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Genova, Italy

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Genova, Italy
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Mandina M.,IIS SERVICE | Magnasco M.,Nuovo Pignone | Moracchioli L.,Nuovo Pignone | Giorgini L.,Nuovo Pignone
Rivista Italiana della Saldatura | Year: 2014

This article provides mention of metallurgy and weldability of 13% Cr-4% Ni steel and the results of experimental welding tests aimed to supporting repair process, using covered electrodes and corresponding filler material, of possible imperfections of forging and / or by mechanical processing in crates and stator parts of centrifugal compressors, in accordance with ASTM A182. The effects of chemical composition of base material, filler material, as well as post-weld heat treatment (PWHT) on the mechanical properties of welded joints have been investigated, in order to minimize hardness in the fusion zone and heat affected zone.


Mandina M.,IIS Service | Magnasco M.,Nuovo Pignone | Zappavigna G.,Nuovo Pignone
Welding International | Year: 2014

In the fabrication of reactors (made of Cr-Mo steel modified with vanadium) operating in high hydrogen pressure and high-temperature service, internal cladding in austenitic stainless steel (typically made of AISI 347) is required in order to guarantee satisfactory corrosion resistance against the process fluids desulphurized hydrocarbons. Application of an electro-slag strip cladding (ESSC) process for internal weld overlay and clad restoring on heads, barrels and nozzles of 2 1/4Cr-1Mo-1/4V reactors (with single-layer or double-layer technique) is described in the paper. The first part of the paper is focused on metallurgical aspects, cracking phenomena (hydrogen cracking, solidification cracking, under-clad cracking and hydrogen-induced disbonding) and cladding residual stresses referable to ESSC process. The second part of the paper is focused on operating aspects of the ESSC process and UT examination of weld overlay and clad restoring, optimized for the detection of planar defects under cladding. © 2014 © 2013 Taylor & Francis.


In the latest edition of the ASME Code, criteria for fatigue assessment in pressure vessels manufactured with 225Cr-IMo-Vsteel are given up to operating temperatures not exceeding 371 °C (700 °F), whilst the design temperature typically adopted (454 °C) is significantly higher. In order to plug this gap, ASME has recently published the Code Case 2605-1, considering the interaction between fatigue and creep phenomena. Material creep behaviour is in particular represented through the "Omega" approach, recently introduced by the API 579-1/ASME FFS-I standard. This article has been written with the aim to present the application of Code Case prescriptions for the fatigue assessment of items F90101AIB (Hot High Pressure Separator), manufactured by ATB Riva Calzoni S.p A. on behalf of ENI R&M. In particular the manufacturing procedures followed in vessels construction and the numerical analyses performed for the assessment of components are described in detail, highlighting, with special attention, those features which mainly affect evaluation results.


Ranieri S.,University of Genoa | Rizzo C.M.,University of Genoa | Cosso G.L.,IIS SERVICE | Servetto C.,IIS SERVICE
Rivista Italiana della Saldatura | Year: 2015

The main aim of this work is the fatigue strength assessment of a butt joint with weld reinforcement, typically used in steel works and especially in shipbuilding applications when varying different geometric parameters of the welded joint; to this purpose, three different approaches for fatigue strength estimates were applied, i.e. the Effective Notch Stress Approach, which is now commonly used and it is supported by a comprehensive bibliography, the Strain Energy Density approach (SED) and the Peak Stress Method (PSM), the latter ones newly introduced in scientific literature and still being tested within industrial practice. Furthermore, all analyses were carried out using two different finite element codes: ANSYS® and ADINA®. The application of different FEM software allowed verifying the quality of obtained results, disclosing certain essential aspects related to the extrapolation of values from integration points of finite elements and extending the Peak Stress Method to an additional software with respect to that proposed by the author of the method, i.e. ANSYS®.


Canale G.,IIS Service | De Marco M.,Italian Welding Institute | Pinca S.,IIS Service
Welding International | Year: 2013

The special process of welding still plays a key role in the fabrication of pressurized equipment for the energy processing and generation industry. Similarly, welding is extensively used in repair, modification and overlay/cladding procedures and during the maintenance operations for large plants. However, the harsh statistics relating to faults shows welded joints to be among the most 'at-risk' areas with regard to various active damage mechanisms. Within the framework of the management of plant risk and equipment integrity, the risk-based inspection method, with the aim of prioritizing and optimizing the inspection strategy, focuses attention on the criticality of welded joints with the framework of problems related to both simple mechanical vulnerability and physicochemical aspects such as corrosion and/or stress corrosion. The aim of this paper is to offer an overview of the interactions existing between the various active damage mechanisms in plants and welded joints in addition to indicating the criticality associated with these interactions, with the purpose of optimizing the management of plant risk and inspection strategies for resolving them. © 2013 Copyright Taylor and Francis Group, LLC.


