STUDY ON CASING PERFORMANCES IN CENTRIFUGAL SLURRY PUMPS

ABSTRACT

The pump casing is the most expensive wear component of a centrifugal slurry pump. It determines to a large extent the hydraulic performance of the pump and plays a major role in the overall wear life of the unit.

This paper suggests a new approach to compute the mixture velocity and solid particle dynamics in the casing, and on this basis the erosion wear distribution inside the pump casing. Numerical analysis was performed using the finite element method. The model was tested using Georgia Iron Works (GIW) pump casings, at flowrates between 2000 and 4000 US-GPM (US gallons ner minute). The experimental results were obtained in the Hydrualic Laboratory and in field applications in mining and dredging industries. The suggested techniques are useful for estimating casing wear rates and for the optimal design and selection of slurry pumps.     

Numerical simulation of a centrifugal slurry pump handling solid-liquid mixture: Effect of solids on flow field and performance

The effect of solids on a centrifugal slurry pump performance is a major concern to the design of slurry transportation system. In the present study, the multiphase modeling of centrifugal slurry pump is performed using two models, Mixture and Eulerian-Eulerian multiphase. Sliding mesh approach is employed for unsteady simulation of the pump. The accuracy of the simulations is ascertained by comparing the performance characteristics of the pump obtained numerically and experimentally. Experimental results are obtained by measurements in a pilot plant test rig with three different mean size sand particulate slurries. The Eulerian-Eulerian multiphase model predicted the effect of the solids on pump performance close to the experimental results as compared to Mixture model. The obtained accuracy with Eulerian-Eulerian model for predicting the effect of solids on head and efficiency is around ±2% and ±3%, respectively. The predicted results using Eulerian-Eulerian model confirm that the head and efficiency of the pump decrease with the increase in particle size and concentration. The particles of high specific gravity show less reduction in head and efficiency of the pump. Further, the effect of variation in particle size and concentration on the flow field in the impeller and casing has also been analyzed at best efficiency point operation. Non-homogeneous suspension of particles inside the blade channels and casing passages is examined. The particulate concentration is observed higher near the impeller back shroud, pressure side of the blades, and non-suction side of the casing as compared to other locations.     

Effect of particle size distribution on performance and particle kinetics in a centrifugal slurry pump handling multi-size particulate slurry

A significant variation in particle size distribution (PSD) is generally encountered in slurry transportation. The goal of this work is to establish the effect of variation in PSD on the centrifugal slurry pump (CSP) performance and particle kinetics. Computational fluid dynamics (CFD) modeling of a CSP with multi-size particulate slurry has been performed with a sliding mesh approach using the granular Eulerian-Eulerian model. The numerical model is validated with the experimental data of the pump performance for multi-size particulate fly ash slurry. The maximum deviations in the predicted head and efficiency compared to the measured values are of the order of ±2% and ±3.5%, respectively. Simulations with a single representative particle size for multi-size particulate slurry using median and weighted mean diameter approach are also carried out to understand the difference in performance prediction with equi-size and multi-size slurry. The predicted trend of pump performance variation with PSD is linear and non-linear with equi-size and multi-size slurries, respectively. The median and weighted mean approaches showed error in capturing the effect of variation in PSD on pump performance. The variation in PSD significantly affects the flow of particles inside the impeller and casing flow passages due to particle kinetics. Reduction in the intensity of granular pressure, maximum granular viscosity, and the head loss due to friction in impeller and casing flow passages are found with the increase in the fine size particles.     

