Internal Pipe Wall Research Articles

Comprehensive study on microwave inspection of internal pipe wall thinning: discontinuities, reflections and signals

Comprehensive study on microwave inspection of internal pipe wall thinning: discontinuities, reflections and signals

Hydrogen embrittlement effects on remaining life and fatigue crack growth rate in API 5L X52 steel pipelines under cyclic pressure loading

Transporting hydrogen gas through the existing natural gas pipeline network offers an efficient solution for energy storage and conveyance. Hydrogen generated from excess renewable electricity can be conveyed through the API 5L steel-made pipelines that already exist. In recent years, there has been a growing demand for the transportation of hydrogen through existing gas pipelines. Therefore, numerical and experimental tests are required to verify and ensure the mechanical integrity of the API 5L steel pipelines that will be used for pressurized hydrogen transportation. Internal pressure loading is likely to accelerate hydrogen diffusion through the internal pipe wall and consequently accentuate the hydrogen embrittlement of steel pipelines. Furthermore, pre-cracked pipelines are susceptible to quick failure mainly under a time-dependent cyclic pressure loading that drives fatigue crack propagation. Meanwhile, after several loading cycles, the initial cracks will propagate to a critical size. At this point, the remaining service life of the pipeline can be estimated, and inspection intervals can be determined. This paper focuses on the hydrogen embrittlement of API 5L steel-made pipeline under cyclic pressure loading. Pressurized hydrogen gas is transported through a network of pipelines where demands at consumption nodes vary periodically. The resulting pressure profile over time is considered a cyclic loading on the internal wall of a pre-cracked pipeline made of API 5L steel-grade material. Numerical modeling has allowed the prediction of fatigue crack evolution and estimation of the remaining service life of the pipeline. The developed methodology presented in this paper is based on the ASME B31.12 standard, which outlines the guidelines for hydrogen pipelines with reference to the ASME BPVC Section VIII, Division 3, Article KD-10.

Numerical Simulation Study on the Performance of Buried Pipelines under the Action of Faults

The present paper investigates the mechanical behavior of buried steel pipelines crossing an active fault. Permanent ground deformation induced by an earthquake will cause serious damage to buried steel pipelines, resulting in buckling failure or even cracking damage to pipelines. Based on ABAQUS software, version 6.13., the model of an interacting soil–pipeline system is established, accounting for large strains and displacements and nonlinear material behavior, as well as contact and friction at the soil–pipeline interface. Numerical analysis is conducted through the incremental application of fault displacement. Combined with the force and deformation characteristics of buried pipelines, a strain-based design criterion is chosen to study the vertical displacement, axial compressive, and tensile strain of buried pipelines, etc. This paper focuses on the effects of horizontal fault displacement, fault type, and fault angle on the structural response of the pipe. The failure of the pipeline, such as wall wrinkling, local buckling, or rupture is identified. Furthermore, the effects of the pipeline internal pressure and pipe wall thickness are investigated. The results show that, when the pipeline depth is 1.5 m under the action of the fault, the buried pipeline will not be subject to beam buckling damage, and both tensile damage and shell buckling damage will occur. In this case, the critical displacement of the tensile failure is more than three times that of the shell buckling failure, which indicates that shell buckling damage is a greater threat to the pipeline. The pipeline is most susceptible to damage under the action of a strike-slip reverse fault. When the fault angle is equal to 45 degrees, the pipeline is more likely to be damaged, while it is relatively safe at a fault angle with 90 degrees. The results of this investigation can determine the fault displacement during pipeline failure and provide some reference for pipeline design.

CFD-FEA based model to predict leak-points in a 90-degree pipe elbow

The aim of this paper is to numerically investigate Vibration-Based Leak Detection (VBLD) method in pipeline systems based on Fluid–Structure Interaction (FSI) analysis to predict leakages. In previous investigations, laboratory tests were widely used to study the VBLD technique in small-diameter water loop system pipes. The current project uses Ansys Workbench to extend these findings by integrating Computational Fluid Dynamics (CFD) with Finite Element Analysis (FEA). The study outlines a numerical method for VBLD to identify leakages in a 90-degree pipe elbow by predicting variations in vibration signals, with applications in the oil and gas industry. Firstly, changes in fluid behaviour (centrifugal force, pressure drop, secondary flow, and frictional force) experienced in the internal pipe wall resulting from a probable leakage (modelled as an additional outlet) are determined using CFD. Subsequently, the CFD results are coupled with FEA to model structural responses of the pipe walls subjected to different forces. This in turn allows the variations in vibration signals to be measured. The numerical approach presented in this paper based on FSI and incorporating the VBLD method provides a practical and convenient early detection tool that can complement physical vibration monitoring equipment in the field.

