Pipe Stress Analysis Research Articles

Improving safety design for gas pipeline installation via horizontal directional drilling: a pipe stress analysis approach

Horizontal Directional Drilling (HDD) has today emerged as a significant and efficient Horizontal Directional Drilling (HDD) has today emerged as a significant and efficient technique for installing pipelines for a variety of purposes, including the production of oil, natural gas, water, sewer, electrical, and telecommunications. Due to the complexity of the technology and the intricate interplay of numerous processes, the safety risks associated with process uncertainty are substantial. However, risk analysis for HDD projects is generally done using qualitative methods. One of the most common factors used for HDD risk assessment is Pipe Stress Analysis (PSA). In this article, a combination of material evaluation and PSA for HDD safety design is suggested to improve the risk analysis. The evaluation will commence with an assessment of the material, followed by an examination of the wall thickness. Subsequently, an analysis of HDD design and pipe stress will be conducted. Using 10-inch API 5L Gr. B pipe, the safety design was successfully tested for a gas pipe project. When using HDD, a natural bend value of no less than 415.3 meters must have a horizontal length of 168 meters. According to the curvature, the length of the entire pipe is 169.03 meters. The combined installation stress was less than 1, while the combined operation stress was 114.87 MPa. These two values met the criteria specified in the standard. Overall, those steps were able to ensure that the HDD installation design is safe for construction.

Test blanket modules piping systems calculation method according to RCC-MRx code

The ITER Test Blanket Modules (TBMs) are installed and operated inside the vacuum vessel (VV) at equatorial ports located within port plugs (PP). The Pipe Forest (PF) is a network of pipes connecting the Ancillary Equipment Unit (AEU) to the TBMs. Depending of the TBM, the Pipe Forest includes various piping system such as Water Coolant (350°, 188 bars), Helium Coolant (500°, 100 bars) Lithium Lead and Tritium Extraction System. During operating states, the Pipe Forest main function is to withstand loads in normal, incidental and accidental situations according to RCC-MRx code criteria (including design rules for mechanical components for fusion installations). It includes severe thermomechanical loadings due to the thermal expansion added to seismic and vertical displacements events. In addition, the PF layout must satisfy constructability in constraint environments and maximize the space available for man access, which constitutes a real challenge for design.Since no existing RCC-MRx post-processing tool exists off the shelves, a specific methodology for pipe stress analysis is being developed by ITER, CEA and ASSYSTEM. This methodology starts with a post-processing calculation tool of stresses and reaction forces for looping back into the structural calculation. Moreover, a specific extraction module from 3D model to processing tool allows the conversion of CAD data to calculation entry files. Finally, a feedback loop is also re-integrated into the core CAD model through an import module, enabling the tracking of displacements and evaluate the impact of incorporating pipe movements into the analysis.This paper describes the pipe stress analysis methodology and its application for Pipe Forest system design life cycle. It covers the historical evolution of the routing including introduction of expansion loops. More recently, it incorporates the integrated calculation of the entire port cell, spanning from the back of the TBM sets, up to the connection pipes of the vertical shaft.

Numerical and semi-empirical models for the stress analysis of flexible pipes tensile armors terminations within end-fittings

The tensile armors of flexible pipes are typically terminated in two configurations, i.e., hook and pigtail, essential to guarantee the tensile armors’ anchorage in the pipe's end-fitting. However, despite its importance for the secure operation of flexible pipes, few works have dealt with the mechanical analysis of these terminations. Hence, this work proposes numerical and semi-empirical models to study the stresses induced on them by operational and extreme loading. Two- and three-dimensional finite element (FE) models are initially proposed, and their advantages and limitations in estimating local stiffness, stresses, and associated failure modes are highlighted. The initial analyses indicated that the two-dimensional model underestimated the terminations’ stiffness, while the detailed three-dimensional model required significant computational effort. However, a simplified three-dimensional model achieved the best compromise between accuracy and computational effort. In common, all models indicated that the hook termination failure is due to a pullout mechanism, while the pigtail induces the tensile armor steel rupture. After that, the simplified three-dimensional model was employed to conduct a parametric study involving several physical and geometric characteristics of the terminations. The importance of these parameters was evaluated using the Design of Experiment (DoE) technique, leading to semi-empirical equations to predict the maximum stresses induced in the terminations due to an axial load imposed on the tensile armor. Finally, the semi-empirical equation obtained for the hook termination was verified using previously presented full-scale experimental test results, showing good agreement.

