FLEXIBLE PIPE EROSION MODELLING

Transcription

1 Eleventh International Conference on CFD in the Minerals and Process Industries CSIRO, Melbourne, Australia 7-9 December 015 FLEXIBLE PIPE EROSION MODELLING Chong Y. WONG 1*, Christoher B. SOLNORDAL 1 and Henri MORAND 1 CSIRO Minerals Resources Flagshi, Clayton, Victoria 3169, AUSTRALIA Techni, Perth, Western Australia 6005, AUSTRALIA *Corresonding author, address: chong.wong@csiro.au ABSTRACT Flexible ies are commonly used by Floating Production Storage Offloading (FPSO) vessels to transort roduced oil and gas fluids in subsea ie network installations in lace of rigid iework. The innermost layer of the ie (interlocked carcass) is in direct contact with the roduced fluids which may also transort sand articles causing inner surface erosion over time. The rate of erosion on a material s surface is aroximately roortional to the square of the article imact velocity and articles in gas flows travel at a greater relative velocity than liquid flows. Therefore, the use of flexible ies in gas dominant fields will be more rone to sand erosion than those in liquid dominant fields. A review of the literature revealed numerous exerimental and modelling aers on smooth bore rigid bent ie, but very limited information is available for roughbore flexible ies. The contribution of the current aer is to roose a new model based on DNV-RP-O501 to analytically redict the erosion rate of the detailed internal carcass of a roughbore flexible ie. The new model, benchmarked against literature data and CFD simulations, accounts for variations in erosion rate with article imact angle to allow more detailed erosion rofiling of the internal carcass. The work will rovide a latform for further develoment, testing and calibration which might ultimately enable flexible ie designers to imrove solid article erosion estimations, secifically in dry gas fields. NOMENCLATURE C1 Model geometry factor,.5 [-] Cunit Unit conversion factor m/s to mm/year Aie Pie internal cross-sectional area [m ] d Particle diameter [m] D Pie diameter [m] d50 Particle diameter at 50 th ercentile [m] e secific erosion rate (kg/s of material removed / kg/s of imacting erodent) [-] EL Lineal erosion rate [mm/year] EW Erosion rate [kg of material removed er sec] F() Mathematical function of article imact angle that tyically includes additional emirical constants, 0<F() 1 [-] G Size correction function in DNV RP O501 K Material scaling coefficient [(m/s) -n ] L Equivalent stagnation length [inches] L [inches] m Gradient value of osition in x-y lane [-] m Mass of articles arriving at target er second [kg/s] n Velocity exonent [-] Rc Radius of bend [m] V Velocity [m/s] x, y Symbols defined in 3a Particle imact angle [degrees] Density [kg m -3 ] Dynamic viscosity [kg m -1 s -1 ] Angular location from start of bend [degrees] Subscrit f SG t INTRODUCTION Particle Fluid Suerficial gas or bulk gas velocity Target material Rough bore flexible ies are commonly used to transort roduced oil and gas fluids in subsea ie network installations in lace of rigid iework. They are esecially suited for use with Floating Production Storage Offloading (FPSO) vessels due to their ability to account for a vessel s dynamic motion. These ies are constructed of multile layers of material with each layer erforming a secific function. The innermost layer of the ie is known as the interlocked carcass and is in direct contact with the roduced fluids. The roduced fluids may also transort sand articles which over time can lead to solid article erosion on the inner surfaces of these carcasses (Togersen, Lejon et al., 006), eventually resulting in ie damage. It is known that the rate of erosion on a material s surface is generally roortional to the square of the article imact velocity (Finnie, 1960). Therefore, the use of flexible ies in gas dominant fields where the article velocities are higher will be more rone to sand erosion than those in liquid dominant fields. As such, there is a need to increase the understanding in the design for erosion rediction of flexible (unbonded) ielines in gas dominant fields. This aer has identified a few erosion methodologies related to curved smooth and curved roughbore ies and rooses an imroved model based on an existing erosion model for curved roughbore ies. The literature covering erosion by sand articles in flow around bends of smooth ies is numerous and there are several erosion models that redict the location and severity of the maximum erosion osition around a bend. Most of these models take the form roosed by Finnie (Finnie, 1960): E e W n (1) KVP F() m Coyright 015 CSIRO Australia 1

