Strength Of Pipes Research Articles

CALCULATION FOR THE STRENGTH AND ENSURING THE OPERATION SAFETY OF PIPELINES WITH EXTERNAL CORROSION

Background The main oil and gas pipelines are mainly laid underground. Under the influence of the environment surrounding the underground pipeline, over time, there is a decrease in the protective properties of the outer insulation coating of the pipeline. In addition, for various reasons, mechanical destruction of the coating occurs in certain sections of the pipeline. These processes lead to external corrosion of the pipe wall in sections of underground pipelines. Corrosion is associated with a decrease in pipe wall thickness and an increase in the level of hoop stresses in them. As a result, the problem arises of assessing the strength of pipes and ensuring the safe operation of pipelines with external corrosion. At present, the installation of a metal sleeve on a pipeline in places with external corrosion has received a fairly widespread use. The coupling takes a part of the load from the operating pressure and thereby reduces the load and hoop stresses on the corroded section of the pipeline. At the same time, the coupling creates a local deformation stiffness under the operating pressure with a significant change in the stressstrain state of the pipeline. The stress-strain state of a pipe-wire with external corrosion and a sleeve installed on it depends on the geometric characteristics of the pipe and sleeve, as well as the residual pipe wall thickness after corrosion. Aims and Objectives Ensuring the strength of a pipeline with external corrosion repaired with the use of a coupling and the safe operation of oil and gas trunk pipelines based on a reasonable calculation of the geometric characteristics of the repair couplings. Results Calculation formulas were obtained and, on their basis, an assessment of the magnitude of stresses from the action of the working pressure in the walls of the pipeline and the coupling in the corroded section, as well as in the sections of the pipeline along the edges of the repair coupling outside of it, was carried out. Technical solutions are proposed to ensure the safe operation of a pipeline section with external corrosion, repaired using repair couplings.

Comparative Study on The Corrosion Behavior of High Strength Pipe Steel After Thermal and Thermomechanical Treatments

The corrosion behaviour of X80 steel samples rolled and other quench-tempered in 3.5% NaCl have been studied. Optical microscopy, scanning electron microscopy, potentiodynamic polarization tests and electrochemical impedance measurements are the techniques used to characterize the samples. The results show that the tempered steel has a low corrosion current density compared to the rolled steel. The impedance measurements show the presence of a single capacitive loop attributed to the load transfer phenomenon.

Tensile Response of a Flexible Pipe With an Incomplete Tensile Armor Layer

Abstract Unbonded flexible pipes are widely utilized in the exploitation of offshore oil and gas resources. They are connected to two of the most critical types of system: floating production platforms and underwater production systems. However, if some tensile armor wires are substituted by cables or broken, the tensile armor layer will be incomplete, which seriously reduces the safety and reliability of the flexible pipe. In the present study, models of a flexible pipe with a complete tensile layer and with the tensile layer partially missing were established. The error for the tensile stiffness obtained by the finite element model of an intact flexible pipe was only 1% compared with experimental results. Because the load borne by the inner tensile armor layer is larger under tension than that borne by the outer tensile armor layer, the loss of inner tensile armor wires has a greater impact on the tensile properties. The maximum axial elongation of the flexible pipe increases with the number of missing inner tensile armor wires as a cubic polynomial. If the distribution of the missing armor wires is too dense, a stress concentration and local bending may occur, which will reduce the tensile strength of the flexible pipe.

Relationship between shear strength and surface roughness of double-layered pipes by cold drawing

Abstract. Pipes applied to marine plants are used in deep-sea environments; therefore, they must be resistant to high pressure and corrosion. Because it is difficult to satisfy both of these factors in a single pipe, studies on a double-layered pipe are continuously being performed. An outer pipe should be made of carbon steel, with high pressure resistance, and an inner pipe should be made of stainless steel, with high corrosion resistance. A pipe formed by combining these two pipes is called a lined pipe. The shear strength of the lined pipe is an important factor because pipe cracking can occur due to stress concentration when two pipes are separated by bending or high pressure. Therefore, various processes have been applied to increase the shear strength. In this paper, we investigate the effect of the surface roughness of the bonding interface on the shear strength. Surface roughness is in units of micrometers, and it cannot be used for finite element method (FEM) analysis. Therefore, surface roughness should be converted into a friction coefficient to perform FEM analysis. The effect of surface roughness on shear strength was studied in the relationship between the results of pressure from FEM analysis and the shear strength test.