Failure of 24 Inches Blowdown Tower Inlet Nozzle Due to Cyclic Surge Forces

Blowdown tower is one of the equipment in closed blowdown system (CBS) in Delay Coker unit in petroleum refinery. The primary intended function of the CBS is to flush out hydrocarbon vapours from coke drum using high pressure steam into blowdown tower. The system is operating in batches and cycles, due to constant operation at various temperature, pressure, and conditions, components are susceptible to various of failures including thermal fatigue, crack, corrosion, and others. Crack incident was observed on the welding of blowdown tower nozzle that connected to closed blowdown system (CBS) piping after 11 years of operation. This paper aims to study the structural integrity and risk level of the CBS system in relation to liquid level in receiving tower (blowdown tower). Dynamic piping stress analysis and Finite Element Analysis (FEA) was conducted on this line and blowdown tower nozzle to evaluate the overall material behaviour and assessed the risk of failure. The acceptance criteria of the analysis were set to be based on ASME VIII-Division 2 part 5.2.2 (Elastic Stress Analysis Method) and ASME II-part D. Findings from FEA shows that the failure occurred on the blowdown tower nozzle was due to surge pressure impact from high pressure steam flow to obstructed high liquid elevation at the inlet nozzle. The high surge pressure that happened near the nozzle has caused the stress to exceed allowable level thus initiated the crack in cyclic/ batch service. It is recommended that petroleum refinery to continuously maintain the blowdown tower level below nozzle to prevent similar phenomenon to happen in future.

Actual Stress Analysis of Small-Bore Butt-Welded Pipe by Complementary Use of Synchrotron X-Rays and Neutrons

Residual stresses in astresses in small-bore butt-welded pipe of austenitic stainless steel have never been measured. It is difficult to obtain a detailed residual stress map of the root welded part, because the gauge volume in neutron diffraction is large. The stress evaluation of the welded part by synchrotron X-rays was also difficult due to the dendritic structure. In this study, a double exposure method (DEM) with high-energy synchrotron X-rays was applied to measuring the details of the residual stress of the welded part, and we succeeded in obtaining the detailed axial and radial stress maps of the root welded part of the plate cut from the welded pipe, though the stress map was under the plane stress condition. The hoop stress map of the butt-welded pipe was obtained using the strain scanning method with neutrons under the triaxial stress state. The axial and radialradius stress maps under a triaxial stress state were made up using the complementary use of the synchrotron X-rays and neutrons. As a result, the detailed stress maps of the root welded part of the butt-welded pipe were obtained. The result of the actual stress analysis sufficiently explained the initiation and propagation of SCC.

The design and construction of divertor primary heat transfer system for EAST Tokamak

The Experimental Advanced Superconducting Tokamak (EAST) had been under major upgrading from 2020 to 2021 in China. In this campaign of major upgrading, the new lower tungsten divertor is successfully installed to achieve the targets of long pulse and high β H-mode plasma operation. High temperature and high pressure Divertor primary heat transfer system (DIV PHTS) is also developed to remove the plasma deposition heat load on the Divertor. This paper presents a description of the design and construction of DIV PHTS for EAST Tokamak. Starting from the requirements specified in the Technical Specifications of DIV PHTS, the process to meet the Divertor cooling and baking requirement is designed and validated by the supported thermal-hydraulic analysis. Then, the piping stress analysis under different types of load combinations is performed to verify the structural design requirements. General layout design is also performed based on the component requirement and the allocated space in the EAST Tokamak hall. Finally, the procurement and test of the system main equipment is also given.

