bluuebunny/crossref_metadata_2025 huggingface dataset:
Disrupting the Metallics Domain in Pressure Vessel and Piping Manufacture-Advanced Manufacturing in the Oil and Gas Sector
Authors: Rafferty John Gerard , Gill David , Kapur Ravi
Published: October 2017

Traditional design and supply chain processes have created well established approaches to the manufacture of metallic engineering products in the Oil and Gas sector. Normative references such as API 6A (Specification for Wellhead and Christmas Tree Equipment) and API 17D (Design and Operation of Subsea Production Systems - Subsea Wellhead and Tree Equipment), as well as national and company-based specifications and requirements (e.g., Brazilian norm NBR 15827 “Industrial Valves for Installations of Exploration, Production, Refining and Transport of Petrol Products - Requirements for Design and Prototype Test” and Chevron specification SSM - PU - 54.02 - A “Qualification Testing of Subsea Equipment”) and the ASME body of pressure vessel code requirements and derived specifications, are largely predicated on traditional design and supply assumptions with respect to metallic materials and components. The further challenge of recovering oil from deepwater basins has generated initiatives such as “Project 20K”, BP’s project to develop, with programme collaborators, the capability to drill, complete, produce and intervene in deepwater reservoirs with pressures of 20,000 psi at the mudline and temperatures up to 350°F (175°C). Here again, design and supply assumptions to date are predicated on traditional design and supply assumptions for metallic materials and components. Notwithstanding the progress being achieved in meeting performance requirements in these and similar programmes, a global paradigm change is underway in respect of the accelerating front of advanced manufacturing. This has been seen especially in the aerospace and aviation sectors, but significantly less so in the Oil and Gas sector. This paper will contribute to addressing this imbalance by presenting work being done by a major subsea equipment supplier to engage with the challenges of this disruptive manufacturing technology. Specifically, the paper will present the holistic approach and results of innovative work being done in the advanced manufacturing of a subsea metallic component using welding arc additive techniques. The work presented will review and evaluate the impact of this manufacturing technology on the core metallic component domains of Metallurgy, Welding Engineering and NDE, utilizing a robotic system for manufacturing the component. The paper directly contributes, therefore, to the emerging roadmap for advanced manufacturing of metallic components in the Oil and Gas sector.
EAM Potential for Hydrogen Storage Application
Authors: Park Y. H. , Hijazi I.
Published: October 2017

Palladium is capable of storing a large atomic percent of hydrogen at room temperature and allows for hydrogen to diffuse with a high mobility. These unique properties make it an efficient storage medium for hydrogen and hydrogen isotopes, such as tritium, a byproduct of nuclear reaction. Palladium thus can be used for applications where fast diffusion and large storage density are important. Better understanding of molecular level phenomena such as hydride phase transformation in the metal and the effect of defects in the materials provides clues to designing metal hydrides that perform better. Atomic simulations are useful in the evaluation of palladium-hydrides (Pd-H) systems as changes in composition can be more easily explored than with experiments. However, the complex behavior of the Pd-H system such as phase miscibility gap presents a huge challenge to developing accurate computational models. In this paper, we present the palladium hydride potentials to investigate and identify the relevant physical mechanisms necessary to describe the absorption of hydrogen within a metal lattice.
Ellipsoidal Head Rules: A Comparison Between ASME Section VIII, Divisions 1 and 2
Authors: Seipp Trevor G. , Barkley Nathan , Wright Christopher
Published: October 2017

In ASME Section VIII, Division 1, rules are provided for calculating the thickness of 2:1 ellipsoidal heads in UG-32. UG-32(c) also states that “an acceptable approximation of a 2:1 ellipsoidal head is a torispherical head with a spherical radius of 0.9D and a knuckle radius of 0.17D”. However, calculating the thickness of a torispherical head with those “equivalent” dimensions results in a thicker head. This result is inherently inconsistent, which starts to bring into question the so-called equivalency.

Code Case 2260 further perpetuates this equivalency by providing alternative rules for calculating the thickness of torispherical heads, and then permitting the engineer to calculate 2:1 ellipsoidal heads implementing this 90-17 equivalency.

Additionally, the calculation methodology for a 2:1 ellipsoidal head in ASME Section VIII, Division 2 uses the torispherical head calculation methodologies and directly implements this 90-17 equivalency. However, this calculation method results, for the same allowable stress basis, in a completely different thickness from the above three methods.

