Pressurized vessels that transfer media from one location to another often contain a bolted connection. Gaskets are essential for these systems since they confer high levels of leak mitigation across of range of operating environments (i.e., internal pressure and temperature). The balance of both sealability and compressibility must be displayed in candidate gasket materials to be subjected to aggressive operating conditions. Historically, thin gauge gasket (i.e., 1/16” thick) confer high sealability while thick gaskets offer superior compressibility (i.e., 1/8”). Fabricated with skive cut, ceramic particle-reinforced PTFE, these materials display linear viscoelastic behavior that allow consolidation to occur. For example, GYLON ® 3504 is filled with Aluminosilicate Microspheres, GYLON ® 3510 is filled with barium sulfate, respectively, to efficiently fill crevices along the surfaces of the flange. Novel textured PTFE gasket (3504 EPX and 3510 EPX) have been developed to simultaneously confer sealability and compressibility compared to flat products. A design of experiments (DoE) approach is applied to characterize the factors that influence load relaxation responses of the both candidate textured PTFE (dual-face honeycomb) and existing (flat) gasket styles. Using an instrumented test platform analyzed. A new parameter is presented to quantify gasket efficiency. The collection of efficiency measurement methods and approach to re-torque optimization convey a novel framework that designers can invoke to facilitate improved flange performance.

The material attributes that are fundamental for developing a candidate textured, ceramic-filled PTFE gasket, such as texture style/dimensions, filler material, thickness and so on, create a set of potential combinations that are not practical to experimentally characterize at the component-level one-by-one. Optimizing gasket performance, however, is essential to the operation of bolted connections associated with pressurized vessels that transfer media from one location to another. Gaskets are essential for these systems since they confer high levels of leak mitigation across a range of operating environments. A balance of both compressibility and sealability must be displayed in an optimal candidate gasket to be subjected to aggressive operating conditions. A novel textured PTFE material (termed textured) characterized using a miniaturized test platform. This new-to-market viscoelastic material features a dual-face, raised honeycomb pattern. Experiments on both flat (termed Flat) and textured are used to identify viscoelastic constitutive model constants associated with Burger theories. Considering that the test platform contains an elastic bolt that is tightened to a prescribe torque level, the gasket is subjected to creep relaxation. Test results on the small samples contribute to constitutive modeling. The influence of parameters such as filler material selection, torque level, dwell period, etc. are presented.

Bulk hydrogen production in a petroleum refinery by steam–methane reforming utilizes high temperatures, moderate pressures and catalyst – filled tubes which generate high tube temperatures of up to 1,690 °F [920 °C] imposing relatively harsh performance demands on system components which are not usually encountered in other refinery or petrochemical plant equipment. Creep rupture and high temperature cycling place a severe service duty on the catalyst tubes, tube outlet pigtails, the subheader train and the downstream steam generator leading to ruptured pigtails, cracking in sub-headers and break up of the ceramic tube sheet ferrules at the steam generator inlet tubesheet. Although the industry has developed specific fit-for-purpose design practice standards augmented with detailed technical reports, reliability issues persist and regularly force premature shutdown of the reformer heater and downstream heat recovery equipment. Among these practices are API Standard 530 and API TR 942-A. API 530 assists designers in the selection of materials and determination of pressure design thickness of heater tubes while API TR 942-A attempts to reconcile the contradictory industry experience where some operators have little or no problems while others suffer premature degradation and cracking of outlet pigtails and manifold components. A reconciliation between application of industry design practices and equipment performance is presented in this paper to determine whether systemic issues contribute to the apparent situation; and, recommendations are made for pressure component design and material selection for steam-methane reformers.

Manufacturing components for the nuclear industry requires large enclosed machining centres capable of accommodating the sheer size of the parts. Those machining centres are expensive to commission and they need a large infrastructure leading to the high costs associated with manufacturing. Robotic machining offers noticeable infrastructure savings. This could narrow down the infrastructure requirements leading to a general reduction of the high cost associated with new nuclear build. Machining robots generally suffer from reduced static and dynamic stiffness when compared with machining centres. This renders them more prone to chatter type of vibrations. Especially at relatively low speed cutting of super-alloys, the low frequency modes of the robot may be excited at high amplitudes due to the high cutting forces at low excitation frequencies. In this paper, the effects of chattering, due to the dynamics of the machining robot, on surface integrity are evaluated comparing stable, mild and severe chattering conditions. Surface roughness and residual stresses are evaluated in robotic milling of alloy 690 using ceramic inserts. The results are discussed focusing on the effects of chatter vibrations due to the machining robot on the surface integrity.

