Fitness-for-Service Evaluation of Thermal Hot Spots and Corrosion Damage in Cylindrical Pressure Components

2007 ◽  
Author(s):  
P. Tantichattanont ◽  
Seshu M. R. Adluri ◽  
R. Seshadri
Keyword(s):  
Hot Spots ◽  
Structural Integrity ◽  
Variational Principles ◽  
Elastic Shell ◽  
Corrosion Damage ◽  
Pressure Vessels ◽  
Alternative Methods ◽  
Linear Interaction ◽  
Reference Volume ◽  
Aspect Ratios

Thermal hot spots and corrosion damage are typical of damages occurring in pressure vessels and piping. Structural integrity of such components needs to be evaluated periodically to determine “fitness-for-service” of the components. In the present paper, three alternative methods for Level 2 FFS assessments (as defined by API 579) are proposed. They are based on variational principles in plasticity, the limit load multiplier m-alpha method, reference volume and the concept of decay lengths in shells. Decay lengths in the axial and circumferential directions for cylindrical shells are derived based on elastic shell theories. They are used to specify the reference volume participating in plastic action and the limit of what can be called “local” damage. Interaction between longitudinal and circumferential effects is investigated. A linear interaction curve is shown to give good estimations of “remaining strength factor” for damages of practical aspect ratios. The stretching and bulging effects due to the damage are also studied. The limit defining the threshold to dominance of stretching action is proposed by using an approximate equilibrium calculation based on yield-line analysis. The effectiveness of the proposed assessments are demonstrated through an example and verified by Level 3 inelastic finite element analysis.

Fitness-for-Service Evaluation of Thermal Hot Spots and Corrosion Damage in Cylindrical Pressure Components

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
P. Tantichattanont ◽  
S. M. R. Adluri ◽  
R. Seshadri
Keyword(s):  
Hot Spots ◽  
Structural Integrity ◽  
Variational Principles ◽  
Elastic Shell ◽  
Corrosion Damage ◽  
Pressure Vessels ◽  
Alternative Methods ◽  
Linear Interaction ◽  
Reference Volume ◽  
Aspect Ratios

Thermal hot spots and corrosion damage are typical of damages occurring in pressure vessels and piping. Structural integrity of such components needs to be evaluated periodically to determine “fitness-for-service” (FFS) of the components. In the present paper, three alternative methods for level 2 FFS assessments (as described in API 579) are proposed. They are based on variational principles in plasticity, the m-alpha method, the idea of reference volume, and the concept of decay lengths in shells. Decay lengths in the axial and circumferential directions for cylindrical shells are derived based on elastic shell theories. They are used to specify the reference volume participating in plastic action and the extent of what can be called “local” damage. Interaction between longitudinal and circumferential effects is investigated. A linear interaction curve is shown to give good estimation of the “remaining strength factor” for damage of practical aspect ratios. The stretching and bulging effects due to the damage are also studied. The limit defining the threshold to dominance of stretching action is proposed by using an approximate equilibrium calculation based on yield-line analysis. The effectiveness of the proposed assessments is demonstrated through an example and verified by level 3 inelastic finite element analysis.

Integrity Assessment of Spherical Pressure Components With Local Corrosion and Hot Spots

2006 ◽  
Author(s):  
Pattaramon Tantichattanont ◽  
Seshu Adluri ◽  
Rangaswamy Seshadri
Keyword(s):  
Lower Bound ◽  
Hot Spots ◽  
Structural Integrity ◽  
Hot Spot ◽  
Corrosion Damage ◽  
Pressure Vessels ◽  
Operating Conditions ◽  
Local Corrosion ◽  
Integrity Assessment ◽  
Spherical Pressure

Corrosion damage and hot spots are typical of damages that can occur in ageing pressure vessels and pipelines used in industrial processes. Internal and external corrosion could be the result of corrosive products stored inside or harsh environmental conditions on the outside. Hot spots are caused by damage due to loss of refractory lining on the inside wall of pressure components or due to maldistribution of flow containing catalyst and reactive fluids. The structural integrity of such ageing components needs to be evaluated periodically to establish the continued suitability of the vessels under operating conditions. The present paper develops a method for Level 2 (as categorized by API 579) structural integrity evaluations of spherical pressure vessels containing local corrosion damage or hot spot. The decay lengths for spherical shells subject to local damages have been studied based on stretching and bending effects using elastic shell theories so as to identify the reference volume participating in plastic action. A limit for “local” corroded spot or hot spot is defined by the size of damage that an onset of pure membrane action occurs inside the damaged area. The size of damage indicating the crossover from dominance of stretching effects on the damage behavior to that of bending effects is also presented. The lower bound recommended “remaining strength factors” for spherical pressure vessels containing corrosion or hot spot are formulated by application of Mura’s integral mean of yield criterion and the improved lower bound mα-multiplier. Three alternative recommendations are proposed. The effectiveness of the proposed methods is evaluated and demonstrated through illustrative examples and comparison with inelastic finite element analyses.

