Experimental stand for internal pressure testing of pipes

2005

To provide a data base for the confirmation of computational and classical residual strength analyses of corroded pipelines subjected to combined loads, full scale experiments of 48-inch diameter pipe sections with artificial corrosion were conducted. Design of the experiments was guided by the prerequisite of testing pipe sections in full scale such that subsequent corrections for the uniform depth and extent of the degraded region, and DA ratios were not required. The testing and analysis procedures were progres sively developed through three distinct phases of the program: 1) one proof of concept experiment performed on smaller diameter pipe with artificial corrosion subjected to internal pressure and axial bending, 2) five 48-inch diameter pipe tests, each with artificial corrosion, subjected to internal pressure and axial bending, and 3) eight 48-inch diameter pipe tests, each with artificial corrosion subjected to pressure, axial bending, and axial compression. Combined loading on the test specimens followed a predetermined path until failure by either rupture or global buckling occurred, while the elastic-plastic load-deflection and large strain behavior was recorded. The uniform depth, axial length, and circumferential length of the degraded region were selected to represent commonly observed general corrosion dimensions found among in-service pipelines, with the maximum and minimum extents reflecting the typical wall loss characteristics at the girth and seam weld locations. The pipe behavior during the experiments and analyses was ultimately modeled and verified by an elastic-shell model capable of defining failure pressure and curvature for a corroded pipe subjected to combined service loads. This paper presents details on the test procedures, specimen preparation and design, and complex data acquisition techniques utilized in the generation of required global and location response information. In addition, significant experimental results from the program which enabled the development and validation of a new procedure for the assessment of corroded pipes under combined loads are reviewed. IN T R O D U C T IO N When corrosion damage in the form of wall loss (referred to in this program as a corrosion patch in the context of a cabbage patch) is discovered by a pigging or excavation operation, a replace/repair/ignore decision must be made. This decision hinges crucially on a prediction of the failure pressure of the corroded pipe. Above all else, because environmental safety is paramount, the failure pressure that is predicted for the observed damage must be reliable and readily obtainable. But at the same time, unneces sary field maintenance operations should not be performed-not only to avoid unnecessary expenses and curtailment of service, but also to prevent the possibility of additional damage that sometimes occurs in field operations. Thus, the prediction must be accurate without being grossly conservative, and should not require a time consuming analysis procedure. The current and potential new ASME B31G guidelines satisfy these requirements for most existing pipelines. However, because the present guidelines are drawn from methods that are both empirically based and have a somewhat limited range of applicabil ity, there are pipeline service conditions for which they may not be entirely appropriate. These include damage regions having a large circumferential dimension, multiple nearby interacting discrete damage zones, damage zones at or near weldments, and combined loading conditions. This study was aimed at providing a theoretically-sound technology for a 48-inch pipeline, that will ultimately be adapted to pipelines in general, by conducting integrated research including (1) full-scale pipe burst experimentation, (2) finite element analyses (FEA), and (3) an engineering model for field use embodied in a PC program. Tests and analyses were conducted to delineate the effects of corrosion patch dimensions on the failure mode. Preliminary work [1] (Phase 1 of the study) consisted of a proof of concept test on a 20-inch (51 cm) diameter, X52 steel pipe with simulated corrosion metal loss under a combination of internal pressure and axial bending. Phase 2 of the study consisted of tests and analyses of full scale 48-inch (1.22 m) diameter X65 steel pipes

Polymer Engineering & Science, 2000

The effects of residual stress in modified poly(viny1 chloride) pipes upon the relationship between pressure tests and C-ring tests have been studied. A series of pressure tests were carried out at different hoop stresses using both fixed-end and free-end enclosures. The C-ring test was used to determine the yield strength of the material as a function of time. The difference in behavior between the fixed end and free end configurations was less than predicted by the von Mises analysis assuming the only stresses in the pipe wall were generated by the applied internal pressure. Both configurations produced lower results than predicted on the basis of the C-ring tests. The residual stresses in the hoop and longitudinal directions were measured. Taking into account the residual and applied stresses, the von Mises criterion for yield was used to calculate the uniaxial yield stress of the material for both end enclosure configurations. The results were similar to the yield stress measured in uniaxiall tension. The von Mises criterion for yield has been shown to provide an acceptable method of analysis of pressure tests with fixed and free end enclosures and the C-ring, when residual stress is taken into account.

This paper described the results of a nonlinear static mode within ANSYS of elastic and elastic-plastic behaviour of thin petroleum pipe that is subjected to an internal pressure and therefore a linear stress analysis performed using ANSYS 9.0 finite element software Such an analysis is important because the shape of most structures under internal pressure is cylindrical[1]. In this paper is considered only. Elastic and elastic-plastic finite element analysis is used to predict the principle stresses, effective stress results are compared with those obtained from theatrical equations in order to predict the limit and failure loads for this type of loading also the relationships between redial, hoop stresses and displacement has been used to develop a through understanding. The analysis was completed using ANAYS Version 9.0. (a finite element program for Microsoft Windows NT). The program allows pre-processing, analysis and post-processing stages to be completed within a single application. The program can be used to model a large number of situations including buckling, plastic deformation, forming and stress analysis problems. In this study ,a thin pipe of internal radiu

