Analysis of manufacturing internal pressure induced defects of the pipe wall with modeling of stresses

2021 ◽  
pp. 49-55
Author(s):  
D. V. Zhukov ◽  
A. A. Melnikov ◽  
S. V. Konovalov ◽  
A. V. Afanasyev
Keyword(s):  
Internal Pressure ◽  
Pipe Wall ◽  
Induced Defects

The Influence of Internal Pressure on Pipeline Natural Frequency

2009 ◽  
Author(s):  
Andre´ Luiz Lupinacci Massa ◽  
Nelson Szilard Galgoul ◽  
Nestor Oscar Guevara Junior ◽  
Antonio Carlos Fernandes ◽  
Fa´bio Moreira Coelho ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Natural Frequency ◽  
Axial Force ◽  
Natural Frequencies ◽  
Pipe Wall ◽  
Element Model ◽  
Straight Pipe ◽  
Temperature Expansion ◽  
Force Concept

Galgoul et al. (2004) have written a previous paper in which they have pointed out the conservatism of the latest recommendations for pipeline freespan evaluations, associated to the way the axial force is considered in the determination of the pipeline natural frequency. First because it fails to consider the fact, that the axial force of a sagging pipe, subject to temperature expansion, is much smaller than that of a straight pipe. Second because the effective axial force caused by internal pressure should not be used to determine the pipeline natural frequency. Fyrileiv and Collberg (2005) also discussed this aspect. In order to back up their previous arguments the authors decided to perform some tests an axially restrained pipeline at both ends, which was pressurized in order to justify their claims that these pipelines are not only under tension (and not compression), but also that their natural frequencies increase instead of reducing, although they do bend out because of the pressure, reaching a point of instability. The authors understand the effective axial force concept and the enormous simplifications, which it brings to an otherwise cumbersome problem, but wish to emphasize that these advantages are not unlimited and that this is one of these restrictions. To back up the text results a finite element model has been produced, in which the internal pressure is taken into account as it actually is (and not as an axial force) to show that the pipe wall stresses can only be obtained correctly in this manner.

Using MFL Corrosion Signals to Determine Biaxial Stress in Operating Pipelines

2000 ◽  
Author(s):  
Alfred E. Crouch
Keyword(s):  
Magnetic Flux ◽  
Internal Pressure ◽  
Pipe Wall ◽  
Axial Stress ◽  
Wall Stress ◽  
Biaxial Stress ◽  
Metal Loss ◽  
Pipe Surface ◽  
The Difference ◽  
Hoop Stresses

Previous work has shown that a corrosion assessment more accurate than B31.G or RSTRENG can be made if pipeline stresses are considered. A shell analysis can be carried out if both the corrosion profile and local pipe wall stresses are known. The corrosion profile can be approximated from analysis of magnetic flux leakage (MFL) signals acquired by an inline inspection tool (smart pig), but a measure of pipe wall stress has not been available. Approximations have been made based on pipe curvature, but a more direct measurement is desirable. Recent work has produced data that show a correlation between multi-level MFL signals from metal-loss defects and the stress in the pipe wall at the defect location. This paper presents the results of MFL scans of simulated corrosion defects in pipe specimens subjected to simultaneous internal pressure and four-point bending. MFL data were acquired at two different magnetic excitations using an internal scanner. The scanner’s sensor array measured axial, radial and circumferential magnetic flux components on the inner pipe surface adjacent to the defect. Comparison of the signals at high and low magnetization yields an estimate of the difference between axial and hoop stresses. If internal pressure is known, the hoop component can be determined, leaving data proportional to axial stress.

Pipeline Dent Fatigue Crack Leak Rate for Liquids Pipelines and the Application to Release Consequence Assessment

2018 ◽  
Author(s):  
Sanjay Tiku ◽  
Mark Piazza ◽  
Vlado Semiga ◽  
Binoy John ◽  
Aaron Dinovitzer
Keyword(s):  
Fatigue Crack ◽  
Internal Pressure ◽  
Failure Modes ◽  
Pipe Wall ◽  
Fatigue Cracks ◽  
Mouth Opening ◽  
Leakage Rate ◽  
Pipeline System ◽  
Crack Mouth ◽  
Internal Pressures