Chemical-technological phenomena occurring during borehole cementing operations in terms of casing design

Borehole design is a complex and multidimensional question in terms of the number of issues to be resolved in terms of mechanical, environmental and public safety engineering requirements. In this article contains a review and evaluation of chemical phenomena and processes (not always correctly evaluated) that occur during the preparation of cement slurry and after its displacement during the formation of the gel structure of cement and cement sheath. As a result of the chemically complicated process of slurry gelation, a new structure is formed, i.e. steel pipe – sheath (cement stone) – a rock which in a specific way produces a specific type of load and stress in the annular space, and thus influences changes in hydrostatic pressure distribution. Such phenomena described in this article allow to understand the methodical approach to the process of designing pipes, especially in the aspect of collapse and burst of pipes with big diameter >13⅜″ and thin wall (in the 4th load regime). This does not mean that the tensile strength of pipes is not an important issue in pipe design, but it mainly concerns very deep boreholes, while collapse and burst of pipes occurs in special (often unforeseen) cases of full or partial evacuation for shallow pipe foundation in the hole. The article is based on extensive professional literature, as well as on numerous tests carried out at Oil and Gas Institute – National Research Institute on different types of cement slurries and drilling muds, and, moreover, on the relevant experience of the authors of the article, both in the field of slurry design and supervision of cement operations, as well as in the design and supervision of works related to drilling of various types of boreholes, including cement job and running casing.

Estimation of pipeline systems flexible connecting pipe strength properties based on numerical study of strain-stress state

Vibration-isolating structures on rubber-cord casings are used in pipeline systems which are of great importance for the transportation of hydrocarbons. Implementation of a compensating pipe eliminates the load transfer from the pressure of the working medium to the structural elements of the pipeline. A three-dimensional model based on a numerical study and reinforced with beam elements is used to estimate the strength properties of a rubber-cord branch. The calculation of the stress-strain state of the rubber-cord casing and the flange connection of the branch pipe has been carried out. The results are to be considered when designing and operating pipe structures based on reinforced casings.

Design Go-Kart Chassis Four Strokes 110 Engine

This study aimed to decide how to design a kart chassis and the strength of the welded joints. In this design, the chassis frame is made of tubular profile steel, which is designed to withstand most of the loads in a vehicle. The chassis was designed using a computer application, namely Auto CAD 2007. Assembly using carbon steel pipes connected using SMAW welding with E6013 RB 2.6 mm welding wire with a current of 75 A, 1G place. The test is carried out with a tensile testing machine. The material is pulled past the most stretch elasticity limit until finally, the specimen reaches the limit (breaks). The tensile test takes about 3-5 minutes with a load of 10-20N. The test results show the average tensile strength of the iron pipe is 0.512 Mpa.

Yield strength estimation of X65 and X70 steel pipe with relatively low t/D ratio

During the pipe forming process, a steel plate undergoes inelastic behavior multiple times under a load condition repeating tension and compression in the circumferential direction. It derives local reduction or increase of yield strength within the thickness of steel pipes by the plastic hardening and Bauschinger effect. In this study, a combined hardening model is proposed to effectively predict variations of yield strength in the circumferential direction of API-X65 and X70 steel pipes with relatively low t/D ratio during the forming process, which is expected to experience accumulated plastic strain of 2~3%, the typical Luder band range in a low-carbon steel. Cyclic tensile tests of API-X65 and X70 steels were performed, and the parameters of the proposed model for the steels were calibrated using the test results. Bending–flattening tests to simulate repeated tension and compression during pipe forming were followed for API-X65 and X70 steels, and the results were compared with those by the proposed model and Zou et al. (2016), in order to verify the process of material model calibration based on tension–compression cyclic test, and the accuracy of the proposed model. Finally, parametric analysis for the yield strength of the steel plate in the circumferential direction of UOE pipe was conducted to investigate the effects of t/D and expansion ratios after O-forming on the yield strength. The results confirmed that the model by Zou et al. (2016) underestimated the yield strength of steel pipe with relatively low t/D ratio, and the parametric analysis showed that the t/D and expansion ratio have a significant impact on the strength of steel pipe.

