bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Exploration of Achievable Tightness in ASME B16.5 Standard Flanges for Various Gasket Technologies
Authors: Bausman Anita R. , Waterland A. Fitzgerald , Rice Dale A. 
Published: October 2017

Many industrial plant sites have assembly torque tables for standard ASME B16.5 flanges as part of their internal procedures for bolted flanged joints. It is common for end-users to change gasket materials and gasket designs to reduce costs and/or improve reliability or as processes evolve and change. As environmental awareness and regulations continue to increase, it is important to understand the different levels of tightness that can be achieved from various gasket technologies. Gaskets do not seal equally at the same assembly load. All bolted flanged joints sealed with a gasket have some emissions rate, albeit some vanishingly small on very tight joints.
The tightness parameter has an inverse relation to leakage; the tighter a joint, the less leakage it has. The less leakage, the less emissions result. Where emissions monitoring is intense, tighter gasket technologies are preferred. These tighter technologies are often more expensive. Where emissions are less a concern, river water as an example, more economical gasket selections are preferred. This paper explores gasket tightness performance of a number of materials and construction types common for industrial and power use. Material classes that will be explored include compressed fiber, polytetrafluorethylene (PTFE), flexible graphite (FG), and flexible vermiculite (FV). Construction types that will be explored include sheet materials, composites with metal inserts (flat or corrugated), grooved metal with soft facings (“kammprofile”), and spiral wound gaskets.
For the purposes of comparison, an example assembly torque table will be used. The table includes ASME B16.5 Class 150 flanges, sizes ½” through 24”, using A105 carbon steel flanges and high strength A193 B7 fasteners. With a better understanding of the general capability of a gasket class — the end user can more quickly select gasket materials and constructions suitable for a particular application. This work follows and expands earlier work done with more limited flange sizes. [1]
Temperature Effects on Fracture Thresholds of Hydrogen Precharged Stainless Steel Welds
Authors: Ronevich Joseph A. , San Marchi Chris , Balch Dorian K. 
Published: October 2017

Austenitic stainless steels are typically used in hydrogen environments due to their resistance to hydrogen embrittlement; however, the behavior of welds is not as well understood and can vary from wrought base materials due to chemical composition differences and the presence of ferrite in the fusion zone of the weld. Applications of welded austenitic stainless steels exposed to hydrogen are not limited to room temperature but also include sub-ambient environments, which can have an additional effect on the degradation. In this study, fracture thresholds were measured of three different austenitic stainless steel welds in the hydrogen-precharged condition. Forged 304L, 316L, and 21Cr-6Ni-9Mn stainless steels were gas tungsten arc welded with 308L filler metal and machined into 3-pt bend bars for fracture testing. Crack growth resistance (J-R) curves were measured of the three welds in the hydrogen-precharged condition at ambient (293 K) and sub-ambient (223 K) temperatures to determine the effects of temperature on fracture threshold. Fracture thresholds were determined using elastic-plastic fracture mechanics through development of J-R curves to determine the stress intensity factor following standard practice for determination of fracture toughness. Fracture threshold tests for the welds revealed significant susceptibility to subcritical cracking when tested in the hydrogen-precharged condition. The 21-6-9/308L and 304L/308L welds exhibited some variability in fracture thresholds that did not appear to trend with temperature, while the 316L/308L weld exhibited a reduction of over 50% in fracture threshold at the lower temperature compared to room temperature.
In addition to fracture testing, mini-tensile specimens were extracted from the weld region and tested at 293 K and 223 K in the hydrogen-precharged condition. Hydrogen-precharging slightly increased the yield strength relative to the as-welded condition for all three welds at both temperatures. For all three welds, hydrogen reduced the total elongation by 3–11% at 293 K, whereas reductions in total elongation from 50–64% were observed at 223 K (relative to room temperature without hydrogen). The role of slip planarity on hydrogen-induced degradation of ductility and fracture resistance is discussed as a function of temperature, nickel content, and hydrogen. The fracture surfaces were examined to elucidate the observed differences and similarities in mechanical properties.
Improvements in the Welding Technology for Heavy Wall Pressure Vessels 2 ¼ Cr 1Mo ¼ V Low Alloy Steels
Authors: Fusari Fausto , Marangoni Paolo , Musti Michele , Alberini Stefano 
Published: October 2017