This research investigated the effects of global (in other words, furnace-based) and local post weld heat treatment (PWHT) on residual stress (RS) relaxation in API 5L X65 pipe girth welds. Two pipe spools were fabricated using identical pipeline production procedures for manufacturing multi-pass narrow gap welds. Non-destructive neutron diffraction strain scanning was carried out on girth welded pipe spools and stress-free comb samples and also thin slices for the determination of lattice spacing. All residual stress measurements were carried out at the KOWARI strain scanning instrument at the Australian Nuclear Science and Technology Organization (ANSTO). Residual stresses of two pipe spools (in the as-welded condition) were measured through the thickness in the weld material and adjacent parent metal starting from the weld toe. Three line-scans were completed 3mm below outer surface, at mid thickness and 3mm above the inner surface. PWHT was adopted for stress relaxation; one pipe was conventionally heat treated entirely in an enclosed furnace and the other was locally heated by a flexible ceramic heating pad. Residual stresses were measured after PWHT at exactly the same locations as those used for the as-welded condition. Residual stress states of the two pipe spools in as-welded condition and after PWHT were compared and the results were presented in full stress maps. Additionally, through thickness residual stress profiles and the results of one line scan (3mm below outer surface) were compared with the respective residual stress profiles advised in British Standard BS 7910 “Guide to methods for assessing the acceptability of flaws in metallic structures” and the UK nuclear industry’s R6 procedure. The residual stress states of the two pipe spools measured in the as-welded condition were similar. With the given parameters, local PWHT has effectively reduced residual stresses in the pipe spool to such a level that it prompted the thought that local PWHT can be considered a substitute for global PWHT.

This study provides effects of bonding temperature conditions on practical strength in ceramic to metal joint system made by two stages bonding process. Ceramic to metal joint system is required to reduce the residual stress near the edge of the interface and to improve bonding strength. The two stages bonding process, which was proposed in PVP2015-45822, can be a useful method to prevent the residual stress from increasing. This process consists of two stages, the first bonding process defined as a ceramic is bonded to thin metal layer at high temperature and the secondary process defined as a thick metal is bonded to the thin metal layer of the joint at lower temperature. It is necessary to provide effects of thickness of thin metal layer on the practical bonding strength in various combinations of the first and the secondary bonding temperature conditions. Past experimental results showed the practical bonding strength would be dominated by the residual stress near the edge of the interface between the thin metal layer and the ceramic. The residual stress can be associated with the first and/or the secondary bonding temperature conditions. Setting the optimum metal thickness improves the bonding strength independent of the bonding temperature conditions in the limited conditions. This paper provided dependence of the optimum metal layer thickness on the first and the secondary bonding temperature conditions was clarified experimentally. It also found effective metal thickness, which is capable of strengthening the siliconnitride to nickel joint system, in the combination of the first bonding temperature ranged over from 880°C to 980°C and the secondary bonding temperature ranged over from 600°C to 700°C. It appeared the first bonding temperature and the secondary one are set at the higher, the optimum metal thickness becomes smaller. The result showed that decreasing metal thickness possesses similar effect to decreasing bonding temperature for reducing the thermal residual stress. Reducing the residual stress is capable of strengthening the part of the edge of the interface on the ceramic side. Setting the metal layer thinner should be applied for producing the high strength ceramic to metal joint system. The two stages bonding process can contribute to achieve the high strength bonded dissimilar materials by setting the optimum thin metal thickness.