This paper reviews the past 90+ years of work on this topic, and presents some theoretical treatment of the different head geometries. A review of the current Code rules is presented, with a comparison of results for several sizes. A survey of head fabricators is presented to show the actual geometries produced for use in ASME pressure vessels. Finally, conclusions regarding whether or not the 2:1 ellipsoidal head is in fact equivalent to the 90-17 torispherical head are presented, and recommendations for future revisions to both ASME Section VIII, Division1 and Division 2 are provided.
Assessment of the Critical Tilting Angle of a Coke Drum Vessel Subject to Seismic Loading
Authors: Penso Jorge , Bedoya Julian J. , Bouse Scott , Ramamoorthy Sathish K.
Published: October 2017

Assessment of a coke drum for seismic stability is generally a well-documented load case, with ample examples and historical design experience. However, the long-term effects of non-uniform temperature distributions have in many cases led to a phenomenon in coke drums commonly referred to as the “banana effect”. The banana effect leads to out-of-plumb, and local weakening of the shell due to bulging, and creates a more vulnerable structure where the contributions of tilting angle and effective seismic loads vary with each stage of the coking cycle. This paper outlines one practical approach to this challenging problem, along with the derivations and analytical techniques necessary to support the resulting conclusions. The framework developed was able to compare the influences of tilting and seismic accelerations independently, even when acting simultaneously. Using this technique, the analysis was able to efficiently predict a relationship between an expected seismic load and the critical drum tilt angle, with only minor adjustments needed to account for non-linear vertical distribution of the shear force.
The Effects of Tube Array Geometry on Fluidelastic Instability in Heat Exchanger Tube Arrays in Cross Flow
Authors: Hassan Marwan , Weaver David S.
Published: October 2017

The shut-down of the San Onofre Nuclear Generating Station (SONGS) has been attributed to damaging streamwise Fluidelastic Instability (FEI) of the steam generator tubes, a phenomenon which has traditionally been assumed not to occur. This has generated a significant research effort to better understand this phenomenon and to develop appropriate design criteria for its prevention. Most current design codes are based on Connors criterion for FEI which neglects both streamwise FEI and the effects of tube array pattern and pitch ratio. It is becoming clear that array geometry and pitch ratio are important determining factors in FEI, especially in the streamwise direction.

This paper presents an extension of the theory of Lever and Weaver to consider arrays of flexible fluid-coupled tubes which are free to become unstable in both the transverse and streamwise directions. This simplified modelling approach has the advantages of being very tractable for numerical parametric studies and having no need for experimental data input. Previous research by the authors has shown that the predictions of this model agree very well with the available experiments for parallel triangular arrays for both transverse and streamwise FEI. In this paper, the results of such studies are presented for the both transverse and streamwise FEI for square inline and normal triangular arrays and compared with the authors’ previous results for parallel triangular arrays. It is shown that FEI is strongly influenced by array geometry, especially for small pitch ratio arrays operating at low values of the mass damping parameter. The results show good agreement with the available experimental data.
Probabilistic Structural Analysis for Aging Management of Reactor Internals Bolting
Authors: Troyer Greg , Waskey Christopher , Somers Jarrett , Fyfitch Stephen
Published: October 2017

In the United States Pressurized Water Reactors, the reactor internals are subject to augmented inspections under the auspices of MRP-227 to ensure safe operation through periods of extended operation. Recent operating experience has revealed degradation of baffle-to-former bolts (BFBs) where emergent and lengthy shutdowns were required to replace non-functional BFBs. A pro-active approach to safely managing BFB degradation requires an integrated analysis approach that addresses uncertainties in non-destructive examination (NDE) techniques, and uncertainties in bolt degradation rate and bolt degradation location. These uncertainties present nearly unlimited permutations of potential degraded bolt conditions, requiring probabilistic treatment to demonstrate structural integrity of the reactor internals assembly over the next inspection interval.

In this paper, we present almost 10 years of experience with probabilistic structural analysis of bolted connections in nuclear reactor internals applications. Modeling techniques for bolt degradation, location of degraded bolts, and uncertainty in NDE techniques are discussed. Techniques for rapidly evaluating millions of bolt failure patterns against the structural design basis are discussed. These techniques permit definition of requirements for an initial examination, requirements for reexamination interval, and prescription replacement bolt patterns optimized to meet the operator’s financial and risk management objectives, while ensuring safety with rigorous demonstration of maintaining design basis.
Crack Analysis of a Pressure Vessel Using the API 579-1/ASME FFS-1
Authors: Carvajalino Jose de Jesus L. , Freire José Luiz F. , Paiva Vitor Eboli L. , Maneschy José Eduardo , Diaz Jorge G. , Rudolph Jürgen
Published: October 2017

This paper presents a structural integrity evaluation of a duplex stainless steel pressure vessel containing several flaws detected in a longitudinal weld. The evaluation had the objective of determining whether the pressure vessel was suitable to continue in operation or whether it should be immediately repaired or even replaced. Due to timely issues, a first analysis was conducted in accordance with the 2007 edition of the API 579-1/ASME FFS-1 Standard [1]. A second analysis was later repeated based on the 2016 edition [1]. Results obtained from both analyses were compared and presented relevant differences caused by the other calculation procedures used to determine residual stresses generated in the longitudinal welding.

