Piping Loads Research Articles

Mechanical failure analysis of drill string aggravated by stuck pipe after high-temperature melting-cutting operations

High-temperature melt cutting is an important technology for fast cutting and unjamming of downhole jammed tubular rods, but due to the well depth and mud environment, it cannot completely cut through the large wall thickness tubular rods such as weighted drill pipe, and it needs to be damaged by external load applied by drilling rig. The shape of the drill pipe kerf after the melt cutting operation is not the same, so the size of the applied external load needs to be further investigated. To address this problem, firstly, this paper establishes the Johnson-Cook ontology and failure model of S135 steel grade drilling tools based on the high temperature tensile test; secondly, according to the characteristics of the weighted drill pipe melt-cutting notch, a finite element model for mechanical damage failure analysis of weighted drill pipe with melt-cutting notch is established, and the reliability of the model is verified; lastly, the influence of high temperature and different notch characteristics (melt-cutting depth, circumferential cutting angle, Finally, the effects of high temperature and different notch characteristics (depth of cut, circumferential cutting angle, number of perforations) on the mechanical failure capacity of weighted drill pipe with fusion notch are analysed. The results show that the errors of the maximum stresses and strains of the samples obtained from the tensile fracture simulations at 20 °C and 400 °C and the maximum stresses and fracture strains obtained from the experiments are within 9 %, which verifies the accuracy of the model. Tensile loading was more effective than compressive loading in destroying the drill pipe; the change in loading speed had a small effect of 4.1 % on the tensile force required to destroy the drill pipe. The damage load of the drill pipe and the pressure acting on the cross-section of the fusion cut decreases with the increase of the fusion cutting depth; the damage load required decreases with the increase of the circumferential cutting angle and the number of openings, but the pressure acting on the cross-section of the fusion cut does not decrease. The softening effect of high temperature on the drill pipe is very obvious, and the tensile capacity of the drill pipe is attenuated by 80.6 % at a temperature of 800 °C. The research work can improve the operation process of cutting and unjamming thick-walled drilling tools in deep wells and guide the field operation to achieve the purpose of rapid unjamming.

Interaction between Pipe Rotation and Cuttings Transport in Extended-Reach Drilling: Mechanism, Model, and Applications

Summary High drag and torque on drillstring and difficulty in hole cleaning are two major challenges in extended-reach drilling, and these two challenges are usually coupled with each other. However, previous studies considered the drillstring mechanics and hole cleaning as two relatively independent issues and studied them separately, which cannot fully reveal the complex mechanisms of pipe sticking and obtain proper drilling parameters to ensure hole cleaning and reduce drag and torque. To solve this problem, in this paper we present the concept of pipe-cuttings interaction and elaborate on the two interaction mechanisms, which are the effect of pipe rotation on cuttings transport and the effect of cuttings distribution on pipe load. Second, we introduce the stirring diffusion factor and pipe-cuttings contact stress to quantify the pipe-cuttings interaction, and we obtain their mathematical expressions through nonlinear regression of numerical simulation results. Third, we establish the mechanical pipe-cuttings interaction model by modifying and combining the tubular mechanical model and the cuttings transport model. Finally, we validate the interaction model and apply it to a case study of extended-reach drilling in the South China Sea. The results show that the interaction model is of high prediction accuracy and is superior to the conventional tubular mechanical and cuttings transport models because the interaction between pipe rotation and cuttings transport is sufficiently considered. The problem of poor hole cleaning for a 12¼-in. section is serious, and pipe sticking occurs frequently for the extended-reach well in the case study because the stationary bed height is more than 10% in actual drilling. It is usually difficult to ensure hole cleaning of a 12¼-in. section by only optimizing a single parameter of rate of penetration (ROP), flow rate, or rotational speed, but optimizing two of the parameters at the same time can achieve better results. Lastly, we establish a recommended chart of drilling parameters, which can aid engineers in making comprehensive recommendations on drilling parameters.