Studying the effect of the force convection boundary condition and radius magnetic field on fluid flow and heat transfer between coaxial pipes

AbstractAn investigation of the heat transfer of Newtonian fluid flow through coaxial two pipes with variable radius ratio has been conducted with the boundary conditions of forced convection on the inner pipe walls and a radius magnetic field. This paper presents an exact analytical solution to the momentum equation and a novel semi‐analytic collocation method for solving the full‐term energy equation that takes Joule heating into account as well as viscous dissipation. Based on the results of the numerical fourth‐order Runge–Kutta method, it was found that increasing the magnetic parameter decreased the amount of friction on the surface of the pipe walls and the rate of heat transfer. As the radius ratio of the two pipes increases, so does the skin friction and heat transfer rate on the internal pipe walls. As Eckert (Ec) and Prandtl (Pr) numbers increase, the mean temperature as well as the dimensionless temperature between the two pipes increases. The increase in Biot number (Bi) has the opposite impact on the mean temperature. As Ec, Pr, and Bi increase, so does the rate of heat transfer on the inner wall of the pipe.

SPECIFICS OF DIAGNOSTICS OF TECHNICAL CONDITION OF TRANSPORT AND TECHNOLOGICAL SYSTEM “MINING GAS PIPELINE – MINE WORKING”

The purpose of the paper is to analyze a deformation mechanism of the mine degassing pipelines to forecast their spatial changes in terms of intensification of underground mining of coal-gas seams.
 Methodology. The paper deals with expert assessment of the available approaches to diagnostics of technical condition of mine degassing pipelines, which are constructed within the in-seam underground mine workings with the floor rocks prone to heaving. The results of scheduled surveying measurements of technical condition of in-seam development workings have helped identify the potentially hazardous zones of rock mass deformation and indices of changes in spatial location of section degassing pipelines mounted in those mine workings. To determine the operating modes of a degassing pipeline under such operating conditions, a computer model of interaction of the elements of transport-technological system “mine gas pipeline – mine working” has been developed
 Findings. Diagnostics of technical conditions of the mine gas transmission lines and examination of their dismantled components have helped understand that deflections, mainly resulting in water accumulation zones, intensive corrosion of internal pipe walls, and mechanical depositions of coal and rock dust take place right within the flange connection areas. Formation of such zones is argued by health of the degassing pipeline as well as mine air inflow. Availability of internal corrosion, water accumulations, and mine air inflow decreases substantially capacity of the underground gas transmission line inclusive of qualitative characteristics of the captured methane-air mixture and efficiency of MDS on the whole.
 Originality. New approaches to diagnostics of technical condition of mine degassing gas pipeline in difficult mining and geological conditions of development of gas-bearing coal seams are substantiated and it is offered to consider indicators of their functioning as interacting in space and time transport-technological system "mine gas pipeline - mining".
 Practical implications. The operational parameters of mine degassing systems notes that the equipment performance with the least underpressure losses created by vacuum pipes requires that the degassing pipeline should have minimum hydraulic resistance of the gas transmission network. Pipeline aeration from the mine workings and water accumulations should be prevented by means of qualitative hermetic sealing of its flange connections as well as the pipeline straightness with the corresponding pitches. Consequently, the basic requirements for operating mine degassing pipelines involve their design profile, tightness of flange connections of pipes as well as operative control of the facility health.