The Numerical Approach to Mosaic Patterns in Filament-Wound Composite Pipes

This paper is focused on radial-compression of filament-wound composite pipes. An important but frequently disregarded is the issue of the choice of the winding pattern. The influence of the pattern on the strength of pipes is the subject of the investigation. Since the real geometry of filament-wound tubes is complicated researchers use simplified models (especially in “zig-zag” area), which are insufficient to reflect real behavior of tubes. An attempt to investigate a more precise geometry is presented in this work. A python script is used to model the particular areas typical for filament-wound elements. Hashin criterion is used to reflect damage in the material during compression. Results of numerical simulations are discussed and compared with experimental from other researchers. Based on the prepared model – the influence of pattern on the strength of a composite pipe is possible. Although some improvements may be introduced, a satisfactory agreement between the experiment and numerical simulation was achieved.

Effect of electric field on push-out strength of cemented steel pipes

<abstract> Cement-steel interfacial strength is an important measure for estimating the robustness and hydraulic sealing ability of wells. In this paper, laboratory experiments were performed in which small steel pipes (10 mm in diameter) were cemented in place within a Portland cement slurry under application of constant electrical potential difference between the pipes. The objective was to investigate whether there might be an observable difference between push-out strengths obtained with the pipes of different polarity (anode vs. cathode vs. reference nonpolarized pipe). The duration of the potential application and the magnitude of the potential difference were varied between the tests. The experiments demonstrated that at the higher potential difference (4 V), the duration of potential application had a noticeable effect on interfacial bonding. Application of 4 V for 24 h resulted in loss of bonding at cement-cathode interface, which could be attributed to massive water transportation to the cathode region by small radii cations. At the lower applied potential difference (1 V), there is an improvement in push-out strength at anode at short duration of potential application. This could be due to pore filling by precipitation of expansive minerals in pores and cement particles migration toward anode. The effect of potential on push-out strength in a hardened cement suggests that low potential difference applied for a short period of time might improve cement-steel interfacial strength. </abstract>

Experimental and Analytical Investigation on the Effect of Heat Treatment Parameters on the Mechanical Properties of an API 5L X65 Steel

High Strength Low Alloy steels (HSLA) for oil and gas pipelines should display high mechanical strength, toughness, ductility and weldability. In this work we studied the influence of quenching and tempering temperature on the yield strength, ultimate tensile strength, percent elongation and hardness of API 5L steel pipes in order to optimize heat treatments to be performed after hot induction bending of the material. The thermal cycles involved soaking temperatures of 880, 920 and 960 °C, cooling water at 15, 23 and 31 °C and tempering at 530, 600 and 670 °C. From this, experimental design techniques were used to reduce the number of experiments. The results from contour maps suggest that soaking temperatures of 910 and 950 °C and tempering between 540 and 610 °C were the most suitable for treatment, regarding mechanical strength. The variation of the water temperature was not significant for the assumed cooling conditions. The prediction regression models of the mechanical properties from the variables involved in the heat treatments showed a good fit between the experimental and predicted results, with correlation coefficient between 0.89 and 0.94.

