Pressure Piping Research Articles

Collapse pressure prediction of mechanically lined pipes using FEM and machine learning techniques

Mechanically lined pipe, which proves to be an economical and reliable way to transport corrosive hydrocarbons, has been used in many offshore projects. The presence of liner and the manufacture-induced changes in mechanical properties for both tubes are expected to affect the collapse performance of lined pipes, which, however, are not suitably captured by the current DNV formula. To this end, a dedicated numerical framework, including the axisymmetric and three-dimensional finite element models, was presented to simulate the manufacturing process and the evolution of the external collapse. Two types of commonly used lined pipes, unbonded (LP) and bonded (LPB), were considered. The results indicate that the DNV prediction mostly overpredicts the collapse pressure of typical LP pipes but underestimates that of the LPB cases. Furthermore, the parametric study of essential variables of the problem reveals that in addition to the strong effect of diameter-to-thickness ratio and initial ovality, the impact of the material hardening and plastic expansion history cannot simply be ignored. Thus, the machine learning technique was applied as a substitute resolution to evaluate the critical collapse capacity of lined pipes. Four algorithms, including RF, MLP, KNN, and SVM, were developed based on a dataset of 86,400 cases involving nine variables. Based on the assessment of typical statistical metrics, it was found that all four machine learning models outperformed the DNV formula. Among them, RF had the best prediction performance, while KNN had the lowest precision among the chosen surrogate models.

Calculation of gas supply pressure using plastic pipes for preventing accidental emissions

Technological (production, operational and repair) risks come to the fore, minimizing which requires optimization of the work of structural units responsible for a reasonable assessment of the technical condition, maintenance and repair of facilities, timely renewal of production facilities with minimization of wear and tear of equipment, which is a risk factor in the failure of the gas transmission system. In addition, based on the noted features of gas transportation enterprises, in the risk management block, logistics risks, safety risks, environmental, social and (in a certain aspect) financial risks should play a significant role. Objectively, in order to establish an acceptable range of risks, it is necessary to collect statistical data on the occurrence of risk factors for the foreseeable period in order to leave for constant monitoring those risk factors that appear regularly in the gas transmission system. The construction and operation of gas pipelines play an important role in the reasonable and technical transportation of gaseous substances. Noteworthy, algorithm for calculating the proposed medium pressure gas pipeline was developed, accordingly, in this research, the gas flow area was determined. The results showed that based on the calculations of underground average pressure of polyethylene pipes, the average gas pressure was 5,733 Pa, withstands pressure was up to 8009.7 Pa, withstands stress on the pipe wall was up to 0.024 MPa, and emission loss was 3964.4 m3 when there was an accident.

Structure formation of hyper-compacted and modified concrete

Production of axisymmetric products -pressure and non-pressure pipes, rings, wells, bridges and drainage elements represents one of the main branches of construction industry in water and wastewater industry of Uzbekistan and Central Asian republics. However, positive tendencies of its development are only emerging and still do not meet the potential of progressive, competitive and economical modern technology, capable of providing significant shifts in reduction of resource intensity of new products, expansion of raw material base of construction industry and involvement of technogenic products into its balance, as well as solution of important economic and environmental problems. Prospects for further development of high-efficiency tubular goods production and scientific and technological progress of their production are largely determined by the importance of regularities and methods of controlling technological processes of structure formation with regard to given high level of product quality and criteria of resource intensity of production. In this regard, the analysis of general regularities of material structure formation in the complex process of hypercompaction and cementations modification in axisymmetric concrete is of primary importance.

