Code Aspects Related to Combination of Stresses due to Hydrogen Detonations: Local Effects

2012 ◽  
Author(s):  
John C. Minichiello ◽  
Stephen D. Ahnert ◽  
Thomas C. Ligon ◽  
David J. Gross
Keyword(s):  
Fatigue Damage ◽  
Pipe Wall ◽  
Axial Strain ◽  
Evaluation Methodology ◽  
Local Effects ◽  
Bending Waves ◽  
Piping Systems ◽  
Asme Code ◽  
Fatigue Evaluation ◽  
Hoop Stresses

This paper addresses the local effects of hydrogen detonations inside piping. It is the first in a two-part series of papers which assess the effects of detonations in piping systems relative to ASME Code allowables. The effects of internal detonations in piping systems are typically separated into two regimes: local effects and system effects. Local effects are often simplistically represented as pure hoop stresses resulting from the pressure acting radially on the inside circumference of the pipe. In reality, the interaction of the pipe wall and the propagating detonation wave is relatively complex, resulting in “waves” or “ripples” in the pipe wall. These areas of local, through-wall curvature lead to substantial axial stresses which may even exceed the hoop stresses. Furthermore, in the elastic regime, there is very little damping present in the pipe wall, leading to numerous stress cycles as the local bending waves move axially along the pipe wall. Fatigue effects of the combined hoop and axial cycling were evaluated using ASME Code Section VIII, Division 2 fatigue evaluation methodology. Analysis of strain gage data from a number of hydrogen detonation experiments in 2-inch and 4-inch Schedule 40 piping showed that the fatigue damage is generally driven by fewer than 10 large-magnitude fatigue cycles, which account for an average of 75% of the total fatigue damage. However, the results also demonstrate that for two detonation events with similar measured peak hoop or axial strain, the number of fatigue allowable events may vary dramatically depending on the shape of the strain response.

Development of Analytical Evaluation Procedures and Acceptance Criteria for Pipe Wall Thinning in ASME Code Section XI

2004 ◽  
Author(s):  
Kunio Hasegawa ◽  
Gery M. Wilkowski ◽  
Lee F. Goyette ◽  
Douglas A. Scarth
Keyword(s):  
Pipe Wall ◽  
Evaluation Methodology ◽  
Current Status ◽  
Evaluation Procedure ◽  
Analytical Evaluation ◽  
Acceptance Criteria ◽  
New Class ◽  
Wall Thinning ◽  
Class 1 ◽  
Asme Code

As the worldwide fleet of nuclear power plants ages, the need to address wall thinning in pressure boundary materials becomes more acute. The 2001 ASME Code Case N-597-1, “Requirements for Analytical Evaluation of Pipe Wall Thinning,” provides procedures and criteria for the evaluation of wall thinning that are based on Construction Code design concepts. These procedures and criteria have proven useful for Code Class 2 and 3 piping; but, they provide relatively little flexibility for Class 1 applications. Recent full-scale experiments conducted in Japan and Korea on thinned piping have supported the development of a more contemporary failure strength evaluation methodology applicable to Class 1 piping. The ASME B&PV Code Section XI Working Group on Pipe Flaw Evaluation has undertaken the codification of new Class 1 evaluation methodology, together with the existing Code Case N-597-1 rules for Class 2 and 3 piping, as a non-mandatory Appendix to Section XI. This paper describes the current status of the development of the proposed new Class 1 piping acceptance criteria, along with a brief review of the current Code Case N-597-1 evaluation procedure in general.

Prediction of Time to Significant Cracking and Actual Behavior of an Impulsively Loaded Detonation Chamber for Chemical Weapons Destruction

2012 ◽  
Author(s):  
Joseph K. Asahina ◽  
Koichi Akasaka ◽  
Robert E. Nickell ◽  
Toshio Hamada
Keyword(s):  
Fatigue Damage ◽  
Structural Integrity ◽  
Actual Behavior ◽  
Design Curve ◽  
Fatigue Design ◽  
Asme Code ◽  
Operation Control ◽  
Fatigue Evaluation ◽  
Estimation Of Time ◽  
Best Fit

For repeated operation of a detonation chamber, evaluation of its fatigue damage and estimation of time to crack initiation are of considerable importance from the aspect of safe operation. This paper proposes the use of a sufficiently conservative operation control fatigue evaluation curve, based upon the ASME Code fatigue design curve and the best fit laboratory air curve upon which the design curve is derived, in order to define operational points for actions to inspect for possible fatigue damage and initiate repairs, as needed. The paper also recommends appropriate actions to verify that any needed repairs maintain structural integrity during subsequent operations.