2 Deending on the form of F(), the model may account for material surface cutting when articles aroach at low imact angles and at higher angles, material removal by deformation due to cratering leading to li formation and material ejection from the li edges. The advantage of this model is that it decoules the fluid mechanics from the erodent-target material interaction. The model shows that secific erosion rate is largely influenced by the article imact velocity and the article imact angle. The scaling coefficient, K, is also required to account for material deendent effects, and this is determined emirically. Care must be taken to associate a articular exerimental condition with the measured erosion rate. For examle, (Ruff, 1986) highlighted the large scatter in inter-laboratory exerimental results of erosion tests for the same exerimental conditions. His study found that small changes in the reorted article velocity, nozzle-material distance and nozzle diameter may lead to large changes in the erosion rate. A thorough search of the related literature on rough bore flexible ie erosion methodology only turned u one source (Kvernvold and Nokleberg, 1989) which reconfigured their smooth ie erosion rediction for rough bore flexible ies. Remaining literature search related to erosion redictions or exeriments in smooth bore ie bends. Most of the smooth bore ie equations contained limited arameters to describe the comlexities inherent in erosion rediction. Of these, (Bikbaev, Maksimenko et al., 1973), (Bourgoyne, 1989), (DNV, 007), (El-Behery, Hamed et al., 010), (McLaury, Wang et al., 1997) and (McLaury, Shirazi et al., 1999) resent models that account for bend radius effects in smooth bore ie bends. From these models, the DNV model was found to be robust in estimating erosion rate as a function of article imact angle. This relationshi is imortant when considering erosion on the non-smooth regions of the internal carcass. As such, the DNV model is roosed as the backbone to develo a configuration-secific erosion model for rough bore flexible ies. CFD was used to examine the fluid flow-fields and rovide further understanding of the erosion hot-sots within the carcass. which is usually lower than Vf. Variations of V and Vf can be seen in Figure 1 (Jordan, 1998), where = Lf / (d), Re =f Vf d / f; for /Re < Particles will not imact walls when /Re is greater than this value. The family of curves in Figure 1 are based on Jordan s reduced-order simlification of the Tulsa E/CRC model (Jordan, 1998). In most industrial cases (for high Stokes number flows), where velocities are high and articles moderately sized, V/Vf is not less than 0.9. In other words, for large articles in low density flows, exect V to be over-redicted by u to 10%. For smaller articles in high density flows, e.g. fines, this over-rediction can be more than 50%. Figure 1: VP/VF versus derived from Jordan s reducedorder model (Jordan, 1998). Function F() Figure comares the variation of F() of two tyical shaes of erosion curves for ductile metals (Menguturk and Sverdru, 1979) and (DNV 007). In the range of interest where erosion is greatest in a curved flexible ie, esecially around = 0 and = 40, F() 0.9. Within this range of article imact angles, the relative difference in F() values between these two rofiles is about 30%. MODEL DESCRIPTION Prior to the develoment of this model, it is necessary to understand the sensitivity of each arameter in the Finnie equation as it relates to a roughbore model, and to examine reasons for the underlying assumtions. Sensitivity Studies Coefficients K and n In Equation (1), the arameter K relates to material roerties of both the eroding surface and the imacting material, while n is a velocity exonent. These arameters are usually determined emirically, and can have a significant imact on the overall results. Linear variations in K will have a linear effect on E, while small variations in n have a ower law effect on E. Parameter V In the absence of available measurement data, the value of a characteristic article velocity chosen is usually a bulk velocity term, VSG. However, this does not reflect the actual velocity of the article aroaching the wall, V Figure : Comaring F(a) curves for ductile metals. Presence of Irregularities on the carcass It is thought that the resence of irregularities on the rough bore flexible ie carcass surface may ose some erosion risk. (Kvernvold and Nokleberg, 1989) attemted to model these irregularities as triangular indentations on the smooth surface. That is, irregularities are defined here as the material excursions in the radial direction. Their simulations suggest that maximum erosion on these irregularities may be u to an order of magnitude higher than the erosion on the smooth art of the carcass. However, this risk has not been reviously quantified for Coyright 015 CSIRO Australia