Semi-Analytical Large Deformation and Three-Dimensional Stress Analyses of Pressurized Finite-Length Thick-Walled Incompressible Hyperelastic Cylinders and Pipes

This research is devoted to semi-analytical stress and large deformation analyses of finite-length thick-walled incompressible Mooney–Rivlin hyperelastic cylindrical pressure vessels/pipes with fixed ends, employing the three-dimensional theory of hyperelasticity. The formulation accounts for the thickness reduction in both radial and axial directions. The governing system of equations and the boundary conditions are assembled using a large-weights penalty method, after utilizing central, forward, and backward second-order point collocation expressions for the discretization of the thick hollow cylinder in both longitudinal and radial directions. The resulting coupled highly nonlinear two-dimensional equations are solved by the Newton–Raphson iterative updating technique. The results include the radial, axial, and three-dimensional distributions of the deformations and all the stress components. Comprehensive parametric studies are accomplished to evaluate the effects of the hyperelasticity parameters, boundary conditions, and thickness and length-to-radius ratios of the pressure vessel/pipe. Results reveal that the sections located in the vicinity of the fixed edges and the mid-section of the cylinder undergo the highest stresses, at low and high pressures, respectively. Moreover, while the pipe undergoes an overall expansion due to the internal pressure, it experiences a bending moment that induces compressive stresses at the outer boundary, due to the fixed edge. The magnitudes of the radial deformation and the circumferential stress significantly grow by increasing the cylinder length and the nonlinearities in the cylinder responses and behaviors increase by increasing the cylinder length.

High pitch sweep rates in supersonic wind tunnel tests

A typical test in a high-Reynolds-number blowdown wind tunnel, such as the VTI T-38 facility in Belgrade, involves a model sweep in a range of angles of attack. Increasing pitch sweep rates can bring two-fold benefit. The angle-of-attack range can be extended in tests at high stagnation pressures with limited run time, or test time can be shortened for the desired angle-of-attack range in other tests, in both cases bringing significant energy savings. The potential effect of the increased pitch rates on measurement data in the VTI T-38 wind tunnel was investigated in a recent supersonic wind tunnel test campaign of a hypervelocity standard model. The Mach 2 tests were performed at pitch rates of 2, 3, 4, 8 and 12° per second. While the wind tunnel balance measurement data were not seemed to be affected, the base pressure data revealed a high dependency on changing pitch sweep rates. It was found that the high lag in pressure piping affected the measured base pressure and, consequently, the forebody axial force, which is an important fact to know when dealing with ‘base drag corrected’ supersonic data. The conclusions derived from the Mach 2 tests have been verified in the additional Mach 4 tests. The verification tests confirmed that, for the currently employed base pressure measurement system, reliable measurement results can be obtained in wind tunnel tests by applying pitch rates up to 3° per second. The recommendations for modifications of the base pressure measurement system have been given.

A Method for Monitoring Operation Status of Oil-immersed Transformer Based on the Baffle Angle Characteristic of Gas Relay

A gas relay in the transformer, an important non-electricity protection equipment, only triggers the stem leaf spring for the serious gas alarm when the baffle rotates to a certain angle, which cannot judge the transformer fault in the event of heavy gas before running state and fault development process, this paper puts forward a kind of based on gas relay panel corner of transformer running state monitoring methods. The partial structure of the gas relay is improved, and the baffle corner signal is extracted by installing a Hall sensor on the back of the baffle. On this basis, this paper develops a test stand capable of simulating the baffle characteristics of gas relays at different fault energies. Subsequently, the baffle angle variation law under different fault energies is studied, and the influence of pipe pressure and pipe flow rate on the baffle angle is given. The results show that, based on this improved gas relay, the real-time baffle angle information can reflect the internal operating state of the transformer and provide an effective method for transformer operating condition monitoring.

Optimizing pressurized agriculture pipe network through simulation modeling techniques in home gardening in Vavuniya area of Sri Lanka