The assessment was based on the Failure Assessment Diagram (FAD). The existing indications were detected by ultrasonic examination and were located in one longitudinal weld. The assessment evaluations used stress intensity factors for the opening mode I, KI, obtained for two cases: 1) the combination of the several supposedly interacting cracks into an equivalent crack using the interaction criteria presented in [1]; 2) the allocation of the multiple cracks into a finite element model that took into consideration, more realistically, the interaction among the individual cracks. The total loads and stresses considered in the analysis resulted from a superposition of the design pressure stress and the residual stresses induced by the welding process.

Due to lack of information on the material fracture toughness for the duplex stainless steel used in the vessel, the material toughness was estimated using a lower bound value suggested in [1] for common welded stainless austenitic steels, although higher values can be predicted for duplex steels by extending the use of a transition master curve as presented and discussed elsewhere [2–7] and by employing specific Charpy test results for the vessel material.

One of the key aspects of the problem was the calculation of the residual stress distribution imposed by the welding process. Two procedures were adopted: one available in the API/ASME Standard issued in 2007, and the other in the 2016 release. The results presented in this paper have demonstrated that the limits of the Standard 2007 are conservatively satisfied when the Level 3 assessment is applied. The re-analysis of the vessel when subjected to the residual stress distribution presented in the newest 2016 edition leads to consider the vessel safe under an assessment Level 2. The overall conclusion was that the damaged pressure vessel could continue in service under restrictions of the development of an inspection plan to verify the absence of future crack growth.
Application of Ultrasonic Phased Array Technique for a Boiler Drum Meeting the Requirements of ASME Sec I
Authors: Saha Santanu
Published: October 2017

Automated or semi-automated ultrasonic examination techniques particularly Time of Flight Diffraction (ToFD) and Phased Arrays (PA) are increasingly being used to replace conventional radiography of various categories of welds in pressure vessels. This is a most important issue when the vessel thickness is quite high with respect to the penetration range of common Ir-192 Radiation source. Although there are high energy alternatives like high energy X ray generators typically Betatrons and Co-60 Radiation source, but use of such high energy pose the high risk of radiation exposures and legal constraints. Moreover, Radiography of a big diameter and very high thick vessel requires considerably long exposure time and results in huge production loss and reshoots in radiographs may make this condition worse. Since ASME BPV Code now approves use of ToFD and Phased Arrays as automated or semi-automated Ultrasonic examination either as a mandatory requirement, alternatively or in lieu of Radiography, applications of these techniques have become quite common in the pressure vessel industry. In this paper we have tried to explain such use of Phased Array technique and its pros and cons while examining a boiler drum welds of 155mm thick shell and 75mm head. This vessel was supposed to be examined by Co-60 Radiography, but since use of such high energy source is prohibited without adequate protective measures, we had no other choice of using Phased Array as an alternative to Radiography. The requirements of ASME Sec I (Power Boilers) and ASME Sec V article 4 Mandatory Appendix VII and how to meet those requirements has been discussed here.
Graphical Material Selection Methods for Multi-Constraint, Multi-Functional Composites Pressure Vessels
Authors: Baur Jeffery W. , Hartl Darren J. , Frank Geoff J. , Bradford Robyn , Huff Gregory
Published: October 2017

Within this paper, we develop an extension to traditional graphical material selection techniques to create maps of the optimal materials for designs with limiting mechanisms which vary. We apply these techniques to pressurized structures that perform multiple functions and have functional systems embedded within them. Specifically, we consider a conceptual analysis for a pressurized radome and a microvascular composite with active thermal management. The latter is the basis for a liquid metal based Structurally Embedded Vascular Antenna (SEVA) with the potential to tune over a broad range of RF frequencies.
Essential Elements of an Asset Integrity Management Program for Ammonia and Methanol Plants
Authors: Jaske Carl E. , Weichel Steven J. , Brongers Michiel P. H.
Published: October 2017

World-class ammonia and methanol plants typically produce more than 500,000 metric tons of ammonia or methanol per year. These plants utilize pressure vessels, piping, and tanks that operate over a wide range of temperatures and pressures. The materials of construction range from carbon steel to corrosion-resistant and heat-resistant alloys. Ensuring the safe and reliable operation of these facilities requires an effective asset integrity management program. This paper reviews the essential elements of an asset integrity management program and provides recommendations for judging the effectiveness of the program. The essential elements of an asset integrity management program include leadership, risk management, personnel and contractor competence, management of change, learning from events, emergency response, and implementation of quality assurance, maintenance, inspection, fitness-for-service assessment, repair, and replacement.