2009

Two layer metal plastic structures with range shape cross-section are frequently used [1 3]. The external plastic rust preventive cowers are applied in metal pressure vessels and pipelines. Plastic tubes with the reinforcing external metal layer are widely used [4]. Stresses distribution in multilayer structures subjected to internal pressure has been successfully determined by FEM [2]. However, it is difficult to use when it is necessary to determine how design parameters affect the stress values and strength of the structure. Mechanically inhomogeneous two-layer pipe may be divided into two pipes with different mechanical properties: internal pipe 1 with modulus of elasticity E1 , Poisson’s ratio v1 , limit of elasticity σe1 , power index of material hardening in elastic plastic zone m01 and external pipe 2 with E2 , v2 , σe2 and m02 (Fig. 1). Due to acting internal pressure p radial stretch and contact pressure pc on the surface materials H (hard) and M (mild) appears. When E1 &g...

Piping stress analysis is a discipline which is highly interrelated with piping layout (Chap. B3) and support design (Chap. B5). The layout of the piping system should be performed with the requirements of piping stress and pipe supports in mind (i.e., sufficient flexibility for thermal expansion; proper pipe routing so that simple and economical pipe supports can be constructed; and piping materials and section properties commensurate with the intended service, temperatures, pressures, and anticipated loadings). If necessary, layout solutions should be iterated until a satisfactory balance between stresses and layout efficiency is achieved. Once the piping layout is finalized, the piping support system must be determined. Possible support locations and types must be iterated until all stress requirements are satisfied and other piping allowables (e.g., nozzle loads, valve accelerations, and piping movements) are met. The piping supports are then designed (Chap. B5) based on the selected locations and types and the applied loads. This chapter discusses several aspects of piping stress analysis. The discussion is heavily weighted to the stress analysis of piping systems in nuclear power plants, since this type of piping has the most stringent requirements. However, the discussion is also applicable to the piping systems in ships, aircraft, commercial buildings, equipment packages, refrigeration systems, fire protection piping, petroleum

International Journal of Automotive and Mechanical Engineering, 2022

Pipelines are structures used primarily for the pressurized transport of flammable substances, which have higher safety requirements due to the risk of leakage or explosion [1]. New pipelines are needed to meet the growing demand for energy, such as gas and oil, among industrial users. Indeed, over the last 50 years, the latter has emerged as the most costeffective and safest mode of long-distance transportation for large amounts of energy [2]. The length of pipelines in Europe was multiplied by four between 1970 and 2007. For the same time period, however, the failure rate was divided by six [2]. To improve the profitability of this mode of supply, manufacturers have increased both the operating pressure and the pipe diameter. Between 1910 and 2000, the largest pipeline's diameter increased fourfold, while transport pressure increased sixtyfold [3]. All of this was made possible by research that improved the mechanical properties of pipelines as well as tools that allow the severity of defects in these pipes to be assessed. Undoubtedly, as with every metal structure, flaws in the pipeline may develop over time and cause it to rupture. Pipe defects can occur during installation, routine maintenance excavations, or new civil engineering work near the pipes [4]. For example, during pipe maintenance operations, mechanical damage may occur as a result of negligence, clumsiness or a lack of precautions. If site workers are unable to precisely locate the buried pipe, this structure may be subjected to shock by a tool like bucket teeth or construction machine. Most of the time, the incident goes unnoticed or unreported. Mechanical interference caused by foreign object contact accounts for approximately 50% of pipeline damage in Europe and 53.5% in the US [5]. This confirms that external damage causes the vast majority of pipeline ruptures, whether on land or at sea. These flaws can take the form of dents, cracks, or a combination of the two [6]. The structural damage induced by the presence of these deficiencies can be exacerbated if the pipeline is subjected to internal pressure of variable amplitude loading, such as water hammer waves [7]. In fact, transient flows in the pipeline network can be created by pump failure, pipe rupture, or a sudden change in the state of the valve that controls the flow of fluid through the pipeline. This can cause a pressure pulse to travel at high speeds along the pipeline in the form of a pressure wave, causing vibrations that can eventually burst the pipe [8]. The industrialists who specializes in the area of piping networks are concerned about the safety of the population as well as the environment, given the impact that a major failure can have, especially in the case of flammable gases or explosives [9]. Besides that, economic and financial aspects must be considered, as financial losses in terms of public works, pipe replacement, and operating losses are substantial. Thus, breakage prevention is critical, and it is achieved through inspection and analysis of the harmfulness of discovered defects [10, 11]. This analysis necessitates the use of specialized tools in order to assess the potential damage caused by a defect in an internally pressurized pipe. There are several methods in the literature for determining the severity of a crack, dent, notch, or corrosion defect in a pipeline [9-14]. They are frequently developed using limit analysis, fracture mechanics, and notch fracture mechanics. Depending on the type of defect, the appropriate tool is selected. The limit analysis is frequently used to assess defects such as corrosion or dents [9]. In the case of defects such as weld cracks, sharp notches, or a combination of a dent and a notch, a mechanical fracture approach is preferable. ABSTRACT-Pipelines are commonly used to transport energy over long distances. If this structure is subjected to an internal pressure of variable amplitude loading, such as water hammer waves, the structural damage caused by the presence of a defect can be exacerbated. Previous research by the authors resulted in the development of finite element models to evaluate crack and dent defects separately. Each model was used to compare and classify defects in their respective categories based on their nocivity in a metal pipe subjected to internal pressure. The primary objective of this paper is to compare the severity of various defect categories on the same scale. A numerical damage assessment model that considers the interaction effect, as well as the loading history, is used to achieve this goal. It takes the output of the two finite element models, as well as the pressure spectrum caused by the water hammer, as inputs. This model is used to analyze the effect of key parameters that influence the severity of the defects, as well as to compare and classify the various types of dent defects with the various types of crack defects found in pipes subjected to variable amplitude loading.

