Accepted Manuscripts

Bipul Mondal and Ashutosh Dhar
J. Pressure Vessel Technol   doi: 10.1115/1.4038720
Burst pressure models are used for the fitness-for-purpose assessment of energy pipelines. Existing burst pressure models for corroded pipelines are unable to predict the pipe capacity correctly. In this paper, an improved burst pressure model is developed for corroded pipelines considering the burst pressure of flawless pipes and a reduction factor due to corrosion separately. The equation for the burst pressure of flawless pipe is revised based on the theory of the thick wall cylinder. A new model for the Folias factor is proposed for calculating the reduction factor. The new model for the Folias factor incorporates the depth of corrosion defect whereas the existing models do not account for the effect of the defect depth. The authors' earlier work revealed that the Folias factor depends on the depth of defect. The proposed burst model reasonably predicts the burst pressures obtained from finite element analysis conducted in this study and the burst test results available in published literature.
TOPICS: Pressure, Pipelines, Pipes, Corrosion, Finite element analysis, Cylinders
Martin P Blackman
J. Pressure Vessel Technol   doi: 10.1115/1.4038721
The required thickness of welding tees is neither specified in ASME B16.9 nor is a clear calculation method provided in Codes such as ASME B31.3. This can lead to uncertainty regarding the pressure capacity of a tee fitting, particularly one that has suffered from erosion or corrosion. Code methods including area replacement or pressure-area do not directly account for the effect which the curvature of the crotch region may have on the stress state in the tee. The approach adopted in this work is to liken the geometry of the tee crotch to the intrados of a torus or pipe bend. The shell theory applicable to the torus is adapted for the tee in order to derive a relationship for circumferential membrane stress. An equivalent tube radius is assigned by determining the local radius of shell curvature in the plane passing through the crotch centre of curvature. The actual stresses in the tee crotch are significantly reduced by the adjoining straight portions. This effect is difficult to quantify theoretically and has thus been investigated by means of FEA-based assessments. An empirical relationship was then established providing a conservative correlation between the theoretical stresses and the program calculated stress intensities.
TOPICS: Pressure, Welding, Stress, Shells, Pipe bends, Computational methods, Uncertainty, Corrosion, Erosion, Finite element analysis, Fittings, Geometry, Membranes
Tianlong Sun, Eyas Azzuni and Sukru Guzey
J. Pressure Vessel Technol   doi: 10.1115/1.4038723
Aboveground vertical steel storage tanks use stiffener rings to prevent their shell wall from buckling under wind loading. The existing stiffener rings design rules from API 650 standard is known to be overly conservative. This study investigates the possibility of modifying the design rules by reducing the required size of the top stiffener ring to the same size as the intermediate stiffener ring. In this study, we used finite element analysis (FEA) to perform linear bifurcation analysis (LBA) and geometrically nonlinear analysis including imperfections (GNIA) to obtain failure load of modeled tanks. The buckling pressure load was obtained to ensure it is larger than the design pressure. Moreover, the effects of higher strength materials, different buckling modes and various wind profiles were also studied to ensure the design suggested by this study is practical and universal to different situations. The results show that for cylindrical storage tanks which only need one intermediate stiffener ring, the size of the top stiffener ring can be set to the same size as the intermediate stiffener ring.
TOPICS: Stability, Wind, Storage tanks, Design, Buckling, Finite element analysis, Pressure, Stress, Steel, Strength (Materials), Bifurcation, Failure, Shells, American Petroleum Institute
Xu Liang, Zeng Cao, Hongyue Sun, Xing Zha and Jianxing Leng
J. Pressure Vessel Technol   doi: 10.1115/1.4038724
An analytical method and a semi-analytical method are proposed to analyze the dynamic thermo-elastic behavior of structures resting on a Pasternak foundation. The analytical method employs a finite Fourier integral transform and its inversion, as well as a Laplace transform and its numerical inversion. The semi-analytical method employs the state space method, the differential quadrature method (DQM) and the numerical inversion of the Laplace transform. To demonstrate the two methods, a simply-supported Euler-Bernoulli beam of variable length is considered. The governing equations of the beam are derived using Hamilton's principle. A comparison between the results of analytical method and the results of semi-analytical method is carried out, and it is shown that the results of the two methods generally agree with each other, sometimes almost perfectly. A comparison of natural frequencies between the semi-analytical method and the experimental data from relevant literature shows good agreements between the two kinds of results, and and the semi-analytical method is validated. Different numbers of sampling points along the axial direction are used to carry out convergence study. It is found that the semi-analytical method converges rapidly. The effects of different beam lengths and heights, thermal stress, and the spring and shear coefficients of the Pasternak medium are also investigated. The results obtained in this paper can serve as benchmark in further research.