The standard practice recommended for high pressure vessels, having heavy walls, requires the implementation of weld joint preparation with narrow gap technique; this generally calls for a ‘two beads per layer’ sequence alongside the use of the submerged arc welding process. This process provides a high quality and uniformed weld joint whilst also reducing the residual stresses after welding.
In refinery equipment that are subjected to high pressures and are exposed to hydrogen environment, high strength materials such as 2 1/4 Cr 1 Mo 1/4 V are commonly used.
A recent study conducted on this material, and the process of submerged arc welding with narrow gap technique ‘two beads per layer,’ had identified a potential issue in complying with ASME Code specified creep resistance properties. In another setting, with regards to the properties of toughness in weld joints, other possible inconsistencies, in the narrow gap weld joint, between the weld centerline and center bead, were found.
In order to overcome the deficiencies stated above, an innovative welding technology is presented in this paper which is based on the preparation of a narrower groove than the commonly used narrow gap technique. Such groove has been designed to implement the ‘single bead per layer’ approach.
This paper illustrates that the use of this new technique results in improved quality of weld seams as applied in heavy wall high pressure vessels used in creep regime. The welding process considered is that of tandem submerged arc welding with two wires. The mechanical characteristics and results obtained by comparing the two techniques ‘two beads per layer’, and the new innovative one ‘single bead per layer’ will be evidenced and discussed.
On the Influence of Flows in Clearances for Thermal Shocks in a Globe Valve
Authors: Meunier Sébastien , Ferrari Jérôme , Rit Jean-François , Hersant David , Mathieu Jean-Philippe 
Published: October 2017

In a nuclear power plant, the functionality of valves must be proven under severe operating conditions. Thermal shocks of approximately 225°C are part of the qualification tests, that fulfill this demonstration.
Such shocks are studied here on a large globe valve (nominal diameter: 150 mm), experimentally and numerically.
The experimental campaign is carried out on the testing loop “CYTHERE” of EDF. 14 thermal shocks are performed successively in pressurized cold and hot water. The tested valve is equipped with 37 thermocouples distributed over its entire height. The 12 studs of the body-bonnet flange are instrumented with strain gauges, which allow the tracking of the clamping forces evolution in the flange.
A 3D numerical simulation of such a shock in the valve is performed. It is carried out by a chained multiphysics simulation: fluid, heat conduction and finally mechanics. The mechanical simulation models around 40 different parts with numerous contacts. Two versions of this simulation are presented, the second one takes into account a heat transfer taking place in clearances.
A good agreement between simulation and experiment is shown for temperature in the studs. For clamping forces, only the second simulation manage to reproduce tightening variations observed experimentally at the beginning of cold and hot shocks.
Calculation of Axial Thermal Expansion for a 1000MW Nuclear Steam Turbine HIP Casing
Authors: Mei Ziyue , Zhang Hengliang , Xie Danmei , Guo Yanan , Hou Xiuqun , Xiong Yangheng 
Published: October 2017

Steam turbine casing axial thermal expansion is of great significance to the safe operation for nuclear units.
Taking a certain 1000MW nuclear steam turbine’s HIP casing as an object, this paper calculates the HIP casing absolute axial thermal expansions under such conditions as: steady-state, startup and load shedding.
Firstly, a 3D model of the nuclear steam turbine HIP casing is this established by using Pro/E software. Secondly, the heat transfer coefficients of every surface of HIP casing are calculated. Finally, the HIP casing temperature field and the absolute axial thermal expansions under three conditions are calculated and analyzed by using finite element analysis software.
The result shows that, the HIP casing axial thermal expansions are 22.642mm and 22.529mm under steady-state condition and startup condition respectively. While, under load shedding condition, minimum axial expansion is 16.202mm and it increases to 22.491mm at rated load.
Fracture Mechanics Analysis of Clad Subsea Equipment in Sour HPHT Conditions
Authors: Holtam Colum , Saraswat Rajil , Thodla Ramgopal 
Published: October 2017

