Mechanical Properties Of Pipes Research Articles

Performance of buried pipeline under reverse fault in permafrost region

Long-distance pipelines may pass through areas of frozen soil sometimes, such as the Trans-Alaska pipeline and the Chinese Northeast pipeline. This work intends to analyze the performance of buried pipeline under reverse fault motion in such regions. A pipe-soil system model was established, and the thermo-mechanical coupling analysis was carried out. The temperature distribution of the soil near the ground and around the pipe is affected by them apparently, especially by ground. For the true temperature field (TTF) and the simplified one (STF), the pipe strain peak value and developing laws differ hugely, because of different soil mechanical properties distribution. The peak strains of the pipe are the largest at +0 °C of the ground, and the local buckling of the pipe appears earlier than the tensile failure. TTF should be obtained, and the peak compressive strain at +0 °C should be taken as the main criterion for seismic design or check calculation, for compressive bearing capacity usually determines pipe mechanical properties.

Effects of Process Parameters on the Microstructure and Mechanical Properties of Large PE Pipe via Polymer Melt Jetting Stacking

The conventional methods for producing large-diameter pipes, such as extrusion and winding fusion welding, suffer from various drawbacks including difficulties in forming, complex molds, and high costs. Moreover, the flexibility and production efficiency of traditional manufacturing processes are relatively low. To address these challenges, this study proposes a new manufacturing process for polymer melt jetting and stacking based on fused deposition modeling (FDM) and rolling forming principles. This innovative approach aims to overcome the limitations of conventional methods and improve the flexibility and production efficiency in large-diameter pipe manufacturing. In the polymer melt jetting and stacking process, a plastic melt with a specific temperature and pressure is extruded by an extruder. The melt is then injected through the nozzle embedded in the previous layer of the pipe blank. By utilizing the localized rolling action of the forming device and adjusting the diameter using a diameter adjustment device, the newly injected plastic melt bonds with the previous layer of the pipe blank. Finally, the continuous large-diameter plastic pipe is formed through cooling and solidification. Experimental investigations demonstrate that the polymer melt jetting and stacking process can produce pipes with diameters ranging from 780 mm to 850 mm and thicknesses of 20 mm to 25 mm. The radial tensile strength, impact strength, and microstructural orientation of the produced pipes exhibit superior performance compared to those in the axial direction. Additionally, process parameters such as rolling speed, cooling temperature, melt extrusion speed, and tractive velocity significantly influence the microstructure and mechanical properties of the pipes.

Stress Shifting Effect of Hydrogen Mixed Natural Gas Pipe Under Seismic Wave

Abstract Hydrogen energy is a kind of clean secondary energy sources. Mixed hydrogen natural gas transportation technology is a new scheme of hydrogen transportation. Using natural gas pipe to transport hydrogen is expected to further promote its application. In order to study the mechanical properties of buried steel pipe under seismic waves, a numerical model is established. The time history and stress distribution of pipe section under seismic wave are analyzed. Effects of seismic intensity, surrounding soil, buried depth and seismic wave type on pipe's mechanical properties are discussed. The results show that the pipe section stress fluctuates under seismic wave, and the stress shifting effect occurs. The maximum stress is located in the directions of 45 deg, 135 deg, 225 deg, and 315 deg. Stress increases with the increasing of seismic intensity, and the stress distribution of pipe section is also changed. Stress responses of the pipe in different soil are different, and the stress distribution of pipe section at the maximum stress time is similar. The deeper the buried depth is, the greater the pipe stress is. Pipe stress is related to the maximum acceleration of the seismic wave and spectrum characteristics. Those results can provide a basis for the design and safety evaluation of mixed hydrogen natural gas pipes.

Selection of heat treatment modes for pipes from alloy TI−3AL−2,5V FOR residual stresses removal at the final stage of production

Purpose of research is to determine heat treatment modes at the final stage of titanium pipes manufacturing to remove residual stresses in accordance with the requirements of ASM standards before delivery of pipes in CWCR condition, after cold pressure treatment and heat treatment to remove residual stresses. Research methods: X-ray diffraction analysis for texture and inverse pole figures construction, evaluation of mechanical properties according to the ASTM standard and residual stresses by the Davydenkov method, as well as production of pipes, according to the developed modes in industrial conditions. Results. The residual stresses level at different heating temperatures of the pipes is evaluated. The mode of final heat treatment to remove residual stresses, which heating temperature in vacuum is 380…450 0C, depending on the previous degree of deformation was selected. Mechanical properties of pipes after rolling and subsequent heat treatment (CWCR state) are evaluated. The texture of the pipes mainly has a radial component and almost does not change during the final heat treatment to remove residual stresses. Practical value is to improve the technological process of titanium pipes production in industrial conditions and the quality of operation. Conclusions. The temperature range for removal of residual stresses, which is 380…450 0С, is set depending on preliminary deformation degree. The selected mode of heat treatment allows ensuring mechanical properties level in according to the requirements of AMS 4946. It is shown that heat treatment does not change the texture of the pipes, retaining more radial component, which provides relative compression ratios.