3 actual rofiles using the carcass detail and accurately accounting for article imact velocity. This aer imroves the technique by accounting for secific carcass detail and article imact velocity (via Jordan s reduced order modification to estimate V). Model Develoment The urose of the model is to rovide a method of estimating lineal erosion rate, EL, in a rough surface ie bend. The develoment of the model is outlined in the following sections. Initially, the assumtions are resented followed by the aroach to develo an equation for EL. Model Assumtions The following assumtions are made when alying the new model to redict erosion on the steel carcass: 1. Particles are uniformly distributed as they enter the flexible ie bend.. Flow velocity distribution is modelled as a lug flow, so the axial flow velocity in any location of the ie cross-section is the same. 3. Particle velocity is calculated based on Jordan s (1998) (Jordan, 1998) reduced-order simlification of Tulsa s ECRC model (Shirazi et al, 1995a) (Shirazi, McLaury et al., 1995). This is the current model that accounts for the deceleration of a article as it aroaches the wall through a stagnation layer encountered in a ie bend. Other models that do not account for this deceleration in article velocity will over-redict the erosion rate in their calculations. 4. Effect of secondary vortices, commonly occurring in bend flows, is neglected since axial velocity comonent is more dominant than the radial velocity comonent in most engineering flows. 5. Particle diameter based on d50 is used. Particle size distribution is not considered. 6. Dilute concentration of articles is assumed, imlying that article-article interaction is negligible. 7. Coefficients used in the model are based on the DNV-RP-O501 model which have been calibrated with secific exeriments and are not suggested for general use, but serve as a qualitative guide only. Physical exeriments are required to determine these new coefficients when a target material or sand tye changes. The coefficients in F() describe the shae of the target material and article interaction for a ductile material tested by DNV. No further information is rovided by DNV as to the source of these coefficients or the derivation of F(). As such, validity ranges for this cannot be obtained. However, variations in F() will account for nominally 30% differences in the redicted erosion rate results. The material constant, K, is for generic steel grades and is exected to vary deending on the tye of steel used (e.g. Stainless steel 316, 304 or Dulex 05). Again, these values have to be determined emirically against a given sand tye and flow regime (e.g. liquid or gas) for a more accurate level of erosion rediction. DNV suggests that for velocities less than 100 m/s, differences in erosion resistance are generally within 10-0%. The velocity exonent n is intrinsically related to K and generally varies between 1.6 and.3 for ductile materials. 8. Gravitational effects on the articles are neglected in this model. Thus the model does not account for the orientation of the entry flow. However, the entry flow has been reorted elsewhere to be an imortant factor in determining the location of the maximum wear oint (Deng et al, 005). Estimation of material-article factors and coefficients The material-article factor (K) rovides an indication of the relative imortance of factors such as sand sharness, material hardness (e.g. Brinell Hardness), material strength, etc. on the model. However, coefficients relating the analytical model to hysical models are necessary. Unfortunately, these coefficients are not generic and have to be determined on a case-by-case basis. O Flynn et al (001) (O Flynn, Bingley et al., 001) and Sundararajan et al (Sundararajan, 1983; Sundararajan, 1991; Sundararajan, 1995) have tried to relate standard material roerties (e.g. material hardness, true uniform strain, toughness, mechanical energy density, etc.) with erosion rate and met with limited success. To date there is no one model that accounts for the comlexity of erosion modelling. Thus, all the models in this review to some degree contain simlification of secific materials-sand interaction. For examle, the DNV model assumes steel to be all tyes of steels, including mild steel, stainless steel, etc. Estimation of article imact velocity As a article enters a bend, it is assumed to slow down. The distance over which the article decelerates from the bulk suerficial fluid velocity, VSG, to its imact velocity at the wall, V, is known as the equivalent stagnation length, L. Shirazi et al (1995) (Shirazi, McLaury et al., 1995) calculated L for a two-dimensional right angle turn and formulated an equation (in inches for Equation only) to aroximate the stagnation length, where D inches: L arctan 1.01D D () L0 To estimate article imact velocity, we require 3 dimensionless grous, namely, V/Vf, Reynolds number (Re = fvfd/f) and ( = Lf /(d)). The reduced