In order to maintain the efficient and reliable operation of pipelines and other equipment engineers need to know what techniques are available to extend the life of new components or refurbish worn or corroded ones and, just as important, what are their cost benefits compared to the use of expensive base materials or replacing the part? here are a number of options available to protect flanges and the internal surfaces of equipment but the final choice will normally be based on an evaluation of factors such as the application, required service life, operational priorities, installation deadlines and, of course, budget restraints. So, how can engineers ensure the long-term integrity of internal surfaces of pipelines, flanges and other equipment against aggressive corrosion caused by hazardous and corrosive LNG environments? Where budget is not a constraint, engineers can simply specify components in corrosion or wear resistant alloys known to withstand the conditions. However, this is rarely the case and other, more cost-effective options are usually sought. Where pipe, flanges or fittings and other components such as valves and pumps, require protection, weld overlay cladding is certainly a versatile option, providing the assurance of a heavy-duty metallurgic-ally-bonded protective layer that will not be degraded in hostile environments. Welding processes after first identifying the surfaces that need to be protected, engineers can choose from a number of welding processes and a wide range of cladding alloys. Weld overlay cladding technology presents the materials engineer with a wide choice of welding processes that offer immense flexibility. An almost infinite range of component shapes and sizes can be protected, with an equally wide range of base material/cladding alloy alternatives. The GTAW (TIG) process can be used in bores as small as 20mm, and is ideally suited for components of varied geometry, where the position of the welding head requires frequent adjustment. These could range from a simple flange that needs to be clad through the bore and across the sealing face, to a complex valve body with several interconnecting bores. This flexibility also lends itself to the cladding of irregular shaped components, such as pump and valve internals. GMAW (MIG), submerged arc and electroslag welding processes are used where large areas and thicker deposits are required. Fast deposition rates mean these methods also offer cost savings. A wider selection of consumable materials, which may not be produced in the standard solid wire form, is also available. Selection of the most appropriate welding process is largely dependent on factors such as the size of the clad area; access to the area to be clad; alloy type, specified clad thickness; chemical composition limits; welding position; and NDT acceptance standards.
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Welding Technology ProgramThe Welding Technology program at Madison High school in Houston TX, prepares students for a variety of occupations in welding. Welding by gas and electricity (either arc or resistance) is a major part of this program. Methods used to fabricate and weld parts made of aluminum, steel, stainless steel and most other alloys are included in this program. Students prepare to take certification exams in welding and safety. This program offers an opportunity for certification from the American Welding Society Archives
March 2023
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