A double load spectrum extrapolation for drill pipe of rotary drilling rig considering load sequence

The load spectrum of rotary drilling rig’s drill pipe is used for drill pipe design, simulated fatigue testing, and reliability assessment. However, the proper extrapolation of the drill pipe double load is challenging, especially to meet the requirements of both load sequence and load strengthening. In this paper, an extrapolation technique for a double load of drill pipe is proposed. The time sequence rainflow counting technique is proposed to keep the torque and pressure sequence. Meanwhile, the individual distributions of the loads are accurately estimated. Finally, the torque and pressure are simulated and extrapolated by the percentile extrapolation method. The results show that the proposed extrapolation method for maintaining the load sequence enriches the dynamics and diversity of the loads while ensuring the load sequence.

Buckling behavior of sandwich pipe under external pressure and lateral load

The buckling propagation in deep-sea service sandwich pipes is prone to occur under the influence of third-party loads. Therefore, it is crucial to determine the carrying capacity of the sandwich pipes under combined loading conditions for safety. Currently, the predominant method for studying the carrying capacity of sandwich pipes relies on hyperbaric chamber tests, which fail to reflect adequately the buckling behavior under lateral loads. In this study, the finite element package ABAQUS was used to establish a finite element model that accounted for the lateral load on submarine sandwich pipes. It was solved for the maximum lateral load and compared the results with experimental tests, and then validated the accuracy of our numerical simulation method. This investigation focused on studying the buckling behavior of sandwich pipes under displacement control, and analyzed the relationship between buckling behavior and external pressure as well as lateral load. Furthermore, the comprehensive parametric studies were performed to analyze the impact of initial ovality, inner pipe thickness, and outer pipe thickness on the maximum lateral load of the sandwich pipe. The findings demonstrated that under coupled loads, sandwich pipes exhibited two types of buckling behavior: local buckling and buckling propagation. Moreover, as the external pressure increased, the buckling tendency in sandwich pipes transited from local buckling to buckling propagation. To enhance the capacity of sandwich pipes, there were two strategies proposed: increasing the thickness of the outer pipe and then reinforce the inner pipe to improve overall strength. Finally, based on an analysis of sandwich pipe applications up to 5000 m water depths, the sandwich pipe structure were proposed suitably for various water depths.

Stresses in pipes subject to thermal fluctuations and linear temperature ramps

Closed-form exact expressions for local and linearized elastic thermal stresses in thick- and thin-walled circular pipes subject to steady-periodic sinusoidal temperature variations are presented. Fourier series are applied to obtain the corresponding response in the pipe wall to rectangular temperature fluctuations and linear temperature ramps. Universal diagrams of resulting temperatures and stress ranges in terms of dimensionless parameters are shown for various pipe cross sections, load frequencies and heat transfer coefficients for the three types of loads.

NONLINEAR BUCKLING SENSITIVITY ANALYSIS OF THIN-WALLED LINED COMPOSITE PIPE LINER

In order to study the buckling failure of lining delamination of thin-walled lined composite pipe, a numerical analysis model was established by using bilinear cohesion relationship, the buckling mode and critical load of the composite pipe obtained by linear buckling are taken as reference values, the interlayer initial defects were introduced to carry out the nonlinear buckling analysis on the composite pipe lining structure with thin wall lining. The relative displacement curve and deformation morphology of the relative displacement of the lining with the change of external pressure were obtained, and the results are consistent with the existing test results. Based on this model, the buckling sensitivity of lining pipe was analyzed. The results show that the size of interlayer initial defect is the main factor that affects the critical buckling pressure of liner, but it has little influence on the propagation pressure after buckling; However, the increase of interlayer bonding effect significantly improves the buckling resistance and propagation pressure of lining pipe; The ratio of outer tube wall diameter to thickness and liner thickness have significant effects on the critical buckling pressure of liner. The research results provide a reference for determining the interlayer bonding effect and the optimal design of the minimum thickness of the inner liner.

