Search Results for ASME SA213-T11

The tubes of a stationary industrial boiler, 64 mm in diam and made of 1.25Cr-0.5Mo steel (ASME SA-213, grade T-11) failed by two different types of rupture. Noticeable swelling of the tubes in the area of rupture was revealed by visual examination. The tubes with slight longitudinal splits were interpreted to have failed by stress rupture resulting from prolonged overheating at 540 to 650 deg C as the microstructure exhibited extensive spheroidization and coalescence of carbides. The larger ruptures were tensile failures that resulted from rapid overheating to 815 to 870 deg C as a completely martensitic structure was revealed at the edges of the ruptures in these tubes because of rapid quenching by escaping fluid. The prolonged-overheating failures were concluded to have been the primary ruptures and that local loss of circulation had caused rapid overheating in adjacent tubes. Poor boiler circulation and high furnace temperatures were believed to have caused the prolonged overheating.

Pendant-style reheater, constructed of ASME SA-213, grade T-11, steel ruptured. A set of four tubes, specified to be 64 mm OD x 3.4 mm minimum wall thickness was examined. A small quantity of loose debris was removed from the inside of one of the tubes. The major constituent was revealed by EDS analysis of the debris to be iron with traces of phosphorus, manganese, sodium, calcium, copper, zinc, potassium, silicon, chromium, and molybdenum. Thus the debris was interpreted to be the scale from ID of the tube with boiler feedwater chemicals from the attemperation spray. The likely cause of failure was concluded to be exfoliation of the scale from the ID surface of the tube. Creep failures were interpreted to be caused by localized temperatures higher than the maximum service temperature. Replacement of the affected tubes was recommended. Inspection of the tubes by radiography to find the circuits with the greatest accumulation of debris and replacing them as necessary was recommended on an annual basis.

Failures in boilers and other equipment taking place in power plants that use steam as the working fluid are discussed in this article. The discussion is mainly concerned with failures in Rankine cycle systems that use fossil fuels as the primary heat source. The general procedure and techniques followed in failure investigation of boilers and related equipment are discussed. The article is framed with an objective to provide systematic information on various damage mechanisms leading to the failure of boiler tubes, headers, and drums, supplemented by representative case studies for a greater understanding of the respective damage mechanism.

Heat exchangers are devices used to transfer thermal energy between two or more fluids, between a solid surface and a fluid, or between a solid particulate and a fluid at different temperatures. This article first addresses the causes of failures in heat exchangers. It then provides a description of heat-transfer surface area, discussing the design of the tubular heat exchanger. Next, the article discusses the processes involved in the examination of failed parts. Finally, it describes the most important types of corrosion, including uniform, galvanic, pitting, stress, and erosion corrosion.