Effect of annular expansion pipe extruder head on mechanical properties of pipes

AbstractWith polymer pipes being used more commonly, performance requirements are increasing. Studies on the enhancement of mechanical properties of polymer pipes are particularly important. In this study, a self‐designed annular expansion pipe extruder head was used to enhance the mechanical properties of HDPE pipes. Different morphologies of the HDPE pipes were produced under different processing conditions. When the extrusion angle was 30° (P30), the best mechanical properties were obtained. The hoop tensile strength and axial tensile strength were 14.5% and 41.0% higher, respectively, compared with the specimen without expansion (P0). This improvement of mechanical properties can be attributed to several reasons. First, the processing parameters of P30 reached the threshold shear rate and strain for shish‐kebab formation, as shown by scanning electron microscopy. Second, P30 has the highest orientation parameter and crystallinity of 0.679 and 67.27%, respectively, from 2D wide‐angle diffraction (WAXD). Polarized FTIR shows the same trend as 2D‐WAXD. Third, the outer bamboo‐like self‐reinforced structure is formed inside the pipe at 30° expansion angle while the core layer has a well‐formed crystal structure; the special structure improves the overall performance of HDPE pipe. This method can be utilized in large‐scale industrial production.

On the issue of technical diagnostics of polyethylene gas pipelines

The article presents the comparative characteristics of polyethylene pipes after a 50-year period of operation, lists the factors affecting the physical and mechanical properties of pipes and requiring consideration when conducting research. Practical possibilities of assessing the technical condition of long-term operating polyethylene gas pipelines and approaches to extending their service life are considered.

Drill String Torsional Vibrations Modeling With Dynamic Drill Pipe Properties Measurement and Field Validation

Abstract This paper aims to present the drill string torsional dynamics through a lumped parameter modeling using the basic physical notions with continuous measurement of drill pipe mechanical properties (inertia, damping, and stiffness). The model represents the mechanical properties as a variable for each drilled stand. A rock bit interactions model is employed in the system considering the kinetic friction as variable and depends on surface drilling parameters and the well length. Field data, including surface and downhole recorded velocities, are used to validate the model by comparing both velocities and to confirm the existence of drill string vibrations together with the simulation results (bit velocity).

Investigation of Compositional Effects of Virgin and Recycled HDPE on Mechanical Properties of Pipe

Nowadays, High-Density Polyethylene (HDPE) polymers are widely being used and its products are preferable than metals having the properties such as lightweight, ease of manufacture, stronger and tough. This makes HDPE polymers as the top choice by manufacturers. However, one of the drawbacks is that this polymer takes time to decay and affects the environment when this material is disposed as wastes. Almost all industries use only virgin imported materials to produce HDPE pipe and fittings, and this leads to increase in manufacturing cost and extraction of virgin material. The aim of this research is to overcome this problem by recycling process. This research work focuses on investigating the compositional effects of virgin and recycled HDPE on the mechanical properties of HDPE pipe fitting. The mixing of recycled with virgin (pure) HDPE were done at different weight percentages (0:100, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10, and 100:0). In this work, 16.5 kg virgin HDPE were used, and 16.5 kg recycled HDPE pellets were prepared. Also, 11 (eleven) T-reducer pipe fitting samples were produced via injection moulding machine. Melt flow rate and ash content of the manufactured recycled materials were tested to determine the quality of the plastics. Tensile strength test was also conducted to investigate the mechanical property in order to determine the percentage which possess the optimum strength. From the experimental results, recycled contents up to 70 wt. % and virgin contents up to 30 wt. % by mass were found to meet the standard requirements. This optimum proportion will help AG Pipe fitting company to save a lot in dollars every year by using the scrap contents.

