FLEXIBLE PIPE

What is flexible pipe?

A flexible pipe is made up of several different layers. The main components are leakproof thermoplastic barriers and corrosion-resistant steel wires. The helically wound steel wires give the structure its high-pressure resistance and excellent bending characteristics, thus providing flexibility and superior dynamic behaviour. This modular construction, where the layers are independent but designed to interact with one another, means that each layer can be made fit-for-purpose and independently adjusted to best meet a specific field development requirement.

Main Characteristics

FLEXIBILITY

Flexibility is the distinctive property of a flexible pipe. A typical 8'' internal diameter (ID) flexible pipe can safely be bent to a radius of 2m or less. This is the reason why flexible dynamic risers have been the enabling technology for floating production systems. This flexibility is also important for flowlines laid on uneven seabed conditions. Flexibility makes it possible to spool the pipe on a reel or in a carousel for efficient and quick transportation and installation.

INSTALLABILITY

Because the flexible pipe comes in a  continuous length, laying speed commonly averages 500m per hour. Separate sections are connected on deck during installation, eliminating the need for any intermediate riser base structure or subsea connections. This elimination of interfaces reduces risk in operation. In November 1971, the first Technip flexible pipe was  installed in Congo. It took 1.5 hour to lay the 650m flowline, including connections.

MODULARITY

The independent layers of a flexible structure enable it to be tailored to the precise needs of a specific deve-lopment. Simple flexible pipes for medium pressure water transport comprise only four layers. The most complex flexible pipes may have up to 19 layers. Beyond the basic fluid barriers and stress-resistant wires, additional layers can be included to prevent wear between steel layers (in dynamic appli-cations) or to provide improved thermal insulation (“standard” flexible pipe already has a much better insula-tion coefficient than that of steel pipe). Besides including new thermoplastic or steel layers within the product, it is also possible to assemble plastic hoses, electrical cables or optical fibers around a flexible pipe to produce an Integrated Service Umbilical (ISU®), or include active heating for flow assu-rance in deepwater to produce an Integrated Production Bundle* (IPB). In 2001/2002, Technip participated in the DEMO 2000 JIP, demonstrating its ability to supply heat traced flexible, including gas lift tubes and tempera-ture monitoring optical fibers within the same line (Integrated Production Bundle). Heat tracing and monitoring allow temperatures to be perfectly tuned within the core production flexible in order to meet flowing or

cool down requirements. This type of flexible pipe provides an “all-in-one” solution for deepwater applications. It has been used several times in West of Africa deepwater fields and will soon be installed offshore Brazil.

 CORROSION RESISTANCE

Since the steel wires are not in direct  contact with the conveyed fluid, they do not require the same  corrosion resistance as steel pipe. This means that our design experience and knowledge of gas diffusion through thermoplastic materials enable us to use carbon steel where the equivalent rigid  pipe appli-cation would require much more expensive corrosion-resistant alloys

Source: http://www.technip.com/sites/default/files/technip/fields/publications/attachments/flexible_pipe_march_2014_web_0.pdf