Integrity Assessment of Pressure Components With Local Hot Spots

2005 ◽  
Vol 127 (2) ◽  
pp. 137-142 ◽  
Author(s):  
R. Seshadri
Keyword(s):  
Hot Spots ◽  
Structural Integrity ◽  
Refractory Lining ◽  
Assessment Method ◽  
Pressure Vessels ◽  
Industrial Processes ◽  
Integrity Assessment ◽  
Piping Systems ◽  
Further Development ◽  
Level 2

Local hot spots can occur in some pressure vessels and piping systems used in industrial processes. The hot spots could be a result of, for instance, localized loss of refractory lining on the inside of pressure components or due to a maldistribution of process flow within vessels containing catalysts. The consequences of these hot spots on the structural integrity of pressure components are of considerable importance to plant operators. The paper addresses structural integrity issues in the context of codes and standards design framework. Interaction of hot spots, as is the case when multiple hot spots occur, is addressed. An assessment method, suitable for further development of a Level 2 “Fitness-for-Service” methodology, is discussed and applied to a commonly used pressure component configuration.

Integrity Assessment of Pressure Components With Local Hot Spots

2004 ◽  
Author(s):  
R. Seshadri
Keyword(s):  
Hot Spots ◽  
Structural Integrity ◽  
Refractory Lining ◽  
Service Evaluation ◽  
Assessment Method ◽  
Pressure Vessels ◽  
Industrial Processes ◽  
Integrity Assessment ◽  
Piping Systems ◽  
Level 2

Local hot spots can occur in some pressure vessels and piping systems used in industrial processes. The hot spots could be result of, for instance, localized loss of refractory lining on the inside of pressure components or due to a maldistribution of process flow within vessels containing catalysts. The consequences of these hot spots on the structural integrity of pressure components are of considerable importance to plant operators. The paper addresses structural integrity issues in the context of codes and standards design framework. The interaction of hot spots as is the case when multiple hot spots occur is addressed. An assessment method suitable for Level 2 “Fitness-for-Service” evaluation is discussed, and applied to a commonly used pressure component configuration.

Fitness-for-Service Methodology Based on Variational Principles in Plasticity

2004 ◽  
Author(s):  
H. Indermohan ◽  
R. Seshadri
Keyword(s):  
Lower Bound ◽  
Hot Spots ◽  
Variational Formulation ◽  
Variational Principles ◽  
Limit Load ◽  
Pressure Vessels ◽  
Load Estimation ◽  
Estimation Technique ◽  
Simplified Procedures

A variational formulation in plasticity has been used to develop improved limit load estimation technique, such as the m-alpha method. Lower bound limit load estimates are especially germane to design and fitness-for-service assessments. The concept of “integral mean of yield” has been applied to problems involving locally thin areas (LTA) and local hot spots in the context of industrial pressure vessels and piping. Simplified procedures for “fitness-for-service” assessment, suitable for use by plant engineers, have been developed. The results are compared with the corresponding inelastic finite elastic analyses.

Fracture Analysis of the Heat-Affected Zone in the NESC-1 Spinning Cylinder Experiment

1999 ◽  
Vol 121 (1) ◽  
pp. 1-5 ◽  
Author(s):  
J. A. Keeney
Keyword(s):  
Thermal Shock ◽  
Heat Affected Zone ◽  
Large Scale ◽  
Structural Integrity ◽  
Plastic Material ◽  
Pressure Vessels ◽  
International Standards ◽  
Integrity Assessment ◽  
Aspect Ratios ◽  
Spinning Cylinder