川东北复杂压力体系气井固井技术

川东北地区普光、河坝、元坝等区块的海相天然气藏勘探取得了重大突破,该地区目的层埋藏深,地层压力和温度高,H2S和CO2含量高,属"三高"气田。陆相和海相地层有多套压力系统,长封固段和小间隙是固井工艺面临的主要挑战,H2S和CO2对气井长期安全造成威胁。2006年以前川东北探井的技术套管和生产套管固井的一次合格率仅为80%和72%。通过研究应用胶乳防腐防气窜水泥浆体系,紧密堆积高密度防气窜水泥浆体系,正注反挤工艺和分段压稳模型设计环空液柱结构等体系和工艺技术,固井质量较2006年前有大幅度提高。普光气田固井质量合格率100%,优良率达到90%,为普光气田顺利投产供气提供了保障。     

Impact of high‐velocity oxy‐fuel sprayed TiAlN surface coating on mechanical and slurry erosion performance of aluminium alloys

TiAlN coatings were deposited on AA1050 and AA5083 aluminium alloys by high‐velocity oxy‐fuel (HVOF) spray process and evaluated for their mechanical and slurry erosion performance. In comparison to base alloys, the mechanical properties were found to enhance upon coating. The effect of working parameters namely impingement angle, impact velocity, erodent size and erodent feed rate on the slurry erosion wear rate has been investigated. The slurry erosion wear rate of the uncoated samples was found to decrease with an increase in the impingement angle whereas for coated samples the slurry erosion wear rate first increased, reached to a maximum value at 60° and then decreased with further increase in the impingement angle. For uncoated and coated samples the slurry erosion wear rate was found to increase with an increase in impact velocity, erodent size and erodent feed rate. Finally, the morphology of the eroded surfaces was analyzed using scanning electron microscopy and the possible erosion mechanisms have been studied.     

Investigation of the ultimate residual strengthen of a worn casing by using the arc-length algorithm

The accurate prediction of the ultimate residual strength (URS) (including collapse, burst, and tensile strength) of worn casing is important in the design and safety assessment of casings for the oil and gas industry. Based on the true stress–strain constitutive relationship of P110 steel, this paper establishes a three-dimensional (3D) finite element model (FEM) to obtain the URS of worn casing by using the arc-length algorithm. The effects of worn defect length, wear percentage, drillstring diameter, and casing thickness on the URS are investigated. Moreover, three full-scale experiments on casings with different wear percentages are conducted to verify the accuracy and reliability of the 3D FEM and of the algorithm. The validation proves that the URS of worn casing can be predicted by the 3D FEM to a satisfactory degree of accuracy. The URS has an exponential relation with defect length, but a linear relation with wear percentage, drillstring diameter, and casing thickness. The effects of numerous factors on the URS are also studied. Regression analysis is conducted on the basis of 3D FEM predictions, and the corresponding design equations for worn casing are presented.     

PARTICULATE MOTION AND CONCENTRATION FIELDS IN CENTRIFUGAL SLURRY PUMPS

ABSTRACT

Erosion wear of centrifugal slurry pumps is primarily governed by the particulate motion and concentration as well as their physical properties. This paper presents a quasi-3D approach to predict particulate phase motion and concentration in an arbitrary radial section of a centrifugal slurry pump. A brief discussion of the fully developed turbulent flow solution of the carrier fluid is followed by a computation of the particulate phase velocity resulting from a force balance between the pressure, gravity, viscous and inertial effects. The concentration distribution is obtained by invoking the convection-diffusion equation. The governing partial differential equation is cast into a weak Galerkin finite element form. The system of algebraic equations is solved by a Newton-Raphson scheme via a frontal solver. An iterative solution scheme is employed to alternate between the fields of particle motion and concentration. Numerical solutions are examined in light of their applicability to the solution of the pump wear problem.     

Experimental investigation of hardfaced martensitic steel under slurry abrasion conditions

Wear by slurry abrasion is a potential problem in engineering components subjected to particulate flow. The life of the components under slurry abrasive wear situations is primarily decided by operating conditions and the materials properties. Martensitic steels are widely used for abrasion resistant applications. The present work reports slurry abrasion response of hardfacing martensitic steel under a wide range of experimental conditions. The response data is generated using systematic and simultaneous variation of test parameters. The experiments were performed using silica sand slurry with different slurry concentration, particle size, sliding distance and load. The results of the investigation suggest that slurry concentration had relatively stronger effect than normal load. The wear volume loss exhibited an increasing trend with increasing severity of test parameters. An empirical equation is proposed to describe the interactive effect of the test parameters, abrasive particle properties and material property. SEM (Scanning Electron Microscope) studies revealed different morphology of the worn surfaces which was attributed to mild to severe slurry abrasion test conditions.     