Coned and threaded type connection valves, fittings and tubing up to sizes of 9/16” are typical high pressure components used on the initiator injection system of a Low Density Polyethylene LDPE facility. The process pressures of up to 360 MPa (52,200 psi) on the reactor side require even higher pressures on the initiator injection lines. Based on the differential pressures and the challenging environment 414 MPa (60,000 psi) has been defined as an appropriate pressure rating for such components. Valves, fittings and tubing with this pressure rating are more or less standardized and available from multiple sources on the market. However, the technical challenges in designing and manufacturing components for this duty are sometimes under-estimated and design improvements can lead to a higher process safety and a reduced downtime. This paper covers the design requirements and has a specific focus on a filter with screwed element and a check valve with ceramic ball. The majority of high pressure in-line filters on the market have a sintered element that is press-fitted into the filter body. This design has some disadvantages in case of fast depressurizations as they occur when a safety valve or a rupture disk blows off. The sudden differential pressure may cause the element to move inside the body, and this can be accompanied by cracking of the element. Parts of the broken sintered element are a risk to the process since they would move downstream followed by a contamination of the reactor. A new generation of such filters with screw-in elements was designed and tested. The R&D work resulted in an extended element that fits into a modified filter body with standard outside dimensions. Before performing a field test at a LDPE plant three prototype samples went through intensive testing at the manufacturer’s facilities. Check valves are typical components used in order to maintain the flow in one direction. For liquids the metal to metal sealing ball type is the most common. Since the process pressure exposes the mating parts — ball and orifice — to high compression forces, imprints and marks on the ball surface are sometimes experienced. The material of these types of balls is typically bearing steel which has high mechanical strength but limited corrosion resistance. In order to improve the cycle life of high pressure ball check valves alternative materials were looked at. During the further product improvement a check valve with ceramic ball was designed and lab tested at the manufacturer’s facilities.

The ASTM E 1820 standard provides procedures and guidelines for the determination of fracture toughness of metallic materials, characterized by the J-integral. The recommended specimens are single-edge bend, SEN(B), compact, C(T), or disk-shaped, DC(T). Two alternative procedures for measuring crack extension are provided in the standard, the basic procedure and the resistance curve procedure. The basic procedure involves physical marking of the crack advance and multiple specimens are used to develop an R-curve (or J-Δa curve). The resistance curve procedure is an elastic-compliance method where multiple points are determined from a single specimen. Other procedures for measuring crack extension are allowed, typically the electric potential drop method. To use the elastic-compliance method, the displacement transducer (clip-gage) must have a very high resolution and stability, and a very low noise. For temperature ranging from −200°C to 100°C, a clip-gage with conventional strain gages (i.e. plastic resistance strain gages) gives generally good results. However, at higher temperatures, one must use either high temperature inductive or capacitive clip-gages, or conventional clip-gages placed outside of the oven and connected to the specimen by ceramic or quartz rods. In both cases, the results are not very satisfactory. So, for the measurement of the load-line displacement, a new method using the digital image correlation technique (DIC) was developed at EDF R&D. The CT specimens have integral-machined knife edges and a thermally resistant paint is sputtered on these edges, in order to have irregular patterns. During the test, a high resolution camera placed outside of the oven takes pictures of the knife edges at regular time intervals. These pictures are real time processed to calculate the relative displacements of the dots, and deduce the load-line displacement. The paper presents the technique and the results obtained on various materials.

This study provides information on the dependence of bonding temperature conditions on metal thickness effects in bonded dissimilar materials as a composite material system. Effects of metal thickness on the bonding strength were confirmed each bonding temperature condition by using silicon-nitride and nickel to confirm for each joint manufactured by a bonding method, two stages bonding process. This process used in this experiment consists of two stages, first bonding process as the ceramic is bonded to thin layer metal at high temperature, and secondary process as thick metal is bonded to the thin metal layer of the joint at lower temperature than first stage’s one. Bonding tensile strength of the joint specimen was evaluated experimentally. The bonding strength was dominated by the residual stress near the edge of the interface on ceramic side. The maximum bonding strength appears at optimum metal thickness. It shows that the optimum metal thickness depends on the first temperature condition. Reduction of the residual stress was considered based on the experimental and numerical results. Two stages bonding process can be applied for high strength bonded dissimilar materials as useful engineering application by setting optimum metal thickness each bonding temperature condition.

A new experimental device was developed to observe and measure the dynamic generation of supercritical CO 2 (scCO 2 ) in a closed chamber. The temperature and pressure were measured locally using a thin thermocouple and a pressure transducer, respectively. The Rayleigh scattering in the chamber was visualized using a high-speed video camera. The liquid CO 2 was heated by a ceramic heater located at the top or bottom of the chamber. Using this new experimental device, the color variation due to Rayleigh scattering was observed. The temperature profile was stable and scCO 2 was generated slowly within a few seconds when heating occurred at the top. For heating at the bottom, scCO 2 was created faster within 1 s. Additionally, natural convection, turbulence, and a phenomenon resembling boiling were observed. Numerical simulations of the scCO 2 creation in a chamber were also performed using the COMSOL Multiphysics application along with the PROPATH package to obtain the thermophysical properties of CO 2 . The simulation results showed that scCO 2 creation for heating at the top was stable due to the gas-like properties of the scCO 2 near the heater. For heating at the bottom, the density distribution initially depended on the temperature distribution. However, as natural convection developed, the flow in the chamber was perturbed and the density distribution depended on both the temperature distribution and the density fluctuation caused by the convection vortices. The same tendency was observed in the experimental results. Using PROPATH, the density variation in the scCO 2 generation was estimated from the measured temperature and pressure. The P-T diagram and density variation were compared in each experiment.

