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Pipe Wall (pipe + wall)

Distribution by Scientific Domains

Chemistry	50%
Polymers and Materials Science	40%

Selected Abstracts

An Ultrasonic Profiling Method for the Inspection of Tubular Structures

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2007
Francisco Gomez
These graphs not only show the inner contour of the pipe but also integrate the intensity of the echoes employed to create the profile. The enhanced profile is generated by superimposing the peak intensity from the returning echoes at the calculated x, y, and z coordinates where it reflected from the pipe wall. The proposed method is capable of showing anomalous conditions, inside pipes filled with liquid, with dimensions smaller than the theoretical lateral and axial resolution of the transducer, in contrast to traditional methods where these kinds of defects are not disclosed. The proposed inspection method and its capabilities were validated through the realization of simulations and experiments. The presented approach was particularly developed with the aim of scanning internal sections of pipes filled with liquid using rotary ultrasonic sonars, but it is expected that this research could be expanded to the inspection of other submerged structures, such as water tanks, or pressurized vessels. [source]

Water pipeline failure due to water hammer effects

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2006
C. SCHMITT
ABSTRACT A numerical model has been established in order to simulate the propagation of pressure waves in water networks. The present model formulation is based on a system of partial hyperbolic differential equations. This system has been solved via the characteristics method. The current model provides the necessary data and the necessary damping of water hammer waves, taking into account the structure of the pipe network and the pressure loss. The numerical algorithm estimates the maximum pressure values resulting from the water hammer when closing valves in the network and consequently, the maximum stresses in the pipes have been calculated. In the case of simultaneous closing of several valves, the over pressure can exceed the admissible pressure. In this case, the severity of a defect such as a corrosion crater (pit) has been estimated by computing a safety factor for the stress distribution at the defect tip. This allows the applied notch stress intensity factor to be obtained. To investigate the defect geometry effects, semi-spherical and semi-elliptical defects are deemed to exist in up to one-half of the thickness of the pipe wall. The outcomes have been introduced into the structural integrity assessment procedure (SINTAP) failure diagram assessment (FAD) in order to obtain the safety factor value. Conventionally, it is considered that a failure hazard exists if this safety factor is less than two. [source]

On the electrostatic equilibrium of granular flow in pneumatic conveying systems

AICHE JOURNAL, Issue 11 2006
Jun Yao
Abstract An analytical methodology involving the concept of "electrostatic equilibrium" is developed for granular flow in pneumatic conveying systems. The methodology can be used for estimation of the electrostatic field distribution at various sections of the system and explanation of the mechanisms involved for various electrostatic phenomena observed. For all cases conducted in the conveying system, there was a "charging time" required for the system to reach the state of "electrostatic equilibrium." Experiments conducted at different sections of the system showed that the time required increased in the order: horizontal pipe, vertical pipe, and pipe bend. Through a physical analysis, it is deduced that electrostatic equilibrium is related to the granules' behavior and local flow characteristics. In general, a longer time duration taken to reach equilibrium corresponds to a process with more complicated granular flow patterns. In the electrostatic equilibrium state, the field distribution shows the highest electrostatic field strength near the pipe wall, and this field strength degrades from the pipe wall to the pipe center. At various pipe sections, the highest strength occurs at the bend, in accord with observations that electric sparking first occurs at that location within the entire pneumatic conveying system. In the vertical pipe, granular distribution was measured using electrical capacitance tomography (ECT), and granular velocities were cross-referenced with those using particle image velocimetry (PIV). The electrostatic force at low air flow rates is found to be the primary cause for granules sticking to the pipe wall and results in the formation of the half-ring or ring structure. The state of electrostatic equilibrium is physically influenced by several elements in conveying systems. In a cyclic conveying system, a new pipe (or low humidity or no antistatic agent) tends to expedite the process to reach electrostatic equilibrium and attain high magnitude of electrostatic current at the state. In a non-cyclic horizontal conveying system, a thin film (pipe) is found to prolong the process duration to reach equilibrium, while the case with charged film (pipe) takes shorter duration to do so. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

Analysis of the Influence of Processing Conditions on the Supramolecular Structure and Antioxidant Distribution in PP-Pipes Using Infrared Microscopy

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2008
Robert Brüll
Abstract The supramolecular structure in pipe walls of isotactic PP-R is a function of compound composition and processing parameters, which both influence the mechanical properties of the pipes. µFTIR shows a gradient of the crystallinity across the pipe wall, with a lower-crystalline outer layer, and a higher-crystalline core layer. The rate of extrusion has an influence on the thickness of the outer layer. The nucleating effect on the morphological profile throughout the pipe wall can be visualised. µFTIR shows a homogeneous distribution of the primary antioxidant in the pipe wall. Both the spectral crystallinity and the antioxidant concentration distribution are calculated. [source]

A method to predict triaxial residual stresses in plastic pipes

POLYMER ENGINEERING & SCIENCE, Issue 10 2004
Z. W. Guan
Significant hoop and longitudinal stresses are present in medium-density polyethylene (MDPE) pipe, arising from differential cooling from the inner and the outer surfaces of a pipe during production. Owing to the difficulty of directly measuring deformations, these stresses have hitherto been almost exclusively estimated indirectly from deflection measurements on large samples cut from the pipe wall. Furthermore, because of procedural problems, only uniaxial hoop or longitudinal stresses are normally attempted, and these are known to be specimen size,dependent. Similar problems are experienced with other polymeric pipes. In this paper, based on direct biaxial strain measurements on small samples cut from the pipe wall, a method to predict triaxial residual stress distributions through the pipe wall is presented. Thermal effects that generate residual stresses in plastic pipe were considered in the theory. The analytical solutions satisfy the self-equilibrating conditions for both the hoop and the longitudinal stresses. Also, the radial stress is shown to be insignificant through the wall thickness of a mildly thick pipe. Polym. Eng. Sci. 44:1828,1838, 2004. © 2004 Society of Plastics Engineers. [source]