Home gardening is identified as one of the remedial measures for food security issues caused by the economic downfall in Sri Lanka. Home gardening contributes to household food security by providing direct access to food. Further, it is also an important source of supplementary income for households. The appropriate function of a pressurized agriculture pipe network system is vital to supply sufficient quantity of water to the plants at sufficient pressure through the sprinkler output. Despite this, very few computer simulation techniques studied the optimization for the case of the home gardening agricultural pipe system. In this study, the WaterGEMS V8i software simulator was used and hydraulic analyses were conducted to design an optimal pressurized agriculture pipe network suitable for home gardening in the Vavuniya area. The water flow rate at sprinkler outlet points for chilli and onion were considered 600 L/h and 325 L/h respectively. The total available land area for home gardening was considered as 50 perches in this study. Fifteen models were developed for different combinations of land use for chilli and onion cultivation. The hydraulic parameters such as nodal pressure, flow velocity, flow rate and head requirement were analyzed under steady-state simulation by using the Hazen-Williams friction method. The proposed simulation model was calibrated and validated by using a previous study. The result revealed that all of the nodes in the system are operating above the threshold pressure limit of 2 bars. It was found that a combination of 20% land (10 perches) for onion and 80% land (40 perches) for chilli required the highest power pump capacity of 3.5 kW. The power of the water pump for chilli only and onion only was positively correlated with the cultivated land extent and R² values were observed to be 0.9991, and 1.0 for chilli and onion respectively. The flow velocity in all pipes was above the minimum level of 0.5 m/s eliminating silt deposition and below the maximum level of 2.0 m/s avoiding the water hammer issues. The proposed pressurized agriculture pipe network design shall be used for modelling of pipe network for home gardening with different crop types by changing the model input parameters by using the WaterGEMS V8i computer simulator.

Investigation of Sealing Performance with Bolted Flange Joints with Gasket using FEA Method

In pressure vessel and pipe systems, gasketed flange joints are quite frequent and are also used in oil and gas wellheads and trees as spool end connections. Flanges are most commonly employed when a joining or disassembling junction is required. The process industry has long been concerned about leakage in gasketed flanged junctions. The installation and stress factors of a gasketed flange joint directly affect its sealing effectiveness. API 6A type 6B flange with a maximum pressure rating of 20,000 psi is examined in this study using API design procedures. Due to the symmetricity of the 8 bolted flange, a 45 section is taken for analysis. The findings of a parametric analysis of flange behaviour and bolt stresses are investigated by altering the bolt preload and internal pressure while keeping other flange independent variables constant.

Development and performance of INCONEL® alloy 740H® seam-welded piping

INCONEL® alloy 740H® is an age-hardenable nickel-based alloy approved for pressure vessels and piping within ASME Section I, VIII, and B31.1. Currently, the code applies a weld strength reduction factor (WSRF) of 0.7 to the allowable stresses for longitudinal seam welds in the time dependent creep regime. In this work, a full-scale seam weld was successfully produced using typical industrial practices. The component was solution heat-treated and aged after fabrication to improve the performance of the weldment. Tensile, bend, impact, and low-cycle fatigue tests showed the component met all the specification requirements and elevated temperature properties were within base metal expectations with failures predominately in the weld metal. Long-term creep tests, including large samples more representative of the entire weldment, were fabricated and tested to times in excess of 10,000 h at multiple temperatures. Analysis of the creep data supports a WSRF of 0.9 for the solution annealed + aged weldments in contrast to the WSRF of 0.7 currently applied to welded + aged weldments. Metallurgical analysis shows that the solution annealing causes recrystallization of the weld metal and reduces the chemical compositional and microstructural gradients in the weldments resulting in acceptable short-term performance. In long-term creep, evidence for coarsened zones in the weldments due to discontinuous coarsening reactions were identified as the mechanism leading to accelerated creep damage formation in the weld metal and sample failure.

Case Study: Successful Application of a Novel Gas Lift Valve in Low Pressure Wells in Fuling Shale Gas Field

The Fuling shale gas field is facing a rapid gas production decline due to heavy liquid loading issues. Given the condition that most wells are located at remote areas in the mountains, the traditional gas lift methods that require either fixed compressor or skid-mounted gas lift trucks do not seem feasible and occur high operation costs. A new type of gas lift valve that can be opened or closed at a low valve dome pressure indicates the high sensitivity to low production pressure. Thus, the piping line pressure can be utilized to activate the valve due to its new advantages. In addition, the specially designed structure of the gas lift valve can be activated via pressure increases in the tubing to create a channel between the tubing and annulus. The valve that previously functioned as a dummy valve was then switched to a gas lift valve. Field application results show that all wells were successfully restarted by only utilizing the low piping pressure, and loaded liquid was lifted with gas production at an incremental rate that reached up to 27.4 × 10 kscm/d per well. Fewer slickline operations were conducted to replace the dummy valve. The result of the application shows that the new type of gas lift system has a wide range of application prospect for low pressure wells, especially for shale gas wells.