Development of an improved structural integrity assessment correlation for circumferential through-wall cracked 90° shape-distorted pipe bends subjected to in-plane opening bending moment

A detailed and systematic assessment of the plastic collapse load of 90° shape imperfect pipe bends subjected to in-plane opening bending was conducted by implementing three-dimensional non-linear finite element analyses. The material considered in the analysis is the elastic-perfectly plastic type with a large change geometry option. Shape distortions in the pipe's cross-section and through-wall circumferential crack at the intrados region were the defects analyzed in this study. Ovality [Formula: see text] and thinning [Formula: see text] were varied from 0% to 20% with a 5% incrementation, and crack angles of 45°, 60°, and 90° were considered at the intrados. The twice-elastic slope method effectively evaluates the plastic collapse moment as mandated by the ASME B&PV code NB-3213.25, section III. The reaction moment and angular rotation curves were generated for all pipe bend models. The outcomes of the analysis revealed that the plastic collapse moment load of pipe bends was affected by through-wall circumferential crack and [Formula: see text], while thinning produced negligible effect, which was subsequently excluded from the analysis. The combined effect of through-wall circumferential crack and [Formula: see text] produces a consequential influence on the pipe bend at 45° angle, which is severe at 60°, and even more critical at 90°. In the analysis, the plastic collapse moment for short bend radius was reduced, while that of thin-walled pipe bends increased with an increase in thickness and bend radius. The plastic collapse moment of the present analysis was validated using experimental data acquired from open literature. An enhanced structural correlation assessment was proposed for through-wall circumferential crack shape-distorted 90° pipe bends.

Strength evaluation of support frame of the low level liquid effluent pipes of nuclear plant

Disposal of low level radioactive liquid effluents of nuclear plant into the sea is carried out through carbon steel pipes inside a guard pipe. The treated effluents are discharged inside the sea beyond breaker zone through two disposal pipes. The disposal pipe discharges the treated effluent to two numbers of 1 m diameter pipe which goes down till sea bed. This guard pipe should be supported on top of the jetty against wind, wave, and dead loads. This study is intended to cover the design adequacy and material selection of the liquid discharge piping support configuration. Material and coating requirements of the support frame is chosen after careful evaluation of the prevailing saline environment and economic consideration. Elastomeric bearing provides necessary support & firm adherence of the support arrangement to the erected pile cap. Elastomeric bearing are easy to install and offer low maintenance. The support frame is checked for dead load, pipe load, live load, wind load, wave ¤t loads, and seismic loads. Wave and current loads were calculated based on Morison semi empirical equation. Linear elastic structural analysis of the support frame was carried out. This article provides insight to the materials used in supporting this pipelines and the basis behind the material selection. After material selection, strength evaluation of the structure is elaborately carried out for all the loads. Indian standards and API recommended practice were adopted for the strength assessment of the structure. Support arrangement is formed using trusses at different levels, spandrel girders and hangers connecting the spandrel girders. All the stresses for structural arrangement for liquid discharge pipe support are checked and found within acceptable limits.

Failure characteristics of concrete pipes with pre‐existing cracks

AbstractUrban ground subsidence accidents have become frequent in recent years, mainly due to cracked concrete sewer pipes. Based on the discrete element method (DEM), the process from crack‐initiation to the formation of penetrating macrocracks were investigated and crack‐initiation load and failure load were calculated. The results showed that numerical results were in good agreement with the experimental results, thus verifying the effectiveness of the DEM calculation results. The crack‐initiation load and failure load of concrete pipes varied when different parameters were involved. The diameter of pipe had the greatest impact on the crack‐initiation load and failure load, followed by the crack position. The crack dip angle did not show any significant influence on the failure load. The crack depth significantly affected the deformation characteristics prior to crack initiation. The diameter of pipe and crack depth had a minor impact on the failure mode of concrete pipes. However, the crack dip angle determined the path of crack propagation while the crack position determined the crack initiation location and failure mode of the concrete pipes.