Effect of pipe flattening on pressure drop in vapor core and thermal characteristic of miniature round and flat-shape heat pipe with sintered fiber wick

The effect of pipe flattening on pressure drop in vapor core and also heat transfer characteristic of the sintered fiber heat pipes has been investigated. The original diameter of heat pipes were 2 mm and 3 mm, respectively, with the effective length of 100 mm. Thermal performance of the flat-shaped heat pipe with the sintered fiber bundle wick was experimentally investigated under a horizontal orientation in this study. The proper fiber bundle wicks were fabricated at porosity of 0.54, and firmly filled within internal heat pipe wall by the sintering process. The heat pipes were pressed into two final thickness by the flattened process which results in vapor core minimizing. The numerical method was established in modified forms to represent the related wick-heat pipe design parameters, for example, wick thickness, wick porosity, wall thickness, flattened width and height, corresponding to thermal performance of fiber wick heat pipes. The numerical analysis for pressure drop was only focused on vapor core region. The vapor flow was assumed to be laminar and incompressible. It is found that when the heat pipe was flattened, the pressure drop increased. The flattening of heat pipe caused the smaller space of vapor core, therefore the working fluid in vapor phase could not easily transfer heat. In this case, the critical final thickness of 0.45 mm (for original diameter of 2 mm) which the vapor core area nearly approaches to zero, has an effect on the high value of thermal resistance considered in vapor core (z5). In addition, the overall thermal resistance estimated from ESDU79012 agrees well with that obtained from the experiment with the standard deviation (STD) of ±15 %, and it shows that the thermal resistance model can provides a reasonable prediction for the thermal resistance of flat-shaped heat pipes with sintered fiber wicks. Moreover, the new normalized parameter h′v/hv is proposed to represent the appearance of vapor core after pipe flattening which can be used to suggest a desirable normal region of flattened heat pipe with the sintered fiber wick. The critical remaining vapor core height after pipe flattening has been further analyzed to be 0.06 (about 74% from original diameter).

Modeling Surface Roughness-Related Uncertainties of Leaky Lamb Wave Clamp-on Ultrasonic Flowmeters

Transit time clamp-on ultrasonic flowmeters (UFMs) are widely used in industry due to their ease of installation. However, these ultrasonic clamp-on flowmeters are also known to be less accurate than ultrasonic inline flowmeters because of the uncertainties induced by the installation process. Amongst the installation-related parameters that influence the measurement uncertainties, internal pipe wall roughness is one of the most significant but uncontrollable parameters. The effect of roughness on accuracy can be reduced by operating the flowmeter at a longer wavelength. This article investigates the effect of roughness on a clamp-on UFM using low-frequency (200 kHz) leaky Lamb waves. This results in operation at roughly five times lower frequency compared with conventional clamp-on UFMs. The ultrasonic signals of this leaky Lamb wave UFM were simulated using the 2-D finite-element (FE) analysis. Using the simulated signals, the roughness effects on the uncertainties were quantified. The simulation results show that the uncertainty related to pipe wall roughness of leaky Lamb wave UFMs is approximately half that of conventional UFMs for corroded pipe walls with rms value larger than 0.1 mm (0.2, 0.35, and 0.5 mm). Demonstration experiments were also carried out to detect leaky Lamb wave using an electromagnetic acoustic transducer (EMAT). The experiment shows that the simulation correctly captures all the physics of the wave propagation and that we, therefore, can trust the simulation results with incorporated roughness.

Stress Analysis and Microstructure Evolution of Titanium Alloy Pipe during Flattening Processing

TA24 titanium alloy pipe with 638mm diameter and 19mm wall thickness is carried out continuous load flatten test, and the stress of internal and external pipe wall during flatten process is studied in this paper. The results show that the TA24 titanium alloy tube has good flattening performance, and the flattening process has experienced original stage, flattened oblate stage, flattened straight wall stage, flattened depressed stage, flattened concave contact stage. During the flattening process, the outer layer of the upper and lower wall of the tube is subjected to compressive stress, and the inner layer material is subjected to tensile stress. The tensile and compressive forces cause the vertical part of the upper and lower walls to be concave. The outer layer of the left and right circular arc parts is subjected to tensile stress and the inner layer is subjected to tensile stress. The compressive stress also causes the radius of the arc to decrease due to the combined force of the tensile and compressive forces, that is, the flattening occurs. With the decrease of and pressing distance under continuous loading condition, the metal on the left and right sides of the pipe gathers toward the middle depression, which aggravates the deformation of the upper and lower walls until the upper and lower walls contact, and the arc radius of the left and right walls decreases until the outer surface cracks. The pipe microstructure changes significantly into elongated deformation structure during the flattening process. The most severe part of the deformation is the left and right end arc of the pipe, followed by the upper and lower end depression.