Development of an improved limit pressure equation for structurally distorted thin-walled pressurized 90 degree pipe bends

PurposeThis paper aims to present the approximate limit pressure solutions for thin-walled shape-imperfect 90° pipe bends. Limit pressure was determined by finite element (FE) limit analysis with the consideration of small geometry change effects.Design/methodology/approachThe limit pressure of 90° pipe bends with ovality and thinning has been evaluated by geometric linear FE approach. Internal pressure was applied to the inner surface of the FE pipe bend models. When von-Mises stress equals or just exceeds the yield strength of the material, the corresponding pressure was considered as the limit pressure for all models. The current FE methodology was evaluated by the theoretical solution which has been published in the literature.FindingsOvality and thinning produced a significant effect on thin-walled pipe bends. The ovality weakened pipe bend performance at any constant thinning, while thinning improved the performance of the bend portion at any constant ovality. The limit pressure of pipe bends under internal pressure increased with an increase in the bend ratio and decreased with an increase in the pipe ratio. With a simultaneous increment in bend radius and reduction in wall thickness, there was a reduction in limit pressure. A new closed-form empirical solution was proposed to evaluate limit pressure, which was validated with published experimental data.Originality/valueThe influences of structural deformation (ovality and thinning) in the limit pressure analysis of 90° pipe bends have not been investigated and reported.

A Creep Constitutive Model, Based on Deformation Mechanisms and Its Application to Creep Crack Growth

In this paper, a constitutive model, based on the creep deformation mechanism in P91 steel, under a wide range of stress levels, was established and embedded into finite element software. The accuracy and reliability of the model was verified by comparing the simulation of uniaxial creep tensile test results and the experimental data under different stress levels for P91 steel at 600 °C. The creep crack growth behavior of P91 steel, under a wide range of stress levels was simulated using a ductility-exhaustion-based damage model, combined with the stress-dependent creep ductility model, and the predicted creep crack growth (CCG) rates were compared with the experimental data. Finally, the established model was used to predict the CCG behavior for the pressurized pipes with axial surface cracks. The results show that the constitutive model, established on the basis of the creep deformation mechanism, agrees better with the experimental data than other constitutive models. The CCG rate varies at different direction angles θ for the axial surface cracks. The direction angle θ corresponding to the maximum creep crack length is about 33°, when the internal pressure exceeds 10 MPa. The initial crack shape (a0/c0) = 1, and it does not change with different initial crack depth ratios (a0/t). The established constitutive model can be well used in CCG life analyses and designs of high-temperature structures.

Real-time self-monitoring and smart bend recognizing of fiber-reinforced polymer composites enabled by embedded magnetic fibers

Multifunctional composites realized by embedded sensing materials draw much attention to structural health monitoring applications. However, conventional composites are not able to recognize their strain behavior, meanwhile, the embedded sensing elements lack compatibility with host structures and inevitably cause the degradation of the properties. Herein, flexible and micro magnetic fibers (MFs) as embedded sensing units enable conventional composites to possess intelligent self-sensing ability. Combining impedance measurement with mechanical test, the sensing mechanism of MFs is elucidated that the stress-sensitivity of MFs derives from the natural ferromagnetic resonance induced by its intrinsic magnetic anisotropy. The uniaxial tensile and cyclic loading are executed to investigate the electromechanical response ability and monitoring stability of MF monofilament as a sensing element. Then, MFs are embedded into glass fiber (GF) reinforced composites to realize multi-functional MF/GF composites with self-sensing capability, which also do not deteriorate their original mechanical properties. The MF/GF composites inherit high strain sensitivity with a maximum gauge factor of 376, and simultaneously exhibit the ability of bending orientation recognition and damage detection. The MF as a low invasive and embedded functional fiber has great potential to realize self-sensing ability of fiber-reinforced composites, which find particular priority application in pressure vessels and pipes.