The Influence of the Initial Billet on the Mechanical Properties of Pipes

The article researched the influence on the pipes mechanical properties initial billet obtained by the traditional method and the proposed method, in which the piercing process is excluded. The proposed method involves casting the initial billet for the production of seamless pipes with a cavity obtained on a continuous casting machine. The production of hot-rolled seamless pipes from a hollow billet is an urgent issue today, since central porosity and axial segregation after casting are excluded, affecting the quality of the pipes obtained in the subsequent stages of production: rolling on a mandrel mill and reducing. The result is a minimal deviation of the mechanical properties of steel samples obtained by double deformation of a hollow continuously cast billet from samples obtained according to the traditional scheme, including the piercing process.

CHANGE OF MECHANICAL PROPERTIES OF ARCTIC PIPELINES

Background Since the active development of the North has been started recently, there are few experimental data on the operation of pipelines. In this regard, there is a need to assess the current state of pipelines and predict their residual life. Long-term operation of pipelines leads not only to the appearance of defects in the micro-structure, but also to a change in the mechanical properties of the pipe metal. Durability of pipelines should be ensured at all stages of their life cycle. Aims and Objectives Development of recommendations for a quantitative assessment of the mechanical properties of metal pipes of long-running pipelines in the Arctic. Results As a result of the analysis, recommendations are given on the use of pipes for arctic conditions. Based on the existing regulatory documentation, at the stage of designing and manufacturing pipe products, only the level of ductility of the metal in the initial state is set according to the value of impact strength. However, the use of only one indicator as the main characteristic of resistance to brittle fracture of steels in the manufacture of pipes, as practice and numerous studies show, does not guarantee trouble-free operation of pipelines. It is noted that reliable operation of Arctic pipelines is ensured by high fracture toughness and resistance of the pipe metal to crack initiation, slowed down to dangerous dimensions, however, a complete solution to the important problem of trouble-free operation of trunk pipelines requires the development of new principles for the quantitative assessment of mechanical properties (for example, crack resistance) of metal pipes in long-running pipelines in the Arctic.

Analysis on Mechanical Properties of the Buried Pipeline Considering Pipe-soil Interaction

Mechanical deformation of buried pipeline under vertical load is the result of pipe-soil interaction. In order to reveal the necessity of pipe-soil interaction while investigating mechanical properties of buried pipeline, the ANSYS commercial software is employed to construct pipe-soil interface and simulate pipe-soil coupling effect. With the newly developed model, mechanical properties of pipe under vertical static load are analyzed. Numerical solution is subsequently compared with analytical solution. The results reveal that (1) There is maximum Von Mises stress at internal surface of pipe side under overlying load, and minimum Von Mises stress appears in the pipe shoulder at angle of about 45°to x-axis; (2) The pipe-soil interaction has significant effect on analyzing the deformation and distribution of stress of buried pipeline; (3) Vertical displacement obtained from Marston model is larger than that obtained from newly constructed numerical model; (4) The deformation of pipe is obviously constrained by backfilled earth around the pipe. For a buried pipe, especially the elastic pipe, it is necessary to consider pipe-soil interaction while analyzing its mechanical properties.

Model test study on mechanical properties of pipe under the soil freeze-thaw condition

Buried pipe is an important structure underneath embankment. In the frozen soil region, the destruction of pipe will directly affect the service life and benefit of road. Based on the effect of freeze-thaw action of embankment filling on pipes in the field, model tests on shallow buried PVC (Polyvinyl chloride) pipe were carried out in the temperature control laboratory. Variation of stress and strain of pipe, earth pressures around pipe and deformations of pipe were investigated under different filling loads, different layers of geogrid, symmetrical and asymmetrical freeze-thaw of soil around the pipes. The test results show that most of the upper half of the pipe is in compressive strain state, except for the 0° measuring point on the crown vertex of the pipe. And most of the lower half of the pipe is in tensile strain state. The maximum compressive stress and the maximum tensile stress are at points with an angle of 45° and 135° from the vertices of pipe, respectively. When symmetrical frost-heave of the soil occurs in the surrounding pipe, load reduction measures should be taken at the crown of the pipe. When asymmetrical frost-heave of the soil occurs in the surrounding pipe, the differential horizontal deformation of the pipe between its left and right halves is obvious, therefore the earth pressures on the lateral of the pipe should be monitored emphatically. The geogrid installed above the pipe effectively reduces the eccentric load on the pipe. The thaw-settlement of frozen soil has the greatest impact on the deformation of shallow buried pipes, which is more threatening to cause pipe damage. The test results can provide a reference for engineering design, construction and maintenance of shallow buried pipe under the soil freeze-thaw condition.