order formula rovided by (Jordan, 1998) is used here: 1 V V f Re Re (3) 1 6 Construct simlified carcass geometry rofile We assume that the most affected eroded region will occur on the surface of the carcass in contact with the sand bearing fluid, esecially on surfaces away from the dee crevices. We can therefore re-draw the actual carcass rofile Figure 3b into the simlified reeating rofile shown in Figure 3c. CFD simulations confirmed that this is a valid assumtion as little or no sand imacts onto the inner crevice surfaces. Estimate article imact angle on smooth surface of carcass Calculate the ath taken by high Stokes number articles to the first oint of imact on the extrados of the bend for a given bend radius and ie diameter. This neglects gravitational effects, article-focusing effects or article deviations by the flow or turbulence effects. The imact angle on the extrados () is shown as Equation (4). R c (4) D Coyright 015 CSIRO Australia 3

4 Equation (4) assumes articles travel in a straight line from the commencement of the intrados to the oint of imact at the extrados. Calculate imacting lug flow angle onto the extrados The imacting lug flow angle,, as the lug flow travels in a straight line from the straight section of the ie to the extrados is calculated based on Equation (4). This concet is analogous to conducting a direct imact exeriment over all the article imact angles whereby all the articles from the ie jet imact onto a circular late with diameter, d, at a given angle,. At = 90, the late cross-section exeriences article imact from all the sand mass emerging from the ie. This is similar to a direct imingement erosion test. At = 0 and in a simlistic way, ignoring any flow searation effects, the late cross-sectional surface does not exerience any erosion. At any angle between this, the rojected area exosed to the sand imacting the circular late surface can be exressed as: Aie At (5) sin() Equation (5) accounts for the decrease in erosion rate on the global surface of the extrados with increasing curvature ratio. However, it does not account for the local variations of article imact effects on the carcass rofile. To account for the local article imact angles at the irregular surface, we do the following: For a given geometry and aroaching article imact to the wall defined by H in Figure 3c and on the horizontal surface (on x-axis), lot (Figure 3c) the various local article imact angles on the undulated surface (e.g. at (x, y)). First obtain the gradient value at (x, y) and (x, y) using the equations: ( y y1) m ( x, y ) (6) ( x x1 ) ( y y 1) m ( x, y ) (7) ( x x ) where, H cos H cos 180 x 180 x 1, y y 1 Arbitrarily set x1 and y1 for a osition above the carcass. Reeating this formula along the extrados over a local carcass element, and calculating the article imact angle (,i) using following equation, 180 ( m m ), i ( x, y ) arctan (8) (1 m m ) 1 we obtain the grah of local article imact angle. Particle Imact Angle, degrees Figure 4: Grah showing local article imact angle (,i) on carcass surface. Next, individual F(,i) values for each i th surface location calculated for each local article imact angle (e.g from DNV, Fig 7-) is included into F(). Re-writing the equation from DNV-RP-O501, we can calculate the erosion rate on the extrados of the flexible ie bend using Equation (9): n m KF(, i )sin( ) V EL, i GC1C unit (9) A t x (along extrados), mm ie Particle velocity is calculated according to Jordan s (1998) reduced order method. Other arameters such as n and K are obtained from DNV (007) directly. An examle of the final result is shown in Figure 5. Figure 3: Details of the flexible ie carcass. (a) Geometry with coordinates defined; (b) detail of actual extrados surface rofile; (c) simlified extrados surface rofile; (d) detail of coordinates. Validation of new model with ublished exerimental data The erosion rate (mm/year) on a stainless steel carcass surface for conditions in a test case (test case 5-0 mv/v) from (Kvernvold, 1990) using shar 50 m sand susended in nitrogen gas flowing at bulk velocity of Coyright 015 CSIRO Australia 4