Management commitment to the program is a key factor in leadership. Risk is managed by mitigating the consequences of an incident as well as minimizing its likelihood; a robust risk-based inspection (RBI) program is typically part of the risk management. In-service degradation mechanisms of the materials that are used in pressure vessels, piping, and tanks include corrosion, fatigue, creep, and metallurgical embrittlement. If defects are identified by inspection, fitness for service assessment is performed to determine what action is to be taken. Training and certification of personnel and contractors is required to make sure that this work is properly performed. Incidents and near misses that occur in the plant and in the industry need to be reviewed to identify areas for potential program improvements. Timely and appropriate emergency response can minimize the consequences of an incident.
Tensile and Fatigue Behavior of an Austenitic Stainless CrNi-Steel at 10 MPa Hydrogen Gas Atmosphere
Authors: Schwarz Martina , Sattler Erich , Zickler Stefan , Weihe Stefan
Published: October 2017

To understand the role of nickel in austenitic stainless steels, six heats were produced from one nominal composition differing in the nickel content between 9 % and 13 %. To characterize the material behavior in hydrogen gas atmosphere at 10 MPa, tensile and fatigue testing was conducted at ambient temperature and at 223 K. The susceptibility to hydrogen embrittlement clearly decreases with increasing nickel content both at ambient temperature and at 223 K. But at low temperature the relative reduction of area is less and thus hydrogen embrittlement is intensified. Fatigue tests confirmed these results as the reduction of the fatigue life is strongly dependent on the nickel content and the temperature. The influence of the test frequency was investigated at 4 different frequency levels. A low frequency slightly increases the susceptibility to hydrogen embrittlement. To gain a better understanding of hydrogen embrittlement and its influences the crack growth behavior was analyzed in detail.
Sensitivity Analysis for XLPR Acceptance Testing
Authors: Sallaberry Cédric J. , Kurth Robert E. , Brust Frederick W. , Kurth Elizabeth A.
Published: October 2017

The US Nuclear Regulatory Commission (US NRC) and the Electric Power Research Institute (EPRI) have jointly funded the development of the probabilistic analysis tool xLPR (extremely Low Probability of Rupture) version 2.0 for calculating the probability of a leak before break for welded pipes [1]. The acceptance testing for the program was completed in July of 2016. This allowed the release of the code to the development team. The released version of xLPR v 2.0 was used to run probabilistic simulations on selected scenarios and then perform uncertainty and sensitivity analysis on selected results. Uncertainty Analysis (UA) informs on how much the uncertainty affect the outputs while Sensitivity Analysis (SA) ranks the uncertain parameters in term of importance (i.e., influence over uncertainty) for selected outputs.

In this paper, we present the methodology used to perform Sensitivity Analysis using three regression techniques as well as scatterplots for graphical study. The results generated are consistent both with the experts’ expectations and our understanding of the equations used in the sub-models.
A History of the Target Torque Values From ASME PCC-1 and Future Direction
Authors: Rodery Clay D.
Published: October 2017

Since its original issue in 2000, ASME PCC-1 has provided guidance to the user for establishing target torque values for bolted flanged joint assembly. The original tables were developed based on a reference bolt stress of 50 ksi (345 MPa) with guidance provided for making adjustments using other bolt stress values. Despite its attempts to provide clarity, the industry perception has been that the 50 ksi (345 MPa) reference bolt stress is a mandatory requirement, which has never been the intent. This paper reviews the basis of the original Table 1M/Table 1 values provided in PCC-1, and provides a forecast of future improvements utilizing a new concept called a Target Torque Index based on a unit bolt stress, allowing the user to utilize the guidance in Appendix O of PCC-1 to define the appropriate bolt stress for their particular situation.
Experimentally Benchmarked Computational Fluid Dynamics Simulations of a 7×7 Array of Heated Rods Within a Square-Cross-Section Enclosure Filled With Rarefied Helium
Authors: Maharjan Dilesh , Hadj-Nacer Mustafa , Greiner Miles
Published: October 2017

Computational fluid dynamics simulations of a 7×7 array of heated rods within a square-cross-section enclosure filled with rarefied helium are performed for heat generation rates of 50 W and 100 W and various helium pressures ranging from 105 to 50 Pa. The model represents a section of nuclear fuel assembly between two consecutive spacer plates inside a nuclear canister subjected to during vacuum drying process. A temperature jump model is applied at the solid-gas interface to incorporate the effects of gas rarefaction at low pressures. The temperature predictions from simulations are compared to measured temperatures. The results showed that when helium pressure decreased from 105 to 50 Pa, the maximum temperature of the heater rod array increased by about 14 °C. The temperatures of the hottest rod predicted by simulations are within 4°C of the measured values for all pressures. The random difference of simulated rod temperatures from the measured rod temperatures are 3.33 °C and 2.62 °C for 100 W and 50 W heat generation rate.
Risk Based Inspection Methodology for Components Subject to High-Temperature Creep
Authors: Jaske Carl E. , Topalis Panos , Loong Wong Sin , Md Sidek Azura Sharina
Published: October 2017

