This paper presents a novel approach for characterizing erosion wear in multiphase flow systems; it is based on Eulerian-Granular theorem rather than the conventional Eulerian-Lagrangian methodology. The first step in the novel approach is to characterize multiphase distribution based on the multi-fluid concept, which treats both the carrying fluid and entrained particles as continuous phases. The second step is to quantify the impinging velocity of particles using the granular model, which introduces particle-particle interaction and turbulence modification to carrying fluids beyond the fluid-particle and particle-fluid coupling considered in the Eulerian-Lagrangian approach. The final step is to determine the erosion rate by applying more representative particle velocity into a selected erosion correlation. In comparison to the Eulerian-Lagrangian approach, the Eulerian-Granular approach is able provide more realistic prediction on erosion profile in full particle loading range due to the least assumptions.
The flow assurance aspects of all subsea projects have a major contribution tothe pipe design, field layout, choice of lifting equipment (subsea-pump or airlift), power requirement and system operability. The context of deepwatermining pushes the design theories beyond the existing application cases due tothe significantly larger particle size combined with small diameter riser andjumper including wave shape to accommodate vessel motions and excursionrequirements. In order to correctly assess pressure drop and erosion rate closeto real flow conditions, TECHNIP and GIW have built a large scale experimentalbench operated at the same flow condition as forecasted for the deepseaproject. This large scale test is using an innovative method to allow thereproduction of realistic erosion rate in the pipe by preventing the solidparticle to be eroded when looping through the pump.
The current paper summarizes the findings and results from this large scaleexperimental set-up, testing concentration from 10% to 45%, velocities from2.5m/s to 5.5m/s in an 8" flexible pipe with equivalent rocks particles.
As described in (Espinasse, 2010), Technip is supporting an internal R&Dprogram that should allow the understanding of critical parameters essential tothe design and operability of a subsea mining system. Within this R&Dprogram, an extensive study of the abrasion and erosion mechanism inside theflowline is needed to:
• Understand the inner pipe wear mechanism function of flow conditions
• Define the proper flowline pipe material providing the best compromisebetween wear resistance and pipe cost.
• Define a procedure to evaluate the lifetime duration of the flowline pipeduring operations to schedule inspection and maintenance.
To capture and understand the abrasion during subsea mining operations, Techniphas setted-up a full scale test with the help of GIW. In addition of tacklingflowline wear issues, this test is used to validate at large scale thehydraulic modeling exposed in (Parenteau, 2010) and (Parenteau, 2011).
STATE OF THE ART
The particularity of subsea mining is to transport large and dense particle inrather small diameter pipe compared to what the industry of slurry transport isused to. Subsea Mining Partcicle size disctribution can range from 1 mm to60mm. Crushing experience conducted in (B. Waquet, 2011) indicated that atleast 50% will exceed 25mm and more than 25% of the solid will exceed 50mm[Figure 1]. The particle densities range from 2500 kg/m3 up to 4000 kg/m3. Pipediameter will range between 8" to 10", and evolving into wavy shapes.