This paper briefly describes the design and the characterization of a new base isolation system for the seismic protection of HV ceramics circuit breakers, in order to be qualified according to the standard CEI 62271-207. The solution adopted is based on the use of Wire Ropes. Accurate numerical analyses and experimental tests performed on a typical HV breaker upon a shaking table demonstrated the effectiveness of the proposed solution. An on-site installation in several Italian substations of this system has permitted to verify the simplicity and rapidity of the intervention necessary for the seismic upgrading of the circuit breaker.

This study provides effects of metal thickness on bonding tensile strength of ceramic to metal joint based on numerical and experimental analyses. Thermal elastoplastic FEA was carried out to clarify effects of the metal side thickness on the stress distribution near the edge of the interface on ceramic side by changing metal side thickness each bonded silicon nitride to nickel joint system. It was confirmed the stress distribution on the ceramic of the joint system depends on the metal side thickness based on the FEM results. Decreasing of metal thickness reduces the intensity of the stress near the edge of the interface on ceramics side. It can be effective for reduction of the residual stress near the edge of the interface to use thin metal layer in the ceramic to metal joint. Reduction effects on the residual stress were confirmed by using two stages of bonding processing. This process used in this experiment consists of two stages, first bonding process as the ceramic are bonded to thin layer metal at high temperature, and secondary process as thick metal are bonded to the thin metal layer of the joint specimen at lower temperature than first stage. The bonding tensile strength of the joint specimens manufactured from the two stages bonding processe was evaluated experimentally. It appears that setting a ratio of metal thickness to length of the interface to approximate t m / W =0.08 achieves maximum bonding tensile strength. Effects of metal thickness on bonding tensile strength of ceramic to metal joint are confirmed based on numerical and experimental results.

The piezoresistivity and the micro fabrication capability have made the polymer derived ceramics (PDCs) an excellent candidate material for high temperature sensors. In this study, it was found that PDCs also exhibit creep and stress relaxation properties. Its electric resistance may change with time under certain loading conditions. In addition, the creep/stress relaxation rate is sensitive to temperature. It is demonstrated that even PDC materials have been processed at high temperatures and formed ceramic structure, they retain certain polymeric characteristics. Due to the piezoresistivity properties of PDC and its resilience to harsh environment, in particular, the predicted resistance to radiation field, the PDC based sensors are ideal for use as sensing media that can be deployed to important to safety (ITS) structures in nuclear systems, such as cooling water system and coolant pumps in light water reactors (LWRs).

Many engineering structures applied for generating energy are said to have been requiring high strength under high temperature conditions. Fine ceramic is expected to be useful in structural applications in various industries by joining to metals. Ceramic can be used in structural parts for engineering where resistance to high temperature and/or high strength are required from the viewpoint of the optimum structural design. Use of ceramic for engineering structures by joining to metal generates a bonded interface between the ceramic and metal.

Spiral Notch Torsion Fracture Toughness Test (SNTT) was developed recently to measure the intrinsic fracture toughness (K IC ) of structural materials. The SNTT system operates by applying pure torsion to uniform cylindrical specimens with a notch line that spirals around the specimen at a 45° pitch. The K IC values are obtained with the aid of a three-dimensional finite-element computer code, TOR3D-KIC. The SNTT method is uniquely suitable for testing a wide variety of materials used extensively in pressure vessel and piping structural components and weldments, including others such as ceramics, their composites, graphite, concrete, and polymeric composites. The SNTT test results for some of these structural materials are demonstrated in this paper.

