Numerical study of a cracked pipeline under internal pressure

INTRODUCTION This thesis aimed to investigate the prevention and compensation of transboundary damage resulting from the construction and operation of oil and gas pipelines. Five research questions were identified in Chapter 1: What are the potential harms associated with cross-border oil and gas pipelines? What is the international legal regime applicable to cross-border pipelines? What are measures used to prevent and reduce damage which may be caused by cross-border pipelines? Is the current international legal regime applicable to cross-border and cross-country pipelines designed in such a way that it enables an effective prevention of trans-boundary damage? Under which conditions can states be held responsible for transboundary damage caused by pipelines? In this Chapter, the key findings of this study are presented along the research questions reflecting the purpose of this thesis. In order to answer the research questions, this thesis employed different research methodologies. A comprehensive literature review and a systematic elaboration of the international legal regime governing cross-border pipelines have been carried out to answer research questions. Furthermore, economic analysis of law has been used to evaluate the design of environmental and safety regulations applicable to such pipelines. CONCLUDING REMARKS RISKS ASSOCIATED WITH PIPELINES The first research question of the thesis concerns the risk associated with the construction and operation of oil and gas pipelines, in particular the possibility of occurrence of trans-boundary damage. In the thesis, an overview of data regarding the number of gas and oil pipeline accidents was provided. By considering the published data, it can be argued that, pipelines have not led to many accidents. Of course, the current number is still considerable. Furthermore, although the number of accidents is high enough to call pipelines hazardous activities, they have not frequently led to transboundary damage. However, as accident reports indicate, pipelines have the potential to cause personal injuries, environmental damage and economic losses in the trans-boundary context. A brief overview of the contribution of various causes of failure has been conducted in the thesis. It was revealed that external impacts and technical defects are the main failure causes in both oil and gas pipelines, although they slightly differ.

Use of coal mine is based on centuries, but the expansion of its usage area has been after the Industrial Revolution in parallel with other mines. With the effect of this revolution; The use of minerals such as coal, iron, copper and tin has increased. Among these mines, coal mine; It has a very important place because it can be used for industrialization, powering machines, generating electricity and heating. In order to provide the increasing need in these areas every year, coal enterprises were established in countries with rich coal deposits and served the energy sector. The share of coal in the energy resources consumed in the world has increased in a short time and has become a determining factor on the world economy. This situation has led to an increase in the number of coal mine enterprises, with developed countries turning to the mining sector for industrialization and economic progress. Accidents in coal mines have increased as the number of mines has grown. Despite the fact that numerous studies have been conducted to prevent these accidents, accidents still occur. Coal mining is regarded as a hazardous work environment due to the high frequency of accidents and their consequences. To minimize these risks and ensure a healthy working environment, the required infrastructure should be established, audit-oriented studies should be conducted, and flaws should be remedied based on the findings. Within the scope of the study, the way and types of coal mine accidents, which are common in Turkey, were investigated, as well as a literature analysis of the reasons of these accidents. The number of accidents and casualties between 2015-2020 were examined and a future situation analysis was made. Regression Analysis Method, one of the statistical analysis methods, was used in the situation analysis phase. The number of coal mine accidents and fatalities in countries around the world since 1902, has been studied. By using the same Analysis Method, the future situation analysis for the next 10 years was made in the light of the data between 1902-2020, and data on the number of accidents and casualties that may occur in the coal mining area were obtained.

Effects of Particle Speed on Erosive Wear Behaviour of API X120 Pipeline Steel

Some solutions have been suggested to avoid failure of casing particularly opposite massive salt bodies.The most effective of these solutions has been the use of multiple cemented casing strings. It has been found that dual cemented-casing strings have a collapse resistance superior to the sum of the collapse resistances of the casing strings composing this system. But, these results do not include the effect of the internal pressure. This paper discusses the influence of a high internal pressure (alone, or combined with external pressure) and the cement properties on the collapse resistance of cemented concentric strings. The resistance of the system depends on the quality of the cement. A low quality cement will continue to creep after setting and will not contribute much to the system under combined pressure loads. The application of an internal pressure that corresponds to normal pressure gradients reduces the tangential stress and increases the collapse resistance of the system by 25% over the same system without internal pressure.