Canale G.,IIS Service | De Marco M.,Italian Welding Institute | Pirica S.,IIS Service
Welding International | Year: 2014

The special process of welding still plays a key role in the fabrication of pressurised equipment for the energy processing and generation industry. Similarly, welding is extensively used in repair, modification and overlay/cladding procedures and during the maintenance operations for large plants. However, the harsh statistics relating to faults shows welded joints to be among the most 'at risk' areas with regard to various active damage mechanisms. Within the framework of the management of plant risk and equipment integrity, the Risk Based Inspection (RBI) method, with the aim of prioritising and optimising the inspection strategy, focusses attention on the criticality of welded joints with the framework of problems related to both simple mechanical vulnerability and physico-chemical aspects such as corrosion and/or stress corrosion. The aim of this paper is to offer an overview of the interactions existing between the various active damage mechanisms in plants and welded joints in addition to indicating the criticality associated with these interactions, with the purpose of optimising the management of plant risk and inspection strategies for resolving them. © 2014 Taylor & Francis.


Cunati C.,Instituto Italiano della Saldatura | Lanza M.,IIS SERVICE | Noli D.,IIS SERVICE
Rivista Italiana della Saldatura | Year: 2016

The large infrastructure management has inspection planning rules based on internal specification and on best practices gained in decades. However, the effective inspection frequency clashes with practical matters: The available resources, the need to choose the operating procedures in relation to age and personnel level, adequate inspection staff. Often the individual delegated to the role of inspection manager has to make priority choices that involve important responsibilities. This paper presents the IIS Group procedure for the Risk Based Inspection - RBI of civil structures. The procedure deal with "ex ante" and "ex post" inspection, assuming that the inspection becomes really necessary. A IIS software, available by engineering staff and inspection technical staff, is developing.


Traditionally the oil companies involved in the refining and marketing of finished products were oriented towards the supply of higher quality crudes (low sulfur and / or low naphthenic acidity). In recent years, however, the evolution of the markets and the trend in crude oil prices, affected also by the availability and the geopolitical context of the traditional areas of supply, has forced the oil companies towards the use of lower quality crude oils to maintain acceptable profit margins. These crudes, often referred to as the opportunity crudes are characterized by high sulfur content and / or high naphthenic acidity. Hence the need to assess the suitability of existing facilities, especially the atmospheric distillation units and vacuum units designed for the processing of crude oil of superior quality, for the use of these feeds with the resulting potential corrosion originally not considered critical during the design phase. This article is inspired by a study, commissioned by a important Italian oil refinery, carried out on its own Topping and Vacuum plants, and proposes a criterion consisting of evaluations of susceptibility to naphthenic acid corrosion based on the corrosion rates estimated according to API RP 581, "Risk Based Inspection Technology", 2nd edition, 2008.


We present the results of an experimental program of fatigue tests carried out on two types of butt-jointed, of thickness 20 and 40 mm respectively, characterized by a significant gap between the flaps, not meeting the requirements of the construction specifications. The tests were conducted on specimens taken from the heels of welding joints representative of the site (butt joints between souls and lintels) and made with the same procedures (welding process, welding position, welding consumables, etc.). The test results were statistically processed to determine the category of fatigue in accordance with the requirements of standard EN 1993-1-9 and IIW Recommendations. The calculations took into account both the thickness of the samples (both tests were conducted on specimens in scale, is the true thickness of samples for validation) both components of the bending stress induced by the non-planarity of the specimen.


We present the results of an experimental programme of fatigue tests carried out on two types of butt joints with thicknesses of 20 and 40 mm respectively, characterized by a significant gap between weld edges, not compliant with the requirements of construction specifications. The tests were conducted on specimens taken from the weld beads of joints typical of those produced at the site (butt joints between web and flanges) and made with the same procedures (welding process, welding position, welding filler, etc.). The test results were elaborated statistically to determine the fatigue resistance category in accordance with the requirements of standard EN 1993-1-9 and IIW recommendations. Calculations took into account both the thickness of the specimens (tests were carried out on both to-scale and true-thickness specimens for the purposes of validation) and also flexural stress components induced by the non-planarity of the specimens. © 2013 © 2013 Taylor & Francis.

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