A Study of Integrity Changes in Structures During Exploitation

2002 ◽  
Author(s):  
Slavko Sebastijanovic ◽  
Milan Opalic ◽  
Nebojsa Sebastijanovic
Keyword(s):  
Stress State ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Critical Crack ◽  
Cylindrical Pressure Vessel ◽  
Before And After ◽  
Useful Life ◽  
Vessel Integrity ◽  
Main Components

Spherical and cylindrical pressure vessels are manufactured as welded structures, where cracks could be initiated/propagated during fabrication, pre-service hydro-test, service itself, service welding repair, or during the service hydro-test. In this case, fracture mechanics approach is necessary. This paper analyzes the stress state around cracks in the bottom head which is one of the main components in a cylindrical pressure vessel (radius of 1056 mm, wall thickness of 92 mm, pressure of 15.5 MPa and temperature of 454°C). Sizes of several detected cracks at the inner surface are determined by the NDE methods. Finite element analysis is performed to determine the stress zones in the vicinity of the most critical crack. Such analysis is done before and after the hydro-test. It will show the influence of the hydro-test on propagation of the existing cracks and fracture behavior of repaired cracks through the stress state analysis. Changes in material properties were analyzed. Results will be used to assess the pressure vessel integrity and estimate its useful life.

A Study on Fatigue Life Evaluation of Pressure Vessel Made of ASME SA240-316L Material Using Numerical Analysis

2019 ◽  
Vol 893 ◽  
pp. 1-5 ◽  
Author(s):  
Eui Soo Kim
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Pressure Vessel ◽  
Life Prediction ◽  
Pressure Vessels ◽  
Physical Damage ◽  
Element Analysis ◽  
Internal Damage ◽  
Life Evaluation ◽  
Fatigue Life Evaluation

Pressure vessels are subjected to repeated loads during use and charging, which can causefine physical damage even in the elastic region. If the load is repeated under stress conditions belowthe yield strength, internal damage accumulates. Fatigue life evaluation of the structure of thepressure vessel using finite element analysis (FEA) is used to evaluate the life cycle of the structuraldesign based on finite element method (FEM) technology. This technique is more advanced thanfatigue life prediction that uses relational equations. This study describes fatigue analysis to predictthe fatigue life of a pressure vessel using stress data obtained from FEA. The life prediction results areuseful for improving the component design at a very early development stage. The fatigue life of thepressure vessel is calculated for each node on the model, and cumulative damage theory is used tocalculate the fatigue life. Then, the fatigue life is calculated from this information using the FEanalysis software ADINA and the fatigue life calculation program WINLIFE.

Study on the Stress Concentration at the Round Corners of Flat Heads in Pressure Vessels Subjected to Internal Pressure

1996 ◽  
Vol 118 (4) ◽  
pp. 429-433
Author(s):  
H. Chen ◽  
J. Jin ◽  
J. Yu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Internal Pressure ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Stress Index ◽  
Element Analysis ◽  
Approximate Formulas

Results from finite element analysis were used to show that the stress index kσ and the nondimensionalized highly stressed hub length kh of a flat head with a round corner in a pressure vessel subjected to internal pressure are functions of three dimensionless parameters: λ ≡ h/dt, η ≡ t/d, and ρ ≡ r/t. Approximate formulas for estimating kσ and kh from λ, η, and ρ p are given. The formulas can be used for determining a suitable fillet radius for a flat head in order to reduce the fabricating cost and to keep the stress intensity at the fillet under an acceptable limit.

Ways for Extending the Reactor Pressure Vessel Lifetime

2008 ◽  
Author(s):  
Milan Brumovsky
Keyword(s):  
Pressure Vessel ◽  
Nuclear Power ◽  
Pressure Vessels ◽  
Reactor Pressure Vessel ◽  
Integrity Assessment ◽  
Low Leakage ◽  
Vessel Integrity ◽  
Direct Use ◽  
Reactor Pressure ◽  
Lifetime Extension

Reactor pressure vessels are components that usually determine the lifetime of the whole nuclear power plant and thus also its efficiency and economy. There are several ways how to ensure conditions for reactor pressure vessel lifetime extension, mainly: - pre-operational, like: • optimal design of the vessel; • proper choice of vessel materials and manufacturing technology; - operational, like: • application of low-leakage core; • increase of water temperature in ECCS; • insertion of dummy elements; • vessel annealing; • decrease of conservatism during reactor pressure vessel integrity assessment e.g. using direct use of fracture mechanics parameters, like “Master Curve” approach. All these ways are discussed in the paper and some qualitative as well as quantitative evaluation is given.

