This paper details the approach taken to maximise the reliability of the Hutton Tension Leg Platform (TLP) production riser tensioners. The design, development, testing and operational performance of the tensioners are described. In addition the paper outlines the reliability analyses and quality assurance procedures which are used. Operational experience of the production riser tensioners installed to date on the Hutton TLP is summarised. Conclusions are drawn and recommendations made for future work of this type.
The Hutton field in the North Sea was discovered and named in 1975. Various development concepts were investigated and in 1980 the decision was taken to utilize a Tension Leg Platform as a production facility.
The Hutton Tension Leg Platform (TLP), being a permanently moored buoyant structure, responds to wind, wave and current forces. The risers, 24 production, one offtake and one drilling, are suspended under tension from the TLP. The tensioners supplying the tension to the risers are all hydropneumatic devices and except for the drilling riser tensioner are modular in concept.
This paper discusses the critical nature of the tensioners, in particular the production tensioners, and the steps taken to obtain maximum reliability in their operations.
In common with all marine risers, the 9-5/8" Hutton production risers must be maintained in tension to avoid bending under column loading with consequent overstressing and possible damage.
Because of the TLP and riser motions, shown in Figure 1, there is relative motion between the riser top connection and the TLP deck. This must be accommodated by a compliant tensioner without introducing large tension variations into the riser.