The Effect of Internal Pipe Wall Roughness on the Accuracy of Clamp-On Ultrasonic Flowmeters

Clamp-on transit-time ultrasonic flowmeters (UFMs) suffer from poor accuracy compared with spool-piece UFMs due to uncertainties that result from the in-field installation process. One of the important sources of uncertainties is internal pipe wall roughness which affects the flow profile and also causes significant scattering of ultrasound. This paper purely focuses on the parametric study to quantify the uncertainties (related to internal pipe wall roughness) induced by scattering of ultrasound and it shows that these effects are large even without taking into account the associated flow disturbances. The flowmeter signals for a reference clamp-on flowmeter setup were simulated using 2-D finite element analysis including simplifying assumptions (to simulate the effect of flow) that were deemed appropriate. The validity of the simulations was indirectly verified by carrying out experiments with different separation distances between ultrasonic probes. The error predicted by the simulations and the experimentally observed errors were in good agreement. Then, this simulation method was applied on pipe walls with rough internal surfaces. For ultrasonic waves at 1 MHz, it was found that compared with smooth pipes, pipes with only a moderately rough internal surface (with 0.2-mm rms and 5-mm correlation length) can exhibit systematic errors of 2% in the flow velocity measurement. This demonstrates that pipe internal surface roughness is a very important factor that limits the accuracy of clamp on UFMs.

Study of water wetting and water layer thickness in oil-water flow in horizontal pipes with different wettability

Two-phase oil-water pipe flow is common in oil production and transportation. Appropriate estimation of phase wetting (oil wet or water wet) of internal pipe walls can significantly reduce corrosion control costs, and increase confidence in measures taken to ensure the integrity of pipelines. Water wetting can be avoided by fully dispersing the water phase into the oil phase. It has been suggested that pipe wettability may affect oil-water flow patterns; particularly, water-in-oil dispersed flow transition boundaries. However, there are no systematic studies in the literature on this matter for carbon steel pipes, which are the preferable choice for economic reasons in the oil and gas industry. Moreover, traditional and widely used models to predict the onset of dispersed flow do not consider the effect of pipe wettability. This work studies phase wetting and water layer thickness in large scale oil-dominated oil-water horizontal flow in carbon steel and PVC pipes of similar internal diameter (0.1 m) and roughness, but different wettability. The effect of wetting hysteresis (oil or water pre-wetted pipe surface) on phase wetting is also investigated. It is demonstrated that pipe wettability plays a very important role on the transition boundaries for phase wetting (oil wet to water wet) and the transition to fully dispersed flow. Water droplet deposition and spreading are identified as the main mechanisms for incipient segregation in a hydrophilic pipe. In a hydrophobic pipe, poor surface wettability hinders the sticking and spreading of water droplets. Water wetting in a hydrophobic pipe requires a sufficient low flow velocity at which local droplet accumulation and coalescence becomes the dominant segregation mechanism. Predictions from available hydrodynamic models are compared with the experimental results and recommendations are provided.

Siderite micro-modification for enhanced corrosion protection

Production of oil and gas results in the creation of carbon dioxide (CO2) which when wet is extremely corrosive owing to the speciation of carbonic acid. Severe production losses and safety incidents occur when carbon steel (CS) is used as a pipeline material if corrosion is not properly managed. Currently corrosion inhibitor (CI) chemicals are used to ensure that the material degradation rates are properly controlled; this imposes operational constraints, costs of deployment and environmental issues. In specific conditions, a naturally growing corrosion product known as siderite or iron carbonate (FeCO3) precipitates onto the internal pipe wall providing protection from electrochemical degradation. Many parameters influence the thermodynamics of FeCO3 precipitation which is generally favoured at high values of temperatures, pressure and pH. In this paper, a new approach for corrosion management is presented; micro-modifying the corrosion product. This novel mitigation approach relies on enhancing the crystallisation of FeCO3 and improving its density, protectiveness and mechanical properties. The addition of a silicon-rich nanofiller is shown to augment the growth of FeCO3 at lower pH and temperature without affecting the bulk pH. The hybrid FeCO3 exhibits superior general and localised corrosion properties. The findings herein indicate that it is possible to locally alter the environment in the vicinity of the corroding steel in order to grow a dense and therefore protective FeCO3 film via the incorporation of hybrid organic-inorganic silsesquioxane moieties. The durability and mechanical integrity of the film is also significantly improved.