This paper presents updated analyses of the cylinder specimen being used in the international Network for Evaluating Steel Components (NESC) large-scale spinning-cylinder project (NESC-1). The NESC was organized as an international forum to exchange information on procedures for structural integrity assessment, to collaborate on specific projects, and to promote the harmonization of international standards. The objective of the NESC-1 project is to focus on a complete procedure for assessing the structural integrity of aged reactor pressure vessels. A clad cylinder containing through-clad and subclad cracks will be tested under pressurized-thermal shock conditions at AEA Technology, Risley, U.K. Three-dimensional finite-element analyses were carried out to determine the effects of including the cladding heat-affected zone (HAZ) in the models. The cylinder was modeled with inner-surface through-clad cracks having a depth of 74 mm and aspect ratios of 2:1 and 6:1. The cylinder specimen was subjected to centrifugal loading followed by a thermal shock and analyzed with a thermoelastic-plastic material model. The peak KI values occurred at the clad/HAZ interface for the 6:1 crack and at the HAZ/base interface for the 2:1 crack. The analytical results indicate that cleavage initiation is likely to be achieved for the 6:1 crack, but questionable for the 2:1 crack.

Shakedown of Pressure Vessels with Ellipsoidal Heads

1972 ◽  
Vol 186 (1) ◽  
pp. 431-437 ◽  
Author(s):  
J. D. Fox ◽  
H. Kraus ◽  
R. K. Penny
Keyword(s):  
Pressure Vessel ◽  
Elastic Shell ◽  
Pressure Vessels ◽  
Aspect Ratios ◽  
Shell Analysis ◽  
Analysis Programme

The shakedown of cylindrical pressure vessels with arbitrary heads is described in general by means of Leckie's adaptation of Melan's shakedown theorem. The procedure is mated with an elastic shell analysis programme, which is then used to calculate shakedown pressures for vessels with ellipsoidal heads that have aspect ratios of 3, 2 1/2, 2, 1 1/2, 1, and a variety of thickness ratios. Comparisons with the design pressures obtained by the methods of the A.S.M.E. Boiler and Pressure Vessel Code are also made.

Simplified Procedure to Assess Hot Spots in Pressure Vessels

2020 ◽  
Author(s):  
R. Adibi-Asl ◽  
M. Rana ◽  
R. Seshadri ◽  
C. Joshi
Keyword(s):  
Hot Spots ◽  
Structural Integrity ◽  
Refractory Lining ◽  
Hot Spot ◽  
Pressure Vessels ◽  
Piping System ◽  
Lower Yield ◽  
Simplified Procedure ◽  
Creep Regime ◽  
Over Time

Abstract In many instances, pressure vessels and piping system designed for high temperature applications are exposed to localized hot spots. Hot spots usually occur as the refractory lining degrades over time during operation or process changes causing the surface temperature of the localized region to exceed Code allowable metal temperature. These localized overheating can reduce the overall structural integrity of the pressurized components due to lower yield and or ultimate tensile strength of the damaged region. If hot spots are left undetected, they can lead to catastrophic failure of the components. This paper provides a simplified procedure to assess the effect of the hot spots on the pressure strength of the vessel. The procedure presented in this paper is applicable for hot spot temperatures in non-creep regime.

A Derivation of Bending Free Toroidal Shell Shapes for Tokamak Fusion Reactors

1979 ◽  
Vol 46 (1) ◽  
pp. 120-124 ◽  
Author(s):  
W. H. Gray ◽  
W. C. T. Stoddart ◽  
J. E. Akin
Keyword(s):  
Internal Pressure ◽  
Pressure Vessels ◽  
Alternative Methods ◽  
Toroidal Shell ◽  
Fusion Reactors ◽  
Membrane Theory ◽  
Aspect Ratios ◽  
Pure Tension

This paper describes an extension of mathematical solutions to bending free shapes of toroidal pressure vessels. Previous work on this subject [1] derived a pure tension shape of a toroidal membrane which was subjected to a uniform internal pressure. This research was directed toward the finding of a pure tension shape of a toroidal membrane which is subjected to a pressure inversely proportional to the square of the toroidal radius. Such a relationship is possible when electromechanical forces are considered. This family of shapes, which are nearly circular for aspect ratios greater than 2.5, is derived by solving the equilibrium, constitutive, and kinematic relationships for a uniform toroidal shell using the linear membrane theory. Serious consideration should be given to these toroidal shapes, as they provide alternative methods of design for Tokamak fusion reactors.

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