Manufacture Of Pressure Vessels Research Articles

Selection of candidate materials for reactor pressure vessels: Application of irradiation embrittlement prediction models and a stringency level methodology

The selection of materials for the reactor pressure vessel manufacturing is a complex process that involves great responsibility because small differences in chemical composition can adversely affect the manufacturing process and the in-service behavior of the material. Thus, it is recommendable to perform previous materials pre-selection stages based on the state-of-the-art knowledge, integrating research results with standardized requirements and using simplifier materials selection methodologies like the stringency level method. To address this issue, an evaluation of the influence of chemical composition on the shift of the ductile-to-brittle transition temperature has been performed using the most used and consolidated prediction models that are R.G. 1.99 Rev.2, NUREG/CR-6551, and ASTM E 900-02. A proposal of maximum limits for copper, nickel, and phosphorous to avoid irradiation embrittlement has been presented to carry out the process. The results have been analyzed by using the stringency level methodology to support the decision process. To this end, a materials data collection has been carried out to analyze the requirements described by 20 different specifications of materials from first to fourth generation of light water reactors, covering the main designs of pressurized reactors from Western Europe, North America, Japan, and Russia. It can be concluded that more recently developed materials exhibit more stringent requirements than earlier developed materials.

Establishing Correlation Between Current and Voltage Signatures of the Arc and Weld Defects in GMAW Process

Welding is one of the major metal-joining process employed in fabrication industries, especially in manufacturing of boilers and pressure vessels. Control of weld quality is very important for such industries considering the severe operating conditions. Industries are looking for some kind of real-time process monitoring/control that will ensure the weld quality online and prevent the occurrence of defects. In this paper an attempt is made to establish a correlation between the current and voltage signatures with the good weld and weld with porosity and burn through defect during the welding of carbon steel using gas metal arc welding (GMAW) process. Experimental setup has been established and experiments were conducted using a welding robot integrated with GMAW power source. The experimental setup includes online current and voltage sensors, data loggers, and signal processing hardware and software. Welding conditions are carefully designed to produce good weld and weld with defects such as burn through and porosity. Current and voltage signatures are captured using data acquisition system (DAS). Software has been developed to analyze the data captured by the DAS. Statistical methods are employed to study the transient data. The probability density distributions of the current and voltage signature demonstrates a good correspondence between the current and voltage signatures with the welding defect.

Evaluation method for pressure vessel manufacturing codes: the influence of ASME unit conversion

This paper presents an assessment of the selection of manufacturing codes for pressure vessels. We focus on one of the most relevant approximation methods used in manufacturing calculations for pressure vessels, i.e., the unit conversions of the ASME boiler and pressure vessels (B&PV) code. To evaluate the influence of its conversions, several errors arising from the manufacturing process and measurement systems have been calculated, estimated and considered. In addition, a decision tool for manufacturing codes of pressure vessels with novel considerations based on stringency levels is presented to improve the current selection process. The general conclusion is that adjusting the pressure units is not recommendable when designing a pressure vessel due to large errors that can accumulate. Furthermore, the length conversion is only suitable for parts manufactured with maximum dimensions of five inches (125 mm).

Evaluation method for pressure vessel manufacturing codes: the influence of ASME unit conversion

This paper presents an assessment of the selection of manufacturing codes for pressure vessels. We focus on one of the most relevant approximation methods used in manufacturing calculations for pressure vessels, i.e., the unit conversions of the ASME boiler and pressure vessels (B&PV) code. To evaluate the influence of its conversions, several errors arising from the manufacturing process and measurement systems have been calculated, estimated and considered. In addition, a decision tool for manufacturing codes of pressure vessels with novel considerations based on stringency levels is presented to improve the current selection process. The general conclusion is that adjusting the pressure units is not recommendable when designing a pressure vessel due to large errors that can accumulate. Furthermore, the length conversion is only suitable for parts manufactured with maximum dimensions of five inches (125 mm).

Narrow gap laser welding for potential nuclear pressure vessel manufacture

High power density electron beam and laser beam welding show their unique advantages in the welding of thick-section steels for potential nuclear pressure vessel manufacture. Compared with traditional submerged arc welding or newly developed narrow-gap submerged arc welding, electron beam welding and laser beam welding techniques offer high welding speeds, low heat inputs, lower levels of residual stresses and distortion, while consuming less filler material and power. As a part of the new nuclear manufacturing EPSRC Program, this study aimed to develop narrow gap laser welding procedures and parameters for joining 30–130 mm thick ferritic steels for potential application to pressure vessel manufacture in civil nuclear power plants. The results showed that high quality welded joints in 30 mm thick steels had been achieved with a combination of an autogenous root pass and multipass narrow gap (4–5 mm parallel grooves) welding with a defocused laser beam welding and filler wire addition, at laser powers of 7.5–8 kW, a welding velocity of 0.4 m/min, a diameter of the laser spot of 6 mm, and wire feed rates of 4–6 m/min. The results also showed that cracking, lack of sidewall fusion, and porosity were the main defects in multiple pass narrow gap laser welds in thick-section ferritic steels if the welding parameters were not optimized. The microhardness of the multipass weld was lower than that of the autogenous weld as tempered martensite was achieved in multipass welding.