High pressure high temperature (HPHT) design is a significant new challenge facing the subsea sector, particularly in the Gulf of Mexico. API 17TR8 provides HPHT Design Guidelines, specifically for subsea applications. This paper presents the results of a fatigue based fracture mechanics assessment case study conducted on a fully clad subsea HPHT component. The component was assumed to be constructed from F22 low alloy steel internally clad with alloy 625 and exposed to 20ksi (137.8MPa) and 400°F (204°C) internal pressure and temperature.
A number of different assessment methods were evaluated as part of this study, including standard failure assessment diagram (FAD) based assessment methods, such as those found in API 579-1/ASME FFS-1 and BS 7910, as well as finite element (i.e. crack mesh) methods.
A detailed description of the finite element analysis (FEA) of the uncracked and cracked component is provided. An internal surface flaw assumed to be exposed to sour production fluids was evaluated. The results of the fatigue and fracture assessments are summarized along with the key differences between the assessment methods adopted. The sensitivity of the assessment results to other variables such as welding residual stresses is also discussed.
A Fracture Mechanics-Based Approach to Establish Minimum Pressurization Temperature Envelopes
Authors: Prueter Phillip E. , Kummari Seetha Ramudu , Osage David A. 
Published: October 2017

Preventing brittle fracture is an essential part of instituting life-cycle management strategies for fixed pressure equipment. Using fracture mechanics principles to establish permissible minimum pressurization temperature (MPT) envelopes for components is one way to mitigate the potential for unstable flaw growth. In the refining industry, heavy-walled, low-alloy hydroprocessing reactors are designed to operate at elevated temperatures and high hydrogen partial pressures. Components that operate in high-pressure hydrogen environments require special treatment and necessitate guidance that falls outside the bounds of current pressure vessel construction codes. This operating environment results in two factors that affect the MPT envelope: long-term temper embrittlement and hydrogen embrittlement. Additionally, hydrogen charging can manifest damage in two ways: fast (brittle) fracture due to a reduction in fracture toughness and slow (subcritical) hydrogen-assisted crack growth. When developing a MPT envelope for a given component, both failure modes need to be considered in addition to residual stress effects from weld overlay or cladding. MPT envelopes provide insight into the permissible pressure-temperature combinations for specific locations and for chosen reference flaw sizes. From a reliability standpoint, understanding the risk of brittle fracture associated with heavy-walled reactors for all operating scenarios is crucial. Furthermore, taking the appropriate life-cycle management steps, such as establishing MPT envelopes, coupling MPT analysis predictions with targeted inspection, optimizing process operating conditions, and developing a flaw acceptance criteria to mitigate the risk of crack propagation and ultimately, brittle fracture is essential.
In this study, a fracture-mechanics based methodology is summarized that is fully documented in upcoming Welding Research Council (WRC) Bulletin 562 [1] to determine MPT envelopes for all components (in any service environment) based on fast fracture with supplemental MPT requirements based on slow fracture for equipment that operates in high-pressure hydrogen environments. Finally, a finite element analysis-based case study of a 2-1/4-Cr-1-Mo hydrotreater reactor is summarized and practical life cycle-management guidance is offered based on analysis results. This example highlights how evaluation of start-up and shut-down procedures for heavy-walled reactors has the potential to save significant time and related cost per unit shut-down cycle, while maintaining an acceptable risk tolerance against subcritical crack growth and brittle fracture.
Susceptibility of Carbon Steel Pipe, Fittings and Flanges to Brittle Fracture
Authors: Messer Barry , Soltaninia Shahab , Hamre Ted 
Published: October 2017

