Fabrication Of Pressure Vessels Research Articles

An assessment of acoustic emission for nuclear pressure vessel monitoring

Recent research has greatly improved our understanding of the basic mechanisms of deformation and fracture that generate detectable acoustic emission signals in structural steels. A critical review of the application of acoustic emission (AE) to the fabrication, proof testing and in-service monitoring of nuclear pressure vessels is presented in the light of this improved understanding. The detectability of deformation and fracture processes in pressure vessel steels is discussed, and recommendations made for improving source location accuracy and the development of quantitative source assessment techniques. Published data suggest that AE can make an important contribution to weld fabrication monitoring, and to the detection of defects in lower toughness materials during vessel proof testing. In high toughness materials, however, the signals generated during ductile crack growth may frequently be too weak for reliable detection. The feasibility of AE for continuous monitoring has not yet been adequately demonstrated because of high background noise levels and uncertainty about AE signal strengths from the defect growth processes that occur in service. In-service leak detection by AE shows considerable promise. It is recommended that further tests are carried out with realistic defects, and under realistic conditions of loading (including thermal shock and fatigue) and of environment.

On the Temper Embrittlement of Manganese-Molybdenum-Nickel Steels

The manganese-molybdenum-nickel steels ASTM A533B and A508 are extensively used in the fabrication of reactor pressure vessels and steam generators in light water reactors. These components receive heat treatments during fabrication and in operational service that could lead to a possible degradation of toughness as a result of grain boundary segregation of alloying and impurity elements promoting temper embrittlement.The susceptibilities to temper embrittlement of commercially produced thick section A533B Class 1 and A508 Class 3 steels have been investigated by Charpy impact testing following isothermal heat treatments in the 300 to 600°C temperature range for periods up to 5000 h. In addition, the combined effects of austenite grain size and impurity content have been studied using experimental melts of the 533B/508 Class 3 type alloy composition doped with specific impurities. The lower and upper shelf fracture modes were examined as a function of aging treatment, and samples exhibiting a low temperature intergranular fracture mode were examined using Auger Electron Spectroscopy to determine the amount and types of elements segregated at the grain boundaries.While the commercial materials have been found to exhibit only small increases in the ductile-brittle transition temperature after isothermal aging at 450 to 500°C, large increases are observed for the experimental material with a high phosphorus content. The degree of embrittlement is strongly dependent on austenite grain size, increasing with increasing grain size. These results indicate the need for close control of chemical composition of the steel in inhibiting embrittlement and cracking in the weld coarse-grained, heat-affected zone regions.

Materials of construction in the fatty acid industry

AbstractThe basic material of construction for the tankage and reactors that are used in the fatty chemical industry is one or another variant of the 300 series stainless steels. The use of these alloys essentially eliminates the possibility of iron and other metal contaminations which may either degrade the product or catalyze undesirable oxidation and other side reactions. With certain exceptions, it has been found that Type 304 stainless steel may be used in fatty chemical processing at temperatures up to 150 C and Type 316 stainless steel for tanks and vessels designed for use above that temperature. Where welding is involved in the fabrication of equipment designed for high temperature usage, it has been found necessary to use either a special low carbon stainless steel or an alloy which contains an extra ingredient that will inhibit carbide precipitation in the weld area since such precipitation usually results in a point of corrosion and ultimate failure. in the fabrication of pressure vessels, it is normal practice to use carbon steel plates of suitable thickness that have a minimal amount of the desired alloy bonded to the surface rather than fabricate of solid alloy. This not only reduces the cost of the vessel but adds greatly to the strength of the sheet since most high alloys lose tensile strength rapidly as temperatures are increased while carbon steel retains strength until very high temperatures are reached. In addition to the 300 series stainless steels, certain highly specialized alloys such as Inconel 825, Carpenter 20 Cb, or Monel are frequently used for extreme acid conditions. The lower cost of aluminum as compared to a high alloy makes it attractive for storage tanks but it can be used only when materials contain no moisture, since even traces of water accelerate the rate of corrosion and rapidly render the tank unusable. New materials on the scene are fiberglass‐polyester tankage and applied linings of the phenolic or the epon‐epoxy type. These materials do not have a wide application, but where their use is possible, it is a lower cost answer to the problem of iron contamination.

Fabrication of Pressure Vessels

Heavy section steel pressure vessels for light water reactor and aluminum tank for liquefied natural gas carrier are chosen to review the fabrication of pressure vessels. With regard to RPV, materials, effects of fabrication thermal history, fabrication procedure and advanced welding technique are dealt with. For the fabrication of aluminum cryogenic tanks for LNG carrier, a special factory equipped with plasma arc cutting, various automatic gas metal arc welding machines and so on, is advisable.

Effect of Mean Stress and of Mean Strain in Low-Cycle Fatigue of A-517 and A-201 Steels

A number of low-cycle fatigue tests has been carried out at room temperature on two materials commonly used in pressure vessel fabrication. For strain-controlled tests, the influence of different mean strains is studied; similarly, the effect of varying the mean stress is analyzed for stress-controlled tests. Relations involving elastic and plastic strain ranges, and the variations of strains or stresses during the fatigue tests are discussed.