First Ocean Going Ships With Springing and Whipping Included in the Ship Design

2011 ◽  
Author(s):  
Gaute Storhaug ◽  
Erlend Moe ◽  
Ricardo Barreto Portella ◽  
Tomazo Garzia Neto ◽  
Nelson Luiz Coelho Alves ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Current Model ◽  
Life Time ◽  
Model Tests ◽  
Full Scale ◽  
Development Projects ◽  
Transient Vibration ◽  
Hull Girder ◽  
Fatigue Evaluation ◽  
Wave Induced

It is well known that ships vibrate due to waves. The wave induced vibrations of the hull girder are referred to as springing (resonance) and whipping (transient vibration from impacts). These vibrations contribute to the fatigue damage of fatigue sensitive details. An Ore Carrier of 400 000 dwt is currently being built by DSME, and at time of delivery, it will be the world’s largest bulk (ore) carrier. The scantlings of large ships must be carefully designed with respect to global loading, and when extending the design beyond experience, it is also wise to consider all aspects that may affect operation and the life time costs. The vessel will also enter a long term contract and is therefore to be evaluated for 30 year Brazil-China operation. In order to minimize the risk of fatigue damage, the vessel is designed according to DNV’s class notation CSA-2 requiring direct calculations of the loading and strength. Further it has been requested to include the effect of springing and whipping in the design. Reliable numerical tools for assessing the additional fatigue effect of vibrations are non-existing. DNV has, however, developed an empirical guidance on how the additional effect may be taken into account based on previous development projects related to the effect of vibrations on large ore carriers Due to the size and route of operation of the new design, it has, however, been required by the owner to carry out model tests in both ballast and cargo condition in order to quantify the contribution from vibration. The results from this project have been used for verification and further calibration of DNV’s existing empirical guidance. A test program has been designed for the purpose of evaluating the consequence in head seas for the Brazil to China trade. Full scale measurements from previous development projects of ore carriers and model tests have been utilized to convert the current model tests results into estimated full scale results for the 400 000 dwt vessels. It is further important to carefully consider how the vibrations are to be included in the design verification, and to develop a procedure for taking into account the vibrations which results in reasonable scantlings based on in-service experience with similar designs and trades. This procedure has been developed, and a structural verification has been carried out for the design. The final outcome of the model test was in line with previous experience and in overall agreement with DNV’s empirical guidance, showing a significant contribution from vibrations to the fatigue damage. The springing/whipping vibrations more than doubled the fatigue damage compared to fatigue evaluation of the isolated wave induced loading. The cargo condition vibrated relatively more than experienced on smaller vessels. Various sources to establish the wave conditions for the Brazil to China ore trade were used, and the different sources resulted in significant differences in the predicted fatigue life of the design.

Coupled Torsional Vibration and Fatigue Damage of Turbine Generator Due to Grid Disturbance

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Chao Liu ◽  
Dongxiang Jiang ◽  
Jingming Chen
Keyword(s):  
Fatigue Damage ◽  
Torsional Vibration ◽  
Coupled System ◽  
Lumped Mass ◽  
Mass Model ◽  
Turbine Generator ◽  
Failure Prevention ◽  
Lumped Mass Model ◽  
Continuous Mass ◽  
Fatigue Evaluation

