Effect of Thickness Measurement Procedure on Stress Analysis of Pipes With Local Metal Loss

2013 ◽  
Author(s):  
Nobuyuki Yoshida ◽  
Atsushi Yamaguchi
Keyword(s):  
Decision Making ◽  
Measurement Procedure ◽  
Thickness Measurement ◽  
Burst Pressure ◽  
Metal Loss ◽  
Element Analysis ◽  
Fea Model ◽  
Laser Displacement Meter ◽  
The Difference ◽  
Corrosion Under Insulation

Fitness-For-Service (FFS) assessment using Finite Element Analysis (FEA) has been a problem in deciding yes-no which vary from evaluator to evaluator. The difference in decision making is caused by the degree of freedom in modeling a FEA model. In this study, burst pressures of pipes with local metal loss were calculated by using FEA in order to investigate the influence of thickness measurement intervals on FFS assessment. The analyzed pressures by FEA were verified by burst tests. A pipe specimen, which was thinned by corrosion under insulation in the actual plant, was used for the burst tests. Shape of the pipe specimen was measured by laser displacement meter and extracted at several types of interval. It is concluded that the analyzed pressures in various measurement intervals showed almost no difference, but were higher than the actual burst pressure of the specimen.

Evaluation of Strength of Pipe With Metal-Loss due to CUI by FFS and FEA Which Considered the Fracture Ductility

2018 ◽  
Author(s):  
Atsushi Yamaguchi ◽  
Nobuyuki Yoshida
Keyword(s):  
Ductile Fracture ◽  
Stress Condition ◽  
Experimental Results ◽  
Burst Pressure ◽  
Metal Loss ◽  
Multiaxial Stress ◽  
Element Analysis ◽  
Domestic Industry ◽  
Corrosion Under Insulation

Corrosion under insulation (CUI) is an aging degradation issue in long-term service vessels and pipes made of carbon steel and low-alloy steel. One of the problems in managing CUI is an equivocal evaluation technique of thinning detected by inspection. A replacement period with more accuracy can be evaluated more appropriately by performing fitness-for-service (FFS) assessment in this equipment. It is important to verify the validity of the FFS assessment using actually corroded pipes in order to promote the spread of FFS assessment in the domestic industry. In the present paper, pipes with complicated metal-loss due to CUI that were used in a chemical plant are burst in burst tests. An estimated burst pressure, which is calculated based on the assessment of metal-loss and through finite element analysis (FEA) based on FFS assessment, is compared with experimentally obtained burst pressures in order to validate the integrity evaluation. The burst pressure is then estimated by FEA, in which the ductile fracture under the multiaxial stress condition is considered. The burst pressure estimated by FFS approximately matched the burst pressure obtained based on experimental results. Fitness-for-service is sufficiently valid for investigating the remaining strength or burst pressure of corroded pipe. In addition, the burst pressure estimated by FEA that considered the ductile fracture under the multiaxial stress condition agreed with the experimental results and is valid so long as the remaining strength factor (RSF) is less than 0.6.

Discussion on Plastic Collapse Criterion at High Temperatures in FFS Assessment Rules

2010 ◽  
Author(s):  
Kenji Oyamada ◽  
Shinji Konosu ◽  
Hikaru Miyata ◽  
Takashi Ohno
Keyword(s):  
Comparative Study ◽  
High Temperatures ◽  
Bending Moment ◽  
Flaw Size ◽  
Metal Loss ◽  
Plastic Collapse ◽  
Loss Assessment ◽  
Element Analysis ◽  
Diagram Method ◽  
The Difference