Simulasi Distribusi Suhu Tekanan dan Kecepatan Gas Dalam Pipa Pirolisis Pada Reaktor - Kondensor

In pyrolysis technology there are various geometric factors that affect the results of pyrolysis, one of which is the connecting pipe between the reactor and the condenser. In this study, simulations were carried out with simscale software to analyze the temperature, pressure and gas velocity in the pyrolysis pipe as the length of the pipe increases. The material used is stainless steel AISI 304. This research begins by determining the dimensions and materials of the pyrolysis pipe, the length of the pipe and the input temperature. The length of the pipe was varied by 1.5 m, 1.75 m and 2 m, with initial temperature variations of 450°C and 550°C, respectively. From the simulation result, Increasing of the pipa’s length then the heat transfer will be close to the optimum condition. So that the output temperature, pressure and velocity will be lower. This happens because the length and diameter of the pipe affect the output. From the simulation results, pipe lengths of 1.5 m, 1.75 m, 2 m with input temperatures of 450°C and 550°C obtained the best results for a pipe length of 2 m with an input temperature of 450°C.

Investigation of refrigerant pipe pressure drop and charge reduction of mobile air conditioning units with R1234yf

In this study, the pressure drop of automotive refrigerant pipes with the refrigerant R1234yf is investigated in detail. For this purpose, 1D and 3D simulations are compared with respect to prediction accuracy using liquid lines from a production car. It is shown that for a combined approach of the methods a very good agreement with the measured values can be obtained, whereas simplified modeling of the line as a straight pipe of equal length significantly underestimates the experimental values. The transition pieces between the pipe and the hose are of particular importance, since they account for up to 85% of the total pressure drop and therefore result in major errors if neglected. If hoses were eliminated, the lines could be designed smaller, resulting in a charge reduction of up to 56%.

A noise-based high-resolution time-reversal method for acoustic defect localization in water pipes.

Pressurized water supply pipeline systems (PWSPS) are quintessential to human development and sustenance, but suffer a multitude of unresolved defects (i.e., leaks, blockages, etc.) due to aging and inaccessibility. In this paper, the ubiquitous high-frequency background noise in PWSPS is harnessed to introduce a high-resolution, passive defect detection technique. The relation between the acoustic Green's and cross correlation functions for a pressurized water pipe is derived for the case of high frequency waves, i.e., acoustic wavelengths smaller than the pipe diameter. This relation is subsequently used to formulate a time-reversal technique for localizing anomalies such as small variations in pipe wall impedance and through-wall defects (i.e., leaks). It is shown that the derived relationship between the cross correlation and acoustic Green's functions enables very accurate defect detection and localization by measuring the background noise at two locations along a pipe. This is an important result given that (i) there is limited access to buried PWSPS to conduct high-frequency active defect detection, and (ii) traditional methods to actively probe pipes (e.g., valve maneuverer) are low-resolution (tens to hundreds of meters) and often result in pipe overloading and fatigue.

Simulation of changes in hydraulic characteristics of pressure pipes depending on temperature

Introduction. Reducing the hydraulic resistance of the inner walls of pressure pipelines made of various materials is an urgent task in the field of pipeline transport, as it allows you to save electricity when transporting liquids. The solution of such problems is possible with the use of physical and mathematical modeling of the operation of pipelines under changing temperature conditions in wide ranges of both the transported medium and the surrounding environment. Physical modeling involves conducting experimental studies of the process of transporting water through pipelines with the identification of the dependence of changes in the hydraulic characteristics of alternative pipe materials on the temperature factor. The goal of modeling hydraulic characteristics depending on temperature is achieved by conducting pilot experiments on a hydraulic stand, as well as using an automated calculation program, where the work of the production system is simulated.
 
 Materials and methods. Materials for scientific research are pipes made of polyethylene (PE). The method of research is to conduct experimental and computational and analytical work.
 
 Results. The result of the work is presented by a comprehensive analysis of experimental and computational and analytical data on hydraulic and energy calculations for polyethylene pipes, taking into account the temperature conditions of operation of pipeline networks and the transported medium.
 
