Objective
The aim of the project is to provide a rational methodology for scheduling of inspection of fixed offshore platforms based on reliability techniques which will result in :
. Improved safety of fixed offshore installations
. Increased effectiveness of subsea work by eliminating unnecessary repairs
and targeting maintenance.
. Enhancement of operating life of the structure by concentrating resources
on critical problem areas.
. Implementation of the developed methodology for a typical fixed platform to
assess the benefits.
The main ocnclusions and achievements of the project are :
1. The reliability analysis methods developed within another European Research programme (BRITE-P2124) have been integrated with validated fracture mechanics models. This has led to accurate modelling of the fatigue crack deterioration process.
2. The reliability analysis programs provide expected cost of inspection, repair and failure in addition to reliability index. This has resulted in a system which allows alternative inspection, maintenance and repair plants to be compared.
3. A module for fatigue crack growth calculations in tubular joints using fracture mechanics was developed.
4. A methodology and module have been developed for providing fatigue loads for reliability calculations.
5. Corrosion fatigue crack growth material properties are required for accurate reliability analysis. An existing corrosion fatigue crack growth database of experimental results was analysed to provide a high level database.
6. The performance of parametric equations was assessed by comparing predicted results with experimental data. From this, recommendations for bias factors have been provided.
7. The inspection reliability data (POD) is normally expressed in terms of crack length. However, for the purposes of fracture mechanics analysis the POD expressed in terms of depth is required. The data for four commonly used NDT methods was re-analysed and POD was expressed in terms of depth.
8. A prototype knowledge based system which can schedule based on reliability index was produced.
9. Knowledge based systems for ranking, scheduling and system control have been developed.
10. A full user interface specification and design has been produced.
11. Validation of database and analysis modules has been performed.
12. Validation of the analysis system using a sample platform structure was carried out.
In order to apply the system in practice, the following work is required :
1. Integrate modules with operators' information systems to provide the RISC system with all the necessary information.
2. Develop user interfaces.
3. Develop modules for automating and interfacing to external analysis modules. In particular, interfaces are required with finite element systems.
4. Carry out calibration studies to gain experience of the overall methodology and to obtain acceptance by Certification Authorities, legal bodies etc.
The above tasks could be carried out as part of a RISC User Group activity or on a case-by-case basis for individual operators.
The development of inspection strategies for offshore structural integrity should be done within a framework giving advanced reliability analysis and utilising a knowledge base approach. It incorporates the latest developments in modelling and the appropriate databases. Finally, a reduction in uncertainty can be obtained by introducing a higher quality of data input through the use of on-line monitoring.
The modelling of the effects of the environment on the structure and the evaluation of inspection results requires up-to-date databases for materials, analysis methods and inspection techniques. In this project suitable database structures have been defined and some sample data provided.
Structural integrity assessment is based on fracture mechanics crack growth analysis.
The physical modelling includes the loading history, stress analysis fracture mechanics calculation of stress intensity factors and the materials response (crack growth data).
The Knowledge Based System for ranking, scheduling and system control will provide an overall framework for RISC.
Programme(s)
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
MK12 5RB Milton Keynes
United Kingdom