Pipeline design and integrity management programs are employed to ensure reliable and efficient transportation of energy products and prevent pipeline failures. One of the failure modes that has received attention recently is pipeline fatigue due to pressure cycling in liquid pipelines, promoting through wall cracking and the release of product. Being able to estimate the leakage rate and/ total release volume are important in evaluating the consequence of developing a through wall crack, operational responses when incidents occur, and remedial action strategies and timelines. Estimates of leak rates can be used in pipeline system threat and risk assessment, evaluation of leak detection system sensitivity, development of Emergency Response Plans and strategies, and post-event evaluation. Fracture mechanics techniques consider the response of crack-like features to applied loading such as internal pressure, including estimation of crack mouth opening. Considering the differential pressure across the pipe wall and the crack opening area, estimated from the crack mouth opening, the flow of fluid through the crack can be conservatively estimated. To understand the conservatism of this analytical estimate of leakage rate, full-scale testing has been completed to evaluate the leakage rate through dent fatigue cracks of differing lengths under a range of internal pressures, and compare the empirical measured results to the analytical/theoretical estimates. The test procedure employed cyclic internal pressure loading on an end-capped pipe with a dent to grow fatigue cracks through the pipe wall thickness. Once a through wall crack was established, the internal pressure was held constant and the leakage rate was measured. After measuring the leakage rate, cyclic loading was employed to grow the crack further and repeat the leakage rate measurement with the increased crack length. The results of this experimental trial illustrate that the tight fatigue crack resulted in a discontinuous relationship between leakage rate and pipe internal pressure. Measureable leakage did not occur at low pipe internal pressures and then increased in a nonlinear trend with pressure. These results illustrate that a liquid pipeline with a through wall fatigue crack operating at a low internal pressure, or one having taken a pressure reduction, can have low leakage rates. The data and results presented in this paper provide a basis for an improved understanding and describing the leakage rate estimates at pipeline fatigue cracks, and providing insights into leakage rates and how to conservatively estimate them for fatigue crack consequence evaluation.

Effects of Bending Moment and Torsion on the Internal Pressure Limit Load of Locally Thinned Pipes

2011 ◽  
Author(s):  
Phuong H. Hoang ◽  
Kunio Hasegawa ◽  
Bostjan Bezensek ◽  
Yinsheng Li
Keyword(s):  
Internal Pressure ◽  
Pipe Wall ◽  
Large Strain ◽  
Bending Moment ◽  
Limit Load ◽  
Evaluation Procedure ◽  
Structural Factors ◽  
Stress Evaluation ◽  
Pressure Limit ◽  
Wall Thinning

The pipe wall thinning stress evaluation procedures in Code-Case N-597-2 [1] of the ASME Boiler and Pressure Vessel (B&PV) Code are essentially based on Construction Code [2] stress evaluation. Stresses in the hoop and the axial directions are evaluated separately to meet the Construction Code allowable stress. Using Construction Code rules for local pipe wall thinning stress evaluation in Class 2 & 3 piping may be too restrictive. An alternative approach is to use the limit loads of locally wall thinned pipe in conjunction with an appropriate Z-Factor and the structural factors of the ASME B&PV Section XI, Appendix C [3]. Such approach may require a combined effect of pressure, bending, axial load and torsion loads on locally thinned pipe. In this paper, the effects of bending moment and torsion on the internal pressure limit load of locally thinned straight pipes are investigated. Large strain finite element limit load analysis with elastic - perfectly plastic materials are performed for a parametric matrix of piping models with various pipe R/t ratios, flaw depths, axial and transverse flaw extents. Based on the results, the allowable pressure for axial flaws in C-5420 of the ASME B&PV Section XI, Appendix C [3] may be used for piping local wall thinning as an alternative evaluation procedure to the current minimum pipe wall thickness evaluation procedure in the Code Case N-597-2 [1].

Crack Opening Displacement Model for Through-Wall Axial Cracks in Cylinders

2013 ◽  
Author(s):  
Michael L. Benson ◽  
Bruce A. Young ◽  
Do-Jun Shim ◽  
Frederick W. Brust
Keyword(s):  
Internal Pressure ◽  
Crack Opening Displacement ◽  
Wall Thickness ◽  
Pipe Wall ◽  
Crack Opening ◽  
Pressure Loading ◽  
Opening Displacement ◽  
Piping Systems ◽  
Displacement Model ◽  
Leak Before Break

For piping systems, leak-before-break calculations rely on estimates of leak rates when postulated cracks grow through the pipe wall. The leak rate, in turn, depends on the crack opening dimensions. Previous work on crack opening displacement (COD) includes recent advances in COD estimates for circumferentially-oriented cracks in cylinders under tension, bending, and internal pressure loading conditions. This paper summarizes previous work in this area and reports on new solutions for COD in the case of axially-oriented cracks under internal pressure. The results reported here include COD solutions at three locations through the wall thickness for axial cracks.