Research on the influence of heat treatment temperature on bearing capacity of high steel grade pipeline during in-service welding

During the welding of in-service pipeline, natural gas is continuously transported in the pipeline, which maintains a high gas pressure. Therefore, the welding process is completed under strong cooling conditions, and welding delay crack is easy to occur. Preheating before welding and heat treatment after welding can effectively control the hardened microstructure, reduce the residual stress and ensure the welding quality. In this study, the influence of heating temperature on the bearing capacity of high steel grade pipe during in-service welding repair was studied. The high temperature tensile test was used to simulate the bearing capacity of the pipe under heating and high temperature environment. It is found that when the heating temperature is below 400°C, the pipe strength remains at the original level. With the increase of heating temperature, when the test temperature is higher than 400°C, the yield strength and tensile strength of the pipe decrease significantly. When the test temperature is 450°C, the yield strength and tensile strength of the material decrease by 15.8% and 11.1%, respectively, compared with the normal temperature, which are lower than the pipe standard requirements. Therefore, it is suggested that when the heat treatment temperature is higher than 400°C during in-service welding repair, it is necessary to consider reducing the pipeline pressure. At the same time, the box furnace heat treatment method was adopted to heat treat the pipe, and the tensile properties of the pipe after heat treatment were tested to analyze the bearing capacity of the pipe after heat treatment. It is found that when the heating temperature is higher than 700°C, the tensile properties of high grade pipeline steel pipe decrease sharply. It is suggested that when the heat treatment temperature is higher than 700°C, the risk assessment of the service safety of the heat treated pipeline should be carried out.

Experimental analysis of compressive behavior of E-Glass fiber reinforced IPN (vinyl ester/polyurethane) composite pipes

The manuscript discusses about the effect of compressive load on the E-Glass fiber reinforced interpenetrating polymer networks (IPNs). In this work, a series of combination of vinyl ester (VER) loaded polyurethane (PU) IPNs have been taken as the matrix material with the E-Glass reinforcement, with the loading of 0%, 10%, 20%, 30%, 40%, 50% PU respectively. Besides hand-layup technique was used to fabricate the cylindrical shells in order to get the final shape of the IPN composite pipe. Simultaneously to validate the compressive strength behavior of the IPN composite pipe, experimental analysis was carried out as per the ASTM D695 standard at normal room temperature to extract compressive strength value of the PU loaded IPN composite pipes. During this test, it was observed that physical strength of the composite pipes reduces gradually as much as PU addition into the IPN composite pipe increases. Surprisingly, another important notification was that, the geometric structure of the composite pipes is not affected as like as the crushing observed on the pure VER pipe. As much as loading of the PU into the IPN, increases the structural integrity of the composite pipes in outstanding (retains structural ability) manner. Further the experimental analysis values are validated with numerical analysis software ANSYS, obtained values and numerical values are shown good agreement each other.

Failure of corrosion affected buried cast iron pipes subject to water hammer

Water hammers can be generated when the steady state conditions change at a given point of pipeline due to some instantaneous events such as fast closure of valves or pump shout down. The magnitude of water hammer pressure in water pipes can well exceed the strength of the pipes, in particular, when they have been deteriorated due to, e.g., corrosion. This paper intends to present a time-dependent reliability method for the prediction of the risk of pipe failures under the adverse combination of the excessive water hammer pressure and corrosion induced reduction of pipe strength. Stochastic models are proposed for both pitting corrosion and water hammer pressure. It is found in the paper that the risk of pipe failures increases with the increase of mean occurrence rate of water hammer and that the sudden closure of pipe valves can have devastating effect on the safety of pipeline networks. The paper concludes that the time dependent reliability method can predict the risk of pipe failure more accurately under the combined stochastic effects of the water hammer pressure and corrosion induced deterioration of the pipe. Accurate prediction of pipe failures can ensure the safe and reliable operation of pipelines, which has the potential to prolong their service life.

Numerical and Experimental Analyses of the Hoop Tensile Strength of Filament-Wound Composite Tubes

The hoop tensile strength of a composite pipe was measured experimentally using the split-disk test method. Then, a finite-element modeling was performed to simulate the split-disk test, and the progressive damage modeling was carried out to predict the maximum load the ring specimen representing the hoop tensile strength can carry. The progressive damage modeling was utilized in the context of continuum damage mechanics, where a failed ply is replaced by a virtual continuum ply with reduced mechanical properties. To degrade the mechanical properties of the failed ply, the linear damage evolution law was used in combination with a linear material softening law. The hoop tensile strength predicted agreed with experimental observations very well, validating the finite-element modeling. The damage progression was monitored during different loading stages, and the sequence of experienced failure modes was investigated. The stress concentration factor at the root of a notch was computed based on the results of finite-element analysis. The stress distribution in the vicinity of the notch was investigated, and a simple manual method was proposed for obtaining the stress in the hoop direction. The stress obtained was compared with results of the numerical simulation, and a good accuracy of the method to determine stresses without employing the finite-element modeling was found to exist.