Definition of limit state of flexible pipe material in coiled tubing technology

Currently, the use of coiled tubing technologies has become widespread in drilling and oil production. The flexible pipes (FP) used in this technology undergo a complex of several impacts that accelerate the process of damage accumulation and thereby cause an accelerated process of seats of destruction formation, which often leads to accidents. Statistics show that the main reason for the destruction of the FP is the fatigue of the material loading and basically it is a cyclic bending according to the repeating stress cycle scheme. This loading scheme has a feature that is associated with the fact that tensile loads occur mainly in the convex zone of the pipe and compressive loads in the concave zone. Since the physical and mechanical properties of steels under stretch and compression are different, the process of damage and destruction accumulation during cyclic stretch and cyclic compression will have a different character. Information about the patterns of changes in the properties of the FP material allows to estimate the period of reaching the limit state and, thereby, prevent accidental destruction. In this regard, fatigue tests were carried out with a step-by-step measurement of magnetic characteristics that are structurally sensitive to the accumulation of fatigue damage. The determination of the stress amplitude for the FP fragment was determined by preliminary calculation in the ABAQUS PC. The test results showed that during cyclic stretch of the samples, the magnetic characteristics for assessing the limit state in the FP material were not informative. Notably in samples loaded with cyclic compression, the results of magnetic characteristics measuring (the resulting intensity and the gradient of the intensity of the constant magnetic field) showed sensitivity to the onset of the limit state. Based on the conducted studies, it is proposed to control the limit state of FP in the concave zone, where compressive loads mainly occur. These measurements allow us to estimate the value of the residual life of the FP material and to put this object out of operation in a timely manner, preventing accidental destruction.

Synchrotron radiation from final doublet magnets in CEPC MDI

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center-of-mass energy of 240[Formula: see text]GeV to measure the properties of Higgs boson and test the standard model accurately. Synchrotron radiation (SR) generated from the final doublet (FD) magnets in the interaction region of CEPC double ring scheme is one of the typical issues. SR photons can contribute to the heat load of the beam pipe and cause photon background to the experiments. Furthermore, the radiation dose can damage detector components. In this paper, SR generated from FD magnets is analyzed when beam is with tails and offset. SR from the dipole leakage field of the FD superconducting magnets is also analyzed and the physics limit is given to protect the detector.

Experimental Study on External Loading Performance of Large Diameter Prestressed Concrete Cylinder Pipe

A prestressed concrete cylinder pipe (PCCP) is created with a complex composition of concrete core, welded steel cylinder, prestressed steel wire, protective mortar and anti-corrosion coating. Due to the economy and complexity of structural prototype tests, the ultimate loading test on PCCP is rarely conducted. In this paper, the three-edge bearing test was carried out on a 3.2 m diameter PCCP with embedded steel cylinder. The strains of concrete core, prestressed steel wire and protective mortar were monitored, and the distribution and width of the concrete cracks were recorded. The test results show that the cracking on the inside concrete at the crown zone occurred before those on the invert zone of the pipe. The prestressed steel wire postponed the tensile stress of out-side concrete at the springing line until subjected to the calculated cracking load (Pc). Due to the moment redistribution caused by the cracking on the inside of the concrete at the crown/invert, the protective mortar at the springing line was cracked at 1.2 Pc and exhibited visible cracking after 1.4 Pc. The prestressed steel wire reached the elastic and strength limit states of 1.4 Pc and 1.6 Pc, respectively. The PCCP designed by the limit state design method can resist the increased external loads after reaching the serviceability limit state. The final failure load of the test pipe is greater than 1.6 Pc, and there is sufficient safety in actual operation. Due to the fact that the damage to the concrete at the crown/invert zone may become a fuse of PCCP failure, the tensile stress of the inside concrete at the crown/invert zone of the PCCP should be accurately verified in the design process.

Creep buckling of long-term-serving super-heating pipes in boilers subjected to high temperature loading

This paper proposes a novel approach to scrutinize the creep buckling of the super-heating pipes in boilers subjected to external pressure in high temperature environment. It is well known that once buckling occurs, cylindrical shells will collapse instantly. As the load carrying capability of the cylindrical shell decreases sharply upon the occurrence of the buckling, the proposed analysis is based on the consideration that the creep will have a significant influence on the material properties only in the pre-buckling stage. According to the creep aging theory, the influence of the creep deformation on the mechanical response of the super-heating pipes is defined by introducing two parameters--the reduced Young's modulus and the reduced Poisson's ratio. The nonlinear constitutive relation for creep deformation of the super-heating pipes in high-temperature environment is established based on the deformation theory in mechanics of plasticity. Governing equations for creep buckling of super-heating pipes in boilers are derived by considering the extra change of curvature due to the initial curvature of the super-heating pipes. MATLAB programs are developed based on the analytical expression for super-heating pipes with simply supported boundary conditions at the two ends and are tested against the available experimental results and the finite element prediction from ABAQUS software. It is found that the components of the creep strain caused by the stress at high temperature far exceeds those of the elastic strain. As a results of that, the creep buckling load of the super-heating pipes is much lower than its elastic buckling load. From this study, an explicit expression to compute the creep buckling load is provided which facilitates engineer to easily predict the residual life of the super-heating pipes at different servo temperature and servo time.