高铬铸铁耐泥沙磨损的机理探讨

在自制的模拟疏浚工况的立式泥沙磨损试验机上，对45钢和含碳量分别为2％和3％的高铬铸铁进行了泥沙磨损试验。运用扫描电镜观察了这几种材料在泥沙磨损条件下的磨损表面形貌，分析了它们的磨损机理。对于象45钢这类较软的材料，在泥沙磨损条件下，材料的磨损机理主要是显微切削和多次塑性变形。对于含有较多高硬度碳化物质点的高铬铸铁类材料，在泥沙磨损条件下，材料的磨损机理主要是基体组织的显微切削和碳化物颗粒的脱落。提出了在泥沙磨损条件下提高材料耐磨性的途径：一方面是如何减少基体组织的显微切削磨损；另一方面是如何使碳化物不易脱落，更好地起到保护基体的作用。     

Erosive Wear and Wear Mechanism of in situ TiCp/Fe Composites

1.IntroductionMetal-based composite is a kind of environmental ma-terial that can be reused.It combines the beneficialproperties of the metal matrix,such as ductility,goodthermal and electrical conductivity and high toughness,with those of the reforcement phase[1~3].The latter isusually a ceramic,serving to increase the elastic modu-lus,shear strength and hot strength,fatigue and wearresistance.Its development has been widely studied[4~8].Wear of metal materials causes a tremendous loss of ec…     

Performance Characteristics of Centrifugal Slurry Pump with Multi-Sized Particulate Bottom and Fly Ash Mixtures

The present study reports on the performance characteristics of the centrifugal slurry pump with multi-sized particulate slurry of bottom ash and fly ash mixtures. The performance characteristic of the pump was experimentally evaluated at rotational speed 1450 rpm for bottom ash slurries with and without the addition of fly ash in the concentration range of 10% to 50% (by weight). Addition of fly ash in the bottom ash was varied from 10% to 30% (by weight). The pump total head, overall efficiency, and pump input power at different flow rates were evaluated. The performance characteristics results show that the value of head and the efficiency of the pump depend on the solid concentration. It was also observed that the performance parameter of the pump strongly depends on slurry properties. The addition of fine particles fly ash in the coarser particles of bottom ash slurry, leads to reduce the additional head losses in the pump. The pump performance in terms of head and efficiency improved with addition of fly ash in bottom ash slurry.     

PARTICULATE MOTION AND CONCENTRATION FIELDS IN CENTRIFUGAL SLURRY PUMPS

Erosion wear of centrifugal slurry pumps is primarily governed by the particulate motion and concentration as well as their physical properties. This paper presents a quasi-3D approach to predict particulate phase motion and concentration in an arbitrary radial section of a centrifugal slurry pump. A brief discussion of the fully developed turbulent flow solution of the carrier fluid is followed by a computation of the particulate phase velocity resulting from a force balance between the pressure, gravity, viscous and inertial effects. The concentration distribution is obtained by invoking the convection-diffusion equation. The governing partial differential equation is cast into a weak Galerkin finite element form. The system of algebraic equations is solved by a Newton-Raphson scheme via a frontal solver. An iterative solution scheme is employed to alternate between the fields of particle motion and concentration. Numerical solutions are examined in light of their applicability to the solution of the pump wear problem.     