Impact of pipe roughness on the performance of a water distribution network: A case study of the Westbury Network, Johannesburg, South Africa

The Westbury area, a suburb of the city of Johannesburg, is characterized by a very old pipe network, high water losses as well as high operating and maintenance costs. Consequently, a network rehabilitation project was proposed for the area, with an overall aim of improving network efficiency through pipe replacement. This proposal led to the current study with the key objective of determining the impact that pipe roughness has on network performance. In order to achieve this goal, a model of the area was obtained and analysed as a gravity-fed network containing 490 pipes, 407 junctions and 5 reservoirs. From the study, key findings reveal that the smoother the internal pipe walls, the higher the pressure at which demand is met. In addition, power delivered to consumers increases with internal pipe smoothness, and power dissipated in the network increases with pipe roughness. On the other hand, the relationship between roughness and leakage is inconclusive.

Predicting the Head-area Slopes of Circular Holes in Water Pipes

Leak openings in water distribution system pipes are not static, but vary with pressure. These changes in area affect the way that leaks respond to changes in pressure, and are thus important for municipal engineers to understand. In this study, the behavior of round holes in pressurized pipes was investigated using finite element analysis (FEA), under the assumption of linear elastic behavior. It was found that the areas of the round holes vary as linear functions of pressure in the pipe. A sensitivity analysis was then carried out to investigate parameters that influence the head-area slope. The elastic modulus, internal pipe diameter and pipe wall thickness were found to be the most important parameters. Solid mechanics theory was used to develop an equation to predict the head-area slope m of round holes in pipes. Finally, the results were compared to the findings of an experimental study. The comparison showed that the head-area slopes for both the equation and the FEA were within or close to the 95% confidence intervals of the experimental study.

Electromagnetic flowmeter with non-insulation pipe wall

The internal pipe wall of the Electromagnetic Flowmeter (EMFM) must be non-conductive to prevent the generated electromotive force from short-circuiting. Usually the inside of metallic pipes is lined with insulating material. The lining limits the applicable temperature range of measured fluid and also its reliability. A new structure is proposed, in which the insulating liner is eliminated and replaced with non-insulation material. A potential distribution is formed on the pipe wall by applying voltage proportional to fluid flow rate. The potential distribution is decided by the conducting pipe wall. In this paper theoretical analysis and experimental results of EMFM with non-insulation pipe wall are described.

Electromagnetic flow meter with non-insulation pipe wall for liquid sodium in nuclear reactors

An electromagnetic flow meter (EMFM) with non-insulation pipe wall that may be used in the Fast Reactor Test Facility (FARET) has been designed and partially tested. The internal pipe wall of EMFMs must be non-conductive to prevent generated electromotive force from short circuiting. Usually the inside of metallic pipes is lined with insulating material. The lining limits the applicable temperature range of measured fluid and also its reliability. A new structure is proposed, in which the insulating liner is eliminated and metallic pipe instead of non-insulation material. Also a servo system is applied. Therefore, the output signal is exactly the same as that of conventional EMFMs. In this paper, an analytical method based on conducting wall boundary conditions and experimental results is described.

Electromagnetic flowmeter with non-insulation pipe wall

The internal pipe wall of the Electromagnetic Flowmeter (EMFM) must be non-conductive to prevent the generated electromotive force from short-circuiting. Usually the inside of metallic pipes is lined with insulating material. The lining limits the applicable temperature range of measured fluid and also its reliability. A new structure is proposed, in which the insulating liner is eliminated and replaced with non-insulation material. A potential distribution is formed on the pipe wall by applying voltage proportional to fluid flow rate. The potential distribution is decided by the conducting pipe wall. In this paper theoretical analysis and experimental results of EMFM with non-insulation pipe wall are described.

