PURE – Premium Upset Riser Ends
PURE is a ready for service solution for offshore applications developed by Vallourec specifically to eliminate the need for pre-matching pipe ends and to give more consistent fatigue Performance.
Driven by Deepwater, the new frontier
The ongoing shift towards deep-water and ultra deep-water fields in Oil & Gas calls for more specialized and superior technologies in pipe design and metallurgy. These new solutions must overcome increasing technical constraints while reducing project and operational costs.
Deep and ultra deep field constraints, like high pressure/ high temperature, high fatigue loads and stresses, lead to a high level of technical and safety requirements to ensure end-to-end integrity.
With exploration in offshore areas for Oil & Gas extending to deeper waters, Vallourec has set out to develop products that can withstand increasing workloads in more extreme environments. High resistance against fatigue, in combination with optimized tolerances at pipe ends, are therefore crucial in selecting products for steel catenary riser (SCR) applications.
The main target for expanding the possibilities of SCR applications is to significantly enhance fatigue life. Technically, that means optimizing the riser pipe-end and welding capabilities to guarantee superior fatigue performance.
PURE stands for “Premium Upset Riser Ends”. It is a ready-for-service solution for offshore applications developed by Vallourec providing an assured pipe end match, minimum stress concentration factors as well as an unaffected media flow. A complex heat treatment and an optimized chemical composition result in assured mechanical properties over the entire upset end line pipe.
SAIPEM, a major EPC in the market explains : “The costs of subsea projects increased a lot, driven by challenging applications like HPHT, Deepwater, and highly corrosive environments. In this context, the welding operations contain a high saving potential within the supply chain (lower defect rates, faster operation). It is important to be aware of the risks at an early stage of the project and to share the responsibility of saving costs between all parties involved in the project. This includes the features of the pipe in terms of materials and geometry which have direct impact on the weldability.”
Welding qualification requirements are indeed getting more and more demanding and can be a critical factor as they can seriously delay a project (delays can amount to 1 million$/day in cost). Today, the biggest challenge for ultra-deepwater projects is that clients are requesting both higher yield strength and heavier walls at the same time. This simultaneous increase of both characteristics was a barrier until PURE was developed. High strength steel and wall thicknesses above 1.0 inch, make it very difficult to meet all the corrosion standards required by NACE1 in the weld, including the heat-affected zone.
Furthermore, the geometrical features of the pipe have a considerable impact on the welding. For Steel Catenary Riser applications, counterbored pipes, and even end-trued pipes, have more limitations than an upset pipe end. Upset pipe ends are ideal as upsetting does not display any eccentricity and machining is perfect: all pipes ends are concentric to each other. This enables an efficient, quick and constant fit-up of the pipes, operating with a very low repair rate.
SAIPEM confirms this with hands-on, with their field experience: “This is a great contribution to the productivity of our laying vessels. Our experience with the installation of PURE Riser for the P55 project offshore Brazil has convinced us that our common route with Vallourec is the further development of pipe end solution concepts like PURE.”
Vallourec Premium Tubular Solutions
The development of innovative pre-material is key. Vallourec is well established in alloying concepts for the X65 and X70 grades with high strength properties. Saipem has successfully pre-qualified the pipes for the Total EGINA project, for instance. Our collaboration comprises a full qualification of high strength steel chemistries, which meet Saipem’s requirements in terms of weldability.
To realize optimal pipe end tolerances for Hi-Lo’s2 in offshore installations, the pipe ends are upset at the outer diameter (OD) and inner diameter (ID). Upsetting is followed by a full body heat treatment. Afterwards, the inside and outside of the pipe ends are machined to achieve the inner diameter tolerance of ± 0.25 mm and the outer diameter +/- 0,75 mm. Since the upset pipe end is machined to nearly original nominal wall thickness, there is no weight increase of the product. Eccentricity and out of roundness are no longer a concern. The flow assurance is unaffected. During laying operations, each PURE steel catenary riser and subsea flowline can therefore be immediately welded to the following pipe with optimal processing para-meters, without prior sorting, thus requiring less weld re-work and cut-outs.
After extensive testing, the PURE design has successfully been used by major Oil & Gas players in deepwater offshore conditions. The PURE design meets the most stringent requirements in terms of fatigue life as well as end dimensioning tolerances. As new offshore discoveries go deeper the need for increas-ed fatigue life will be of major importance together with reduced times for line-up and welding. Vallourec is once again a pioneer and leader in developing and industrializing the most complex solutions for the most demanding Oil & Gas players in the world.
1 – NACE is a standards-writing organization accredited by the American National Standards Institute (ANSI).
There are three categories of NACE standards: Standard Practices (SPs), Material Requirements (MRs) and Test Methods (TMs).
2 – Hi-Lo stands for the difference of either the external ot internal diameter of 2 pipe ends which will have to be welded together. The bigger the Hi-Lo the less mechanical strength the final weld will have.