High performance flexible pipe can be designed to fit
Water depth, internal pressure, temperatures considered
Shankar Bhat - DeepFlex Inc.
Paul Jacob - MMI
The need for composite flexible fiber reinforced pipe (FFRP) becomes more critical as the industry moves out to 3,000 m (9,842 ft) water depths. Earlier generations of fiberglass reinforced plastic bonded pipe systems have been in use for over 40 years in shallow water applications. The challenge for the next generation was to design and produce a new all-composite type of pipe to withstand the greater external hydrostatic pressures, higher internal wellhead pressures, and temperature extremes that accompany deepwater.
Constructed from extruded polymeric layers reinforced with laminated glass-fiber tape stacks, DeepFlex Inc. has a next generation lightweight, nonmetallic, unbonded FFRP developed for subsea and deepwater floating system applications. To maximize the strength of its composite-only pipe, DeepFlex created overlapping layers of composite reinforcement, using multi-start stacks of specially made, pre-cured unidirectional glass fiber composite tapes. Pipe is continuous, and is made in lengths limited only by storage capacity.
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All-composite flexible fiber reinforced pipe (FFRP) can be used for dynamic risers, subsea flowlines and pipelines, subsea jumpers and surface jumpers on hybrid risers or on platform decks.
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Tests of the 2-in. (5-cm) pipe have demonstrated its ability to survive the pressure found in the Marianas Trench, the deepest spot in any ocean. A 4-in. (10-cm) pipe has been tested to a collapse pressure of 10,000 psi (689.5 bars), the equivalent of more than 6,000 m (22,482 ft) of seawater. The pipe is designed to take a tremendous compressive load with a generous safety factor.
While the plies within each FFRP stack are bonded together by epoxy resin, each stack remains unbonded from the others, ensuring true flexibility under extreme conditions and increasing fatigue resistance in dynamic applications. Unbonded construction also allows the pipe to be produced and installed in continuous lengths. In addition, the composite materials act as effective insulators, keeping product flowing through pipes at colder temperatures. The all-composite makeup results in pipe that is lighter than steel or other types of flexible pipe, allowing significant reduction of loads on host facilities in deep water.
Finite element analysis
The way FFRP is constructed permits tailoring to the variables of the particular environment. A cross section lay-up allows each layer to be designed to meet specific requirements for burst, collapse, axial extension, bending, and torsion. To meet exacting specifications, further insight was needed into the performance of each layer of composite to optimize pipe cross section configuration. DeepFlex worked with structural mechanics consultants at MMI Engineering Inc., who applied Abaqus unified finite element analysis (FEA) software, from Dassault Systèmes’ SIMULIA brand, to model FFRP.
Model creation, testing
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Volume 68 Issue 5
May 2008
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