There are several Fitness-For-Service (FFS) standards with evaluation rules in terms of plastic collapse for a pressure vessel or piping component possessing a local metal loss area simultaneously subjected to internal pressure and bending moment. The authors have already reported the results of a comparative study of FFS rules, including the remaining strength factor (RSF) approach in Part 5 of API 579-1/ASME FFS-1 and the p-M diagram method, which pointed out that there could be significant differences in allowable flaw sizes. This paper describes an additional comparative study on the difference of allowable flaw size for local metal loss assessment between the RSF approach in Part 5 of API 579-1/ASME FFS-1 and the p-M diagram method, focusing on the effect of decreasing yield strength of the material at high temperatures, such as 350 degrees C. The allowable flaw depth at high temperatures derived from API579-1/ASME FFS-1 is larger than that derived by means of the p-M diagram method. However, it is verified by the finite element analysis that the allowable flaw size of the p-M diagram method is set on the stress state of general yielding near a local metal loss area if safety factor is not considered and it is possible to evade ratcheting due to cyclic bending moment in service, such as that caused by earthquake, etc.

Evaluating Dents With Metal Loss Using Finite Element Analysis

2016 ◽  
Author(s):  
Justin Gossard ◽  
Joseph Bratton ◽  
David Kemp ◽  
Shane Finneran ◽  
Steven J. Polasik
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Laser Scanner ◽  
Mechanical Damage ◽  
Third Party ◽  
Burst Pressure ◽  
Metal Loss ◽  
Surface Mesh ◽  
Element Analysis ◽  
3D Surface

Dents created by third party mechanical damage are a severe integrity threat to onshore and offshore transmission pipelines. This type of damage is often associated with metal loss, which can be introduced during the initiation of a dent or develop as a result of the presence of a dent and associated coating damage. Once a dent has been found to be associated with metal loss through excavation, there is little guidance to determine the serviceability of the anomaly. In this study, dents with associated metal loss due to corrosion examined in the field are evaluated to determine the contribution of the interacting dent and metal loss features to the associated burst pressure of the feature. Twenty dents with metal loss flaws were identified through an ILI survey while in service to capture dimensions of the dent and metal loss features. Each site was excavated and measured using a laser scanner. The laser scanner produced 3D imaging with sufficient resolution of both the dent and metal loss areas as a 3D surface mesh. The 3D surface mesh was transformed into a 3D solid mesh and analyzed using a finite element analysis software package in order to determine a predicted internal pressure that would cause failure. A subsequent statistical assessment was performed to analyze the relationship between the ILI measurements and the predicted burst pressure resulting from finite element analysis of each dent with metal loss feature. Statistical analyses were used to evaluate the prediction capabilities of burst pressures of dent with metal loss features identified through ILI, prior to excavation and direct examination.

New Safety Assessment System for Corroded Underground Pipelines

2009 ◽  
Author(s):  
Szabolcs Sza´vai ◽  
Gyo¨ngyve´r B. Lenkey
Keyword(s):  
Safety Assessment ◽  
Safety Margin ◽  
Assessment System ◽  
Metal Loss ◽  
Safety Factors ◽  
Element Analysis ◽  
Underground Pipelines ◽  
Corrosion Defects ◽  
The Difference ◽  
External Corrosion

The most important question for the user is if pipelines having metal loss defect could be operated safely, if any pipe sections should be repaired or replaced, and how much is the reserved safety against a possible failure. There are several engineering methods for determining the safety margin of operation but those are usually quite conservative. For this reason Lenkey has proposed safety diagrams based on finite element analysis of external corrosion defects in underground pipelines [4]. These safety diagrams could be used to determine safety factors in a less conservative way for critical situations during the pipeline operation. The FEM calculations have been verified by burst tests carried out on several pipe sections. In the present paper the results of some further analyses are presented about the difference between the measured, numerically and analytically determined failure pressure values.