The focus of this study is to clarify a dependence of bonding strength of ceramic to metal joint on interface wedge angle in metal side. Each plate Si 3 N 4 -to-Cu or Ni joint with plane interface is produced by electric discharge machining. Geometrical shape at the edge of the interface is characterized by wedge angle defined as a configuration angle between free surface of each material and the interface. As the wedge angle of Si3N4 is right angle, the wedge angle of metal is set over from 30° to 180°. Each joint is bonded at high temperature by using thin braze metal under vacuum and slowly cooled. Tensile bonding strength of the joint is evaluated. Result shows that decrease of the wedge angle of metal side from right angle improves the bonding strength since it decreases the residual stress near edge of the interface on ceramic side. The highest bonding strength appears at the identical interface condition where fracture pattern changes. It appears that optimum edge angle for obtaining the highest bonding strength depends on bonding temperature and combination of bonded materials. This paper provides a useful geometrical interface shape to improve tensile bonding strength of ceramic to metal joint.

The Calcine Disposition Project (CDP) of the Idaho Cleanup Project (ICP) has the responsibility to retrieve, treat, and dispose of the calcine stored at the Idaho Nuclear Technology and Engineering Center (INTEC) located at the Idaho National Laboratory. Calcine is the granular product of thermally treating, or calcining liquid high-level waste (HLW) that was produced at INTEC during the reprocessing of spent nuclear fuel (SNF) to recover uranium. The CDP is currently designing the Hot Isostatic Pressure (HIP) treatment for the calcine to provide monolithic, glass-ceramic waste form suitable for transport and disposition outside of Idaho by 2035 in compliance with the Idaho Settlement Agreement. The HIP process has been used by industry since its invention, by Battelle Institute, in 1955. Hot isostatic pressing can be used for upgrading castings, densifying pre-sintered components, and consolidate powders. It involves the simultaneous application of a high pressure and temperature in a specially constructed vessel. The pressure is applied on all sides with a gas (usually inert) and, so, is isostatic. The CDP will use this treatment process (10,000 psi at 1,150 C) to combine physically and chemically a mixture of calcine and granular additives into a non leachable waste-form. The HIP process for calcine involves filling a metal can with calcine and additives, heating and evacuating the can to remove volatiles, sealing the can under vacuum, and placing the can within the HIP machine for treatment. Although the HIP process has been in use for over 50 years it has not been applied in large scale radioactive service. Challenges with retrofitting such a system for Calcine treatment include 1) filling and sealing the HIP can cleanly and remotely, 2) remotely loading and unloading the HIP machine, and 3) performing maintenance and repair on a 300 ton, hydraulically actuated machine in a highly radioactive hot cell environment. In this article, a systems engineering approach, including use of industry-proven design-for-quality tools and quantitative assessment techniques is summarized. Discussions on how these techniques were used to improve high-consequence risk management and more effectively apply failure mode, RAMI, and time and motion analyses at the earliest possible stages of design are provided.

In this study the combination effects of shot peening (SP) and crack-healing on the contact strength of ceramics were examined. Si 3 N 4 /SiC composite ceramics with high crack-healing ability were used and the specimens were subjected to shot peening with several peening pressures and shot diameters. Then, some specimens subjected to SP were heat-treated in air to heal surface cracks introduced by shot peening. Sphere indentation tests were carried out on the specimens and investigated the Weibull distribution of the contact strength. As a result, it is found that the combination of shot peening and crack-healing is effective to increase contact strength and decrease the scatter of the contact strength.

This study was performed to clarify dependences of bonding strength on the interface wedge angle in the metal side of ceramic-to-metal joint. Each plate Si 3 N 4 and Ni used for this experiment is produced by wire electric discharge machining. The geometric interface shape at the edge of the interface is characterized by wedge angle on both side of the ceramic and metal defined as a configuration angle between the free surface of each material and the interface. As the wedge angle of Si 3 N 4 is a right angle, the wedge angle of Ni is set from 30° to 180°. Joint specimens were bonded at high temperature using braze metal of 0.05mm thickness under vacuum and cooled slowly. The tensile bonding strength of the ceramic-to-metal joint was evaluated to determine the optimum interface shape. The highest bonding strength appeared under identical interface conditions where the fracture pattern changed. This study provided a useful geometric interface shape to improve the tensile bonding strength of ceramic-to-metal joint.

Ceramic tiles are the main ingredient of a multi-layer multi-material composite being considered for the modernization of tank armors. The high stiffness, low attenuation, and precise dimensions of these uniform tiles make them remarkable resonators when driven to vibrate. Defects in the tile, during manufacturing or after usage, are expected to change the resonance modes. The comparison of a pristine tile/lay-up and a defective tile/lay-up will thus be a quantitative damage metric. This study is aimed at examining the vibration modes of the tiles and the composite lay-up and using these vibrations to detect and characterize defects.