Structural design and analysis of EAST TCWS pipeline

EAST (Experimental Advanced Superconducting Tokamak) Tokamak Cooling Water System (TCWS) provides cooling and baking functions to the in-vessel component and vacuum vessel of the tokamak. A section of high stiffness pipes in the system is difficult to compensate for the reaction from thermal expansion caused by high temperature nitrogen baking operation. Under seismic loads, additional acceleration may have serious impact on piping network and produce more complex reactions to equipment.This paper describes EAST Tokamak Cooling Water System (TCWS) system layout design, piping support design, methodology and results of pipe stress analysis. The sustained and occasional load responses of piping network are analyzed, natural frequencies of the Baking system pipes are calculated. The calculation results are verified by the experimental data pipeline displacement at 200°C. The process piping code ASME B31.3 is used for pipe stress analysis. The least available stress margin is 7% and the calculated stresses are in acceptable limit. The maximum displacement of the pipeline is within the requirements of the spatial layout. The results would be used in further loop optimization and analysis of fire case.

IEA-R1 Renewed Primary System Pump B1-B Nozzles Stress Analysis

The present report is a summary of the structural analysis of the pump nozzles applying the finite element method by using the Ansys computer program. The IEA-R1 RR is an open pool-type moderated and cooled by light water using beryllium/graphite as a reflector. The reactor can reach up to 5MW of thermal power cooled by the primary and secondary systems. The primary coolant system consists of a piping arrangement, a decay tank, two pumps, and two heat exchangers. The primary pump B1-B presented some failures requiring refurbishment by a new one. The pump used in the IEA-R1 must meet the requirements inherent to the nuclear installation, in addition to the operational requirements for rotating equipment, such as flow and pressure, and structural integrity of the body and nozzles. The supplier specified the type of pump suitable for the System. The pump furnished granted mechanical allowable loads for the nozzles that were lower than the loads imposed by the piping on the nozzles. To enable the installation of the pump in the primary circuit, new support was inserted in the piping system next to the pump minimizing efforts and deformations. A piping stress analysis was carried out to obtain the new efforts imposed on the nozzles. For validation of the motor pump set, a verification of the nozzles was done compared with API 610 standard loads, and the allowable loads of the provider. Finally, a structural analysis of the pump nozzles with the new loads was developed using the finite element method. The calculated stresses meet the limits prescribed by the ASME code; therefore, the new B1-B Pump is approved for operation at the IEA-R1 Nuclear Research Reactor primary circuit.

Stress analysis and thermal performance of ultra-thin heat pipes for compact electronics

The ultra-thin heat pipe (UTHP) has been established as a highly effective thermal control component for cooling electronics with large heat generation rate and limited space for cooling. However, UTHP has been severely limited in application because of buckling or breaking on the shell of UTHP during the flattening process. In this study, a series of high-accuracy UTHPs with a thickness of 0.38–0.47 mm were fabricated by the phase-change flattening process. An internal vapor pressure model of the heat pipe during flattening was constructed and the heat transfer performances of UTHPs under different working conditions were experimentally investigated. According to the internal vapor pressure model, the pipe wall stress after flattening was the first to reach the yield strength of the material, and the upper limit heating temperature of UTHPs decreased with the decrease of flattened thickness. The maximum heat transfer capacity decreased with the decreased flattened thickness. UTHP with a thickness of 0.47 mm has a maximum heat transfer capacity of 4.5 W and a minimum thermal resistance of 0.64 °C/W. Moreover, gravity appeared to impose minimal effects on the heat transfer performance of UTHPs and the heat transfer capabilities of the UTHPs fluctuated within ±0.5 W for different gravity orientations.