Risk-based inspection (RBI) methodologies are widely used by industry to develop effective inspection programs for pressure vessels and piping. The RBI approach use data on equipment design, maintenance, and operation along with inspection history to evaluate both the likelihood and consequences of failure. RBI results provide a basis for selecting inspection methods and establishing inspection intervals and coverage. API RP 580 provides guidance on developing a RBI program for fixed equipment and piping, while API RP 581 provides quantitative procedures for establishing RBI methodology. Appendix J of the first edition (2000) of API RP 581 contained procedures for application to creep damage of furnace tubes. However, the second (2008) and third (2016) did not contain any procedures for application to creep damage of equipment, including furnace tubes. DNV GL undertook a RBI project for a coal-fired power plant in Malaysia that required evaluation of components subject to creep damage. As part of this project, a detailed likelihood of failure (LoF) model for creep was developed. This paper reviews the creep LoF model that was developed and discusses a case study of its application. The LoF is estimated using a limit state function where the resistance is characterized using Larson-Miller parameter creep-rupture expressions for the materials of interest and the load is characterized by the time in service. A mean value first order second moment (MVFOSM) method is employed to numerically compute LoF. Guidelines for including metallurgical replication results in the LoF estimate and for assigning inspection effectiveness for creep damage also are discussed.
Long Term Operation of Safety Valves at Pressures Near the Set Pressure
Authors: Ezekoye L. Ike , Beagen Thomas , Gordon Brian S. , Boufford John W.
Published: October 2017

Safety valves in nuclear power plants provide over pressure protection of pressurized systems. Accordingly, these valves are required to open quickly and stably (i.e., open, relieve pressure and close) during postulated transients to protect the integrity of the protected systems. Typically, postulated transients are classified as fast or slow. Fast transients have high system pressurization rates that proceed very quickly thereby requiring the safety valves to pop open. On the other hand, there are transients that proceed very slowly that are less challenging to the system but may initiate leakage across the installed safety valve seat. There is very limited knowledge on the impact of prolonged operation of safety valves during slow pressurization accident events. The integrity and functionality of these valves during such slow pressurization events are often in question. This paper examines analytically the behavior and the integrity of safety valves during slow pressurization transient events at pressures near the valve set pressure. This paper considers extended periods of valve simmering that may progress to valve cycling (popping fully open) during such events. To validate the analytical performance prediction, steam tests were performed with safety valves which confirmed that these valves can operate extensively under slow pressurization transient events while maintaining their capability to perform their intended design function.
Fracture Initiation in Compact Tension Specimens of Hydrided Irradiated Zr-2.5Nb Materials With Split Circumferential Hydrides
Authors: Sung Shin-Jang , Pan Jwo , Lam Poh-Sang , Scarth Douglas A.
Published: October 2017

Fracture initiation in compact tension (CT) specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides is examined by conducting three-dimensional finite element analyses with submodeling. The stress-strain relation for the irradiated Zr-2.5Nb materials is based on the experimental results of transverse tensile tests. For CT specimens with split circumferential hydrides, plastic strain concentration is observed in the middle of the ligaments ahead of the crack front. With a strain-based failure criterion with consideration of stress triaxiality, the necessary fraction of the load for crack initiation is about 0.55 to 0.70 to fracture the ligaments when compared to that for a CT specimen without split circumferential hydrides. The computational results can be used to explain the near 40% reduction of the fracture toughness at room temperature obtained from hydrided irradiated curved compact tension specimens (CCTSs) when compared with that from unhydrided irradiated ones.
Component Low Cycle Fatigue Behavior Based on Standard Calculation Procedure and Non-Linear FEA
Authors: Rudolph Jürgen , Willuweit Adrian , Bergholz Steffen , Philippek Christian , Kobzarev Jevgenij
Published: October 2017

Components of conventional power plants are subject to potential damage mechanisms such as creep, fatigue and their combination. These mechanisms have to be considered in the mechanical design process. Against this general background — as an example — the paper focusses on the low cycle fatigue behavior of a main steam shut off valve. The first design check based on standard design rules and linear Finite Element Analysis (FEA) identifies fatigue sensitive locations and potentially high fatigue usage. This will often occur in the context of flexible operational modes of combined cycle power plants which are a characteristic of the current demands of energy supply. In such a case a margin analysis constitutes a logical second step. It may comprise the identification of a more realistic description of the real operational loads and load-time histories and a refinement of the (creep-) fatigue assessment methods. This constitutes the basis of an advanced component design and assessment. In this work, nonlinear FEA is applied based on a nonlinear kinematic constitutive material model, in order to simulate the thermo-mechanical behavior of the high-Cr steel component mentioned above. The required material parameters are identified based on data of the accessible reference literature and data from an own test series. The accompanying testing campaign was successfully concluded by a series of uniaxial thermo-mechanical fatigue (TMF) tests simulating the most critical load case of the component. This detailed and hybrid approach proved to be appropriate for ensuring the required lifetime period of the component.
A Study for Evaluating Local Damage to Reinforced Concrete Panels Subjected to Oblique Impact of Deformable Projectile
Authors: Nishida Akemi , Ohta Yoshimi , Tsubota Haruji , Li Yinsheng
Published: October 2017

Many empirical formulas have been proposed for evaluating local damage to reinforced concrete structures caused by impacts of rigid projectiles. Most of these formulas have been derived based on impact tests perpendicular to the target structures. Up to now, few impact tests oblique to the target structures have been carried out. This study has been conducted with the purpose of proposing a new formula for evaluating the local damage caused by oblique impacts based on previous experimental and simulation results.