Brittle fractures in parent material carbon steel pipe, fittings, and flanges are surfacing in recent ASME B31.3 refinery and gas plant construction and facility start-ups with unexpected low toughness of 3J (2.2 ft-lb) to 7J (5.2 ft-lb) at −10°C (14°F) to −29°C (−20°F). The issue is becoming wide-spread globally, affecting up to 30 percent of materials tested, although many manufacturers are not experiencing this issue. The issue creates a new brittle fracture risk that needs to be addressed as the uncertainty of not knowing suitability for service at temperatures down to −29°C (−20°F) is concerning for reliability and safety.
These components are considered by ASME VIII Div I and ASME B31.3 Code as being inherently ductile, and brittle fracture resistant without any Charpy impact testing requirements. Testing showed brittle transgranular cleavage cracks. The components were deemed to be unsuitable and not safe for use at low temperatures even though they complied with the applicable ASME Codes [1, 2] and ASTM material standards. Low toughness can result in brittle fracture of the material during hydrostatic tests, cold start-ups, or upset conditions that result in low temperature operations. Additionally, some ASTM A350 LF2 CL1 [3] forged flanges certified to −46°C (−50°F) exhibited the same 3J (2.2 ft-lb) to 7J (5.2 ft-lb) at −46°C (−50°F).
This paper discusses historical literature, metallurgical investigations, findings, and factors that contribute to susceptibility to brittle fracture including chemistry, grain size, heat treatment and forming techniques and also issues of ductile to brittle temperature transition shift, and fracture mechanical assumptions. This paper provides guidance to ensure the components are suitable for service and proposes options in addition to the current minimum Codes requirements to mitigate risks of in-service brittle fracture.
Comparative Creep Life Evaluation of HR3C Using Creep Damage Models
Authors: Kang Seok-Jun , Lee Hoomin , Kim Moon-Ki , Choi Jae-Boong 
Published: October 2017

Recently, due to both environmental and energy efficiency, the designed life cycle of many power plant have been extended and also their operating temperature increased. When a material is exposed to high temperature over 50% of its melting temperature, it often shows unusual creep behavior in which the long time exposure of high temperature causes a microstructural degradation in the material and leads to creep rupture at a stress much lower than yield. Thus, there is a great significance in evaluating the creep life of high temperature components in power plant. In this study, accelerated uniaxial creep tests have been conducted to obtain material properties of HR3C at high temperature.
The material properties of three damage models were derived from the accelerated short term creep tests in different stress conditions and the constitutive equation was the form of a power-law for the Kachanov and Liu-Murakami damage models and a hyperbolic sine function for the Dyson model, respectively. Based on these three damage models, the long term creep life was also evaluated. Using the creep rupture envelope, a modified grain boundary constrained cavitation coefficient function is proposed to resolve the constant failure strain problem. Also another modifications is made to the aging coefficient calculation by suggesting a new type of optimization function. By this, the classical problem of rupture time underestimation in the original Dyson model has been resolved. Consequently, the suggested creep life evaluation technique with a simple uniaxial creep example can be extended to more complicated engineering components at high temperature.
Recent Developments of Fracture Mechanics Tools for Nozzle Corners
Authors: Blouin Arnaud , Chapuliot Stéphane , Marie Stéphane , Jaubert André , Courtin Stephan 
Published: October 2017