A study on sliding and erosive wear behaviour of atmospheric plasma sprayed conventional and nanostructured alumina coatings

Alumina coatings on stainless steel substrate (SS304) were deposited by using atmospheric plasma spray technique with a feed stock of manually granulated and sieved nano Al₂O₃ powder. The hardness, sliding, and erosive wear of the nanostructured alumina coatings (NC) were investigated and compared with that of conventional alumina coatings (CC). Pin-on disc type sliding wear test on the alumina coatings (NC and CC) was performed with load varying from 30 N to 80 N at a sliding speed of 0.5 m/s. Pot type slurry erosion test of the coatings was conducted for different concentrations of Al₂O₃ and a mixture of Al₂O₃ and SiO₂ slurry. The microstructural features of both NC and CC of alumina were characterized by using FE-SEM/EDS and SEM analysis to substantiate the failure of coatings due to wear. Wear and erosion resistance of nano alumina coating is better than the conventional alumina coating as observed in the present work. The bimodal structure of NC contributes for the enhanced wear resistance. The high fracture toughness of NC is due to suppression of cracks by partially melted particles in the coatings.     

Slurry erosive wear behavior of Ni–P coated Si3N4 reinforced Al6061 composites

Ni–P coated Si₃N₄ reinforced Al6061 composites were fabricated by liquid metallurgy route. Percentage of reinforcement was varied from 4 wt% to 10 wt% in steps of 2. The developed composites were subjected to microstructure and sand slurry erosive wear studies. The influence of experimental parameters such as slurry concentration, rotational speed of slurry, size of impinging particles and the test duration on slurry erosive wear behavior of developed composites have been studied. Results reveals that, Al6061–Si₃N₄ composites exhibited improved wear resistance when compared with the matrix alloy under identical test conditions. With increase in slurry concentration, rotational speed of slurry, test duration, size of impinging particles, the slurry erosive wear rates of both matrix alloy and developed composites increases. However, under all the tests conditions studied, the developed composites possess higher wear resistance when compared with that of matrix alloy. Energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS) techniques were used to identify the oxides/passive layer formed on the worn surfaces. Scanning Electron Microscopy (SEM) examinations were also carried out on worn surfaces to observe the possible mechanisms of material removal in the matrix alloy and developed composites.     

Modeling and optimizing of factors affecting erosion–corrosion of AA6063–(TiC/Al2O3) hybrid composites by experimental design method

In this article, modeling and optimizing of factors affecting erosion–corrosion wear of aluminum alloy A6063 reinforced with (Al₂O₃/TiC) particles have been determined by experimental design method. The erosion–corrosion wear characteristics and mechanism of AA6063–(TiC/Al₂O₃) with experimental parameters namely; type and concentration of corrosive media in the slurry, erosion speed and time have been investigated. Two models for reinforced and unreinforced alloys were applied to describe the influences of these factors on the erosion behavior of alloys. The erosion–corrosion mechanisms of the AA6063–(TiC/Al₂O₃) were dominated by particles erosion wear in alkaline slurry, and by the interaction of particle erosion wear and medium corrosion in acidic slurry. The results of experimental work are coinciding with that of calculated ones confirming the successful modelization.     

莫来石与碳纤维协同填充的聚四氟乙烯基复合材料及其摩擦学性能

为了提高聚四氟乙烯（PTFE）的摩擦学性能,采用机械混匀、带温预压及烧结等工艺制备了莫来石和碳纤维填充的PTFE基复合材料,并通过FTIR、XRD、万能材料试验机、洛氏硬度计、DSC及热机械分析分别表征了PTFE基复合材料的显微结构、力学性能和热学性能;然后,使用MRH-3 型高速环块磨损试验机测定了复合材料的摩擦系数和磨损率,通过自制的硅油砂浆磨损装置测定了复合材料在不同温度下的耐砂浆磨损性能;最后,借助3D测量激光显微镜研究了复合材料摩擦面形貌,并分析了摩擦磨损机制。结果表明:莫来石和碳纤维在PTFE体系中起到填充增强作用,20wt%莫来石-10wt%碳纤维/PTFE复合材料的弹性模量由364 MPa增加至874 MPa;20wt%莫来石-10wt%碳纤维/PTFE复合材料的干摩擦系数较大,但其磨损率与纯PTFE相比降低了3个数量级以上,且此复合材料在水摩擦条件下仍能保持较好的摩擦系数和磨损率,摩擦系数为0.157,磨损率为7.40×10-6 mm3·N-1·m-1;此外,20wt%莫来石-10wt%碳纤维/PTFE复合材料在较高温度下仍能表现出良好的耐砂浆磨损性能。所得结论表明改性得到的PTFE 基复合材料的摩擦学性能显著提高,复合材料可用于有杆抽油井防偏磨。      