Societies and Academies

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%.

In order to research the new integrity evaluation technology of gas pipeline and promote the mature development of gas pipeline integrity management, this paper deeply analyzes the characteristics of Beijing gas pipeline and combines with the methods of finite element modeling, statistical analysis, mathematical fitting and experimental verification. Based on the Spangler-lowa method, the load effects of gas pipelines with different pressure grades are analyzed, a new method for evaluating the external load carrying capacity of gas pipeline with local corrosion defects was developed, and a method for evaluating the internal pressure carrying capacity of gas pipeline was determined. The research shows that the integrity structure evaluation of gas pipeline should be evaluated according to the pressure level. Medium- and low-pressure gas pipeline is mainly affected by external load, and deformation is the evaluation basis. The sub-high-pressure gas pipeline is affected by both external load and internal pressure, and its deformation and stress are taken as the evaluation basis respectively. High-pressure gas pipeline is mainly affected by internal pressure, and stress is the evaluation basis.

Background Analysis of failure and destruction of pipelines, oil and gas equipment and hydrocarbon storage tanks after long-term operation shows that the main cause of basic elements mechanical failure is the loss of carrying capacity expressed in embrittlement of the metal under the various factors, including low temperatures. In recent years a number of regulations on structural analysis of oil and gas pipelines specify an assessment of the critical stress intensity factors K c and their average value  oð. However, at present there are no avowed or adequate methods of quantitative assessment of oil and gas equipment and pipelines safety based on time criteria and fracture processes reflecting changes in thermal strain state and depressurization of the basic bearing elements, in particular pressurized environmentally hazardous corrosive operating media at subzero temperatures. Aims and Objectives To investigate the correlation of low-cycle fatigue life and service life of the basic elements of oil and gas equipment and pipelines under the action of pulse change of internal pressure causing low-cycle fatigue. Results There are provided the assessment of the quantitative correlation characteristics of basic elements low-cycle fatigue life for various equipment and pipelines and static stretching of standard specimens for uniaxial tensile in air and in hydrogen sulfide environments as well as at low temperatures. It was proved that the degree of low-cycle fatigue life is not constant, but varies depending on the work-hardening coefficient of the steel from one to two. There are obtained the formulas for calculation of various shell – type elements durability for equipment and pipelines under low-cycle loading applying the fracture toughness criteria for different operating environments.

The mechanical resistance of API 5L X52 steel with stepping lamination in the base metal (BM), heat affected zone (HAZ) and welding bead (WB) was studied by using the finite element method (FEM) in the present work. Both internal working pressure in the pipelines and internal pressure in the stepping laminations were studied to analyze the mechanical behavior of the pipelines. 3D FEM models and kinematic hardening were activated in the software used, while tests for the mechanical properties (true stress–strain curve) of BM, HAZ and WB were also conducted. The results demonstrated that stepping laminations in the BM–HAZ–WB zone reduced the ability to support internal pressure; therefore, the failure pressure (Pf) is also reduced. Pipeline failures occurred when the Von Mises stresses reached or exceeded the ultimate tensile stress (σUTS) of the material in the outer and inner wall and the stepping lamination sizes were too large. Failure in pipelines with stepping laminations occurred on the left side of the crack on the outer wall of the BM–HAZ zone; on the inner right side of the stepping laminations, the failure takes place on the inner wall in the WB.