Establishing Allowable Nozzle Loads

2011 ◽  
Author(s):  
William Koves ◽  
Elmar Upitis ◽  
Richard Cullotta ◽  
Omar Latif
Keyword(s):  
Finite Element Analysis ◽  
Pressure Vessel ◽  
Heat Exchangers ◽  
Pressure Vessels ◽  
Nozzle Design ◽  
Engineering Project ◽  
Element Analysis ◽  
Design Loads ◽  
External Forces ◽  
Design Pressure

Every engineering project involving the design of pressure equipment, including pressure vessels, heat exchangers and the interconnecting piping requires that the interface loads between the equipment and piping be established for the pressure vessel nozzle design and the limitations on piping end reactions. The vessel or exchanger designer needs to know the external applied loads on nozzles and the piping designer needs to know the limiting end reactions on any connected equipment. However, the final loads are not known until the piping design is completed. This requires a very good estimate of the piping end loads prior to completing the vessel or piping design. The challenge is to develop a method of determining the optimum set of design loads prior to design. If the design loads are too low, the piping design may become too costly or impractical. If the design loads are too high the vessel nozzle designs will require unnecessary reinforcement and increased cost. The problem of the stresses at a nozzle to vessel intersection due to internal pressure and external forces and moments is one of the most complex problems in pressure vessel design. The problem has been studied extensively; however each study has its own limitations. Numerous analytical and numerical simulations have been performed providing guidance with associated limitations. The objective is to establish allowable nozzle load tables for the piping designer and the vessel designer. The loads and load combinations must be based on a technically accepted methodology and applicable to all nozzle sizes, pressure classes, schedules and vessel diameters and thicknesses and reinforcement designs within the scope of the tables. The internal design pressure must also be included along with the 3 forces and 3 moments that may be acting on the nozzle and the nozzle load tables must be adaptable to all materials of construction. The Tables must also be applicable for vessel heads. This paper presents the issues, including the limitations of some of the existing industry approaches, presents an approach to the problem, utilizing systematic Finite Element Analysis (FEA) methods and presents the results in the form of tables of allowable nozzle loads.

Thermomechanical Creep Analysis of FGM Thick Cylindrical Pressure Vessels with Variable Thickness

2018 ◽  
Vol 10 (01) ◽  
pp. 1850008 ◽  
Author(s):  
Mosayeb Davoudi Kashkoli ◽  
Khosro Naderan Tahan ◽  
Mohammad Zamani Nejad
Keyword(s):  
Temperature Gradient ◽  
Differential Equations ◽  
Variable Thickness ◽  
Pressure Vessel ◽  
Shear Deformation Theory ◽  
Pressure Vessels ◽  
Mechanical And Thermal Properties ◽  
Creep Response ◽  
Cylindrical Pressure Vessel ◽  
Creep Analysis

In the present study, a theoretical solution for thermomechanical creep analysis of functionally graded (FG) thick cylindrical pressure vessel with variable thickness based on the first-order shear deformation theory (FSDT) and multilayer method (MLM) is presented. To the best of the researchers’ knowledge, in the literature, there is no study carried out into FSDT and MLM for creep response of cylindrical pressure vessels with variable thickness under thermal and mechanical loadings. The vessel is subjected to a temperature gradient and nonuniform internal pressure. All mechanical and thermal properties except Poisson’s ratio are assumed to vary along the thickness direction based on a power-law function. The thermomechanical creep response of the material is described by Norton’s law. The virtual work principle is applied to extract the nonhomogeneous differential equations system with variable coefficients. Using the MLM, this differential equations system is converted into a system of differential equations with constant coefficients. These set of differential equations are solved analytically by applying boundary and continuity conditions between the layers. In order to verify the results of this study, the finite element method (FEM) has been used and according to the results, good agreement has been achieved. It can be concluded that the temperature gradient has significant influence on the creep responses of FG thick cylindrical pressure vessel.