Crack failures continually occur in shafts of turbine generator, where grid disturbance is an important cause. To estimate influences of grid disturbance, coupled torsional vibration and fatigue damage of turbine generator shafts are analyzed in this work, with a case study in a 600MW steam unit in China. The analysis is the following: (i) coupled system is established with generator model and finite element method (FEM)-based shafts model, where the grid disturbance is signified by fluctuation of generator outputs and the shafts model is formed with lumped mass model (LMM) and continuous mass model (CMM), respectively; (ii) fatigue damage is evaluated in the weak location of the shafts through local torque response computation, stress calculation, and fatigue accumulation; and (iii) failure-prevention approach is formed by solving the inverse problem in fatigue evaluation. The results indicate that the proposed scheme with continuous mass model can acquire more detailed and accurate local responses throughout the shafts compared with the scheme without coupled effects or the scheme using lumped mass model. Using the coupled torsional vibration scheme, fatigue damage caused by grid disturbance is evaluated and failure prevention rule is formed.

Load Factor for Evaluating Non-Planar Flaws in Carbon Steel Piping Using Limit Load Methodology

2016 ◽  
Author(s):  
Phuong H. Hoang
Keyword(s):  
Carbon Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Pipe Wall ◽  
Local Strain ◽  
Limit Load ◽  
Evaluation Methodology ◽  
Load Factor ◽  
Wall Thinning ◽  
Steel Piping

Non-planar flaw such as local wall thinning flaw is a major piping degradation in nuclear power plants. Hundreds of piping components are inspected and evaluated for pipe wall loss due to flow accelerated corrosion and microbiological corrosion during a typical scheduled refueling outage. The evaluation is typically based on the original code rules for design and construction, and so often that uniformly thin pipe cross section is conservatively assumed. Code Case N-597-2 of ASME B&PV, Section XI Code provides a simplified methodology for local pipe wall thinning evaluation to meet the construction Code requirements for pressure and moment loading. However, it is desirable to develop a methodology for evaluating non-planar flaws that consistent with the Section XI flaw evaluation methodology for operating plants. From the results of recent studies and experimental data, it is reasonable to suggest that the Section XI, Appendix C net section collapse load approach can be used for non-planar flaws in carbon steel piping with an appropriate load multiplier factor. Local strain at non-planar flaws in carbon steel piping may reach a strain instability prior to net section collapse. As load increase, necking starting at onset strain instability leads to crack initiation, coalescence and fracture. Thus, by limiting local strain to material onset strain instability, a load multiplier factor can be developed for evaluating non-planar flaws in carbon steel piping using limit load methodology. In this paper, onset strain instability, which is material strain at the ultimate stress from available tensile test data, is correlated with the material minimum specified elongation for developing a load factor of non-planar flaws in various carbon steel piping subjected to multiaxial loading.

Leak Testing

2021 ◽  
pp. 143-147
Author(s):  
Charles Becht
Keyword(s):  
Wall Thickness ◽  
Pipe Wall ◽  
Piping System ◽  
Pipe Wall Thickness ◽  
Pressure Testing ◽  
Leak Testing ◽  
Piping Systems ◽  
Design Pressure ◽  
Important Test

While the exercise of pressurizing a piping system and checking for leaks is sometimes called pressure testing, the Code refers to it as leak testing. The main purpose of the test is to demonstrate that the piping can confine fluid without leaking. When the piping is leak tested at pressures above the design pressure, the test also demonstrates that the piping is strong enough to withstand the pressure. For large bore piping where the pipe wall thickness is close to the minimum required by the Code, being strong enough to withstand the pressure is an important test. For small bore piping that typically has a significant amount of extra pipe wall thickness, being strong enough is not in question. Making sure that the piping is leak free is important for all piping systems.

Fatigue Evaluation in Mixing Zones: Comparison of Different Criteria of Fatigue

2008 ◽  
Author(s):  
J. M. Stephan ◽  
C. Gourdin ◽  
J. Angles ◽  
S. Quilici ◽  
L. Jeanfaivre
Keyword(s):  
Fatigue Damage ◽  
Thermal Stresses ◽  
Plastic Material ◽  
Material Behavior ◽  
Damage Evaluation ◽  
Elastic Plastic ◽  
Different Types ◽  
Elastic Plastic Material ◽  
Fatigue Evaluation

The distribution of unsteady temperatures in the wall of the 6" FATHER mixing tee mock-up is calculated for a loading configuration: The results seem realistic even if they are not still very accurate (see paper PVP2005-71592 [11]). On this basis, thermal stresses are evaluated for elastic and elastic-plastic material behavior. Then, different types of fatigue criteria are used to evaluate the fatigue damage. The paper develops a brief description of the criteria, the corresponding fatigue damage evaluation and attempts to explain the differences.