INFLUENCE ANALYSIS OF DESIGN SOLUTIONS OF UNDERGROUND PIPELINES CURVED SECTIONS ON THEIR STRESS-STRAIN STATE

Background Underground pipelines of main oil and gas pipelines are being built in all climatic and geographical zones of the country. A significant part of the main oil and gas pipelines are laid in flat-hilly and mountainous terrain. In hilly and mountainous areas, pipelines are laid in a trench with a vertical turn. During the operation of oil and gas main pipelines, longitudinal compressive forces arise under the influence of a positive temperature difference and operating pressure. These forces lead to longitudinal and transverse movements of the underground pipeline in convex sections of the turn in the vertical plane. When the underground pipeline moves in the longitudinal and transverse directions, additional bending stresses arise. At the same time, a decrease in longitudinal compressive forces occurs, which leads to a decrease in the values of longitudinal compressive stresses. In accordance with the requirements of SP 36.13330.2012 «Trunk Pipelines», the maximum total longitudinal stresses acting in the pipe wall should be determined from all (taking into account their combination) standard loads and actions, taking into account the longitudinal and transverse displacements of the pipeline. At the same time, the longitudinal and transverse movements of the pipeline and the resulting stresses due to these movements depend on the design solutions for underground pipeline laying. Aims and Objectives Ensuring the strength of pipes and the safe operation of oil and gas pipelines based on the improvement of calculation methods and design of curved sections of underground pipelines. Results The assessment of the level of the maximal longitudinal stresses in the underground pipeline is carried out for various design solutions of the angle of rotation on convex areas of the terrain. Technical solutions to ensure the strength of pipes for oil and gas trunk pipelines have been proposed.

Performance of Thin-Wall Synthetic Fiber–Reinforced Concrete Pipes under Short and Long-Term Loading

Abstract Synthetic fibers have been recently used as a replacement for conventional steel reinforcement in concrete pipes to enhance their durability, ductility, shear strength, and flexural strength. However, there is very limited understanding of the long-term performance of thin-wall synthetic fiber–reinforced concrete pipes, as synthetic fiber has material properties that may change with a sustained load over time. This research investigates the performance of polypropylene fiber–reinforced concrete pipe under short and long-term loads in terms of strength, deflection response, strain response, crack width, and crack patterns. Concrete pipes with diameters of 1,200 and 1,500 mm with respective wall thicknesses of 50 and 63 mm were subjected to the short-term three-edge bearing test. To ensure maximum fiber contribution to pipe strength, a 9 kg/m3 fiber dosage was used with different amounts of steel reinforcement. For the long-term three-edge bearing test, a pipe with a diameter of 1,200 mm reinforced with fiber dosage of 9 kg/m3 along with steel reinforcement with an area of 5.7 cm2/m was tested for 30 days at 40 % of the ultimate load (Load Stage 1) obtained from the short-term test, for another 30 days at 50 % ultimate load (Load Stage 2), and subsequently at 70 % ultimate load for a final 30 days (Load Stage 3). Short-term results showed that synthetic fiber was a viable replacement for the steel reinforcement cage, as some of the tested pipe achieved the strength requirement specified by ASTM C76-15a, Standard Specification for Reinforced Concrete Culvert, Storm Drain, and Sewer Pipe. In response to sustained load, the tested pipe initially exhibited a linear response, followed by a stable response with a slight increase in deflection over time. Fiber creep did not significantly increase the crack width or affect the time dependence of the strain, indicating that the fibers adequately transfer the stress in the pipe wall and limit the crack width. The cracks propagated longitudinally at the invert, crown, and springline, where there were high flexural tensile stresses.