Influence of Girth Weld Flaw and Pipe Parameters on the Critical Longitudinal Strain of Steel Pipes

2012 ◽  
Author(s):  
Celal Cakiroglu ◽  
Kajsa Duke ◽  
Marwan El-Rich ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Wall Thickness ◽  
Tensile Strain ◽  
Critical Strain ◽  
Pipe Wall ◽  
Pipe Wall Thickness ◽  
Strain Capacity ◽  
Steel Pipes ◽  
Tensile Strain Capacity ◽  
Maximum Minimum

The design of steel pipelines against longitudinal loading induced by soil movement and temperature requires an understanding of the strain demand induced by the environment in comparison with the strain resistance of the pipes. Girth weld flaws have been identified as the potential location of failure under longitudinal tensile strains due to being the least ductile. Strain based design for the prediction of the longitudinal tensile strain capacity of steel pipes have been extensively studied by Wang, et al and included in the Canadian standards association code of practice CSA Z662.11 [1]. The extensive track record of tests have culminated into two sets of equations for the critical strain in girth welded pipes with surface breaking and buried defects as functions of the different pipe and flaw parameters. The CSA Z662.11 strain capacity equations were developed using wide plate tests with the obvious limitation of the inability to consider the effect of the internal pressure of the pipe. However, recent studies by Wang et al led to the development of a new set of equations that predict the tensile strain capacity for pipes with an internal pressure factor of 0.72. This paper analyses the two critical strain equations in CSA Z662-11 to understand the effect of different girth weld flaw and pipe parameters on the expected behavior of pipes. Also the critical strain equations developed in [2]have been analysed and compared to the equations in CSA Z662-11. Using the equations in CSA Z662-11, a 34 and 36 full factorial experimental design was conducted for the planar surface-breaking defect and the planar buried defect respectively. For the case of surface breaking defects the dependence of the tensile strain capacity (εtcrit) on apparent CTOD toughness (δ), ratio of defect height to pipe wall thickness (η), ratio of yield strength to tensile strength (λ) and the ratio of defect length to pipe wall thickness (ξ) has been studied. εtcrit has been evaluated at the maximum, minimum and intermediate values of each parameter according to the allowable ranges given in the code which resulted in the evaluation of εtcrit for 81 different combinations of the parameters. The average value of εtcrit at the maximum, minimum and middle value of each parameter has been calculated. The visualization of the results showed that η, δ and ξ have the most significant effect on εtcrit among the four parameters for the case of surface breaking defect. Similarly for buried defects the dependence of εtcrit on δ, η, λ, ξ, and the pipe wall thickness (t) has been studied. The evaluation of εtcrit for all possible combinations of the maximum, intermediate and minimum values of the 6 parameters resulted in εtcrit values for 729 different combinations. The variation of the average εtcrit over the maximum, intermediate and minimum values of the parameters showed that δ, ψ, ξ and η are the parameters having the greatest effect on εtcrit for the case of a buried defect. Further investigations could be carried out to determine suitable upper and lower bounds for the parameters for which no bounded range is defined in the CSA Z662-11 code.

Modeling of Pipeline Repair Sleeves

2002 ◽  
Author(s):  
Robert Lazor ◽  
L. Blair Carroll ◽  
Michael E. Bloom ◽  
Robert F. Booth
Keyword(s):  
Fatigue Crack ◽  
Internal Pressure ◽  
Pipe Wall ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Stress Fields ◽  
Element Analysis ◽  
Weld Toe ◽  
Line Pressure ◽  
Local Stiffness

Full encirclement repair sleeves with fillet-welded ends are used as a permanent repair on pipelines to reinforce areas with defects such as cracks or corrosion which may penetrate the pipe wall subsequent to the installation of the repair. CSA standards require that these sleeves be tapped to relieve the stress field surrounding the defect unless an engineering assessment indicates that the defect will not extend beyond the ends of the sleeve during future operation of the pipeline. This paper describes an engineering assessment recently completed to establish the relative performance of a sleeved pipe with and without a pressurized annulus. Finite element analysis (FEA) was used to relate changes in stresses in the weld region to internal pressure fluctuations. The FEA included an estimate of the effects of circumferential fillet weld shrinkage on local stiffness due to residual stress fields. Relationships between stress and internal pressure were used to convert the line pressure history to local weld stress fluctuations. This stress history was then used to assess the potential for fatigue crack propagation of possible circumferentially-oriented weld flaws using a fatigue crack growth algorithm. The results showed that the highest stresses were developed in the weld toe and root regions. The operating conditions of the line, as well as the pipe and sleeve dimensions, were considered when making recommendations concerning sleeve tapping.

