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From cutting edge research of new processes for the manufacture of equipment for the energy production industry: Walter Tosto S.p.A. demonstrates in this paper, its experience in the highly specialized robotic welding process TIG narrow gap, widely used in the construction of the European segments of the Vacuum Vessel for ITER, in material 316L (N)-IG (ITER Grade). Following a brief general introduction of the process of TIG welding, this paper analyses: the technological, metallurgical and constructive features of TIG narrow gap, and combined with WT's technical know-how, shows how it was possible to overcome every critical aspect of its implementation. [ABSTRACT FROM AUTHOR]

The inner surface of pressure vessel steel used in the petrochemical industry is often coated with corrosion resistant materials. The industrial process that combines increased productivity with controlled dilution is ESSC (ElectroSlag Strip Cladding). The paper aims to overcome the current ESSC process limitations, analyzing the possible benefits introduced by Multi Strip technology, Twin type. The tests with combinations of carbon steel coated with Alloy 625 and Type 347 deposit on creep resistant low alloy steel were conducted. [ABSTRACT FROM AUTHOR]

This paper describes an experimental analysis of residual stresses conducted on thick and high constraint low alloy Cr-Mo-V welded joints, by the method called hole drill test. Data was collected on test specimens with nozzle geometry, welded with SAW process. The results were analyzed by comparison with manufacture requirements of pressure vessels for critical applications. In light of data collected, it was discussed the need of an Intermediate Stress Relief (ISR) heat treatment for this joint, required by applicable regulations and standards. [ABSTRACT FROM AUTHOR]

EST Plant (Eni Slurry Technology) consists of about 300 pressure vessels in the following principal units and section: * EST unit (unit 90); * Hydrogen production plant (Unit 95); * SWS sulphur recovery and tail gas treatment (Unit 92 and 94). More than 100 "critical" equipments exist in the EST complex, divided in units and sections on the basis of their type of service. In detail, the considered critical items include: carbon steel and low alloy steels heavy wall pressure vessels for high temperature, high-pressure hydrogen service; carbon steel pressure vessels in sour (wet H^S service) and amine service. For fabrication of such "critical" items special base materials and filler metals were adopted according to specific material requirement, special welding processes and fabrication sequences (including advanced automatic systems for non destrucutive testing) were used. This paper shows an overview on some critical aspects and experience of fabrication of main "critical" equipments of EST Plant. [ABSTRACT FROM AUTHOR]

Modern superaustenitic stainless steels are quaternary alloys extensively used to resist severe aqueous corrosive service, with large contents of Cr, Ni, Mo and PREn index generally higher than 45. Fusion welding is the major joining method for fabricating components and vessels using these grades. In this paper, the behavior of these alloys and the consequence of their use infusion welded structures are illustrated. The typical microstructures of the base materials, the transformations followed during welding or heat treatment and their influence on the mechanical properties and corrosive resistance of the joints are presented. Fabrication practices, filler materials and the aspects common to the nickel alloys welding are discussed, as well. During the welded fabrication, the major difficult is to retain the fully austenitic microstructure with sufficient homogeneity throughout all the high temperature manufacturing operations, and to limit the tendency to the hot solidification cracking. The recent understanding of the segregation mechanisms during the solidification and the associated kinetic will allow a more effective control of the micro structural evolution, also by using high energy welding methods and newly formulated filler materials with non-austenitic primary solidification mode. [ABSTRACT FROM AUTHOR]

In recent years ultrasonic flaw detection in welded components has taken advantage from the developments in robotic, electronic and IT fields. New ultrasonic techniques, such as TOFD and Phased Array, have deserved an increasing interest in NDT market. Their main purpose is to increase the reliability and repeatability of the results through the registration of data, allowing the substitution of radiographic technique which has well-known problem of safety and is time-consuming for thicker components. These techniques, in front of undeniable advantages, are limited by technical constraints that have to be taken into account in order to detect and evaluate in a proper way the defects. This paper focuses on experience gained by IIS Service in this field, showing the advantages and limitations possibly arising from a not correct application of automatic ultrasonic techniques. [ABSTRACT FROM AUTHOR]

This paper has the target to summarize which are the fillers to be used in the pressure vessels cladding processes. We evaluate the most common requests in the customer's specifications and how to meet them while checking the results during construction. We gave great emphasis to the applications with austenitic stainless steels (series 300), without neglecting other applications such as Ni-based alloys. We evaluated the different processes to be used and the role of "b ferrite" which, besides being often a specific requirement of the customer, is also the key factor to control the cladding during the construction. We examined the various processes used in terms of thickness and dilution. The dilution is a key output, which depends on the process used and the parameters reported in the WPS. The accurate assessment of the dilution allows to choose the most suitable filler material and to avoid problems. The power source must be reliable and allow the repeatability of the process, as well as having a "duty cycle" adapted to production demands. It is important to underline that often being the surface to be plated several hundred square meters, the correct selection of the power sources reduce the cycle times and the delivery times. In fact, very often the cladding is on the production critical path. We presented some real cases, demonstrating how it is possible to meet the specification requirements with a careful analysis of a few experimental data. We dedicated a chapter to cladding repair defects subject. Cladding repairing defects need to be evaluated on a case by case basis, but in this presentation we propose some key guidelines that can be used to develop the repair specifications avoiding common problems. [ABSTRACT FROM AUTHOR]