Effect of structure on operational properties of welded joint made of heat-temperature alloy Fe—25Cr—35Ni

The structure and mechanical properties of pipe welded joint made of heat-resistant austenitic alloy based on the Fe —25Cr—35Ni system are studied by optical and electron microscopy and X-ray spectral microanalysis. Signifi cant structural inhomogeneity in various zones of the welded joint and the formation of intermetallic G-phase in the heat-affected zone and weld metal are revealed. It is shown that the changing in the alloy structure during welding leads to signifi cant decrease in the mechanical properties of the welded joint.

Research on the reasons for premature destruction of boiler pipes when operating in a boiler

Purpose is to establish the reasons for the premature failure of low alloy steel boiler tubes operating in a waste heat boiler in the ammonia synthesis workshop. Methodologies. The work performed: chemical analysis of low-alloy pipe steel on a spectrometer SPECTROMAX company SPECTRO, Germany; visual inspection and study of the surfaces of boiler pipes using a scanning electron microscope REM 106 I; metallographic studies of the structure of steel along the cross section of completely destroyed and non-destroyed pipes; tensile testing of pipe mechanical properties. Results. Based on comprehensive studies, an unsatisfactory initial structure of boiler pipes was established, characterized by pearlitic banding of score 4 and fine grain No. 7−8, as well as a significant change in the structure of steel during operation of pipes in a waste heat boiler in an oxidizing furnace gas environment at elevated temperature and pressure. Based on comprehensive studies, a significant change in the structure and properties of low-alloy pipe steel was established during the operation of boiler pipes in a waste heat boiler in the environment of furnace gases at elevated temperature and pressure. Scientific novelty. It is scientifically substantiated that the cause of the destruction of boiler pipes is the degradation of the structure of low alloy steel, which consists in its decarburization and internal oxidation as a result of physicochemical processes occurring in an oxidizing medium at high temperature and pressure. It is scientifically substantiated that the cause of the destruction of boiler pipes is the degradation of the structure of low alloy steel as a result of physicochemical processes occurring in the environment of furnace gases at high temperature and pressure. Practical relevance. An accident associated with the explosion of a waste heat boiler with unfavorable environmental consequences and possible human casualties was prevented at the chemical industry enterprise. Recommendations are given on improving the operational reliability and durability of boiler pipes without capital expenditures.

Mechanical Properties of Large Diameter Pipe with Increased Deformation Capacity (For Active Tectonic Fracture Zones)

Results are summarized for testing the mechanical properties of pipe of strength class K60 (corresponds approximately to strength category X70) with increased deformation capacity 1420 mm in diameter with wall thickness of 25.8 and 32.0 mm of industrial batches. The change of tensile test properties of basic pipe metal of the pipes after simulating application of an anticorrosive coating (200–250 °C, 5 min) and strain ageing is shown. After heating the pipe base metal retains low values of σy(Rt0.5)/σf ratio (along the rolling direction 0.75–0.84) and good ductility (along the rolling direction δ5 ≈ 22–23% and δt ≈ 8–12 %; across the rolling direction δ5 ≈ 21–22 % and δt ≈ 8–12 %). Relationships are determined for properties whose values depend on the specific nature of the steel microstructure of these pipes σy(Rt0.5)/σf, δt, KCV–40, CTOD–20). An increase in strength (σf) of the basic metal up to the upper standard limit does not lead to a reduction in ductility. However, with high strength pipe base metal there is a tendency towards a reduction in CTOD–20 values of base metal and fusion zone metal.