Application of carbon fiber-reinforced plastics in the manufacture of toroidal pressure vessels

This paper provides a comparative analysis of two design variants of two types of pressure vessels, metal and hybrid, the latter of which consists of metal and carbon fiber-reinforced plastics. The experimental results show that there is a reserve of strength that allows reducing the weight of the metal toroidal pressure vessel by thinning its metal wall and auxiliary winding with carbon-fiber prepreg. As compared with the allmetal tank, the savings in weight was 45% under the same operating characteristics. A pressure vessel design and its basic properties are provided.

The decoupling visual feature extraction of dynamic three-dimensional V-type seam for gantry welding robot

During the welding manufacturing of a circular pressure vessel, the V-type seam’s position relative to welding torch varies dramatically due to the seam curvature change or axial asymmetry movement. Thus, a decoupling visual seam detection method for a 3-axes gantry welding robotis developed to implement automatic welding. Firstly, a visual system with laser structured light is developed to measure the deviation between the torch and welding seam in horizontal and vertical directions. Secondly, a multiple peak detection algorithm for laser profile is proposed to overcome the interference in high strength reflection area. Then, a decoupling visual detection algorithm is presented to gain approximately uncoupled relationship between the image feature and the movement of adjustment mechanism. Finally, in a gantry robot system, some experiments that verify the proposed methods are well illustrated with satisfactory performance.

A physically-based constitutive model for SA508-III steel: Modeling and experimental verification

Due to its good toughness and high weldability, SA508-III steel has been widely used in the components manufacturing of reactor pressure vessels (RPV) and steam generators (SG). In this study, the hot deformation behaviors of SA508-III steel are investigated by isothermal hot compression tests with forming temperature of (950–1250)°C and strain rate of (0.001–0.1)s−1, and the corresponding flow stress curves are obtained. According to the experimental results, quantitative analysis of work hardening and dynamic softening behaviors is presented. The critical stress and critical strain for initiation of dynamic recrystallization are calculated by setting the second derivative of the third order polynomial. Based on the classical stress–dislocation relation and the kinetics of dynamic recrystallization, a two-stage constitutive model is developed to predict the flow stress of SA508-III steel. Comparisons between the predicted and measured flow stress indicate that the established physically-based constitutive model can accurately characterize the hot deformations for the steel. Furthermore, a successful numerical simulation of the industrial upsetting process is carried out by implementing the developed constitutive model into a commercial software, which evidences that the physically-based constitutive model is practical and promising to promote industrial forging process for nuclear components.

The potential of dry winding for rapid, inexpensive manufacture of composite overwrapped pressure vessels

We are proposing a methodology for reducing manufacturing time and cost of composite overwrapped pressure vessels (COPVs). Dry winding methodology promises to increase bonding speed enabling rapid vessel winding (10 min vs. 3 h with today's wet winding approach) with no need for oven curing. Faster winding is likely to reduce vessel cost due to higher throughput enabling increased productivity from expensive winding machines as well as reduced labor cost per vessel. Tape manufacture in large scale in a central facility minimizes tape handling and distribution costs. Finally, high ratio of fiber to resin reduces resin cost as well as the wall thickness for any necessary strength, increasing the packaging efficiency of the vessel and reducing weight.

Investigation on Mechanical Behaviors of Cold Stretched and Cryogenic Stretched Austenitic Stainless Steel Pressure Vessels