A recent effort was performed within AREVA-NP in order to develop and validate specific tools dedicated to the Fracture Mechanics Assessment of nozzle and penetration corners. This work is motivated by the need to perform accurate defect assessments for this geometry potentially submitted to a high level of stress. It includes:
• The development of a specific compendium for the calculation of the Stress Intensity Factor under various types of loading like internal pressure or cold thermal shocks;
• The evaluation of the effect of plasticity through simplified analytical schemes;
• The validation through the comparison to existing solutions.
One important target of those tools being the Fatigue Crack Growth evaluation under cyclic thermal shock loading situations, a validation of the fully analytical evaluation scheme was performed by a comparison to a complex 3D Finite Element Modelling of a defect propagating at a flange corner. This comparison is presented in the paper and illustrates the large benefit in terms of time and simplicity of the analytical scheme for such evaluation.
Large SA-508 Class 2 Nozzle Forging Near-Surface Fracture Toughness
Authors: Hall J. Brian , Mays Benjamin E. , DeVan Matthew 
Published: October 2017

The current approach in evaluating the Pressurized Water Reactor (PWR) inlet and outlet nozzle corner regions with respect to plant heat-up and cool-down pressure-temperature limit curves contains a number of conservatisms. These conservatisms include postulation of a large ¼ thickness flaw at the nozzle corner region and use of RTNDT (reference nil-ductility temperature) or an estimation of RTNDT. The paper herein discusses generic fracture toughness of nozzle forging material SA-508 Class 2 for use with postulated smaller surface flaws in developing pressure-temperature limit curves for nozzle corners for nuclear power plant operations.
ASME Appendix G uses the lower bound KIC curve, which has inherent margin since RTNDT is a conservative method for locating the KIC curve. RTNDT is based on the drop weight test, which is a crack arrest transition temperature measurement, and the Charpy impact test, which is a blunt notch impact test. These data are conservatively bounded by the KIC curve, which is a lower bound crack initiation toughness curve. In contrast, the master curve method is based on an initiation transition temperature fracture toughness test technique per ASTM E1921. The master curve index temperature (T0) provides a more accurate measure of the material fracture toughness than KIC indexed with RTNDT. Since many of the nuclear pressure vessels were fabricated to ASME Code editions prior to 1972, RTNDT was not measured for the nozzles. In many cases, RTNDT has been estimated. Therefore, for this work, the fracture toughness was generically established based on conservative T0 measurements of 22 representative forgings with a margin of two standard deviations to ensure a conservative lower bound toughness using ASME Appendix G, G-2110.
The properties of a forging are better near the surface due to the faster cooling rate during heat treatment. The difference in reactor pressure vessel fracture toughness was established for forgings near the surface at the postulated flaw location as allowed by ASME Section III, NB-2223.2 relative to the traditional ¼ thickness location. The near-surface forging toughness was conservatively determined through evaluation of 31 near-surface and approximate ¼ thickness location fracture toughness measurements.
Leak Detection Assessment of a Through Wall Crack in a Circumferential Weld
Authors: Gill Peter , Madew Colin , Booth Steve 
Published: October 2017

A leak detection assessment at a circumferential weld has been carried out to support a Leak-before-Break argument. This was performed using detailed finite element analysis (FEA) of the component to determine limiting defect sizes and crack opening areas. Leak rates of CO2 were then calculated and were found to be at an acceptable level.
The loading on the component were complex, including thermal, pressure and weld residual stresses. The thermal field originated from both a steady state operating condition and hold point during start up plant state. Computational Fluid Dynamics (CFD) was used to generate the thermal fields for this component and the crack was postulated to occur at the region of highest opening stress along the weld. In addition to the thermal field, the weld was also subjected to a residual stress, which was applied in the model via a novel application method that is described in the paper.
The FEA incorporated temperature dependent Ramberg-Osgood stress strain data that was generated from tensile data. For the limiting defect size calculation, lower bound material properties were used, and for the crack opening area, mean properties were used.
Various crack sizes were considered and J-integrals were calculated and compared against the material toughness of the weld. This enabled the calculation of a limiting defect size, and crack opening area, so that a leakage rate could then be calculated. Contour independence was observed for the J-integral evaluation giving confidence that the finite element meshes were fit for purpose.