Experimental and Numerical Validation of Fitness-for-Service Assessment for Cylindrical and Spherical Pressure Vessel With Local Metal Loss

2008 ◽  
Author(s):  
Takuyo Kaida
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
Axial Stress ◽  
Large Diameter ◽  
Metal Loss ◽  
Assessment Procedure ◽  
Element Analysis ◽  
Longitudinal Length ◽  
Spherical Pressure

Fitness-For-Service (FFS) assessment procedure can be also used to determine a reduced Maximum Allowable Working Pressure (MAWP) for cylindrical and spherical pressure vessel with local metal loss. A reduced MAWP is calculated from the Remaining Strength Factor (RSF). RSF is defined as ratio between plastic collapse load of the damaged component and that of the undamaged component. RSF needs to be calculated accurately in order to continue the damaged component in service safely. In this paper, RSFs of the damaged components with variously-shaped local metal loss were investigated. Especially, effects of circumferential width of local metal loss for cylindrical pressure vessel are investigated by both hydrostatic burst test and finite element analysis (FEA). The configurations of the local metal loss are rectangle. The longitudinal length and minimum thickness are fixed. FEA using the criterion proposed by Miyazaki et al. is effective to estimate fracture ductility under the multi-axial stress condition accurately, and effects of circumferential width is evaluated. In addition, RSF for spherical pressure vessel with relatively large diameter/thickness ratio was calculated by finite element analysis. Both results were compared to the calculation results using the equation in API 579-1/ASME FFS-1. The FFS assessment procedure is validated as conservative assessment experimentally and numerically.

Design of Ellipsoidal Heads Using Elastic-Plastic Finite Element Analysis

2002 ◽  
Author(s):  
Donald J. Florizone
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
Large Strain ◽  
Large Diameter ◽  
Spherical Shape ◽  
Element Analysis ◽  
Perfectly Plastic ◽  
Section Viii ◽  
Design Calculations

Traditional design techniques result in excess material being required for ellipsoidal heads. The 2001 ASME Boiler and Pressure Vessel Code Section VIII Division 1, UG-32D and Section VIII Division 2, AD-204 limit the minimum design thickness of the heads. ASME Boiler and Pressure Vessel Code Case 2261 provides alternate equations that enable thinner head design thickness. VIII-2 Appendix 3 and 4 methods potentially could be used to further optimize the head thickness. All the equations in the code use one thickness for the entire head. On large diameter thin heads the center or spherical area is often thicker than the knuckle area due to the method of manufacture. Including this extra material in the design calculations results in an increase of the MAWP of large diameter thin heads. VIII-2, AD-200 of the code permits localized thinning in a circumferential band in a cylindrical shell. Applying these same rules to elliptical heads would permit thinning in the knuckle region as well. Engineers have powerful finite element analysis tools that can be used to accurately determine levels of plastic strain and plastic deformed shapes. It is proposed that VIII-2 Appendix 4 and 5 methods be permitted for the design of elliptical heads. Doing so would permit significant decreases in thickness requirements. Different methods of Plastic Finite Element Analysis (PFEA) are investigated. An analysis of a PVRC sponsored burst test is done to develop and verify the PFEA methods. Two designs based on measurements of actual vessels are analyzed to determine the maximum allowable working pressures (MAWP) for thick and thin heads with and without local thin regions. MAWP is determined by limit analysis, per VIII-2 4-136.3 and by two other proposed methods. Using Burst FEA, the calculated burst pressure is multiplied by a safety factor to obtain MAWP. Large deflection large strain elastic perfectly plastic limit analyses (LDLS EPP LL) method includes the beneficial effect of deformations when determining the maximum limit pressure. Elliptical heads become more spherical during deformation. The spherical shape has higher pressure restraining capabilities. An alternate design equation for elliptical heads based on the LDLS EPP LL calculations is also proposed.