In this paper, the results of simulation analyses for evaluating the local damage to reinforced concrete panels subjected to normal and oblique impacts by deformable projectile, by using the simulation method that the validity was confirmed through simulation analysis of past impact experimental results. Based on the results of these simulation analyses, the quantitative evaluation of reduction effects in the local damage caused by the difference of the impact angle is investigated.
The Effect of Materials and Design Geometry on Tube Plugs at High Pressure Steam Super Heater
Authors: AlSaud Mohammed S. , AlDakhil Abdulrahman D. , Van Zyl Gys
Published: October 2017

A high-pressure (HP) steam super heater located in the primary reformer of Ammonia Plant of Saudi Arabian Fertilizer Company (SAFCO) has ruptured twice in two different tubes, in 2009 and again in 2014. On both occasions, the repair was performed by removing and plugging the failed tube. In January 2015, the new plug that was installed in 2014 failed and led to an emergency shutdown. The older plug was found to be in good condition. An investigation was initiated to determine the reason for failure of one plug within nine months of operation while another was still in good condition after 6 years of operation. The failed plug was subjected to a metallurgical failure analysis where visual and stereoscopic inspection, scanning electron microscopy, metallographic examination, and chemical analysis were performed. The two plugs had different geometric designs, and thermal and static structural finite element analyses were performed to compare the 2009 and 2014 designs. Based on the outcome of the investigation, the cause of failure and the reason for the discrepancy in lifetimes of the two plugs was determined. This paper will present the conclusions of the metallurgical failure analysis and design review which was performed, and the improved repair design that was developed as a result of the investigation.
Fatigue With Hold Times Simulating NPP Normal Operation Results for Stainless Steel Grades 304L and 347
Authors: Karabaki H. Ertugrul , Solin Jussi , Twite Marius , Herbst Matthias , Mann Jonathan , Burke Grace
Published: October 2017

The cyclic behavior and endurance of austenitic stainless steels tested under NPP-relevant laboratory conditions has been studied. It had been earlier shown that long intervals between fatigue transients can affect the fatigue performance in stainless steels that are generally used in NPP primary piping. If this can be confirmed, then the transferability between laboratory results, design curves and the fatigue behavior of NPP components during plant operation shall be addressed. In addition to coolant water environmental effects, the material response during steady state normal operation should also be accounted for.

Advanced Fatigue Methodologies (AdFaM), a joint project of European research laboratories, vendors and plant operators was focused on empirical and mechanistic investigations to confirm the claimed effects of hold times on fatigue life.

Strain-controlled fatigue tests incorporating accelerated hold times at temperatures between 290°C and 420°C were performed on stabilized and non-stabilized stainless steel grades, which are used in Germany and the UK. Two material batches of both alloy types (304L and 347) were studied. The mechanisms responsible for the observed variations in stress response and fatigue life have been investigated using a range of microscopy techniques.

The results confirmed the extension of fatigue life due to hold times in both stabilized and non-stabilized grades. This life extension appears to be linked to hold hardening observed in the cyclic behavior of both alloys.

Tests incorporating hold times may be more representative of material behavior in NPPs, where temperature transients due to start-ups, shutdowns and major power changes may be separated by long periods of steady state operation. This gives reason to consider the transferability of standard laboratory test data to fatigue assessments of NPP components, and to propose a new factor ( Fhold ) as part of an advanced fatigue methodology and realistic transferability factor: Freal = Fen × Fhold.
Technical Basis for Flaw Acceptance Criteria for Cast Austenitic Stainless Steel Piping
Authors: Shim D. J. , Cofie N. G. , Dedhia D. , Harris D. O. , Griesbach T. J. , Amberge K.
Published: October 2017

According to the current ASME Code Section XI, IWB-3640 and Appendix C flaw evaluation procedure, cast austenitic stainless steel (CASS) piping with ferrite content less than 20% is treated as wrought stainless steel. For CASS piping with ferrite content equal or greater than 20%, there is currently no flaw evaluation procedure in the ASME Code.

In this paper, the technical basis for a proposed flaw acceptance criteria for CASS piping is presented. The procedure utilizes the current rules in ASME Code Section XI, IWB 3640/Appendix C and the existing elastic-plastic correction factors (i.e., Z-factors) for other materials in the Code. The appropriate Z-factor to use for the CASS piping is determined based on the ferrite content (using Hull’s equivalent factor). Experimentally measured fully saturated fracture toughness and tensile data of the three most common grades of CASS material in the US (CF3, CF8 and CF8M) were used to determine the flaw acceptance criteria in the proposed method. The proposed method is conservative since it utilizes the fully saturated condition of CASS materials. In addition, it is simple and consistent with current regulatory guidance on aging management of CASS piping.
Probabilistic Assessment of CANDU Reactor Core for Risk of Pressure Tube Failure due to Presence of In-Service Flaws
Authors: Cho David , Mok Danny H. B. , Xu Steven X. , Scarth Douglas A.
Published: October 2017