A computational and experimental assessment of the pipeline stress state under bending load and internal pressure

2021 ◽  
pp. 114-126
Author(s):  
A. A. Ignatik
Keyword(s):  
Plastic Deformation ◽  
Stress State ◽  
Internal Pressure ◽  
Central Region ◽  
Pipe Wall ◽  
Combined Loading ◽  
Von Mises Stress ◽  
Bending Load ◽  
Stress Zone ◽  
Von Mises

Main pipelines are subjected to a complex of loads during operation. Monitoring of the stress state of the pipeline wall is necessary for performing strength calculations and evaluating the pipeline reliability.The article is devoted to the method of computational and experimental study of the stress state of a pipe under a bending load and combined action of a bending load and internal pressure.The experiments have been carried out on a laboratory bench. The object of the study is a pipe that has the following characteristics: an outer diameter of 325 mm, a wall thickness of 8.5 mm and steel grade of "14XGS". Electrical resistance strain gages were used to measure the strain of the pipe wall. Formulas for calculating the stress state components of the pipe wall in the elastic-plastic deformation stage are proposed. It is given formulas for calculating the stress state components of the pipe wall in the elastic-plastic deformation stage. Plots of hoop and longitudinal stresses as well as von Mises stress are obtained for the case of bending load on the pipe and the case of combined loading under bending and internal pressure. The areas of maximum values of von Mises stress where the transition to the limiting state is most likely have been determined.When only the bending load is applied, the maximum von Mises stress zone is observed on the lower area of the pipe in its central region. When combined loading under bending and internal pressure, the maximum von Mises stress zone is observed on the lateral area of the pipe in its central region.

Effect of Crack Depth on Burst Strength of X70 Linepipe With Dent-Crack Defect

2016 ◽  
Author(s):  
Hossein Ghaednia ◽  
Sreekanta Das ◽  
Jamshid Zohrehheydariha ◽  
Rick Wang ◽  
Richard Kania
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Wall Thickness ◽  
Parametric Study ◽  
Oil And Gas ◽  
Pipe Wall ◽  
Crack Depth ◽  
Fe Model ◽  
Burst Strength ◽  
Crack Defect

External interferences cause various defects, which significantly affect the transportation of oil and gas in pipelines. Corrosion, crack, puncture, dent, gouge, and combination of such damages from a variety of external interferences are some common examples of surface damage in pipelines. Gouges, dents, cracks, and punctures that form in the pipe wall as a result of contact and/or impact from foreign objects are often referred to as mechanical damage. Structural integrity of oil and gas transmission pipelines is often threatened by these mechanical damages and as a result, a failure of the pipeline may occur. A defect that contains both dent and crack, often known as dent-crack defect, may lead to a rupture or leak in the pipe wall. This kind of defect is a matter of serious concern for the pipeline operator since a rupture or a leak may occur. Hence, an experimental study was completed at the Centre for Engineering Research in Pipelines (CERP), University of Windsor on 30 inch (762 mm) diameter and X70 grade pipes with D/t of 90. This project was undertaken through laboratory based experimental work and numerical study using non-linear finite element analysis (FEA) method. The purpose of full-scale test was to collect test data to be able to validate finite element (FE) model. The validated FE model was then used to undertake parametric study for determining the effect of the crack depth and operating (internal) pressure on the burst strength of NPS30 X70 grade oil and gas pipe. The parameters chosen in the FE based parametric study are: (1) crack depth which was varied from 0.25 to 0.75 of pipe wall thickness and (2) internal pressure applied during denting process (operating pressure of linepipe) was varied from no internal pressure to 0.75py. This study found that the dent-crack defect with crack depth of 75% of wall thickness could reduce the pressure capacity by 54%.

Quantitative defect studies in semiconductor TEM samples prepared by low angle ion milling

1995 ◽  
Vol 53 ◽  
pp. 512-513
Author(s):  
L. Mulestagno ◽  
J.C. Holzer ◽  
P. Fraundorf
Keyword(s):  
Sample Preparation ◽  
Milling Time ◽  
High Density ◽  
Low Density ◽  
Ion Milling ◽  
High Quality ◽  
Variable Angle ◽  
Major Disadvantage ◽  
Induced Defects

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).

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