Technology of Steel Pressure Vessels for Water-Cooled Nuclear Reactors

A synopsis of the report Technology of Steel Pressure Vessels for Water-Cooled Reactors, USAEC Report ORNL-NSIC-21, December 1967 is presented. Current practices employed in the United States for the design and fabrication of steel pressure vessels for commercial station light water cooled nuclear reactors are reviewed. The specified service and predicted environmental conditions are identified, along with an evaluation of the effects of these parameters on materials behavior. Materials properties of interest in pressure vessel fabrication are reviewed. The codes and standards applied in the technology are identified and the methods of inspection discussed. The methods of surveillance and potential techniques for post-operational and in-serve inspection are summarized.

Pressure Vessels of High Proof Strength Warm Worked Stainless Steel

In order to establish the necessary data to enable high proof strength austenitic stainless steels to be used for the fabrication of pressure vessels, plates were produced with an increased proof stress obtained by the warm working method. The laboratory investigation then showed that it was practicable to raise the proof strength of this material to twice the normal value for fully softened plate with an improvement in the ultimate tensile strength. Following this, two similar experimental vessels were manufactured in normal and high proof strength 18% Cr-8% Ni-Ti stabilized steel and these were subjected to hydraulic pressure testing. The vessel tests showed how stainless steel vessels behave under static pressure application at room temperature, and the behaviour of the high proof strength vessel indicated that it would be quite safe at nearly double the design pressure for the fully softened vessel. The strain hardening of stainless steel, fabricating techniques and weld quality have also been investigated and these are reported upon in the paper. Proposals for design stress criteria and stress values are made in relation to an examination of existing pressure vessel codes and the experimental data.

Quality control and nondestructive testing in reactor pressure vessel fabrication

The objectives of this paper are to briefly outline a quality control program for the design and fabrication of a nuclear reactor pressure vessel which will meet all nuclear and safety requirements, and to show how nondestructive testing can help to achieve the broad objective. Failure in materials, components, and assembly has demonstrated that our present techniques of fabrication are not sufficient alone to assure repeated reliability in critical components. Flaws and inhomogeneities occur even when using the best processes and properly controlled procedures. Thus an adequate and well integrated nondestructive testing program is necessary to assure the quality level required in a nuclear reactor pressure vessel. The principal nondestructive methods used in the fabrication of reactor pressure vessels are: visual, X-ray and gamma radiography, ultrasonics, magnetic particle, and liquid penetrant. The nondestructive testing program must include the inspection of plate material, forging, casting, cladding, and welds. Various methods and their application to the nondestructive testing of pressure vessels and components will be illustrated and discussed.

Quality control and nondestructive testing in reactor pressure vessel fabrication

The objectives of this paper are to briefly outline a quality control program for the design and fabrication of a nuclear reactor pressure vessel which will meet all nuclear and safety requirements, and to show how nondestructive testing can help to achieve the broad objective. Failure in materials, components, and assembly has demonstrated that our present techniques of fabrication are not sufficient alone to assure repeated reliability in critical components. Flaws and inhomogeneities occur even when using the best processes and properly controlled procedures. Thus an adequate and well integrated nondestructive testing program is necessary to assure the quality level required in a nuclear reactor pressure vessel. The principal nondestructive methods used in the fabrication of reactor pressure vessels are: visual, X-ray and gamma radiography, ultrasonics, magnetic particle, and liquid penetrant. The nondestructive testing program must include the inspection of plate material, forging, casting, cladding, and welds. Various methods and their application to the nondestructive testing of pressure vessels and components will be illustrated and discussed.

原子炉圧力容器の製作と検査

原子炉圧力容器の製作と検査

Practical Considerations in Applying Laboratory Fracture Test Criteria to the Fracture-Safe Design of Pressure Vessels

Trends in pressure vessel applications involving higher pressures, lower service temperatures, thicker walls, new materials, and cyclic loading require the development of new bases in the supporting scientific and technological areas. This report presents a “broad look” analysis of the opportunities to apply new scientific approaches to fracture-safe design in pressure vessels and of the new problems that have arisen in connection with the utilization of higher-strength steels. These opportunities follow from the development of the fracture analysis diagram which depicts the relationships of flaw size and stress level for fracture in the transition range of steels which have well-defined transition temperature features. The reference criteria for the use of the fracture analysis diagram is the NDT temperature of the steel, as determined directly by the drop-weight test or indirectly by correlation with the Charpy V test. Potential difficulties in the correlation use of the Charpy V test are deduced to require engineering interpretation of Charpy V test data rather than to involve basic barriers to the use of the test. The rapid extension of pressure vessel fabrication to Q&T steels is expected to provide new problems of fracture-safe design. These derive from the susceptibilities of steels within this family to tear fractures of low energy absorption. This fracture mode does not involve a transition temperature and is therefore relatively independent of temperature. It is emphasized that such susceptibilities are not inherent to the family of Q&T steels of low and intermediate strength levels, but are related to specific metallurgical conditions of the plate and particularly the HAZ (heat-affected-zone) regions of Q&T steel weldments.