2 3 Preface The report has been prepared for the PSA by SINTEF Department of Safety Research, in co- operation with various NTNU and SINTEF departments, in particular NTNU Engineering Design and Materials. The following colleagues have made a notable contribution: Stig Berge (NTNU MARINTEK) Inge Carlsen (SINTEF Petroleum and Energy) Martin Fossen (SINTEF Petroleum and Energy) Stein Hauge (SINTEF Technology and Society, Safety Research) Per J. Haagensen (NTNU Structural Engineering) Ole Meland (SINEF Technology and Society, Safety Research) Erlend Olsø (SINTEF Materials and Chemistry) Tor Onshus (NTNU ICT, Technical Cybernetics) Peter Sandvik (SINTEF MARINTEK) Anders Valland (SINTEF MARINTEK) We have had several meetings with the PSA, and would like to thank Gerhard Ersdal, Oddvar Øvestad, Ola Heia, Reidar Hamre and Hans Spilde for useful discussions and valuable input to this report. A draft version of the report was reviewed by John Sharp (Cranfield University) David Galbraith (Ocean Structures) Mamadouh Salama (ConnocoPhillips) Jan Andreassen (Eon Ruhrgass) Svein Bjørberg (Multiconsult/NTNU) And we would like to thank them for their consultative capacity. Trondheim 2010-03-19 Per Hokstad 4 5 Summary and conclusions A large number of facilities and parts of the infrastructure on the Norwegian Continental Shelf (NCS) are approaching or have exceeded their original design life. Many fields, however, have remaining recoverable oil and gas reserves which may be profitable if the field’s life time is extended. From a safety point of view, the condition of systems, structure and components (SSC) may not be acceptable for extended operation. The main objectives of this report are: To give an overview of and discuss various aspects of ageing related to offshore facilities, the risk they represent to the integrity of a facility and how to deal with them in an LE process, i.e. the basis for deciding on LE. How to document the safety of an ageing facility, in particular, and how to uphold the safety level by means of a maintenance programme balancing the ageing mechanisms. To identify possible knowledge gaps and suggest recommendations for those facing LE of offshore facilities. The report considers three aspects of ageing, illustrated in the figure below: Material degradation. Obsolescence, i.e. operations and technology being “out of date”. Organisational issues. LE process The report describes an LE process consisting of six main steps, see figure below. These are: 1. Data & information collection required to identify and analyse relevant risk factors and required risk reducing measures. This also includes establishing (risk) acceptance criteria to carry out LE. 2. Criticality (primary) screening of SSC, to identify critical units and barriers with respect to failure consequence and probability. Other aspects such as redundancy, common cause failures, detectability of failure and system availability are also considered. 6 3. Analysis of failures and challenges With respect to material degradation it is necessary to perform a secondary screening considering the Availability for inspection/monitoring of the SSC, to obtain knowledge about its current state. Accessibility for maintenance and/or modification of the SSC With respect to obsolescence and organisational issues it is necessary to identify challenges and gaps in relation to current requirements. 4. Identification and evaluation of potential risk reducing measures. 5. An assessment of the overall risk picture based on all aspects of ageing, given the risk reducing measures. 6. If the overall risk picture is acceptable, an LE management plan should be implemented that ensures integrity throughout the LE period and Makes sure that the facility’s technical, operational and organisational integrity level is maintained during the LE. Is adjusted to today’s and (expected) future type of operation, organisation and requirements. If the overall risk picture is not acceptable, additional risk reducing measures must be identified and a new maintenance and modification plan prepared. The report presents some “case studies” to illustrate aspects of the LE process. Relevant questions with respect to obsolescence and organisational issues are exemplified by: Lifting equipment and material handling. The following systems are investigated and exemplified mainly with respect to material degradation: Wells. Subsea production and transportation systems. o Pipelines. o Flexible risers. o Subsea production systems. Topside process equipment. Safety systems. Note that structures are not dealt with specifically in the report, as much has been written on ageing and structures. However, the general part (chapters 1-3) in the report is also applicable to structures and other systems. 7 Knowledge gaps related to ageing In this report the following knowledge gaps have been identified: Understanding and assessing degradation mechanisms and modelling of degradation mechanisms for various materials and equipment. Developing and applying reliable methods for subsea inspection and monitoring. Understanding and increasing awareness of common cause failures of equipment due to ageing. Assessing the effects of and utilising methods for monitoring of facility loads. Understanding ageing of electronic equipment and cabling. Optimising test intervals for safety systems with respect to material degradation. Understanding the results of testing, inspection and monitoring of process equipment with respect to degradation mechanisms. Understanding the consequences of combining old and new equipment. Assessing the effects of subsidence on relevant SSC, such as structure, helideck and free fall lifeboats. 8 Important issues to consider for operators in a life extension process The operator should ensure the technical, operational and organisational integrity of the facility during an LE period; in particular, (analogue to the abovementioned LE process): Ensuring that safety is maintained throughout the entire LE period. Preparing a screening process to identify which SSC are critical with respect to ageing. Establishing a reliable estimation of material degradation of the critical SSC caused by degradation mechanisms relevant to the given SSC. Specifying an analysis (e.g. by providing a check list) for identifying obsolescence and organisational risk factors, e.g. deviations from requirements, lack of spare parts and lack of competence. Establishing a process for identifying cost-effective measures to close identified gaps. Including uncertainties and future changes of the system, also considering possible impacts from the surroundings. Ensuring sufficient competence to carry out LE assessments and to follow them up during the LE period. Further research and development In the report, the following recommendations for research and development have been found: 1. Initiating an interdisciplinary project on analyses of degradation mechanisms of critical systems, comprising: a. Modelling of the main degradation mechanisms, also considering the combined effect of various degradation mechanisms, common cause failures and effect of operational conditions. b. Development of systems for data collection and use of field experience with degradation failures. 2. Developing a general guideline for design of the LE processes encompassing the entire facility, e.g. by means of a case study. 3. Improving maintenance management systems for ageing and life extension so that all three ageing aspects are being “processed” in parallel, in order to evaluate and improve the operator’s maintenance systems prior to and during life extension. Such management would mean improved awareness and overall knowledge of the SSC on the facility, e.g. combinations of old and new equipment, availability of spare parts, common cause failures, new types of operation and new technology. 9 TABLE OF CONTENTS Preface 3 Summary and conclusions ............................................................................................................5 1 Introduction 13 1.1 Background ....................................................................................................................13 1.2 Objectives.......................................................................................................................13 1.3 Structure of report ..........................................................................................................13 1.4 Limitations and assumptions..........................................................................................15 2 Ageing and life extension management..............................................................................17 2.1 Categorisation of ageing management issues.................................................................17 2.2 Main tasks of a Life Extension process..........................................................................18 2.3 Data and information collection.....................................................................................21 2.4 System breakdown and criticality (primary) screening..................................................22 2.4.1 System breakdown structure ...........................................................................22 2.4.2 Main systems on a facility...............................................................................23 2.4.3 Criticality classification and primary screening..............................................23 2.5 Secondary screening and detailed