Verifying Structural Integrity of Repaired Cylindrical Pressure Vessels by Partitioning Method

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Husain J. Al-Gahtani ◽  
Mahmoud Naffa'a
Keyword(s):  
Pressure Vessel ◽  
Structural Integrity ◽  
Welded Joint ◽  
Test Validity ◽  
Pressure Vessels ◽  
Testing Method ◽  
State Of Stress ◽  
Cylindrical Pressure Vessel ◽  
Pressure Test ◽  
Alternative Test

Pressure vessels that undergo repairs are normally pressure tested to verify their structural integrity before returning into service. Conventionally, the entire vessel is pressure tested, according to the relevant construction code. In this paper, partitioning the pressure vessel is suggested as an equivalent alternative test arrangement, where pressure testing is limited to the zone where a repair has been performed. Use of such an arrangement would alleviate potential concerns associated with the conventional testing method. Procedures are provided to specify the position of the partition relative to the repair location, in order to maintain the state-of-stress to that achieved in a conventional pressure test. Validity of this approach has been demonstrated for a repaired full-circumferential welded joint in the wall of a cylindrical pressure vessel.

Optimal Shapes for Axisymmetric Pressure Vessels: A Brief Overview

2000 ◽  
Vol 122 (4) ◽  
pp. 443-449 ◽  
Author(s):  
Lei Zhu ◽  
J. T. Boyle
Keyword(s):  
Pressure Vessel ◽  
Limit Load ◽  
Pressure Vessels ◽  
Load Carrying Capacity ◽  
Element Analysis ◽  
Limit Pressure ◽  
Optimal Shapes ◽  
Load Carrying ◽  
Analysis System ◽  
Elastic Compensation Method

This paper describes how optimal shapes for axisymmetric pressure vessels can be established based on maximizing limit pressure. This type of problem has been rarely examined in the literature due to the difficulty of evaluating limit loads. However, the “elastic compensation method” is used to approximate the limit load using elastic analysis alone, which opens the possibility of studying shape optimization based on limit pressure. The basic procedure, using a commercial finite element analysis system, is described and three example problems are examined. The aim is to investigate how much of an increase in load-carrying capacity could potentially be achieved if nonstandard pressure vessel shapes could be employed in practice. Of course, this may not be possible, but the results described here do contribute to a better understanding of the role shape plays in providing strength to a simple pressure vessel. [S0094-9930(00)00304-8]

Second Marshall Study Group Report on PWR Pressure Vessel Integrity

1983 ◽  
Vol 105 (1) ◽  
pp. 52-57 ◽  
Author(s):  
L. M. Davies ◽  
L. Garne ◽  
J. G. Collier
Keyword(s):  
United Kingdom ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Atomic Energy ◽  
Study Group ◽  
The United Kingdom ◽  
Atomic Energy Authority ◽  
Group Report ◽  
Vessel Integrity

The Second Report of the Marshall Study Group, entitled “An Assessment of the Integrity of PWR Pressure Vessels,” was published recently by the United Kingdom Atomic Energy Authority. The Report considers the integrity of a 4-loop PWR pressure vessel as now made, from the best available materials and using the most modern fabrication practices.

Fibre Reinforced Composite Pressure Vessel Heads Subject to External Pressure

2017 ◽  
Author(s):  
Martin Muscat ◽  
Duncan Camilleri ◽  
Brian Ellul
Keyword(s):  
Pressure Vessel ◽  
Weight Ratio ◽  
External Pressure ◽  
Pressure Vessels ◽  
Design Codes ◽  
Element Analysis ◽  
Inelastic Analysis ◽  
Reinforced Composite ◽  
Composite Pressure Vessel ◽  
Composite Pressure Vessels

The increase in stiffness to weight ratio and relative ease of manufacturing fibre reinforced composite pressure vessels, have put such vessels at the forefront of technology. However only limited research and specific codes pertaining exclusively to composite pressure vessel design can be found in literature. The ASME Boiler and Pressure Vessel (BPVC) Section X Code and the European design codes EN 13121-3:2016 (GRP tanks and vessels for use above ground) together with EN 13923:2005 (Filament wound FRP pressure vessels — materials, design, manufacturing and testing) are some of the few known design codes applicable to composite pressure vessels. These codes utilise both design by rule (DBR) and design by analysis (DBA) methods. The authors believe that more studies along the DBA route would benefit the composite pressure vessel design community and make it more accessible to designers and engineers. A similar scenario has already been seen in the last 10 to 15 years for steel pressure vessel design codes when DBA based on inelastic analysis was introduced. In line with these thoughts, this study compares the different design methods to prevent buckling and applies finite element analysis (FEA) to analyse a hemispherical GFRP pressure vessel head subjected to external pressure. The effect of material damage and geometrical imperfections on the final collapse failure is examined and discussed.

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