Assessment of the interaction of corrosion defects on steel pipelines under combined internal pressure and longitudinal compression using finite element analysis

A limiting factor of high pressure die cast (HPDC) Mg alloys is the presence of porosity, which has a detrimental effect on the mechanical strength and gives rise to a large variability in the ductility. The application of hydrostatic pressure after casting is known to be beneficial to improve the mechanical response of HPDC Mg alloys. In this study, a combined experimental and simulation approach has been developed in order to investigate the influence of pressurization on the 3D porosity distribution and on the mechanical behavior of an HPDC Mg AZ91 alloy. Examination of about 10,000 pores by X-ray computed microtomography allowed determining the effect of hydrostatic pressure on the bulk porosity volume fraction, as well as the change in volume and geometry of each individual pore. The evolution of the 3D porosity distribution and mechanical behavior of a sub-volume containing 200 pores was also simulated by finite element analysis. Both experiments and simulations consistently revealed a decrease in the bulk porosity fraction and a bimodal distribution of the individual volume changes after the application of the pressure. This observation is associated with pores containing internal pressure as a result of the HPDC process. Furthermore, a decrease in the complexity factor with increasing volume change is observed experimentally and predicted by simulations. The pressure-treated samples have consistently higher plastic flow strengths.

This article focuses on the number of accidents at work in enterprises in the steel industry. Accidents have a significant effect on the operations of enterprises due to the social and economic costs they generate. This article presents the dependence between the number of accidents at work, demographic characteristics (sex, age) and work experience of injured persons, which allows for the identification of risk groups based on to the tested feature. The scope of the analysis covers the structure of accidents at work in the steel industry in the years 2009-2015. The aim of this article is to present the dependence between the number of accidents at work and the demographic characteristics and work experience of workers employed in the industry under examination. The conducted analysis led to the conclusion that there is a relation between the number of accidents at work and the demographic characteristics of persons sustaining an accident at work. In the period between 2009-2015, male workers aged 30-39 were involved in accidents at work the most frequently. The research methodology applied in this article consists of: absolute and generic analysis of work accidents, ratio analysis and statistical analysis of the relation between the number of accidents at work and the demographic characteristics of workers injured in accidents. The applied methodology of analysis of accidents at work may be used for a benchmark analysis of various industry sectors in any country or the same sectors in various countries.

Performance assessment of buried steel pipelines reinforced with carbon fibre-reinforced polymer under reverse fault movement

Feature of stress corrosion cracking of degraded gas pipeline steels

Before being put into operation, gas pipelines are subjected to leakage and strength pressure testing. In the case of plastic gas pipelines, a combined leakage and strength test is performed at a pressure of 1.5 ´ MOP. In Poland, in accordance with the applicable regulations, the plastic material from which gas pipelines can now be built is polyethylene. In other countries gas pipelines are also built of another material, which is PA12 polyamide. Piping systems made of this material are used to transmit gas at a pressure of 1.6 MPa. Both polyethylene and polyamide gas pipelines, after loading them with internal pressure, will undergo deformation with time, which is called the material creep phenomenon. As a result, in pressure leakage tests of gas pipelines made of thermoplastics, such as polyethylene and polyamide, it is necessary to take this phenomenon into account. Due to the different properties of polyethylene and polyamide, the amount of deformation per unit time will be different, and therefore the test procedures that are used for polyethylene gas pipelines cannot be directly used for testing polyamide gas pipelines. An example of such a procedure is the one described in point A.27 of PN-EN 805: 2002. It is mainly used for leakage testing of polyethylene water pipelines and its application for leakage testing of PA12 polyamide gas pipelines with a MOP of 1.6 MPa requires changes in the test conditions. The article presents the concept of modifying the parameters of the hydrostatic method, taking into account the different properties of PA12 pipes compared to polyethylene pipes. Particular attention was paid to the higher value of Young's modulus and the related ring stiffness of PA12 polyamide pipes compared to polyethylene pipes. In order to obtain the appropriate deformation of the pipe resulting from the material creep, the time of holding the sample under pressure was experimentally extended before starting the actual test. After establishing the required test conditions for the sealed system, tests with simulated leaks were carried out. The obtained results of tests on airtight samples and with simulated leakage confirmed the possibility of using the modified method to test the tightness of PA 12 polyamide gas pipelines with a MOP of 1.6 MPa.