Bitumen effects on pipeline hydraulics during oil sand hydrotransport

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2000
R. Sean Sanders
Abstract Oil sand hydrotransport technology has become increasingly important to Syncrude Canada Ltd. and the oil sands industry. Oil sand slurries are complex, multiphase mixtures of bitumen, coarse solids, fine solids, water and air that can exhibit time-dependent behaviour, wherein pipeline friction losses increase drastically with time. Four separate experimental programs were conducted to study the effect of bitumen on pipeline hydraulics using 100 mm and 250 mm (I.D.) recirculating and once-through pipeline loops. The results show that pipeline friction losses increase as a bitumen coating forms on the pipe wall. The effect is more pronounced at 50°C, but also occurs at lower temperatures. La technologie de l'hydrotransport des sables pétro-lifères revêt une importance de plus en plus grande pour Syncrude Canada et l'industrie des sables pétro-lifères. Les boues des sables pétrolifères sont complexes; elles contiennent des mélanges de bitumes multi-phasiques, des solides grossiers, des solides fins, de l'eau et de l'air qui peuvent parfois montrer un comportement évolutif, en particulier les pertes par frottement dans les conduites qui augmentent considérablement avec le temps. Quatre programmes expérimentaux différents ont été menés pour étudier l'effet du bitume sur les conditions hydrauliques des conduites au moyen de boucles de conduites en recirculation et sans recyclage de 100 et 250 mm de diamètre intérieur. Les résultats montrent que les pertes par frottement dans les pipelines augmentent lorsqu'une couche de bitume se forme sur la paroi de la conduite. L'effet est plus prononcé à 50°C, mais survient également à des températures plus basses. [source]

Fluid flow in an impacting symmetrical tee junction III: three-phase air/water/oil flow

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009
A. P. Doherty
Abstract Results are presented on three-phase air/oil/water horizontal flow in a 0.026 m i.d. symmetrical impacting tee junction. The flow regimes observed agreed with an existing three-phase flow map. The inversion from water-dominated (WD) to oil-dominated (OD) flow was at an oil-to-liquid volumetric ratio of fo = 0.285. The inversion was at a low fo value because of the relatively tranquil conditions studied. Retention of oil on the pipe wall at the air/water two-phase condition at fo = 0 resulted in a dramatic increase in the pressure drop above that expected for the two-phase flow. The pressure drop in the tee junction arms increased with liquid-flow rate. The actual tee junction pressure drop showed a similar pattern to that observed in the inlet arm. The pressure drop was relatively constant in the OD region but showed a dramatic increase in the WD and inversion regions at low fo values. Non-dimensionalising the junction pressure drop as le/d gave a similar pattern but the scatter of data increased. The tee pressure loss data were modelled using the Lockhart-Martinelli ,G parameter and gave similar but different correlations for the WD and OD regions. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Two-phase bifurcated dividing pipe flow

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009
A. Murphy
Abstract Data are reported on the pressure drop of co-current air,water two-phase flow through 0.0454 m i.d. bifurcations with included angles of 60°, 90°, 120° and 180°. The pressure changes on account of the angles at the junctions depended on the superficial phase velocities and the angle of bifurcation. For the 60° lowest angle of bifurcation the pressure drop was insensitive to flow rates if the superficial liquid velocity was in the lower range at and below 0.1 m s,1. For higher liquid flows the pressure loss increased dramatically, particularly in the annular-type regimes. When the angle at the junction was increased, negative values of pressure loss, i.e. an increase in pressure was recorded across the bifurcation in the gas velocity region under 10 m s,1 and liquid rates at and above 0.1 m s,1 in the slug and blow-through slug regimes. The effect coincided with liquid separation from the inner inlet pipe wall of the junction and its subsequent reformation on the downstream walls. A second less dramatic increase in junction pressure drop occurred at the lowest liquid flow rate of 0.05 m s,1 for the tee (180° bifurcation) that was due both to the smooth transition of liquid through the junction and the damping of surface waves in stratified-type flow. A flow regime map was presented for the tee junction. The inlet flow showed agreement with the map but the flow regimes found in the outlet arms of the junction tended to form earlier than expected being triggered by the pressure disturbances in the passage through the bifurcation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

A Study of Gypsum Scale Formation using Quartz Crystal Microbalance

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2006
T. A. Hoang
The quartz crystal microbalance (QCM) has been used extensively as a mass sensor due to its extremely high sensitivity to small mass loadings. Conventional measurement of the amount of scale deposited on a surface is restricted by the sensitivity limit of analytical balances. Thefirst attempt to investigate the deposition of gypsum scale on a surface using a rotating electrochemical QCMsystem was carried out to investigate the eflects of many factors at the early stages of scale formation. Results indicated there was almost no induction time for this system, and the long induction time observed in the conventional system was due to the limited sensitivity of the analytical balance. A slow increase in scale amount was observed at the beginning of the scaling process as shown by the plot offrequency or mass change against time. After this period the curve rises steeply and becomes almost linear. The supersaturation level of the solutions and the rotating speed have significant effects on the gypsum scaling. A QCM flow-cell system has also been developed to investigate the scaling of gypsum on the pipe wall. This system is similar to a conventional pipe flow system except that its size is much smaller and the deposition of scales can be monitored with the QCM electrode throughout the scaling process. The mass change is plotted against time and results are compared for the rotating QCM system and the conventional system. It is noticed that the formation of gypsum on the QCM electrode is greatly dependent on both the supersaturation of the solution and the flow rate of the fluid passing through the flow cell. [source]