 Conclusions. Mathematical dependences describing the change in pressure losses from the flow rate for the corresponding temperatures of the pipe wall and the transported water are obtained. On the basis of the use of an automated complex, boundary values of ambient temperatures and transported water have been established, allowing for an assessment of electricity consumption.

Throttle and expansion characteristics of supercritical carbon dioxide during its venting

Supercritical CO2 has important applications in the fields of power cycle generation systems and carbon capture, utilization and storage (CCUS). The venting equipment represents a fundamental pressure-relief method for the purpose of depressurizing sections of those systems for inspection, maintenance or repair. The extremely low temperatures, dry ice blockage and overpressurization will appear in the system due to the throttling and expansion effect during venting. Meanwhile, the released CO2 may cause the exposure for the high density gaseous CO2, solid CO2 particles and cryogenics to the people in the venting area. The study of flow characteristics during CO2 venting is absolutely essential for assessing the hazard probability of dry ice formation and the blockage of relief valves during emergency or routine operational venting. In this paper, the theoretical analysis and experimental tests were conducted to study the throttle and expansion characteristics through the elbow, valve and orifice during straight vertical venting of supercritical CO2 with a 258 m long, 233 mm inner diameter pipeline system. The pressures and temperatures inside the main pipe and vent pipe, and the temperatures near field region were recorded during venting. After the valve was opened, the pressure in the vent pipe rose rapidly, and the rising range decreased with the decrease of the distance from the orifice. The temperature drops of CO2 were obvious after supercritical CO2 passed through the bend, the valve and the orifice. The supercritical CO2 in the main pipe changed into gas-liquid two-phase, and the liquid CO2 were produced in the vent pipe due to the throttling expansion effect. The CO2 temperature near the orifice were in quasi steady state after reaching the lowest value due to the continuous vaporization of liquid-phase CO2 and sublimation of dry ice particles, accompanied by the air entrainment process.

Leak identification in non-pressurized concrete pipelines by the use of geophysical methods

The production of treated water is a social service and leakages are also related to issues of sustainability of water resources. Water distribution losses can reach 40% in certain parts of Brazil and are common even in European countries, where, on average, 23% of the water does not reach the final consumer. Different factors may cause leakage and there are several methods for leak detection. Most studies focus on estimative of loss quantification, without worrying about the failures' location, and on the problems of pressurized pipe in small diameters (< 1 m). This study aimed to determine the usefulness of the Ground Penetrating Radar (GPR) and Electrical Resistivity (ERT) in leak detection from failures of a concrete large (> 1 m) and unpressurized pipeline. Both methods were able to indicate soil zones with features related to water losses, which were previously identified by visual analyses of failures in the pipeline. The accuracy of these methods depends on environmental factors (soil moisture and granulometry) and the time of the leaking opening. In this study, the leak zones varied from 6 to 15 m in the horizontal and 2.5 m in the vertical direction. The geophysical technologies may be helpful to improve the management of water resources especially in areas with significant losses in the water supply system.

Ratcheting response and boundary of austenitic stainless steel in a pressurized straight pipe subjected to in-plane bending cycles

Ratcheting behavior of pressurized straight pipes made of Z2CND18.10 austenitic stainless steel alloy was evaluated under in-plane bending cycles and under displacement- and force-controlled conditions by means of the Ahmadzadeh-Varvani (A-V) kinematic hardening rule. Ratcheting tests were conducted on straight pressurized steel pipes under bending cycles. Ratcheting response of steel pipes was also numerically simulated through inclusion of the A-V framework into ABAQUS software. The simulated ratcheting results along the axial and circumferential directions were found in good agreement with those of experimental values in the pressurized steel pipes. It was found that variables including the magnitude of internal pressure, cyclic bending moments, loading spectra, material properties, and FE element types, size and numbers noticeably impacted simulated ratcheting values. Ratcheting boundaries were further determined through coupling design codes of KTA/ASME and RCC-MR plus committee of three-dimensional finite element stress evaluation (C-TDF) with the A-V model. Both experimentally obtained ratcheting boundaries and those determined by design codes agreeably revealed the shakedown occurrence.