Experimental Investigation Into the Relationship Between the Roughness Height in Use With Nikuradse or Colebrook Roughness Functions and the Internal Wall Roughness Profile for Commercial Steel Pipes

The relationships between the sand grain roughness height (ks) in use with Nikuradse or Colebrook correlations for the roughness function (RF) and the internal pipe wall roughness element described by the root-mean-square (RMS) of the roughness profile (Rq) for turbulent flow in pipes are experimentally examined. Flow tests were conducted on a total of 13 commercial steel pipes of two sizes: 168.3 mm and 114.3 mm outer diameter (OD). The aim was to provide further insight into relationship between ks and Rq, for use with either RF correlations. The tests were conducted on high-pressure pipeline quality natural gas in the range of Reynolds number (based on pipe internal diameter) of 9 × 106–16 × 106. For commercial carbon steel pipes, the relationship between ks and Rq was found in the form ks=1.306 Rq+0.078 Rq2 and ks=2.294 Rq (both ks and Rq in μm), for use with Colebrook and Nikuradse RF correlations, respectively. These correlations cover a wide range of Rq from 2.7 μm to 12.5 μm which is typically found in commercial carbon steel pipes. For stainless steel (SS) pipes, preliminary results indicate that other surface roughness profile parameters need to be employed to better define the values of ks for these types of commercial steel pipes.

Degradation of Plastic Pipe Surfaces in Contact with an Aggressive Acidic Environment

Polyethylene (PE) pipes transporting water are vulnerable to aggressive agents which are able to diffuse through buried plastic pipes causing oxidative degradation. The latter may occur as a result of a spontaneous chemical reaction with atmospheric oxygen or as an induced oxidizing reaction with disinfectant agents (i.e. chlorine or hypochlorous acid ions) which are commonly added to municipal water supplies for public health reasons. Basically, PE pipes surfaces undergo undesired oxidation reactions whenever they are in contact with adverse external environments and/or when conveying fluids which tend to modify internal pipe wall structure. In this work, the effects of distilled water and diluted hydrochloric acid at different concentrations on the external and internal surfaces of a high density polyethylene (HDPE-100) pipe are studied. The measured parameters are roughness and hardness in order to appreciate surface quality variances in as-received and degraded materials. Initially the outer surface is rougher than the inner's one but in contact with distilled water, the external surface roughness increased by 6% although the internal face of the tube revealed a small decrease (<5%). When exposed to hydrochloric acid, pipe roughness (μm) showed a substantial increase as a function of increasing medium concentration. Crystallinity (χ in %) measurements confirmed the gap between outer (51.55%) and inner (61.31%) surfaces indicating that degradation has taken place at the structural level when HDPE was in contact with such aggressive agents. On the other hand, it is revealed that after exposure to oxidizing environments, crystallinity dropped by approximately one third when compared to as-received material; therefore reducing resistance to fracture and subsequently pipe lifetime.

Application of EVM to determine pipe internal surface conditions in complex natural gas lateral networks

This paper describes the use of the Error-in-Variable Model (EVM), a type of parameter estimation techniques, for the determination of the internal pipe wall surface conditions (effective surface roughness) of pipe segments in complex natural gas pipeline networks and sub-lateral gathering networks. This technique uses SCADA data collected over a period of time such as pressures, temperatures and flow rates at boundary points of the network, i.e. at receipt and delivery points. These data are used as input to the EVM along with pertinent objective functions that are based on dimensional mass, momentum and energy conservation equations. The main focus of the technique is to extract reliable and accurate information with regard to the internal wall surface condition of pipe segments within the network that are showing evidence of fouling or under-performing from the flow efficiency perspective. The EVM is most suited for this problem as it accounts for uncertainties in the SCADA data from errors in the measurement instrumentations, the time averaging processing of the data and the inherent assumption of the quasi-steadiness of the flow rates. Insight into the implication of pipe segments arranged in series or in parallel within the network is highlighted. Guidance as to the relationship between the number of necessary distinct data sets required for a given number of parameters (surface roughness of pipe segments) to be estimated and the number of independent objective functions that can be written for a given network is provided. Finally, the EVM technique is demonstrated by an existing sub-lateral natural gas receipt network feeding into a main gas transmission pipeline (DN750), 21.1 km upstream of a compressor station.