Austenitic stainless steel is widely used in pressure vessels for storage of liquid gas, such as LN2, LO2, LH2. To make wall thin and weight light, cold stretching technology is applied in cryogenic pressure vessel manufacture. Cold stretching is performed by pressurizing a vessel to a specific pressure and maintaining the pressure for a moment to produce a certain amount of plastic deformation, so that the yield strength of the vessel material could be strengthened after releasing the pressure. Cryogenic stretching is similar in principle to cold stretching, but the medium is liquid nitrogen instead of water in cold stretching. Cold stretching has been recorded in standards such as Cold-Stretching Directions 1991, AS 1210-Supp2-1999, EN 13458-2:2002, EN 13530-2:2002, ASME BPVC VIII-I Code Case 2596, ISO 20421-1:2006, ISO 21009-1:2008. Nevertheless, cryogenic stretching is not applied in pressure vessels manufacture due to lack for detailed investigation. To investigate mechanical behaviors of cold stretched and cryogenic stretched austenitic stainless steel pressure vessels, a series of tests for S30403 were performed at 20°C (temperature in which cold stretching proceeds) and -196°C (temperature in which cryogenic stretching proceeds), the difference of martensite transformation, strength and plasticity in which were compared. Finite element analysis method based on MISO model was used to simulate cold stretching process of pressure vessel, including the process of loading to strengthening pressure, unloading to no-load state and reloading to design pressure. Considering material properties difference, different types of strengthening pressure methods for cryogenic stretching were performed to confirm a rational strengthening pressure value. Mises equivalent stress, tresca equivalent stress, circumferential stress, axial stress and deformation were taken into consideration. The investigation has shown that compared with cold stretching, cryogenic stretching could improve material properties more significantly. In other words, pressure vessels could have thinner wall and lighter weight after cryogenic stretching.

English

Gas Tungsten Arc Welding is most commonly called Tungsten Inert Gas welding .TIG welding has become indispensible as a tool for many industries because of the high quality welds produced at relatively low equipment cost. Aluminum Alloy 6082 [AA 6082] is typically used in highly stressed applications, trusses, bridges, cranes, trusses, milk churns, transport applications etc. Aluminum Alloy 5083 [AA 5083] is commonly used in the manufacturing of pressure vessels, marine vessels, storage tanks shipbuilding, armored vehicles, aircraft cryogenics, drilling rigs, structures and even in missile components etc. In this research, AA5083 and AA6082 welds are made with gas tungsten arc welding (GTAW) using AA 5356filler wire with non-pulsed current and pulsed current at different pulse frequencies like 2 pulses/sec, 4 pulses/sec, and 6 pulses/sec using precision TIG 375 welding machine. This report to investigates the weld quality through non destructive testing(NDT) to study the porosity and surface cracks and also the mechanical properties like ultimate tensile strength(UTS), 0.2% yield strength(YS) and % of elongation using GTAW with non-pulsed current and pulsed current at different pulse frequencies were studied and also to find the weld joint efficiency of the weldments

Continuous Cooling Transformations in Nuclear Pressure Vessel Steels

A class of low-alloy steels often referred to as SA508 represent key materials for the manufacture of nuclear reactor pressure vessels. The alloys have good properties, but the scatter in properties is of prime interest in safe design. Such scatter can arise from microstructural variations but most studies conclude that large components made from such steels are, following heat treatment, fully bainitic. In the present work, we demonstrate with the help of a variety of experimental techniques that the microstructures of three SA508 Gr.3 alloys are far from homogeneous when considered in the context of the cooling rates encountered in practice. In particular, allotriomorphic ferrite that is expected to lead to a deterioration in toughness, is found in the microstructure for realistic combinations of austenite grain size and the cooling rate combination. Parameters are established to identify the domains in which SA508 Gr.3 steels transform only into the fine bainitic microstructures.

Characterization of Local Stress-Strain Behavior in WWER 440 Weld and Base Metal by Instrumented Indentation Technique

15Ch2MFA (base metal) as well as 10ChMFT (weld) steels used for WWER 440 nuclear reactor pressure vessel manufacturing present a gradient in mechanical properties through the wall thickness, which can hardly be assessed by conventional testing such as tensile or Charpy tests. Mechanical properties in the weld and base metal were therefore determined by performing a series of instrumented indentations across the weld at room temperature. The results were treated by so-called automated ball indentation technique. Local stress-strain behavior obtained by instrumented indentation was correlated to the tensile test data and microstructure characterized by metallographic analysis.

Structural integrity of nuclear reactor pressure vessels

The paper starts from concerns expressed by Sir Alan Cottrell, in the early 1970s, related to the safety of the pressurized water reactor (PWR) proposed at that time for the next phase of electrical power generation. It proceeds to describe the design and operation of nuclear generation plant and gives details of the manufacture of PWR reactor pressure vessels (RPVs). Attention is paid to stress-relief cracking and under-clad cracking, experienced with early RPVs, explaining the mechanisms for these forms of cracking and the means taken to avoid them. Particular note is made of the contribution of non-destructive inspection to structural integrity. Factors affecting brittle fracture in RPV steels are described: in particular, effects of neutron irradiation. The use of fracture mechanics to assess defect tolerance is explained, together with the failure assessment diagram embodied in the R6 procedure. There is discussion of the Master Curve and how it incorporates effects of irradiation on fracture toughness. Dangers associated with extrapolation of data to low probabilities are illustrated. The treatment of fatigue-crack growth is described, in the context of transients that may be experienced in the operation of PWR plant. Detailed attention is paid to the thermal shock associated with a large loss-of-coolant accident. The final section reviews the arguments advanced to justify ‘Incredibility of Failure’ and how these are incorporated in assessments of the integrity of existing plant and proposed ‘new build’ PWR pressure vessels.