离心泵作透平流体诱发外场噪声特性及贡献分析

以某离心泵作透平为研究对象,对流体诱发的外场噪声特性进行了数值计算和试验研究。在典型流量下,采用雷诺时均方法获取壁面偶极子声源,并利用FEM/AML方法求解出叶轮和壳体偶极子源作用的流动噪声,基于声振耦合法计算出流体激励结构振动产生的外场流激噪声,分析不同性质噪声源的频谱特性,同时评估外场声源在各个频段下的贡献量。借助模态试验对透平壳体结构的模态参数进行了识别。结果表明,计算与试验振型近似,固有频率平均相对误差小于4.60%。结构的影响使得外场五阶叶频处声压最高,二阶叶频处次之。壳体偶极子作用的流激噪声对外场噪声的贡献最大,其次是壳体偶极子作用的流动噪声,叶轮偶极子作用的流激噪声对外场噪声贡献最小。研究结果为低噪声叶轮机械设计提供了一定的参考。     

A review on particulate slurry erosive wear of industrial materials: In context with pipeline transportation of mineral−slurry

Pipeline transportation of slurry is being carried out all over the world. Slurry pipeline wear is one of the major problems associated with it. The wear rate of the slurry pipeline depends upon factors such as slurry properties, slurry particle properties, flow properties, and pipeline wall properties. Any change in these properties results in change in pipeline wear rate. There is a need to study the effect of individual properties, for predicting the slurry pipeline life span and also to find the methods to minimize the wear rate. In this review paper, an attempt has been made to discuss the parameters which are believed to be the primary factors that affect material wear rate. Several mechanisms and equations suggested by various researchers for the prediction of wear of materials are also reviewed. Most of the models incorporate the effects of only few parameters involved during the wear process. These equations are specific and valid up to limited operating conditions. No general equation have been evolved which can be used under any operating condition, with better accuracy. This can be attributed to lack of data at microscopic level and also to change in the wear mechanisms under various operating conditions.     

长庆油田渗氮套管的耐腐蚀性能研究

针对长庆油田油井套管腐蚀问题,采用并评价了真空渗氮工艺.该工艺处理套管表面形成氮化层,在不降低原有机械性能的前提下提高了表面耐磨、抗蚀能力.经室内、现场试验发现,渗氮管在长庆油井腐蚀情况下的耐腐蚀性能优良.此外,还就渗氮层在不同弯曲、拉应力条件下的微观表面变化对使用性能的影响进行了研究,确定了渗氮套管下井条件.并于2003年首次在2口井得以应用.该工艺为低产低渗透油田的防腐蚀研究提供了新思路.     

Effect of increased manganese addition and mould type on the slurry erosion characteristics of Cr-Mn iron systems

The wear resistance of high chromium iron is well recorded. However, the same is not the case as regards the use of manganese at higher percentages in high chromium irons and its influence on wear behaviour. Hence, this work highlights the slurry wear characteristics of chromium (□ 16–19%) iron following the introduction of manganese at two levels i.e. 5 and 10%. It is known that the wear properties are dictated by the microstructural features. To alter the structure, the cooling rate of casting has been varied by adopting two different types of moulds (i.e. sand and metal) and subsequently subjecting to thermal treatment. The as-cast and heat treated samples are examined for microstructure and then evaluated for hardness and slurry erosion properties. As the manganese content is increased from 5 to 10%, the hardness showed a decrease in value both in the as-cast and heat treated conditions. The slurry erosion loss, expectedly, showed an increase irrespective of the sample condition (i.e. mould type/heat treatment adopted). The findings are corroborated with the microstructural features obtained through optical and scanning electron microscopy.