Prediction of Closure Bolt Loads in Small Pressure Vessels: NUREG/CR-6007 vs. Detailed Finite Element Analysis

2010 ◽  
Author(s):  
Charles A. McKeel
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Small Diameter ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Containment Vessel ◽  
Fea Model ◽  
Significant Difference ◽  
Load Increase ◽  
The Difference

Closure bolt loads in a flanged cylindrical containment vessel under internal pressure are determined by detailed Finite Element Analysis (FEA) and compared to values determined using NUREG/CR-6007 equations. The containment vessel is of small diameter with an inwardly dished bolted head that geometrically contrasts with the large, flat lidded casks which the NUREG addressed. The comparison showed a significant difference in the magnitude of pressure driven prying load between the FEA model and the NUREG approximate equations. This difference affected the predicted pressure that overcomes preload, and the rate of load increase after preload was exceeded. The difference was likely due to the contrasts between this vessel’s closure shape compared to the more typical flat cask lid shape used in the NUREG development.

Reliability-Based Assessment of Safe Excavation Pressure for Dented Pipelines

2020 ◽  
Author(s):  
Chike Okoloekwe ◽  
Matthew Fowler ◽  
Amandeep Virk ◽  
Nader Yoosef-Ghodsi ◽  
Muntaseer Kainat
Keyword(s):  
Numerical Models ◽  
Mechanical Damage ◽  
Structural Response ◽  
Assessment Method ◽  
Full Scale ◽  
Burst Pressure ◽  
Operating Pressure ◽  
Element Analysis ◽  
Fea Model ◽  
Full Scale Tests

Abstract Dents in a pipe result in alteration of its structural response when subjected to internal pressure. Excavation activities further lead to change in load and boundary conditions of the pipe segment which may exacerbate the stress state within the dented region. Depending on the severity of a dent, excavation under full operating pressure may lead to failure, injuries or fatalities. Although uncommon, an incident has been reported on a gas pipeline where a mechanical damage failed during investigation leading to one death and one injury [10]. While current pipeline regulations require that operators must depressurize a line to ensure safe working conditions during repair activities, there are no detailed provisions available in the codes or standards on how an operator should determine such a safe excavation pressure (SEP). As a result, the safe excavation process of dents has received attention in the industry in recent years. A detailed review of the recent research on dent SEP showed that the current recommendations are primarily dependent on one of two aspects: careful assessment of inline inspection (ILI) data, or a fitness for service (FFS) assessment of the dent feature leveraging numerical models. Enbridge Liquid Pipelines had previously demonstrated a feature specific assessment approach which incorporated both ILI data and finite element analysis (FEA) to determine the SEP. This assessment also accounted for uncertainties associated with material properties and ILI tool measurement. In the previous publication, the authors demonstrated a methodology for assessing the SEP of dents at a conceptual level from both deterministic and reliability-based standpoints. In this paper, a validation study has been performed to compare the results of fracture mechanics based FEA models against ten full scale burst tests available in literature. The study showed good agreement of the burst pressure of dent-crack defects predicted by FEA models with those observed in the full-scale tests. The assessment method is further streamlined by incorporating the API 579 [14] Failure Assessment Diagram (FAD) method on an uncracked FEA model as opposed to explicitly incorporating the crack geometry in the FEA model. The results of FEA in conjunction with FAD are compared with the full-scale tests to ensure accuracy and conservatism of burst pressure prediction. A reliability-based approach is then designed which accounts for the uncertainties associated with the analysis. A case study is presented where the reliability-based SEP assessment method has been implemented and feature specific SEP has been recommended to ensure target reliability during excavation.

Experimental measurement of energy density of a vibrating beam

2016 ◽  
Vol 24 (24) ◽  
pp. 5735-5746 ◽  
Author(s):  
A Nokhbatolfoghahai ◽  
HM Navazi ◽  
Y Ghobaad ◽  
H Haddadpour
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Energy Density ◽  
Potential Energy ◽  
Vibrational Energy ◽  
Random Force ◽  
Measurement Procedure ◽  
Element Analysis ◽  
The Difference ◽  
Energy Finite Element Analysis

This paper presents a method for calculating vibrational energy density from experimental data in a uniform beam. The input excitation is a point random force that induces transverse vibration along the beam. Using finite difference method and four accelerometers, both translational and rotational terms of kinetic and potential energy densities are measured. Also, an energy finite element analysis based computer program is developed. The results of the measurements achieved by developed formulation are compared with those of energy finite element analysis results. It is found that there is a fair agreement between them at relatively lower frequencies. But, in high frequencies, the difference between analytical and experimental results increases which stems from occurrence of errors in calculation of potential energy density. Finally, a comparison between kinetic and potential terms of the energy density is done. It is concluded that an efficient and very simple measurement procedure can be used based on kinetic energy measurement only.