Framework for probabilistic leakage resistance envelopes of casing connections

Probabilistic well casing design is a recent trend in Oil & Gas exploration, especially for ultra-deep and HPHT wells. Reliability-based design allows safety margins to be optimized, while managing the corresponding risks. Statistics for pipe body geometry and strength are today widely available, but most reported incidents are related to connection failures. In this context, a methodology is proposed herein to construct probabilistic leakage resistance envelopes for casing connections. The methodology is based on extensive axisymmetric Finite Element analysis, considering geometric variabilities resulting from manufacturing tolerance. Maximum internal pressure is found for different values of axial load. Multi-dimensional response surfaces are constructed to take into account individual effects, and cross-effects for the most relevant variables. Regression analysis is used to construct failure envelopes for pre-defined probability levels. These are also converted into probabilistic envelopes for arbitrary combinations of axial load and internal pressure. The API 8 Round 5½ J55 14 lb/ft LTC connection is employed as study object, but the methodology can be readily extended to other connections with metal-to-metal seal. To the best of our knowledge, this is the first time such a probabilistic framework for leakage resistance of casing connections is presented in the literature. This framework, and the resulting models, are fundamental for the proper reliability-based design of well casing.

Study on Limit Load of Orthotropic Cylindrical Pipe Under Different Combined Load Conditions

Abstract In engineering, many pressure pipes are made of steels with good plasticity, which are subject to internal pressure, axial force, shear force, bending moment, torsion moment or their combined loads. The plastic limit load is an important indicator of the load capacity of pressure pipe. According to Hill yield function, the theoretical solutions of limit load of orthotropic cylindrical pipe under various combined loads under internal pressure, axial force, shear force, torsion moment, and bending moment have been derived on the basis of elastic perfectly plastic constitutive model. The effects of radial stress on different combined limit loads of cylindrical pipe are explored and these results show that the radial stress should be considered about the limit load calculation especially for thick-walled cylindrical pipe. The interactions of various load combination are analyzed in detail and drawn with the interaction curves. For isotropic cylindrical pipe, the limit load increases with the yield strength. For the orthotropic cylindrical pipe, the limit loads of cylindrical pipe under axial force, bending moment, shear force, and torsion moment without internal pressure are only related to the axial yield strength. The limit bending moment is mainly dependent on the axial yield strength when internal pressure is lower, while the impact of the circumferential yield strength of orthotropic cylindrical pipe is obvious when internal pressure is some higher. When the axial yield strength of orthotropic cylindrical pipe is the same, the circumferential yield strength can enhance the limit axial load, limit torsion moment, and limit shear load. Under the different load conditions including internal pressure, bending moment, axial force, shear force, and torsion moment or their combined loads, the relation of limit bending moment with yield strength ratio is diverse, which is decide by the load combination, the circumferential yield strength, and the axial yield strength.

Fatigue evaluation of drill pipe by considering ship motions and its application in scientific drilling

The fatigue strength of a drill pipe is a critical factor governing the performance of drillings. Substantial research has been conducted related to fatigue evaluation and various factors that have an effect on fatigue. However, earlier studies have expressed concerns over the use of fatigue curves obtained from full scale tests and stress responses obtained via finite element analysis for evaluation: (a) fatigue curves were obtained by utilizing the stress measured at a point far away from the failure area rather than the stress exerted at the failure point, (b) the stress response is not equivalent to the stress expressing the fatigue curve. It is also important to obtain the stress-response amplitude by precisely considering the irregular wave and ship motion response. This study proposes a method to obtain stress and moment responses due to ship motion in irregular waves. Secondly, it proposes a method to obtain the fatigue curve from a full-scale fatigue test suitable for evaluating the cumulative fatigue with stress response and moment response results. Then, the cumulative fatigue is calculated by applying Miner’s rule. This paper also applies the proposed method to a scientific drilling program amid strong ocean currents and uses a special drill pipe. The results by the proposed method are compared with those obtained by previous methods.