Experimental study on uplift mechanism of pipeline buried in sand using high-resolution fiber optic strain sensing nerves

Reliable assessment of uplift capacity of buried pipelines against upheaval buckling requires a valid failure mechanism and a reliable real-time monitoring technique. This paper presents a sensing solution for evaluating uplift capacity of pipelines buried in sand using fiber optic strain sensing (FOSS) nerves. Upward pipe-soil interaction (PSI) was investigated through a series of scaled tests, in which the FOSS and image analysis techniques were used to capture the failure patterns. The published prediction models were evaluated and modified according to observations in the present study as well as a database of 41 pipe loading tests assembled from the literature. Axial strain measurements of FOSS nerves horizontally installed above the pipeline were correlated with the failure behavior of the overlying soil. The test results indicate that the previous analytical models could be further improved regarding their estimations in the failure geometry and mobilization distance at the peak uplift resistance. For typical slip plane failure forms, inclined shear bands star from the pipe shoulder, instead of the springline, and have not yet reached the ground surface at the peak resistance. The vertical inclination of curved shear bands decreases with increasing uplift displacements at the post-peak periods. At large displacements, the upward movement is confined to the deeper ground, and the slip plane failure progressively changes to the flow-around. The feasibility of FOSS in pipe uplift resistance prediction was validated through the comparison with image analyses. In addition, the shear band locations can be identified using fiber optic strain measurements. Finally, the advantages and limits of the FOSS system are discussed in terms of different levels in upward PSI assessment, including failure identification, location, and quantification.

Determination of bend angle and shape imperfection effect on collapse load of pipe bends under in-plane opening moment

This study uses a three-dimensional nonlinear finite-element method to investigate the effects of bend angle ([Formula: see text]) and shape imperfection on the collapse load of pipe bends subjected to in-plane opening bending moment using large displacement analysis. ABAQUS was used to create a pipe bend model, whereas by virtue of symmetry about the longitudinal axis, half of the pipe bend model was built. The bend angle was varied from 30° to 180° with an interval of 30°, and shape imperfections, namely ovality ( Co) and thinning ( Ct), were varied from 0% to 20% each at 5% intervals. Elastic-perfectly plastic is thought to be the material of choice for the pipe bend. The results show that the bend angle has a significant impact on the collapse load of pipe bends between 30° and 120°, after which a significant decline was observed. The ovality impact increases with an increase in bend angle for pipe bends with a large thickness, whereas the opposite effect was found for smaller thicknesses with a small bend radius. The effect of bend radius and thickness was significant for large bend angles. Thinning ( Ct) and thickening ( Cth) have no effect on collapse load. A new mathematical equation has been proposed to predict the integrated effect of bend angle and shape imperfection.

Experimental Study on Damage Characteristics of Corroded Steel pipe Based on Acoustic Emission Technology

The corrosion damage of steel pipe is mainly characterized by crack initiation and local wrinkling. One of the effective methods to evaluate the damage degree of steel pipe is to find out the law of crack initiation. The research object of this test was Q235 steel pipe specimen with diameter of 700mm, wall thickness of 5mm and height of 260mm. Acoustic emission technology was used to conduct real-time axial compression detection on corroded steel pipe specimens. The relationship between acoustic parameters (cumulative ringing number and amplitude) and the damage degree of steel pipe specimens was established, and the crack propagation law and crack initiation load of steel pipe after corrosion damage were obtained. By analyzing the different characteristics of the relationship between the displacement of loading point and acoustic parameters, the general position of steel pipe damage was detected and the exact value P of crack initiation load was determined. The experimental results provide a basis for further research on the damage mechanism of steel tube specimens. The test results provide a certain basis for further research on the damage mechanism of steel pipe specimens.