3D Residual Stress Simulation of an Excavate and Weld Repair Mockup

2016 ◽  
Author(s):  
Francis H. Ku ◽  
Pete C. Riccardella ◽  
Steven L. McCracken
Keyword(s):  
Residual Stresses ◽  
Weld Metal ◽  
Nuclear Power ◽  
Three Dimensional ◽  
Weld Repair ◽  
Element Analysis ◽  
Pressurized Water ◽  
Piping Systems ◽  
Asme Code ◽  
Original Construction

This paper presents predictions of weld residual stresses in a mockup with a partial arc excavate and weld repair (EWR) utilizing finite element analysis (FEA). The partial arc EWR is a mitigation option to address stress corrosion cracking (SCC) in nuclear power plant piping systems. The mockup is a dissimilar metal weld (DMW) consisting of an SA-508 Class 3 low alloy steel forging buttered with Alloy 182 welded to a Type 316L stainless steel plate with Alloy 82/182 weld metal. This material configuration represents a typical DMW of original construction in a pressurized water reactor (PWR). After simulating the original construction piping joint, the outer half of the DMW is excavated and repaired with Alloy 52M weld metal to simulate a partial arc EWR. The FEA performed simulates the EWR weld bead sequence and applies three-dimensional (3D) modeling to evaluate the weld residual stresses. Bi-directional weld residual stresses are also assessed for impacts on the original construction DMW. The FEA predicted residual stresses follow expected trends and compare favorably to the results of experimental measurements performed on the mockup. The 3D FEA process presented herein represents a validated method to evaluate weld residual stresses as required by ASME Code Case N-847 for implementing a partial arc EWR, which is currently being considered via letter ballot at ASME BPV Standards Committee XI.

Experimental Study of Flow Induced Vibration on Heat Transfer Helical Tube Bundle

2008 ◽  
Author(s):  
Lixia Gao ◽  
Jie Yang ◽  
Zilong Jiang ◽  
Jianzhong Ma ◽  
Song Li
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
High Pressure ◽  
Tube Bundle ◽  
Flow Induced Vibration ◽  
Steady State Operation ◽  
Helical Tube ◽  
Asme Code ◽  
Fatigue Evaluation ◽  
Large Flow

In this paper, the Flow Induced Vibration (FIV) tests of heat transfer helical tube bundle have been carried out. The results show that the more large flow velocity in tube becomes, the more high pressure drop of bundle is. The dynamic buckling of bundle does not occur during steady-state operation. The fatigue evaluation has been done according to ASME code and the structure is founded to satisfy the ASME code requirements.

Application of Draft Regulatory Guide DG-1144 Guidelines for Environmental Fatigue Evaluation to a BWR Feedwater Piping System

2007 ◽  
Author(s):  
Hardayal S. Mehta ◽  
Henry H. Hwang
Keyword(s):  
Fatigue Life ◽  
Thermal Cycle ◽  
Light Water Reactor ◽  
Piping System ◽  
Low Alloy Steel ◽  
Light Water ◽  
Asme Code ◽  
Fatigue Evaluation ◽  
Cycle Diagram ◽  
Analytical Expressions

Recently published Draft Regulatory Guide DG-1144 by the NRC provides guidance for use in determining the acceptable fatigue life of ASME pressure boundary components, with consideration of the light water reactor (LWR) environment. The analytical expressions and further details are provided in NUREG/CR-6909. In this paper, the environmental fatigue rules are applied to a BWR feedwater line. The piping material is carbon steel (SA333, Gr. 6) and the feedwater nozzle material is low alloy steel (SA508 Class 2). The transients used in the evaluation are based on the thermal cycle diagram of the piping. The calculated fatigue usage factors including the environmental effects are compared with those obtained using the current ASME Code rules. In both cases the cumulative fatigue usage factors are shown to be less than 1.0.

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