Finite Element Analysis Improves Design of Hot Metal Ladle Car

1995 ◽  
Author(s):  
Daniel H. Suchora ◽  
Harry S. Perrine ◽  
Bradley Chamberlain
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Load Flow ◽  
Hot Metal ◽  
Element Analysis ◽  
Fea Model ◽  
Final Design ◽  
The Difference ◽  
End Use ◽  
Hot Metal Ladle

Abstract An electric powered Hot Metal Ladle Car was designed to safely transport a ladle filled with 160 metric tons of molten steel. The ladle geometry and space constraints within the use environment were specified. A final design was prepared and documented which met the design requirements and could be efficiently manufactured. An initial design was developed using past designs of a similar nature as a basis. By hand stress calculations were performed and the design modified to get stress values to acceptable levels. Preliminary design drawings were developed. At this stage of the design, some engineering personnel felt that the “by hand” stress analysis was sufBciently accurate to go ahead with fabrication. After much discussion it was decided to perform a Finite Element Analysis (FEA) to verify the design stresses calculated “by hand”. The FEA analysis predicted stresses that were significantly higher than indicated “by hand” in some critical change of section regions. These stress levels were much higher than the allowable stresses for this design. The difference between the FEA stresses and “by hand” stresses were evaluated. After much discussion and thought an insight to the actual load flow was developed which was consistent with the FEA results. With this insight, modifications were made to the design and incorporated into the FEA model. These changes needed to be practical from a manufacturing and end use viewpoint. After a few iterations on the design tire FEA stresses were reduced to an acceptable level. These changes were incorporated into the design. The final design of the ladle car was fabricated. The design was significantly improved due to the ability to accurately calculate stresses in transition regions of the frame where “by hand” methods were not really applicable. The combination of “by hand” methods to ballpark a design and FEA methods to reftne a design proved to be a powerful method to get a truly good design.

Numerical Study on the Effect of Defect Length upon Burst Capacity of Composite Repaired Pipe

2021 ◽  
Vol 879 ◽  
pp. 179-188
Author(s):  
Kah Qi Lim ◽  
Chao Bao ◽  
Mohd Syahrul Hisyam Mohd Sani ◽  
Lim Kar Sing
Keyword(s):  
Oil And Gas ◽  
Numerical Study ◽  
Burst Pressure ◽  
Pipeline System ◽  
Repair System ◽  
Operating Pressure ◽  
Long Distance ◽  
Element Analysis ◽  
Frp Composites ◽  
The Difference

Pipeline system is one of the essential infrastructures in oil and gas industries as it is used to transport oil and gas over long distance. However, pipelines will undergo damages and deteriorations after being used for some years, especially when corrosion occurs. Corrosive pipes will experience reduction in wall thickness resulted a lower remaining strength of the pipe, and consequently lead to failure once the remaining strength unable to withstand the desired operating pressure of the pipe. Therefore, additional strength from repairing job needs to be provided, for instance, by using fibre-reinforced polymer (FRP) composites. Unlike the corroded pipeline assessment codes, the pipeline repair codes that are used to design composite repair system of corroded pipe do not include the defect geometries such as defect length. In this study, burst pressure of the composite repaired pipeline with different defect lengths and the effect of the defect length upon the burst capacity of composite repaired pipe are investigated. The study is carried out by finite element analysis on various defective pipes with different defect length sizes. The results show that the difference of the burst pressure subjected to various defect lengths is 15.59% and this had proved that there is effect of defect length upon the burst capacity of composite repaired pipe. This finding can be very useful for optimizing the existing repair design.

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