2003

In previous publications CINI presented finite element models that simulated the collapse and post-collapse behavior of steel pipes under external pressure and bending. Those finite element models were used to analyze the effect of different imperfections on the collapse pressure and collapse propagation pressure of steel pipes. Laboratory tests were performed on TENARIS seamless steel pipes at CFER (Edmonton, Canada) in order to obtain experimental results that could be used to enhance the reliability of the numerical models. In this paper we compare the numerical and experimental results for the case of external pressure without bending.

2021

Circular thin-walled pipe bends are frequently used as a key part in pipeline connection either in the vertical direction or the horizontal direction due to their high flexibility. The high flexibility of pipe bends is due to the ability of their cross-section to ovalize when subjected to internal pressure and/ or bending moments that lead to high-stress concentrations at bend locations within the pipeline system. Moreover, the surface geometric characteristics of bends may cause some unbalanced outward forces caused by the induced internal pressure loading only which leads to an outward resultant force that tends to straighten out the bend causing a rise within the deformations and stress levels. This phenomenon was known as "The Bourdon effect". In addition to that, external bending moment load acting on the pipe bends may result from either occasional loadings such as; seismic loads, soil settlement, and/ or secondary loadings exerted on the pipe due to thermal expansions resulted in additional stresses. These additional stresses resulting from bending loads acting on the pipe bend are accounted for in the design codes using stress intensification factors (i) and flexibility factors (K). These factors are presented in the current American code ASME B31.3.Although they have been derived for a 90-degree pipe bend subjected to in-plane closing bending moment with long bend radius(R), they cannot be used for other loading cases such as in-plane opening moment or out-of-plane bending moment. Previous studies showed that the direction of bending moment affected the distribution and magnitude of stress levels found on the bend. However, previous studies considered only small pipe sizes of NPS 16 (406mm) and smaller under bend angles of 90 degrees or less. This paper extended the investigation on smooth pipe bends with initial circular cross-sections and uniform wall thickness with large pipe size from NPS20 (508mm) up to NPS 72 (1829mm) under a wide range of bend angles (Ø)(from 30° up to 160°). The loading considered in this study is the internal pressure and the in-plane opening/closing bending moment. In this respect, an extensive parametric study is conducted using a numerical finite element analysis (FEA) simulation using ABAQUS software to model Pipe bends with different nominal pipe sizes (NPS), bend angles (Ø), bend wall thickness (t), and various bend radius (R). The results showed that as the bend angle increases, the flexibility of the bend increases as well leading to higher stresses on the pipe bend. Finally, from the finite element analysis results depicted through curves, it could be concluded that the codes do not cover the stress distribution for large pipe bends accurately.

Volume 1: Project Management; Design and Construction; Environmental Issues; GIS/Database Development; Innovative Projects and Emerging Issues; Operations and Maintenance; Pipelining in Northern Environments; Standards and Regulations, 2006

A nonlinear finite element model was developed to assess stress concentration factors induced by plain dents on steel pipelines subjected to cyclic internal pressure. The numerical model comprised small strain plasticity and large rotations. Six small-scale experimental tests were carried out to determine the strain behavior of steel pipe models during denting simulation followed by the application of cyclic internal pressure. The finite element model developed was validated through a correlation between numerical and experimental results. A parametric study was accomplished, with the aid of the numerical model, to evaluate stress concentration factors as function of the pipe and dent geometries. Finally, an analytical formulation to estimate stress concentration factors of dented pipelines under internal pressure was proposed. These stress concentration factors can be used in a high cycle fatigue evaluation through S-N curves.

Pipeline Engineering [Working Title]

Pipelines are one of the most practical and economically efficient ways to transport dangerous and/or flammable substances, for which road or rail transport is often impossible. The evaluation of the processes that can negatively influence the performance of the pipelines is particularly important for assessing the risk associated with the operation of these technical systems and the potential for technical accidents. The anomalies that can be found on the pipes can be classified into two main categories. Imperfections that do not inadmissibly affect their load-bearing capacity and defects with significant negative influences on the correct operation and load-bearing capacity of the piping, which require supervision and maintenance measures. The influence of these anomalies and the processes that lead to the decrease of the pipeline-bearing capacity constitutes the main objectives of the analysis performed. The local elastic-plastic deformation anomalies are considered, for which th...