Theoretical Study on Thermal Hydraulic Expansion Process of Stainless Steel Lined Clad Pipe

Abstract The stainless steel lined clad pipe (SSLCP) can be widely used in different fields. Industrial SSLCP are generally manufactured by the cold hydraulic expansion (CHE) method which requires high hydraulic pressure and good sealing property. The interlayer bonding force is difficult to obtain by the CHE when there is little difference between the yield strengths of inner and outer pipes. Furthermore, the hydraulic expansion process nearly cannot be achieved when the yield strength of inner pipe is higher than that of outer pipe. The thermal hydraulic expansion (THE) method can overcome these difficulties. In this paper, the graph method was adopted to analyze the THE principles for “inner strong and outer weak (ISOW)” and “outer strong and inner weak (OSIW)” pipes. The effective hydraulic expansion criterion conditions of SSLCPs were proposed and can be used as basis of clad pipe material matching and forming process selection. Through the stress and strain analysis of inner and outer pipes during THE process, the deformation coordination conditions of elastic deformation and thermal deformation of the inner and outer pipe were established. The correlation between the residual contact pressure p*c, the hydraulic expansion pressure pi, and the effective temperature difference ΔTe were derived. The calculation formula of the maximum expansion pressure pimax and the minimum expansion pressure pimin was obtained. The maximum heating temperature of outer pipe was also derived. Furthermore, the finite element analysis (FEA) method was adopted and simulated results verify the feasibility and applicability of the theory study.

Actor-Critic reinforcement learning for optimal design of piping support constraint combinations

Piping systems operating under various conditions may cause extremely unstable structural stress and deformation, leading to permanent deformation and damage to the piping structure, bringing about serious safety problems. So, piping stress analysis shall be performed along with proper design. Meanwhile, structural instability due to local stress concentration, which is one of the main interests of stress analysis, can be resolved through the appropriate selection of constraint conditions of piping supports at a relatively low cost. However, selecting an appropriate combination of constraints is time-consuming because analysis results are derived through many iterations. In addition, there is a big difference in the quality of the final design according to the experiences and capabilities of engineers. As a solution to this situation, this paper introduces a reinforcement learning strategy for deriving the optimal combination of constraints of piping supports. Primarily, we suggest applying the Actor-Critic(AC) learning algorithm for this problem, which is a type of reinforcement learning that has recently been in the spotlight for this problem because it can evaluate an action policy directly by the on-policy method inside the AC algorithm. During learning, it traces the correspondence between State and Action and suggests appropriate labeling criteria. We present the suitability and usefulness of the algorithm applied to the pipe stress analysis procedure through comparative verification between the results derived from the well-trained AC model and the results accomplished by engineers.

Stress analysis of double-walled pipes undergone mechanical drawing process

Double-walled metal pipes are important components for heat exchange and liquid transportation. They can be manufactured by mechanical drawing of two concentric pipes. In this work, a mechanical model is developed to analyze the stress state evolution during the manufacturing process, and the criterion for forming the double-walled pipe was given under the ideal elastoplastic and thick-walled assumptions. The model also encompasses the results deduced under the thin-walled assumption. Numerical simulations confirmed that the accuracy of the analytical model was within 5%. The application on actual steel materials with various parameters varied, including the wall thickness and initial gap, was analyzed. This work can provide theoretical support to industrial manufacturing procedures and help to reduce costs by eliminating required test procedures.

Recommendations for determining nonlinear Winkler spring parameters for buried steel pipe stress analysis applications

Permanent ground movements due to seismic fault rupture, ground subsidence or liquefaction-induced lateral spreading may result to failure of buried pipelines crossing the affected areas, due to the development of excessive bending and axial pipe strains. Verification of pipe integrity against such actions and design of mitigation measures is based on analyses with nonlinear beam-on-non-linear Winkler foundation models, where the soil reaction developing on a pipe as result of differential ground movements is modelled by means of elastoplastic springs. This note presents a new set of guidelines and expressions for determining the parameters of Winkler springs applicable to the analysis of steel pipes backfilled with sand and subjected to differential movement with a lateral, vertical-upwards and/or vertical-downwards component. The guidelines, collectively referred to as UoN recommendations, are accordingly employed in the parametric stress analysis of a buried steel pipe crossing an oblique seismic fault. Results of this parametric analysis demonstrate that adoption of the UoN recommendations in the analysis workflow results in considerably lower pipe axial and bending strains, compared to analyses based on current conservative methods, and thus more realistic and economical design solutions.