Study on cyclic plastic behaviour of sandwich pipelines subjected to cyclic thermo-mechanical loads

Subsea pipelines are generally used to transfer hydrocarbons from ultra-deep seawater to facilities on the shore. Typically, sandwich pipelines are filled with polymeric cores for thermal insulation, with structural reinforcements also used as a deep-water application. Sandwich pipelines are subjected to either monotonic or cyclic loads, such as bending moment, buckling, internal and external pressures during their installation or operation. It is necessary to evaluate the cyclic plasticity of sandwich pipelines under complex loading combinations to prevent structural failures caused by applied loads. In this research, limit load and shakedown analyses of sandwich pipes subjected to complicated cyclic thermo-mechanical loadings are conducted using a Linear Matching Method (LMM). Temperature-dependent material properties are employed to simulate actual pipeline behaviour, and an elastic perfectly plastic model is considered with regard to geometric non-linearity issues. Numerical results are validated via a full cyclic incremental analysis, also known as a step-by-step analysis. Moreover, comprehensive parametric studies are conducted with respect to changes in the geometry of sandwich pipelines. This research presents valuable insights into the most severe loading types and combinations affecting the structural integrity of sandwich pipelines. In addition, allowable load boundaries against existing geometric parameters can be determined.

Considerations Pertaining to Exerted Piping Loads on Pressure Vessel Nozzles

This technical note is intended to make the engineer involved in the design of pressure vessels with connected piping aware of the possible options that yield the most advantageous design from an economic perspective. Pressure vessels are connected to external piping by a nozzle welded to the vessel wall and a flange connection. Due to expansion or contraction of the piping system connected to the pressure vessel, which is caused by the difference in installation and operating temperatures, the piping system exerts forces and moments on the nozzle of the pressure vessel. This means that nozzle loads therefore impose an important constraint in the design of pressure equipment. It is important that such loads do not overstress the vessel-nozzle intersection. This technical note is limited to the interface of the pressure vessel piping system's imposed external loads.

Variables affecting unstable fracture load of cracked pipes under hydrogen environment

This paper presents an analytical equation for the reduction of the unstable fracture load for a cracked pipe due to hydrogen embrittlement. The proposed equation shows that the reduction of the unstable fracture load due to hydrogen embrittlement depends not only on the toughness reduction due to hydrogen embrittlement but also on plastic tensile properties and the degree of plastic yielding at fracture of a pipe without hydrogen embrittlement (quantified using the proximity parameter for plastic collapse). Note that the proximity parameter for plastic collapse is affected by the pipe and crack geometries, loading condition and fracture toughness before hydrogen embrittlement. Two case study results are presented using published material data. The first case considers stainless steel data to demonstrate the effect of the toughness reduction due to hydrogen exposure and the degree of plastic yielding at fracture on the reduction of the unstable fracture load for a cracked pipe under hydrogen embrittlement. The second case uses two sets of API 5L X42 and X70 pipeline steel data to illustrate the effect of plastic tensile properties.

Finite Element Analysis of the Limit Load of Straight Pipes with Local Wall-Thinning Defects under Complex Loads

Local wall thinning is a common defect on the surface of pipelines, which can cause damage to the pipeline under complex pipeline loads. Based on the study on the limit load of straight pipes with defects, the nonlinear finite element method was used to analyze the limit load of straight pipes with local wall-thinning defects under internal pressure, bending moment, torque, axial force, and their combinations, and the empirical limit-load equations of straight pipes with local wall-thinning defects under single and complex loads were fitted. Based on the allowable load on the equipment nozzles, the influences of torque and axial force on the load-bearing capacity of straight pipes with local wall-thinning defects were quantitatively analyzed. For medium and low-pressure equipment, the load-bearing capacity was reduced by 0.59~1.44% under the influence of torque, and by 0.83~1.80% under the influence of axial force. For high-pressure equipment, the load-bearing capacity was reduced by 10.07~20.90% under the influence of torque, and by 2.01~12.40% under the influence of axial force.