TOPICS: Thermoelasticity, Laplace transforms, Springs, Shear (Mechanics), Thermal stresses, Hamilton's principle
Sergey Vinogradov, Thomas Eason and Mark Lozev
J. Pressure Vessel Technol   doi: 10.1115/1.4038726
Many piping networks in processing plants, such as refineries, chemical plants, and electric power generation plants, are operated at elevated temperatures (= 250°F or 121°C). Failure of these insulated high temperature pipes can cause a major disruption of plant operation. In addition to inspection during the regular plant shutdowns, processing industries are looking for ways to inspect and monitor these pipelines on-line to ensure safe operation of the plants.Permanent monitoring of high temperature structures would require addressing the following technical problems: supporting the sensor functionality at high temperatures, ensuring the probe durability, and maintaining good coupling of the probe to the structure. In this work, a probe utilizing magnetostrictive transduction was tested on a mockup at 200°C and produced a steady high amplitude signal over a period of 270 days. Probe performance parameters such as signal to noise ratio, data reproducibility, and sensitivity to anomalies are discussed.
TOPICS: Waves, Pipes, Magnetostrictive devices, Probes, High temperature, Signals, Electric power generation, Failure, Temperature, Sensors, Inspection, Signal to noise ratio, Durability, Pipelines
Enrico Deri
J. Pressure Vessel Technol   doi: 10.1115/1.4038725
Flow-induced vibrations of tubes in two-phase heat exchangers are a concern for the nuclear industry. EDF has developed a numerical tool, which allows one to evaluate safety margins and thereafter to optimize the exchanger maintenance policy. The software is based on a semi analytical model of fluid-dynamic forces and dimensionless fluid force coefficients which need to be evaluated by experiment. A test rig was operated with the aim of assessing parallel triangular tube arrangement submitted to a two-phase vertical cross-flow: a kernel of nine flexible tubes is set in the middle of a rigid bundle. These tubes vibrate as solid bodies (in translation) both in the lift and drag directions in order to represent the so-called in-plane and out-of-plane vibrations. This paper presents some extended physical analysis applied to some selected points of the aforementioned experiment series: the response modes are identified by means of operational modal analysis (i.e. under unmeasured flow excitation) and presented in terms of frequency, damping and mode shapes. Among all the modes theoretically possible in the bundle, it was found that some of them have a higher response depending on the flow velocity and the void fraction. Mode shapes allow to argue if lock-in is present and to clarify the role of lift and drag forces close to the fluidelastic instability.
TOPICS: Cross-flow, Modal analysis, Flow (Dynamics), Drag (Fluid dynamics), Mode shapes, Fluid-dynamic forces, Damping, Flow-induced vibrations, Heat exchangers, Vibration, Computer software, Porosity, Fluids, Locks (Waterways), Maintenance, Safety, Excitation, Nuclear industry
Hongsong Zhu
J. Pressure Vessel Technol   doi: 10.1115/1.4038655
Based on the unified analytical method of stress analysis for Tubesheet(TS) presented in Part I, theoretical and numerical comparison with ASME method are performed in this paper as Part II. Theoretical comparison shows that ASME method can be obtained from the special case of the simplified mechanical model of the unified method. Numerical Comparison results indicate that predictions given by the unified method agree well with finite element analysis (FEA), while ASME results are not accurate or not correct. Therefore, it is concluded that the unified method deals with thin TS of different type HEX in equal detail with confidence to predict design stresses.