Application of laser welding technology in manufacture of pressure vessels of titanium alloy

Some features of the reducing of weight and size of high pressure vessels (HPV) with using of a thin-walled metal shell-liner from titanium alloy VT-1,0 are considered in this paper. The main difficulties are encountered under the manufacture of welded titanium alloy liner VT-1,0. There are presented the results of the selection of welding titanium alloy VT-1,0, shown the influence of technology of edge preparation on the quality of welded joints as well as the possibility of using laser welding technology in the liner of the VT-1,0.

A fuzzy multi-attribute approach to select the welding process at high pressure vessel manufacturing

Metal welding process selection calls for extensive know-how which deals with a huge amount of knowledge. Hence, the automation of knowledge through a knowledge-based system will greatly enhance the decision-making process. Fuzzy analytical hierarchy process (AHP)-TOPSIS investigates the relative welding process selection factors and it can compare and evaluate different welding processes between 0 and 1.This paper describes a knowledge-base system developed for identifying the most appropriate welding processes to suit specific circumstances. In the present study, nine important welding processes were used in the system. Ten parameters namely alloy class, material thickness, deposition rate, design application, joint configuration, operator factor, capital cost, equipment portability, filler metal utilization and welding position, are used to determine the best selection among competitive welding processes for high pressure vessel production. Also the sensitivity analysis was carried out for five cases.

Function Design of PDM System for Small-Medium Scale Pressure Vessel Manufacturing Enterprises

According to the process feature of Pressure Vessel Manufacturing Enterprises,a PDM system for Small-medium Scale Pressure Vessel Manufacturing Enterprises was designed .The system includes many functions such as document management,project management,BOM management,changement management, user’s permissions management.The integration with CAX，ERP，etc．were also considered in the system．The key techniques and conditions in software to realize the functions were explained．The system avoids information isolated between workshops and sections, improves the sharing and Integrality of enterprise’s information．It is useful for management and controlling of Pressure Vessel process and product quality．

Analysis of Pressure Vessel Manufacturing Technology Development

With the rapid development of modern industry, pressure vessel technology has been widely applied in research and industrial production, and some of pressure vessels have been required under more harsh applied conditions such as severe bearing loads and large-sizes, making higher demands on the manufacturing and security for them. This paper outlines the various pressure cylinder structures that have emerged in history and their evolution processes, and proposes a reasonable interlocking steel strip wound cylinder and analyses its structural characteristics. It can not only resolve the issue of the axial bearing load of the winding cylinder well but also be manufactured economically

Características microestructurales de la aleación AA6061 repujada

El proceso de repujado para la fabricación de tubos de aluminio ha sido muy poco estudiado, quizá debido al bajo tonelaje procesado por este método, lo que lo hace poco relevante frente a otros procesos de deformación plástica. Sin embargo, es un método económicamente competitivo para la fabricación de recipientes de presión livianos, consistentes en un liner de aleación de aluminio reforzado con fibra de vidrio. Los efectos producidos sobre la microestructura de una aleación de aluminio AA 6061 durante el proceso de repujado son poco conocidos. Sin embargo, los cambios pueden llevar a provocar o favorecer el agrietamiento (fisuración) de la aleación durante el proceso de deformación plástica. En este trabajo se estudian los cambios microestructurales producidos por la deformación plástica durante el repujado y el tratamiento térmicos final de un cilindro de aluminio y los efectos de las variables de procesamiento

Microfisuración en el proceso de repujado de aluminio

El repujado de aleaciones de aluminio es un proceso muy antiguo, pero muy poco estudiado, quizá debido al bajo tonelaje procesado por este método, lo que lo hace poco relevante frente a otros procesos de deformación plástica. Sin embargo, es un método económicamente competitivo para la fabricación de recipientes de presión livianos, consistentes en un liner de aleación de aluminio reforzado con fibra de vidrio. Este proceso presenta el inconveniente de la formación de microfisuras que sirven como concentradores de tensión y provocan la fractura del recipiente durante la carga cíclica. Se encontró que esto sucede aún con longitudes de grieta muy inferiores a las predichas en la bibliografía para la aleación AA6061. Se estudió la formación de las microfisuras y la influencia de dos variables de proceso, temperatura de calentamiento y velocidad de deformación plástica, sobre las características de las mismas. Las experiencias muestran que temperaturas más altas y menores velocidades de conformación reducen la formación de microfisuras.