Pipe Stress Analysis of Pump System in Process Plant

Every process and LNG plants operate many pumps and compressors in the processing unit. Performing the pump stress Analysis is immensely critical. The Pump’s high vibration on the process plant will seriously affect the pipe and equipment’s smooth operation. The resonance effect between pipe and equipment will create a severe additional desecration. Before installation or formal process, we need to perform static analysis, and dynamic analysis (modal, forced response analysis) is mandatory for the pump system. The pump vendor must perform a Pulsation analysis on the piping system for reciprocating machinery subject to pulsation flow. In this study, flexibility analysis of pump piping system as per process piping code B31.3 using CAESAR-II programming followed by placing of diverse pipe supports. The support type and position of the supports as per the output get from static and dynamic examination. By the software analysis of CAESAR II, the efficiency of pipe flexibility and expansion of the piping system’s natural frequency is authenticating by include more oriented and load-bearing support to the elbow and Valve, which prevents the resulting of resonance successfully. The stress analysis, modal analysis, pulsation analysis, and vibration analysis method proposed in this paper will increase the lifespan and operation reliability of pipe and equipment.

Finite element analysis of 90 degree pipe elbow sustained stress indices

Paper deals in-depth with the topic of sustained stress indices applicable to 90° elbows based on non-linear finite element analysis models. A comprehensive overview of the existing literature sources is given in the first part of the paper, showing that there are little sources which deal specifically with this topic and that the ones that do exist result in important scatter of the results. As a result, more than few of the existing sources are non-conservative in their nature. Dedicated non-linear finite element studies have been performed on shell and solid models which are used in conjunction with the regression analysis in order to obtain explicit equations which can be used to calculate both in- and out-plane sustained stress indices in 90° pipe elbows, which can then be used in the typical pipe stress analysis. Newly proposed equations prove to be a good fit for the numerical data, showing little deviation as shown by the correlation parameters presented in the paper. Final part of the paper presents a dedicated section on the high wall thickness elbows and shows the relationship between elbow wall thickness and maximum stress location. It is shown that beyond certain thickness, the maximum stress location shifts from the typical failure location (i.e., side wall) to the locations which are not typically expected (i.e., intrados or even away from elbow). This shifting may have an important effect on the theoretical models which assume failure location.

Health-Monitoring Methodology for High-Temperature Steam Pipes of Power Plants Using Real-Time Displacement Data

We developed a health-monitoring methodology for high-temperature steam pipes that estimated the life prediction of creep–fatigue interaction by directly measuring the displacement of hot parts. Three different methods (boiler code, design stress, and operating stress) were used to estimate the stress of the high-temperature pipe system. As a theoretical approach, the German boiler standard code calculates the stress according to the pipe shape, while design stress, which is also called allowable stress, was determined by a function of the operating temperature. The operating stress was immediately calculated using the surrogate model, with maximum displacement measured using the 3D displacement measurement system. To achieve the surrogate model, the stress was estimated by the pipe-stress analysis under the given displacements, and the surface-response model was developed to relate the stress and displacement. We showed that those methods are efficient methods to predict the stress and are applicable in health-monitoring methodology. Finally, the creep life and the low-cycle fatigue life were investigated using the Larson–Miller parameter equation, as well as the Smith, Hirschberg, and Manson equations. Our proposed monitoring system can be used to predict the fatigue and creep life of high-temperature steam pipes in real time, and we believe that the system can be applied to actual maintenance in thermal power plants.

