Rising to the challenge of flexible pipes

Mathias Norlin, Project Sales Manager, explains how Outokumpu meets exacting specifications set by oil and gas engineers when specifying material to manufacture flexible pipes for offshore projects.

flexpipe and risers oil and gasFlexible pipe is used as risers to transport oil and gas product from the seabed to the surface, as well as flowlines on the sea bed. It can handle dynamic situations that arise from tide and wave action.

Our alloys are used as the corrosion resistant carcass that contain petrochemical or other flows, with multiple outer layers providing mechanical strength and flexibility.

We’ve been supplying alloys for flexible pipes for more than 20 years and have built our process around delivering to the precise specifications set by the leading manufacturers of flexible pipe. We meet their approach to design and we typically adjust our production to also meet the technical specification of the final customer, the oil company.

We provide material in the form of strips that range in width from 25 mm to 200 mm and are up to 4 mm thick, depending on the specification. Our customers form the strip into profiles and interlocks them to create long flexible tubes to encapsulate the flow lines.

Austenitic grades such as Supra 316L might be used for projects in shallow seas and some customers specify alloys with high corrosion resistance such as Ultra 254 SMO and Ultra 6XN for sites where seas are shallow with high salt content.

However, duplex grades such as Forta LDX 2101, DX 2304, DX 2205 and SDX 2507 are specified more often as they provide both corrosion resistance and high strength.

However, while the outer layers of a flexible pipe include strengthening elements, the need for flexibility limits their ability to withstand loads. Therefore, the additional strength provided by duplex grades is helpful in extended the performance of flexible pipes to withstand both the dead loading and the hydrostatic pressure of deeper waters, preventing pipe collapse.

 

Complete consistency

Once we take the technical requirements of the oil company and the flexible pipe producer into account, we are faced with a thick document of specifications and certifications. Traceability is important in oil and gas projects because it helps to control the risks associated with exploration and production.

Outokumpu has the capabilities to deliver the high level of consistency required to meet quality and certification standards.

Outokumpu has the capabilities to deliver the high level of consistency required to meet the quality and certification standards in the customer’s specification. Many stainless steel producers can supply the right grade – but few can produce material that reproduces identical mechanical properties and dimensions.

The key to success is strong project management, the long experience that we have with producers of flexible pipe and the experience of our site technicians, who oversee production to very fine tolerances and mechanical specifications.

We meet requirements set by bodies such as ASTM and Norsok, the EN 10204 standard with 3.1 and 3.2 certification. In addition, our customers also have their own bespoke sets of standards to meet.

Recommended reading

Article

Choose duplex stainless steel for your storage tanks

Article

New lean alternative to nickel-based alloys

Webinar

Successful welding of duplex stainless steels

Webinar

Specifying and testing alloys for Oil and Gas applications

Webinar

Meeting the material challenges of Oil and Gas corrosion

Technical article

Solving the material challenges of plate heat exchangers

Case Rotoko machining operations

Where high machinability and superior quality meet

Case oil platforms

When corrosion is not an option

Case biogas plant

Securing the circular economy