Safe Operation and FFS Assessment for Pressure Equipment: Updated With Study for Local Metal Loss Assessment

2006 ◽  
Author(s):  
Atsushi Ohno ◽  
Yoshiaki Uno ◽  
Takayasu Tahara
Keyword(s):  
United States ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Metal Loss ◽  
Assessment Procedure ◽  
Loss Assessment ◽  
Safe Operation ◽  
Element Analysis ◽  
Assessment Procedures ◽  
Design Margin

Recently, Codes and Standards for FFS assessment has been developed and applied in United States and other countries such as API RP579 as a series of maintenance procedures for pressure equipment. Activities developing FFS assessment procedures in conjunction with new safe inspection standards are also progressing in Japan. In order to prove applicability of the FFS procedure for assessment of damaged pressure equipment, it is also important to validate how much of inservice safe margin is derived from the FFS assessment procedures in compared with design margin of pressure equipment. Local metal loss assessment procedure specified by API RP579 is studied using finite element analysis and discussed how much of in-service safe margin will be sufficient as standardized FFS assessment procedure.

scholarly journals Finite Element Analysis of Skirt to Shell Junction in a Pressure Vessel

2017 ◽  
Vol 10 (25) ◽  
pp. 1-10
Author(s):  
Deepali Mathur ◽  
Mandar Sapre ◽  
Chintan Hingoo ◽  
◽  
◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
Element Analysis

Using Finite Element Analysis to Prioritize ILI Calls for Combined Features: Dents in Bends

2018 ◽  
Author(s):  
David Kemp ◽  
Justin Gossard ◽  
Shane Finneran ◽  
Joseph Bratton
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Metal Loss ◽  
Remaining Life ◽  
Case Scenario ◽  
Element Analysis ◽  
Pipe Bend ◽  
Worst Case ◽  
Worst Case Scenario ◽  
Combined Features

Pipeline in-line-inspections (ILI) are used to assess and track the integrity of pipelines, aiding in identifying a variety of features such as: metal loss, dents, out-of-roundness, cracks, etc. The presence of these features can negatively affect the operation, integrity, and remaining life of a pipeline. Proper interpretation of the impacts these features may have on a pipeline are crucial to maintaining the integrity of a pipeline. Several codes and publications exist to assess the severity of these features under known operating conditions, either through empirical formulations or more detailed analysis, in order to aid the operator in determining a corrective action plan. These empirical formulations are generally applicable to assess a singular defect but require a more detailed assessment to evaluate combined defects (i.e. dent in a bend). These detailed assessments typically require a higher level numerical simulation, such as Finite Element Analysis (FEA). This detailed FEA can be quite costly and time consuming to evaluate each set of combined features in a given ILI run. Thus, engineering judgement is critical in determining a worst-case scenario of a given feature set in order to prioritize assessment and corrective action. This study aims to assess dent features (many associated with metal loss) occurring in a pipe bend to determine a worst-case scenario for prioritization of a given feature listing. FEA was used to simulate a field bend of a given radius and angle in order to account for residual stresses in the pipe bend. A rigid indenter was used to form a dent of the approximate length, width, and depth from the ILI data. Separate models were evaluated considering the dent occurring in the intrados, extrados, and neutral axis of the pipe bend to evaluate the worst-case scenario for further assessment. The resulting stresses in the pipe bend-dent geometry, under proper loading were compared to the same dent scenario in a straight pipe segment to develop a stress concentration factor (SCF). This SCF was used in the API 579-1/ASME FFS-1 Fitness for Service (API 579) [1] methodology to determine the impact on the remaining life of the combined features.

Standardization of Flattening Procedure of Transverse to Pipe Axis Strap Tensile Samples

2018 ◽  
Author(s):  
M. Rashid ◽  
S. Chen ◽  
L. E. Collins
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Tensile Testing ◽  
Standard Procedure ◽  
Large Diameter ◽  
Spring Back ◽  
Pipe Axis ◽  
Element Analysis ◽  
Line Pipe ◽  
Experimental Approaches

Tensile testing on large diameter line pipe is generally done using strap samples obtained in the transverse to pipe axis (TPA) orientation of a pipe. The strap samples are then flattened and machined prior to testing. Although the standardized tensile testing is well documented, the variability in the reported TPA tensile properties of the same material tested within a lab or at different labs has always been an issue. Recent work conducted at EVRAZ NA research lab has identified flattening as the main source of the variability in reported yield strength (YS) values for line pipe. The lack of a standard procedure for flattening TPA strap samples is a major obstacle to obtaining consistent results. Therefore, the main objective of this current study was to establish a standardized flattening procedure for TPA strap samples. Both finite element analysis (FEA) and experimental approaches were adopted. Various flattening methods and fixtures were studied. Extensive flattening experiments were conducted on TPA samples from different line pipe products. Results showed that the spring back after flattening in a TPA sample is different for pipes with different gauge and grades. It was established that consistent flattening can be achieved using appropriate fixtures for differerent ranges of tubular products defined by grade, diameter and gauges. Evaluation of the flattening fixture designs and experimental results are discussed in this paper.

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