5 18 m/s in a 50.8 mm ID (D) ie with a bend centerline radius ratio (Rc/D) of 19.7 is shown in Figure 5. No mention of sand rate is rovided thus a conservative figure of 0 m-v/v is used for the calculations. Using the F() data from DNV (007) and for each carcass element, a eak erosion rate occurs on the transition between the curved surface and the smooth surface. The outline of the carcass is also shown as a hysical reference. The regular surface is defined as the outline of the extrados surface for a smooth ie while the irregular surface is any surface deviating outwards from the extrados surface. E_L (mm/year) Figure 5: Erosion rate estimation on the carcass detail. The new model, reresented by Equation (9), is further validated with five other exerimental dataoints covering the following test arameter variations with exerimental details shown in Table 1. Results of the new model are comared with other literature models that account for ie curvature. These are shown in Figure 6. The new model redicts cases to 5 within 50% of the exerimental data excet for case #1 which is the low velocity and low curvature case. This is a reasonable result considering the comlexity of erosion redictions and that exerimental variations in K, n and F() determined for limited cases of materials and articles by DNV (007) could reliably redict the erosion rates from different exeriments conducted by different researchers (e.g. Bourgoyne, 1989). Test # Tye of Bore D [m] Rc/D Peak of linear erosion rate Pie Material Regular surface x (along extrados), mm Sand vol. d50 rate, [m] Q [m 3 /s] (m Vol) Outline of carcass rofile VSG [m/s] 1 Smooth Steel (68) (Air) Smooth Steel (Air) (55) 3 Smooth Steel (Air) (1351) 4 Smooth Steel (Air) (676) 5 Rough SS L (0) Irregular surfaces Reference (Bourgoyne, 1989) (N) (Kvernvold, 1990) Note: 1. Steel-1 is Seamless steel grade WPB;. Steel- is Cast grade WBC Table 1: Summary of main hysical test conditions for model comarisons. Figure 6: Validation of model with exerimental data. Cases are labelled 1 to 5 adjacent to each data cluster. CFD SIMULATION AND RESULTS A CFD study for a 6 ID flexible ie carcass assing through a bend angle of 90 (Rc/D = 18) was also erformed to understand the flow aths and erosion effects of the articles within the flexible ie. The flow conditions were natural gas (f = 77.3 kg/m 3, f = 1.5 Pa s) at 100 bar-g and 110 C with 15 m/s bulk gas velocity. The sand used was quartz (600 kg/m 3 ) with a mean size distribution of 55 m and one standard deviation of 15m at a feed rate of kg/s. Commercial CFD software ANSYS-CFX14 was used to calculate the dynamics of the fluid flow, the article tracks and erosion redictions. The erosion model used was from (Elfeki and Tabakoff, 1987) using emirical constants resented in (ANSYS, 01) for quartz on stainless steel. As these were not calibrated for secific conditions related to the flexible ie, the simulations results should only be used as a guide. It was observed that searated flow structures occurred on the intrados of the ie most likely attributed to turbulent searated flow. This led in a narrowing of the bulk fluid flow through the non-searated regions of the ie resulting in higher flow velocities in the vicinity of extrados of the bend. It was therefore not surrising that the maximum flow velocity and hence material removal rate were found on the extrados. In Figure 7, article aths were concentrated towards the extrados of the bend, with the majority of article imacts occurring on the forward-facing edge of each carcass rib giving the results resented in Figure 9. In Figure 8, the erosion distribution was redicted to follow that of the article ath imacts, so that the highest erosion occurred on the extrados of the bend, on the forward-facing edge of each carcass rib. A region of reduced erosion was redicted to exist on the extrados surface, aroximately along its intersection with the vertical centre-lane. The redicted erosion attern was in good qualitative agreement with ublished erosion observations in flexible ie bends (Togersen, Lejon et al., 006). The location of maximum erosion was redicted to occur at an azimuthal angle of = 3.75 into the 90 bend (Figure 8). This location corresonded to the oint at which the high velocity gas entering the bend first encounters the extrados of the bend. Coyright 015 CSIRO Australia 5

6 Figure 10 shows the various hand calculations comared with results from the CFD simulations on the regular and irregular walls of the carcass. For regular wall redictions, some of the literature models (i.e. Bikbaev, El-Behery and McLaury-1997) over-redict the CFD results by greater than orders of magnitude. However, DNV, Bourgoyne, McLaury-1999 and the resent models rovide redictions of about one order of magnitude to the CFD redictions for regular walls. For irregular wall redictions, the resent model redicts within one order of magnitude to the CFD results. Therefore, in the absence of further hysical erosion data, the new methodology will be at best an order of magnitude first guess. 