Wire rope for installations of subsea components offshore have been used for years in different configurations as single-fall or multi-fall. With greater water depths multi fall solutions become more challenging as even low torque ropes induce some torque and great technical effort has to be made to overcome this problem. An alternative solution is the use of a single-fall system employing a large diameter wire rope. Installations are often carried out with the aid of a heave compensation system to keep the load steady during final approach or to pass through resonance zones. As a result such a large diameter wire rope is subjected to frequent bending. It is well known that cyclic bending over sheave (CBoS) can significantly reduce the lifetime of ropes depending on rope utilisation factors and sheave diameters. While there is a lot of data available for smaller rope sizes, very limited data has been generated with large diameter ropes. It was therefore considered necessary to build a bending fatigue test rig and perform bending fatigue tests with the aim of reducing the uncertainty in the fatigue life of large diameter wire ropes. This paper presents the bending fatigue test rig capable of testing O̸109 mm wire rope to up to 330 t, describes the bending fatigue tests carried out and presents bending fatigue test results. Furthermore, results from non-destructive tests, which were frequently performed during the fatigue tests to obtain further information of rope deterioration over its lifetime, will be presented in this paper.
This paper explains how digital technology combined with standardisation is used to improve Subsea 7's offshore operations with the aim to avoid incidents, increase efficiency and reduce cost and schedule. A new way to write, use, and complete offshore installation task plans has been developed. Using an electronic database and application-based system, Electronic Task Planner (ETP), hard copies will become redundant. Integration of Standard Task Plans (STP) in the ETP enables re-use of procedures, ensuring best practices are consistently applied during offshore operations, and will significantly reduce time to produce and review documents. The system will auto-generate as-built documentation and input to the vessel daily progress reports. Offshore operations are supported by means of 3D virtualisation technology and animations. VR models are used to visualise the work environment for familiarisation and for design and procedure planning. 3D models can easily be integrated into the VR environment, combined with vessel and ROV models from the 3D model library to quickly analyse a proof of concept for the engineering planning. An emulation room and testing lab has been set-up, and by creating virtual models of the vessels, control systems can be effectively tested under near to "live" conditions. By integrating a physics engine into the emulator system, projects can be verified against expected sea states and can confirm the control system will allow project operations to be completed. Using the emulation techniques means operators can be trained on exact same virtualised control system software in advance of actual construction, or control functions can be tested before delivery to the vessel. The same model can also be used to facilitate efficient planning and familiarisation of deck operations.
It is clear that the offshore industry is striving to develop fields in deeper and deeper water and that subsea production is a key element in this development. This then leads to the question of what is the most efficient method of installing subsea production equipment in very deep water. This paper will address the issues associated with using conventional lifting technology based on steel wire rope for deep water applications. The new deep water construction ships being brought into operation have conventional lifting equipment based on steel wire rope. The requirement to be able to handle loads in excess of 300 t in great water depths leads to the need for large diameter multi-strand ropes with low spin characteristics. The long term behaviour of these ropes particularly in applications which require the use of heave compensator is uncertain due to the lack of any suitable test data. This paper will describe a full scale testing program to determine the fatigue performance of large diameter steel wire rope, including the design and building of a new testing machine, together with a summary of the results and the impact the results have on installation operations.
The offshorepipeline market remains a large segment of oil and gas expenditure inAsia-Pacific and is forecast to continue apace. Design and installation ofpipelines in Asia and Australia is generally no more arduous than usual butthere are some distinctive characteristics of the continental margins withinthis region that are not commonly found in other oil and gas producing areas. In particular, the continental margins of the South China Sea and NW Australiaare much wider, and can be far more topographically uneven than those found elsewhere. This has a profound impact on pipeline design and integrity with specificrespect to spans. Of interest tothis study are: the underlying causes of on-bottom roughness, pipeline routing, critical span predictions and, from an installation perspective, spanrectification measures. It is not uncommon for on-bottom roughness and spananalyses to significantly over-predict quantities of critical spans in theearly design stages. Many of these will be marginal and in all likelihood neverappear once the pipeline is laid. Effort to eliminate these at the earliestpossible stage is worthwhile. This paper firstfocusses on the physical features of the continental margin that give rise toon-bottom roughness to help understand what are the particular soils and seabedfeatures that cause the spans which is information vital to the selection andapplication of span mitigation measures. The study then considers how thenumber of predicted spans can be reduced through a process of preliminary routeoptimisation and other measures including recommendations for optimisationsthat can be applied to input parameters used in span analyses. Lastly the paperconsiders the challenges of remedial work in the field. There are many spanrectification methods available but none are appropriate for all circumstances. The technology is reviewed and a matrix is presented assigning levels ofsuitability to each method depending on seabedconditions and water depth. Bothpre-lay and post-lay rectification measures are considered. Improvements in pipelinerouting and span analysis should result in more reliable predictions of therectification required and provide more realistic scopes of works for planningand costing.
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