Technical requirements for analytical evaluation of in-service Zr-2.5Nb pressure tubes in CANDU(1) reactors are provided in the Canadian Standards Associate (CSA) N285.8. The evaluation must address all in-service degradation mechanisms including the presence of in-service flaws. Flaws found during in-service inspection of CANDU Zr-2.5Nb pressure tubes, including fuel bundle scratches, debris fretting flaws, fuel bundle bearing pad fretting flaws, dummy bundle bearing pad fretting flaws, erosion-shot flaws and crevice corrosion flaws, are volumetric and blunt in nature. These in-service flaws can become crack initiation sites during pressure tube operation and potentially lead to pressure tube failure. Any detected flaws that do not satisfy the criteria of acceptance as per CSA N285.4 must be analytically evaluated to justify continued operation of the pressure tube. Moreover, the risk of pressure tube failure due to presence of in-service flaws in the entire reactor core must be assessed.

A review of assessment of the risk of pressure tube failure due to presence of in-service flaws in CANDU reactor core is provided in this paper. The review covers the technical requirements in the CSA N285.8 for evaluating degradation mechanisms related to flaws in the reactor core. Current Canadian industry practice of probabilistic assessment of reactor core for pressure tube failure due to presence of in-service flaws is described, including evaluation of flaws for crack initiation, subsequent crack growth to through-wall penetration, and pressure tube rupture due to unstable crack growth prior to safe shutdown of the reactor. Operating experience with the application of probabilistic assessment of reactor core for the risk of pressure tube failure due to presence of in-service flaws is also provided.
Comparison of Methods for Structural Stress Determination According to EN 13445-3 Annex NA
Authors: Trieglaff Ralf , Beckert Martin , Rudolph Jürgen , Hauser Fabian
Published: October 2017

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18). Clause 18 “Detailed Assessment of Fatigue Life” is under revision within the framework of the European working group CEN/TC 54/WG 53 - Design methods to reach a significant increase in user-friendliness and a clear guideline for the application.

This paper is focused on the new informative annex NA “Instructions for structural stress oriented finite elements analyses using brick and shell elements”. As an essential amendment for the practical user the determination of structural stress ranges for fatigue assessment of welds is further specified in this new annex. Different application methods for the determination of structural stresses are explained in connection with the requirements for finite element models and analyses.

This paper will give an overview of the proposed approaches of structural stress determination in annex NA of the revised EN 13445-3. It will present the results of fatigue analyses according to EN 13445-3 Clause 18 from a round robin test with participants of the German working group for different application examples. The estimated structural stress ranges for the proposed approaches of structural stress determination will be compared. This comparison leads to general remarks and open points for the different approaches.

Furthermore it is concludes that further comparisons, e.g. with results of other pressure vessel design codes are desirable.
Ultrasonic Inspection Technique for Inside Pressurized Pipe Elbows
Authors: Miao Cunjian , Guo Weican , Du Xingji , Ling Zhangwei
Published: October 2017

Elbows in pressure pipes are important parts in the pipe inspection, which may become serious corrosion locations. Ultrasonic detection is a main technique for pipe inner inspection, and the use of traditional ultrasound and phased array technique for in-line inspection are advanced, long-term interesting and known by researchers. Several devices were invented for inside pipeline inspection and is suitable to some extent such as detecting long-distance pipelines. However, elbows especially tight elbows are still difficult to implement inner detection or travelling. To obtain a good effect in detecting elbows with ultrasound, the inner inspection technique was investigated. Spherical and flat cylindrical probe holder structures were proposed to ensure the ability to pass through elbows, while the spherical holder has a large number of conventional probes in its shell with a uniform arrangement and was designed to give a full view for ultrasonic detecting. As regards the flat cylindrical probe structures, it is more suitable for phased array ultrasonic technique to form a convex array. Both methods were proposed for better echo directions and amplitudes, and aimed to obtain the information of elbow characteristics. CIVA simulation was conducted based on the above design, and the focal effects were analyzed. Comparing with detecting precision and manufacture process, the phased array technique with flat cylindrical probe holder was chosen, and its device manufacturing and elbow inspection experiments were carried out. CIVA simulation was also used to analyze the influence of array and element parameters on the echo detection, and the design parameters were determined about the convex phased array. The experimental elbow was designed and manufactured with specific artificial defects. The ultrasonic system was taken by a robot to travel through the elbow, and the experimental data were used to verify the applicability of the ultrasonic inspection technique.
Elevated Temperature Cracking Resistance of Ta-Bearing High Chromium Ni-Base Filler Metals
Authors: Fink Carolin , Lippold John C. , Hope Adam T. , McCracken Steven
Published: October 2017

