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Steel Tubes (steel + tubes)
Selected AbstractsAXIAL IMPACT STUDIES ON STEEL TUBES AND ZIRCALOY RODEXPERIMENTAL TECHNIQUES, Issue 1 2009R. Rajendran First page of article [source] A framework for continuous design of production systems and its application in collective redesign of production line equipmentHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 1 2002Françoise Darses The continuous design of production systems is a major challenge facing companies, and one that requires organization and systematization. This article describes one of the continuous design endeavors implemented in a factory manufacturing steel tubes. We have studied the collective redesign of production line equipment. For 2 years, we followed the operations of a multioccupational group composed of the various actors involved in manufacturing (including the operators). Their task was to redesign the tools used in their production line. Our analysis is focused on the cognitive side of the activity and especially on the collective redesign processes. From the transcripts of the meetings, we have examined how the codesigners come to an agreement about the redesigned equipment. We show that the criteria spontaneously used for the evaluation of the solution are far wider (quantitatively and qualitatively) than the list of functional criteria prescribed to the codesigners for the decision-making process. This analysis leads us to propose three conditions that have to be met to guarantee success: (a) a true systemic view of the production system must be developed by all the continuous design actors, (b) there must be support for the collective decision-making process, and (c) new forms of knowledge must be institutionalized. © 2002 John Wiley & Sons, Inc. [source] Erosion-corrosion of laser and thermally deposited coatings exposed in fluidised bed combustion plantsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2006A. Hjörnhede Abstract Coated low alloyed steel tubes were exposed in two combustion power plants of the type Circulating Fluidised Bed (CFB) and Pressurised Fluidised Bed Combustion (PFBC). The power plants were fired with wood chips and coal with a small addition of olive seeds, respectively. In addition to laser coating two thermal spray techniques were used; arc-spray (air as carrier gas) and High Velocity Oxy Fuel (HVOF). The sample locations in the PFBC plant were at the highest and lowest loops of a platen immersed in the fluidising bed. The material temperatures in each loop were 450 °C and 400 °C, respectively. The exposure lasted over two firing seasons for a total time of 8089 h. In the CFB plant a probe was located at the cyclone entrance where the material temperature was 630 °C for an exposure time of about 2100 h before being reduced to 480 °C for a further 920 h. The material wastage was determined from metallographic studies on cross-sections of rings cut from the exposed tubes. The nature and chemical composition of the corrosion products and deposits formed were determined by SEM/EDX, Auger spectroscopy, XPS and XRD. Cobalt based coatings show the best performance in both the PFBC plant and the CFB plant, while nickel based coatings are resistant to a corrosive atmosphere but very sensitive to erosion. The degree of corrosion is much larger in the CFB plant as is clearly seen from the chromium carbide containing coating, which totally degraded in this environment. Contrary the performance of the same coating was excellent in the fluidised bed due to its high erosion resistance. The material wastage of a coating with a specific composition is independent of the deposition method. No significant differences in spallation behaviour occurred among coatings deposited with the different techniques. [source] A case of nitridation, carburization and oxidation on a stainless steelMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2005H. J. Grabke Abstract A case of corrosion was studied on stainless steel tubes, exposed to a nitriding, carburizing and oxidizing environment (mainly NH3 and CO2) at 390,450°C. Due to the high nitriding potential prior formation of internally nitrided layers occurs, at higher temperatures (> about 425°C) under precipitation of CrN in the layer and at lower temperatures under formation of the ,N -phase, i.e. austenite with high N-content and expanded lattice. The latter process causes more severe corrosion, due to the high expansion, the stresses in the nitrided layers lead to bursting and repeated spalling of the scales. Carburization and oxidation are less important. The carburization is slower than nitridation, Fe3C formation is observed and carbon deposition. Also the oxidation by CO2 is slow and converts the nitrides and carbides formed before, to unprotective oxide flakes. [source] Field study on superheater tubes in the loop seal of a wood fired CFB plantMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2004A. Nafari Abstract Two full scale superheaters were exposed in the loop seal of a 30 MW wood-fired CFB plant in Nässjö, Sweden, for one firing season each. Some austenitic steel tubes from the first tube bundle were reinstalled in the second superheater. The superheater tubes were made from one ferritic steel, X10 (Fe8.8Cr) and three austenitic steels; Esshete 1250 (Fe15Cr9Ni6Mn), 347H (Fe17Cr11Ni) and AC66 (Fe27Cr32Ni). Commercial coatings mainly on iron, nickel and carbide base were deposited on some of the X10 and 347H tubes. The material wastage kinetics was non-linear showing that pure corrosion and not erosion-corrosion is the major degradation mechanism in the loop seal. It is however clear that the environment is not very aggressive and the corrosion attack on the uncoated tubes is very small. The largest oxide thickness was only about 150 ,m recorded on the X10 alloy. The austenitic steels mainly suffered from internal corrosion and grain boundary corrosion, the extent and distribution of which strongly depended on the alloy composition. Generally, it was more pronounced in the regions with the thinnest deposit layers. Eight out of 17 coating qualities tested were unaffected by the exposure. Corrosion was only recorded on the lowest alloyed iron based coatings. The only coatings which could not resist the conditions in the loop seal were the carbide containing Metco 3006 and Metco 3007, where severe oxidation and delamination took place. Also the thermally sprayed Inconel 625 coating delaminated, but this was rather due to a mechanical failure resulting from thermal expansion. [source] | ||||||||||