분기연결에서의 강성도 차이에 의한 변형률집중을 고려한 배관응력해석

배관응력해석은 탄성거동의 보 이론을 기반으로 한 선형해석으로 수행되어 빠르고 직관적인 결과를 얻을 수 있는 장점을 가지나 과변형거동이 적절하게 구현되지 않는 제한을 가지고 있다. 구조물 간에 강성도가 크게 차이가 나는 상황에서 열팽창에 의한 변형이 구조물 간에 균등하게 배분되지 않고 강성도가 작은 쪽으로 집중되는 변형률집중은 과변형거동의 대표적인 현상이다. 변형률집중은 탄성추종이라고도 하며 재질의 비선형특성에 의한 것으로 선형해석 시 주의가 필요하나 이를 평가하기 위한 방법은 Code에서 제시하고 있지 않다. 주배관과 분기배관이 연결되는 분기연결에서 주배관에 비해 상대적으로 강성도가 작은 분기배관은 변형률집중에 취약구간이다. 이러한 분기연결에 대해 선형해석 시 강성도 차이에 의한 변형률집중을 고려할 수 있는 방법을 제시하였다.

Shortcut Method for “L” and “Z” Pipe Bend Sizing

Abstract In the engineering practice, it may often prove necessary to provide quick and relatively accurate estimates of piping routing and material requirements in very early stages of a project. In these cases, there is typically no time to perform detailed pipe stress analysis in order to obtain accurate routing, which allows for sufficient piping system flexibility, and the designer is constrained to the use of rule of thumb approach and good engineering judgment. This approach, although often used, may prove challenging in many situations, one of which is establishing sufficient pipe loop dimensions. Method proposed by the authors in Jacimovic and Ivosevic (2020, “Shortcut Method for Pipe Expansion Loop Sizing,” ASME J. Pressure Vessel Technol. 142(4), p. 041505) provides a procedure for quick estimation of U loops, while the present procedure aims to provide additional procedures for estimation of L and Z bends, thus completing the circle of shortcut methods for quick estimation of expansion requirements of piping systems.

Application of Stress Analysis Software in Oil and Gas Pipeline

With the rapid development of China’s national economy, the development of the petrochemical industry is particularly rapid, high-temperature and high-pressure pipelines are widely used in the oil and gas storage and operation industries. The design level becomes the key to measuring whether a design unit can win in the fierce market competition, and one of the core technologies is the stress analysis of the pressure pipeline. CAESAR II pipeline stress analysis software is more popular in the international one of pipe stress analysis software. Its data input is simple and the graphic display is intuitive, which is easy for beginners to master, but also has a strong engineering practicality. This article will discuss the advantages and problems of CAESARII stress analysis software in practical applications, and use examples to perform relevant analysis.

ROUTING DESIGN ON THE PRIMARY COOLING PIPING SYSTEM IN PLATE-TYPE CONVERTED TRIGA 2000 REACTOR BANDUNG

In 2015, research activities to modify TRIGA 2000 Reactor Bandung fuel element from cylindrical to plate-type have been initiated. By using plate-type fuel elements, core cooling process will be altered due to different generated heat distribution. The direction of cooling flow is changed from bottom-to-top natural convection to top-to-bottom forced convection. This change of flow direction requires adjustment on the cooling piping system, in order to produce simple, economical, and safe piping route. This paper will discuss the design of suitable piping routing based on pipe stress and N-16 radioactivity. The design process was carried out in several stages which include thermal-hydraulic data of reactor core to determine the process variables, followed by modeling various pipeline routes. Based on available space and ease of manufacture, four possible alternative routings were determined. Four routings were produced and analyzed to minimize the amount of N-16 radioactivity on the surface of the reactor tank, prolonging the cooling fluid travel time to reach at least five times of N-16 half-life. Subsequent pipe stress analysis using CAESAR II software was conducted to ensure that the piping system will be able to withstand various loads such as working fluid load, pipe weight, along with working temperature and pressure. The results showed that the occurred stresses were still below the safety limit as required in ASME B31.1 Code, indicated that the designed and selected pipeline routing of primary cooling system in the Plate-type Converted TRIGA 2000 Reactor Bandung has met the safety standards.Keywords: TRIGA reactor, Cooling system modification, Pipeline routing design, Pipe stress analysis, N-16 radioactivity