Tantalum is investigated in this work as an alternative eutectic forming element to replace niobium in high chromium, Ni-base filler metals. Three experimental Ni-30Cr filler metals with additions of tantalum (Ta) and molybdenum (Mo) were studied in order to investigate eutectic constituent formation at the end of weld solidification and to determine weld metal cracking resistance. The cast pin tear test (CPTT) and the strain-to-fracture (STF) test were utilized to determine solidification cracking and ductility-dip cracking (DDC) susceptibility, respectively. Differences in the morphology of the eutectic constituents were observed as a function of Ta and Mo additions. Mo appears to participate in the eutectic reaction at the end of solidification, but does not affect the solidification temperature range. The experimental filler metals showed good resistance to solidification cracking and were remarkably resistant to DDC, especially at higher levels of Ta and Mo.
Decay Length in Pressure Vessels
Authors: Adibi-Asl R. , Seshadri R.
Published: October 2017

In theory of shell, decay length is defined as the distance affected by localized external (applied loads) or internal (edge effect, discontinuity) forces and moments, beyond which the effect of these loads becomes negligible. The concept of decay length becomes relevant when assessing the interaction effects caused by adjacent discontinuities.

In this paper, the decay lengths for several shells geometries, specifically cylindrical, spherical and conical shells, are reviewed. The available expressions for decay lengths in the literature are listed and are compared with finite element analysis to demonstrate the accuracy of some of the solutions.
Acceptance Limits for Subsurface Voids in HDPE Piping
Authors: Rush Phillip J. , Scarth Douglas A. , Munson Douglas
Published: October 2017

Mandatory Appendix XXVI in Section III of the ASME Code (2015 Edition) includes the requirements for the construction of Class 3 high density polyethylene (HDPE) pressure piping. Currently, there are no acceptance limits for subsurface voids in HDPE piping included in the Code. Data from recent EPRI tests conducted to determine the rate of growth of flaws in HDPE piping can be used to develop acceptance criteria for subsurface voids. The tests exposed specimens with surface flaws to sustained loads under elevated temperature and stress conditions. No failures were observed in the tests. Therefore, the results are useful to establish lower bound lifetime estimates for flawed piping under the maximum allowable temperature and stress conditions for buried pipe. The HDPE material has considerable ability to resist crack growth at temperatures well above the maximum allowable service conditions permitted in Appendix XXVI. The test data were used to establish allowable subsurface void sizes in HDPE piping. Correlations for rupture time that are based on the applied stress intensity and net section stress were used to determine an allowable subsurface void size. Because the creep failure mechanism in HDPE piping is time-dependent, an allowable void size was developed to ensure HDPE pipe integrity at the void location for a 50-year service life. The allowable flaw sizes can be used for the disposition of void indications identified in piping both before and after installation.
BWR Shroud Weld Off-Axis Crack Growth Investigation
Authors: Broussard John E. , Lunceford Wayne
Published: October 2017

Recent inspections have identified cracking in the core shroud that is atypical in that the cracks exhibit characteristics inconsistent with traditionally reported intergranular stress corrosion cracking (IGSCC) occurring within stainless steel weld heat-affected zones (HAZs). These flaws are oriented transverse to the weld and are observed to propagate significantly beyond the weld HAZ. This paper describes the investigations which have been performed to quantify the likely limits on growth of these “off-axis” SCC cracks. The investigation includes welding residual stress analysis to determine the stress field present adjacent to the weld and crack tip SIF calculations for the bivariant stress field.
Monitoring Crack Propagation of High Pressure and High Temperature Components by Multi-Physics Numerical Analysis Approach
Authors: Ahmadi Moghaddam Hamid R. , Mertiny Pierre
Published: October 2017

The safety of high pressure and high temperature components is paramount, and therefore, developing effective and reliable methodologies to improve the prediction of crack propagation is an important task. The present paper describes and demonstrates a multi-physics numerical analysis approach for assessing crack propagation using a sensor device. This method employs a coupled structural-thermal-electric analysis in conjunction with a thermal-fluid-structure interaction analysis to study the structural health of a high pressure and high temperature component.
Signal Analysis and Processing for Magnetic Flux Leakage Inspection Device for Underground Storage Tank
Authors: Ling Zhangwei , Zheng Mulin , Wang Min , Guo Weican , Tan Wuhao
Published: October 2017

The underground storage tank usually has small volume and typically cylinder shape. A magnetic flux leakage (MFL) inspection device was developed for underground storage tank. In order to be suitable for curvature plates, the magnetization structure was designed, which contains three substructure and can cause the non-uniform magnetic field appeared on the cross section. The impact by the non-uniform magnetic field and uneven placement sensors were analyzed. The MFL testing requires effective signal progressing methods. A signal circuit without high-pass filter was used in hardware signal progressing. A zero-phase filter was adopted in the digital signal processing. The defect was characterized by peak-peak value of defect signal. The channel independent calibration method was carried out. An experimental underground tank with a diameter of 2.4m was established. The experimental results for cracks with different depths, lengths and widths were presented, and the results proved that the presented signal progressing was effective.