Author(s):  
P. May ◽  
D. Sanderson ◽  
J. V. Sharp ◽  
A. Stacey

The use of structural integrity monitoring techniques on offshore installations provides the potential to reduce the risk of structural failure. The Health and Safety Executive’s (HSE’s) Offshore Division has funded a review of relevant technologies in structural integrity monitoring with potential application to offshore installations as well as practical offshore experience with structural integrity monitoring. The purpose of the study was to identify current capabilities of structural integrity monitoring techniques for structural integrity management of offshore installations (i.e. offshore jackets and semi-submersible structures used for drilling and or production operations but excluding FPSOs), to identify limitations in current approaches and identify areas for further development, to identify opportunities for technology transfer from other industries and to review and assess key research and development including current initiatives. The key structural integrity monitoring methods relevant to offshore structures were reviewed. It was found that offshore experience of structural integrity monitoring is limited to date and that all current systems are for bespoke applications. Current codes and standards refer in a limited sense to the use of structural integrity monitoring and this may influence the limited take up to date of this technology. However, there is a regulatory requirement for leak detection in ageing semi-subs as a recent introduction to DNV classification rules OSS-101 [1].

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Ajith Kumar Thankappan ◽  
M. Fazli B. M. Yusof

This paper highlights the key differences in practices employed in managing hull structure integrity of permanently moored floating offshore structures as against sailing vessels which are subject to periodic dry docking. During the design phase, the structural integrity management over the life of a sailing vessel is primarily taken into account by means of Class prescribed Nominal Design Corrosion Values which are added to minimum scantling requirements calculated based on strength and fatigue criteria. In contrast, for permanently moored offshore installations like FPSOs, FSOs etc. the hull structure integrity over the entire design life of the asset is a key design consideration both for new buildings and conversions. Analytic methods and tools (primarily those developed by Class Societies) are available to evaluate the strength requirements (based on yielding, buckling and ultimate strength criteria) and fatigue life of the hull structure. Typically three levels of analysis with increasing degree of complexity and analysis time are used to predict the structural response and fatigue life of the Hull during design phase. The degree of detailed analysis required needs to be determined in light of the expected optimization in terms of savings in scantlings for new building or for steel renewal requirements in case of conversions.


Author(s):  
S. Gupta ◽  
D. Sanderson ◽  
A. Stacey

The effective structural integrity management of the ever-increasing population of ageing offshore installations on the UKCS requires the identification of key parameters which provide a measure of the criticality of installations to structural failure, thus enabling priorities to be set. This paper describes a model for the evaluation of the criticality rating of fixed offshore installations.


Author(s):  
A. Stacey ◽  
M. Birkinshaw ◽  
J. V. Sharp ◽  
P. May

In recent years, a significant amount of effort has been expended by HSE and the offshore industry on the development of good practice for structural integrity management in the new code for offshore structures, ISO 19902. However, a review of the structural integrity management of fixed offshore installations operated on the UKCS has indicated that duty holders adopt varying approaches, in terms of both the methods used and effectiveness. The elements of a framework for the management of the structural integrity of fixed jacket structures are presented.


Author(s):  
A. Stacey ◽  
M. Birkinshaw

With an ever-increasing population of ageing offshore installations in the North Sea, the Health and Safety Executive’s (HSE’s) Offshore Safety Division has focused its front-line operational activity in recent years on the structural integrity management process and establishing the extent of any deterioration in structural integrity. The current phase of work, the Structural Integrity Management Inspection Programme (SIMIP), is described and the findings to date are presented in this paper.


Author(s):  
Torgeir Moan

Based on relevant accident experiences with oil and gas platforms, a brief overview of structural integrity management of offshore structures is given; including an account of adequate design criteria, inspection, repair and maintenance as well as quality assurance and control of the engineering processes. The focus is on developing research based design standards for Accidental Collapse Limit States to ensure robustness or damage tolerance in view damage caused by accidental loads due to operational errors and to some extent abnormal structural damage due to fabrication errors. Moreover, it is suggested to provide robustness in cases where the structural performance is sensitive to uncertain parameters. The use of risk assessment to aid decisions in lieu of uncertainties affecting the performance of novel and existing offshore structures, is briefly addressed.


Author(s):  
A. Stacey ◽  
J. V. Sharp

This paper presents a primary integrity management (PIM) framework for mobile installations (semi-submersibles and self elevating installations) and permanently moored floating installations (FPSOs, FSUs, etc.). The primary integrity of self-elevating and floating installations depends on both the primary structure and additional systems. The framework is based upon the UK regulatory requirements for offshore installations, including the need for a thorough review of the safety case accounting for any changes in condition and future plans and verification of the primary integrity management (PIM) process. Requirements and guidance are provided for all aspects of the integrity management process covering: • primary integrity hazard identification and risk control; • resources, organisation and management, including competency assurance; • information management and documentation; • primary integrity management policy, objectives and strategy; • inspection, examination and testing; • evaluation of structure and other primary systems; • maintenance, repair and upkeep; • audit, review and continual improvement. The framework also contains guidance based on the application of existing standards and industry published documents. Finally, guidance is given on the implementation of the framework.


Author(s):  
Ingar Scherf ◽  
Trine Hansen ◽  
Gudfinnur Sigurdsson

Offshore Structures operate for decades in extremely hostile environments. It is important during this period that the structural integrity is efficiently managed to ensure continuous and safe operation. Increased use of enhanced oil and gas recovery means it is likely that many existing installations will remain operational for a significant period beyond the original design life. The operator needs to capture, evaluate and, if necessary, mitigate design premise changes which inevitably occur during the life of a structure. Further, advances in knowledge and technology may imply changes in codes and standards as well as in analysis methodologies. Changes in corporate structures, transfer of operator responsibility and retirement of experienced engineers call for reliable means to transfer historical data and experience to new stakeholders. Effective emergency preparedness capabilities, structural integrity assessments and inspection planning presuppose that as-is analysis models and corresponding information are easily accessible. This paper presents an implementation of the in-service integrity management process described in the new revision of NORSOK standard N-005 [1] for a large fleet of jackets at the Norwegian Continental Shelf. The process, comprising management of design premise changes as well as state-of-the-art technical solutions over a range of disciplines, has enabled the operator to prolong the service life with decades at minimum investments. A structure integrity management system (SIMS) has been developed and digitized over years and streamlined to meet the needs and challenges in the operation and management of the jacket platforms. SIMS enables a rather lean organization to control the structural integrity status of all load-bearing structures at any time. Platform reinforcements and modifications along with other operational risk reducing measures like unman the platforms in severe storms enable continued use with the same level of safety as for new manned platforms. Advanced analyses are used to document regulatory compliance. Modern fatigue and reliability based inspection planning analyses have reduced the costs needed for inspection of fatigue cracks significantly. The benefits from the SIMS system are substantial and the resulting safety and productivity gains are apparent. The continuity of knowledge and experience is maintained, reducing risk to safety and regularity. The digital transformation related to management of structural integrity status as described in NORSOK standard N-005 is realized through SIMS.


Sign in / Sign up

Export Citation Format

Share Document