TOPICS: Stress analysis (Engineering), Finite element analysis, Stress, Design
Andrew J. Slifka, Elizabeth S Drexler, Robert Amaro, Louis E Hayden, Douglas G Stalheim, Damian S Lauria and Nik W Hrabe
J. Pressure Vessel Technol   doi: 10.1115/1.4038594
A comprehensive testing program to determine the fatigue crack growth rate of pipeline steels in pressurized hydrogen gas was completed. Four steels were selected, two X52 and two X70 alloys. Other variables included hydrogen gas pressures of 5.5 MPa and 34 MPa, a load ratio, R, of 0.5, and cyclic loading frequencies of 1 Hz, 0.1 Hz, and 0.01 Hz. Of particular interest was whether the X70 materials would exhibit higher fatigue crack growth rates than the X52 materials. The American Petroleum Institute (API) steel designations are based on specified minimum yield strength, and monotonic tensile tests have historically shown that loss of ductility correlates with an increase in yield strength when tested in a hydrogen environment. The X70 materials performed within the experimental spread of the X52 materials in fatigue crack growth rate, except for the vintage X52 material at low (5.5 MPA) pressure in hydrogen gas. This program was developed in order to provide a modification to the ASME B31.12 code that is based upon fatigue, the primary failure mechanism in pipelines. The code modification is a three-part Paris law fit of the upper bound of measurements of fatigue crack growth rate of pipeline steels in pressurized hydrogen gas. Fatigue crack growth data up to 21 MPa (3000 psi) are used for the upper bound. This paper describes, in detail, the testing that formed the basis for the code modification.
TOPICS: Steel, Fatigue, Pipelines, Hydrogen, Fatigue cracks, Yield strength, American Petroleum Institute, Testing, Alloys, Stress, Ductility, Failure mechanisms, Pressure
Hongsong Zhu
J. Pressure Vessel Technol   doi: 10.1115/1.4038516
The stress analysis method for fixed tubesheet (TS) heat exchanger (HEX) in pressure vessel codes such as ASME VIII-1, EN13445 and GB151 are based on the classical theory of equivalent solid thin plate on elastic foundation in which the TS perforated area is replaced by an equivalent solid plate. Hence, the method as such precludes the pressure effects in TS perforations. The temperature gradient through the TS thickness direction was also ignored in these codes. In addition, aforementioned codes all assume a geometric and loading plane of symmetry at the midway between the two TSs so that only half of the unit or one TS is need be considered. In this study, the mid-plane symmetry assumption is discarded and all aforementioned situations are considered. Based on the classical thin plate and shell theoretical solution, a unified analytical method for stress analysis of fixed TS, floating and U-tube HEX is presented. Theoretical comparison shows that ASME method can be obtained from the special case of the simplified mechanical model of the unified method. Numerical Comparison results indicate that predictions given by the unified method agree well with finite element analysis (FEA), while ASME results are not accurate or not correct. Therefore, it is concluded that the presented method provides a unified method, dealing with thin TS of different types of HEX in equal detail, with confidence to predict design stresses.
TOPICS: Stress analysis (Engineering), Finite element analysis, Heat exchangers, Shells, Temperature gradient, Design, Pressure, Pressure vessels, Stress
Technology Review  
Kyle Gough and Daniel Peters
J. Pressure Vessel Technol   doi: 10.1115/1.4037197
Layered vessels have been in-service for many years which use layered construction. This construction technique has been employed since the 1930's. This generally involved either concentric plates or spirally wrapped plates to manufacture vessels with thick walls that otherwise would require very thick and heavy forgings. Long term asset management of these vessels, including non-destructive evaluation of the vessels welds and life assessment of the vessels due to operational cycling the vessels experience can be challenging. This paper is meant to address some of the challenges in managing these critical assets and provide a discussion on the application of state of the art techniques which are being applied today.
TOPICS: Design, Vessels, Fitness-for-service, Plates (structures), Construction, Nondestructive evaluation, Forgings (Products), Welded joints

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In