Study of Expandable-Tubular Collapse Leads To Risk-Based Strength Development

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 187460, “The Study on Expandable-Tubulars Collapse Performance and the Development of Risk-Based Design-Collapse Strength,” by X. Long, S.M. Roggeband, H. Pasaribu, and M. Jabs, Shell, and F.J. Klever, SPE, BetaTech Consulting, prepared for the 2017 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 9–11 October. The paper has not been peer reviewed. Solid expandable technology is helping the industry reach more challenging wells. The objective of this study is to investigate comprehensively the effects of the expansion process on the pipe mechanical properties and collapse performance and to develop a reliable risk-based collapse-strength design for the expandables. Introduction Expansion technology allows for tubulars to expand in situ, thus maintaining downhole size. It has been used successfully for zonal isolation in depleted or trouble zones as a drilling liner. It was also found to be very useful for extended reach in brownfields without losing the tubular diameter for maximum production. Another application is to repair existing casing worn by drilling. Several expansion technologies have been developed since the first concept test was performed in 1993. Currently, an expansion system called top anchor and pull (TAAP) is being developed, and multiple liners have been installed in the Gulf of Mexico. The TAAP expansion system currently uses 50-ksi-grade expandable seamless tubulars. This material exhibits a large degree of work-hardening and, therefore, is suited for use in expandable tubulars. The collapse strength of tubulars, one of the major concerns during well design, is generally determined by the diameter-to-thickness (D/t) ratio as well as pipe material yield strength and geometric factors such as ovality, eccentricity, and residual stresses. Earlier studies have shown that the expansion process can affect the factors influencing tubular collapse performance significantly. One of the objectives of this study is to develop a better understanding of collapse-failure mechanisms of expanded tubulars. The other objective is to develop collapse-strength design formulas and methodologies for expanded tubulars with the same reliability level used currently, taking into account the additional aspects and uncertainties related to expandable tubulars. Expandable Tubular Collapse Mechanisms On the basis of a review of the literature, factors such as expanded pipe yield strength, stress/strain curve, geometry factors, and residual stresses, as well as their effects on pipe-collapse performance, have been investigated in the present study by both experimental measurements and numerical finite-element analysis (FEA). Residual Stresses. The split-ring and hole-drilling methods for pipe residual-stress determination produce approximate or average measurements that do not accurately represent residual-stress distribution through the pipe wall thickness. In this study, through-wall residual stresses in an expanded pipe were measured by X-ray diffraction (XRD).

Effect of Pipe Flattening in API X65 Linepipe Steels Having Bainite vs. Ferrite/Pearlite Microstructures

The influence of microstructure on pipe flattening response was assessed using two different commercially produced U-ing, O-ing, and expansion (UOE) pipes from API X65 steels having either a bainitic microstructure (steel B) or a ferrite/pearlite microstructure (steel FP). A four-point bending apparatus and distinctive procedure were used to minimize strain localization during flattening. The flattened specimens were sectioned at different positions through the thickness, and tensile tested in both the longitudinal (LD) and transverse directions (TD) to assess the through-thickness variation in properties. Yield strength (YS) distributions in the LD show V-shaped profiles through thickness in both steels, whereas the YS in the TD nearest the outside diameter (OD) surface is reduced. These variations in YS are due to the Bauschinger effect associated with the compressive flattening pre-strain. The uniform elongation (UE) of steel FP is almost independent of specimen position through the thickness, but for steel B there is a substantial reduction of the UE at both the inside and outside diameter positions and this reduction is greater in the LD. This work confirms that flattened pipe mechanical properties exhibit an important dependence on their microstructure type and it is postulated that the flattening procedure also influences the mechanical properties.

Effect of welding technology on the mechanical properties of welded joints in pipes for deep water offshore gas pipelines

Results of investigations into the dependence of mechanical properties of welded joints of pipes for offshore pipelines on welding conditions are presented. In particular, the results show that the mechanical properties of pipes of the strength categories K60 (X70) and K56 (X65) are influenced mainly by the heat input, the fracture toughness of welded joints, and pipes of a high strength category are lower by 30–35% than in the case of the K56 (X65) pipes. The hardness of the weld metal in the upper layers is 15–17% higher for automatic submerged arc welding and in the lower layers for gas-shielded automatic arc welding. In inspecting the mechanical properties of the welded joints, special attention must be given to the longitudinal welded joints in the pipes.

Influence of Steel Chemical Composition and Modes of the Thermomechanical Treatment on Mechanical Properties of a Hot Rolled Plate

A mathematical model for calculation of rolling pipe mechanical properties has been developed. The influence of alloying elements in steel by means of optimal process parameters of thermomechanical rolling was analyzed. There are two methods of mathematical modeling used in the study: the neural network modeling used to select the optimal chemical composition and the finite element analysis used to optimize the process parameters. Due to large availability, low cost and high accuracy of the results, these methods are considered to be the most promising ones. Two ways to reduce the cost of a hot-rolled plate from microalloyed steels have been developed. A complex of technological processing replacement was developed.

Corrosion Failure Analysis of a New L360 Pipeline

In this paper, the optical microscope, scanning electron microscope (SEM), X-ray Diffraction (XRD) and simulation test were utilized to study the corrosion failure of L360 pipeline. The results show that the corrosion pits distributed around the pipe inner surface. The pipe mechanical properties, chemical constituents and inclusions grade satisfied the requirements of the technical conditions. Inclusions were composed of Ca, S, Al and O. Corrosion products consisted of the Fe3O4, Fe2O3 and FeO (OH). The compositions of corrosion products within and around the pits were similar to the inclusions. Due to the combined effects of water and high pressure air sealed in the pipeline, the pits formed around inclusions, and developed into occluded cells which accelerating the corrosion and leading to the failure finally.