Sand Erosion Experiments and Model Development for UNS N06625 Cladding and UNS S32750
Authors: Zhang Yongli , Gharaibah Emad , Friedemann John D. , Kulkarni Guruprasad , Devi Ravindra , Dasan Biju , Mathew Paul 
Published: April 2012

Abstract
Material loss due to sand erosion can cause severe damage to oil and gasproduction facilities and lead to leaks and ruptures if left undetected. Thedesign of oil and gas production equipment to safely withstand sand erosion andsimultaneously optimize production requires a reliable erosion prediction tool. One of the key requirements for such a tool is that it correctly models boththe erosion resistances of the exposed materials and the effects of theparticle impact trajectories and velocities.
Key to this is a full understanding of the individual materials and theirimpact resistance. This is because the impact behavior varies very much betweenmaterials and models cannot be simplified to two approaches: ductile orbrittle. Model validity must be questioned as the oil industry begins toimplement hardened and high chrome content materials.
UNS N06625 and UNS S32750 are two of the popular alloys in the subsea industry. Despite the popularity of these materials, little erosion data or validatedmodels for either application are found in the literature. Another significantgap is related to experimental studies aimed at understanding the erosioncaused by fines.
To fill this gap and provide verification of the existing models, a series ofexperiments were conducted and analyzed. Direct impact erosion experiments forUNS N06625 cladding and UNS S32750 were conducted using sand particles carriedby air at ambient temperature and pressure. The sand particle sizes ranged from27 µm to 619 µm, sand particle velocities from about 25 m/s to 160 m/s, andimpact angles from 15° to 90°. An erosion correlation for each material wasderived from these experimental data. The erosion correlations were thenapplied within a CFD (Computational Fluid Dynamics) model for a typical subseaassembly to demonstrate the applications. A significant contribution is thatthese experiments and correlations provide an input to the understanding oferosion for the full range of particle size, impact angles, velocities, and howthese are related to erosion in modern corrosion resistant alloys (CRAs).

Introduction
Sand erosion is commonly encountered in the oil and gas industry. Severe damageto the production facilities can occur if the sand is not handled properly. Thesand produced with oil and gas is normally filtered the down hole and monitoredat various critical locations in the pipeline. The down hole sand screen limitsthe size and amount of the sand that can move through it. The material of thepipeline and other components is also important for mitigating the sand erosiondamage. UNS N06625 and UNS S32750 are two of the popular alloys in the subseaindustry. Sometimes, the oil and gas production rate has to be limited due toexcessive sand erosion. The design of the oil and gas production systems tosafely withstand sand erosion and simultaneously optimize production requires areliable sand erosion prediction tool. The Tulsa SPPS [1] and DNV RP O501 [2]are the two methods being widely applied in the oil and gas industry forpredicting sand erosion. One of the key ingredients of these methods is theerosion correlation, which calculates the erosion rate from the parameters thatare believed to affect the erosion rate the most. The accuracy of the erosioncorrelation is thus very important for the erosion rate prediction.