0.1 Figure 7: CFD of article tracks through bend: (a) Plan view and (b) elevation view. location of maximum mass removal rate 3.75 mass removal rate Mass removal rate (mm year -1 ) Aroximate location of carcass wall Maximum mass removal here Angle through bend (degrees) Figure 9: Mass removal rate at maximum erosion location (= 3.75 into bend), from CFD Figure 3 8: Mass removal 1 rate shown 0 diagrammatically -1 around the flexible ie bend, from CFD. Flow enters from lower left. In Figure 9, the redicted maximum erosion rate is 0.08 mm/year for the conditions studied, while the nominal erosion rate on the regular smooth surface is mm/year, a difference of 700%. The results from the hand calculated model only redicts a difference of about 6%. One hyothesis for the higher than exected maximum erosion rate could be due to enhanced article imacts there. The increased number of imacts is in turn ostulated to be due to referential clustering of articles and turbulence couled with the comlex searated flows above the crevices of each carcass segment Figure 10: Comarison of modified DNV with CFD results on the 6 flexible ie simulation. CONCLUSIONS The literature study has found that there very few methodologies that redict erosion by sand articles in bent ies with smooth bores. Prediction among these models with a selected range of actual exerimental data suggests that none of them can redict each set of exerimental data consistently within ±50%. Most of the models generally redict the selected exerimental data within one order of magnitude at best. An attemt was made to develo a new methodology to redict the erosion rate on rough bore flexible ie. The roosed methodology is based on the DNV-RP- O501 model. CFD flow and erosion simulations of a 6 flexible ie steel carcass revealed that the erosion distribution around a corrugated carcass detail Coyright 015 CSIRO Australia 6

7 qualitatively comares well with hand calculations where erosion on the curved forward-facing side of the carcass geometry is consistently higher than the smooth carcass walls. ACKNOWLEDGEMENTS The authors acknowledge Techni for funding this work. The authors also thank CSIRO, Techni and conference eer-reviewers for their constructive and thoughtful comments. REFERENCES ANSYS, (01), "ANSYS-CFX 14.0 User Manual". Canonsburg, PA, USA, ANSYS Inc. BIKBAEV, F.A., MAKSIMENKO, M.Z., BEREZIN, V.L., ZHILINKSI, I.B. and OTROSHKO, N.T., (1973), "Main factors affecting gas abrasive wear of elbows in neumatic conveying ies. ", Khimicheskoe I Neftyanoe Mashinostroenie 1, BOURGOYNE, A.T., (1989), "Exerimental study of erosion in diverter systems due to sand roduction". SPE/IADC Drilling conference, New Orleans, Louisiana, 8 Feb 3 Mar. DNV, (007), "Recommended Practice RPO501 Erosive Wear in Piing Systems Rev 4.". EL-BEHERY, S.M., HAMED, M.H., IBRAHIM, K.A. and EL-KADI, M.A., (010), "CFD evaluation of solid articles erosion in curved ducts", J.Fluids Engng 13, ELFEKI, S. and TABAKOFF, W., (1987), "Erosion Study of Radial Flow Comressor with Slitters", Journal of Turbomachinery-Transactions of the Asme 109(1), FINNIE, I., (1960), "Erosion of Surfaces by Solid Particles", Wear 3(), JORDAN, K., (1998), "Erosion in Multihase Production of Oil and Gas". Corrosion 98, San Diego, Ca. NACE International. KVERNVOLD, O. and NOKLEBERG, L., (1989), "FPS000/Flexible ies - Erosion in flexible ies". Veritec KVERNVOLD, O., SANDBERG, R., RONOLD, A., (1990), "Exerimental investigation of the erosion characteristics of the steel carcass in COFLEXIP flexible ies. Rough Bore flexible ie, gas hase only.". Veritec Reort No MCLAURY, B.S., SHIRAZI, S.A., SHADLEY, J.R. and RYBICKI, E.F., (1999), "How Oerating and Environmental Conditions Affect Erosion". Corrosion 99. NACE International. MCLAURY, B.S., WANG, J., SHIRAZI, S.A., SHADLEY, J.R. and RYBICKI, E.F., (1997), "Solid Particle Erosion in Long Radius Elbows and Straight Pies". SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 5-8 Oct. MENGUTURK, M. and SVERDRUP, E.F., Calculated tolerance of a large utility gas turbine to erosion damage by coal ash articles.. Erosion: Prevention and Useful Alications, ASTM STP 664. W. F. Adler, ASTM: O FLYNN, D.J., BINGLEY, M.S., BRADLEY, M.S.A. and BURNETT, A.J., (001), "A model to redict the solid article erosion rate of metals and its assessment using heat-treated steels", Wear 48(1 ), RUFF, A.W., (1986), "Analysis of interlaboratory test results of solid article imingement erosion", Wear 108(4), SHIRAZI, S.A., MCLAURY, B.S., SHADLEY, J.R. and RYBICKI, E.F., (1995), "Generalization of the API RP 14E Guideline for Erosive Services", J. Pet. Tech, SUNDARARAJAN, G., (1983), "An analysis of the localization of deformation and weight loss during singlearticle normal imact", Wear 84(), SUNDARARAJAN, G., (1991), "The deth of lastic deformation beneath eroded surfaces: The influence of imact angle and velocity, article shae and material roerties", Wear 149(1 ), SUNDARARAJAN, G., (1995), "The solid article erosion of metallic materials: The rationalization of the influence of material variables", Wear , Part 1(0), TOGERSEN, T.G., LEJON, K., KVERNVOLD, O. and TOBERGSEN, L.E., (006), "SNORRE A sand roduction management exerience and solutions.", TUV NEL Sand roduction management seminar. Coyright 015 CSIRO Australia 7