ABSTRACT

A programme of research has been carried out under the "Umbilicals - the Future" joint Industry umbilical research project, in which possible laboratory accelerators were assessed for the use In compatibility testing of thermoplastic lined hoses with subsea fluids The accelerators, which were assessed over 18 months of continuous testing, were, pressure - cyclic or constant, hose configuration - straight, coded and reversible bending, and temperature Mechanical property measurements and scanning electron microscopy (SEM) examination of the liner material were used to evaluate the above individual effects Although it was not possible, using the techniques available to demonstrate conclusively that cyclic pressure is an effective accelerator, it is recommended that the currently used cyclic pressure test specified In API 17E 1s retained as the Industry standard. Neither the hose configuration tests nor the constant pressure tests showed any tendency to make the conditions more onerous from a compatibility standpoint, although there is evidence that the flexing test Introduced spurious mechanical effects

INTRODUCTION

In 1989 the Department of Energy's Offshore Supplies Office (OSO) commissioned a study into the reliability and performance of permanently installed subsea umbilicals The study was camed out by the ERC and the results were published in a comprehensive document in July 1990 (1) As a result of that study ERC, OSO and representatives from the operators concluded that two basic requirements needed to be addressed the reliability of umbilicals was to be Improved These requirements were

  1. Guidelines to cover all aspects of subsea umbilical design, manufacture, installation and use in specific applications These guidelines should be armed at standardization of test procedures within the industry and should incorporate the best engineering solutions and working practices which are currently available

  2. The industry should embark upon a programme of structured research, targeting those areas where there is a limited knowledge and lack of consensus on the best working practice

In 1991 the OSO commissioned a further study related to subsea umbilicals which addressed the second requirement This study, which was only partially funded by the OSO, was undertaken jointly by ERC and NEL The study solicited the view of both operators and suppliers in an attempt to prioritize suitable areas for investment In umbilical research and development One of the findings was that 61 per cent of operators and 58 per cent of suppliers considered that compatibility was a major problem which required further investigation The outcome of this work was the Proposal Document " Umbilicals - the Future " (2) which resulted in the existing study

In the offshore industry the full service life requirement for umbilicals could be up to 20 years Any laboratory assessment technique which therefore evaluates the effects upon liner material caused by the action of the fluid, needs to be based on accelerated testing techniques Once a particular test method has been established it should be possible to accurately scale the results to provide data for design optimisation This will enable manufacturers and end users to design and predict with confidence the compatibility performance of hoses used within subsea umbilicals

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