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boiler tubes

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Published: 01 January 1990
Fig. 16 100,000-h creep-rupture strength of various steels used in boiler tubes. TB12 steel has as much as five times the 100,000-h creep-rupture strength of conventional ferritic steels at 600 °C (1110 °F). This allows an increase in boiler tube operating temperature of 120 to 130 °C (215 More
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Published: 01 January 2002
Fig. 9 Microstructures of specimens from carbon steel boiler tubes subjected to prolonged overheating below Ac 1 . (a) Voids (black) in grain boundaries and spheroidization (light, globular), both of which are characteristic of tertiary creep. 250×. (b) Intergranular separation adjacent More
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Published: 01 January 2002
Fig. 10 Typical microstructures of 0.18% C steel boiler tubes that ruptured as a result of rapid overheating. (a) Elongated grains near tensile rupture resulting from rapid overheating below the recrystallization temperature. (b) Mixed structure near rupture resulting from rapid overheating More
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Published: 01 January 2002
Fig. 12 Plots of scale thickness versus temperature for two sizes of boiler tubes and two values of heat flux. (a) and (b) The effect of scale thickness on the temperature gradient across the scale. (c) and (d) The effect of scale thickness on the temperature of the metal at the outer surface More
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Published: 15 January 2021
Fig. 19 Oxygen pitting along the outside-diameter surface of boiler tubes from a fire-tube boiler. (a) Through-wall pitting due to oxygen pitting. (b) Oxygen pitting had penetrated approximately 80% of the boiler tube wall thickness on this sample. More
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Published: 15 January 2021
Fig. 9 (a) Short-term and (b) long-term overheating of boiler tubes. Long-term overheating usually is caused by creep as the microstructure of the material degrades at temperature over time. Grains do not deform, but voids develop at grain-boundary junctions and grow and coalesce over time More
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Published: 01 January 2002
Fig. 20 Hydrogen damage (dark area) in a carbon steel boiler tube. The tube cross section was macroetched with hot 50% hydrochloric acid. More
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Published: 01 January 2006
Fig. 24 Cross section through a studded carbon steel boiler tube, showing reduction in dimensions of the studs that occurs in operation. Note the loss of wall thickness in the tube around the entire fireside circumference, including the crotch of the tube near the membranes. More
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Published: 01 January 2005
Fig. 37 Short-term and rapid overheating of a steel boiler tube (reheater, superheater, or similar—source unknown) resulted in a longitudinal “fish-mouth” rupture. The tube had experienced elevated temperatures (455 to >730 °C, or 850 to >1350 °F) where the metal strength is markedly More
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Published: 01 December 1998
Fig. 44 Corrosion-fatigue cracks in carbon-steel boiler tube originated at corrosion pits. Corrosion products are present along the entire length of the cracks. 250× More
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Published: 01 January 2000
Fig. 14 Most of the damage in a boiler tube is related to loss of wall thickness due to corrosion. Creep damage occurs late in life due to stress increase. More
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Published: 01 January 1990
Fig. 15 Creep-rupture strengths of various boiler tube steels at 600 °C (1110 °F). Source: Ref 21 More
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Published: 01 January 2002
Fig. 8 Failure wheel for boiler tube damage mechanisms. Underlined mechanisms are always secondary in this system. More
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Published: 01 January 2002
Fig. 7 Thin-lip rupture in a boiler tube that was caused by rapid overheating. This rupture exhibits a “cobra” appearance as a result of lateral bending under the reaction force imposed by escaping steam. The tube was a 64-mm (2 1 2 -in.) outside-diameter × 6.4-mm (0.250-in.) wall More
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Published: 01 January 2002
Fig. 18 Micrograph of an etched specimen from a carbon steel boiler tube. Decarburization and discontinuous intergranular cracking resulted from hydrogen damage. 250× More
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Published: 01 January 2002
Fig. 22 Carbon steel boiler tube that ruptured due to hydrogen damage. More
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Published: 15 January 2021
Fig. 7 Failure wheel for boiler tube damage mechanisms. Underlined mechanisms are always secondary in this system. More
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Published: 15 January 2021
Fig. 16 Schematic of three-layer deposit on a boiler tube experiencing coal-ash corrosion. The middle layer tends to be molten, which reacts and dissolves the protective tube oxides, leading to corrosion at the 10 and 2 o’clock positions relative to the crown of the tube (12 o’clock). Adapted More
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Published: 30 August 2021
Fig. 2 Classification of boiler-tube damage mechanisms More
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Published: 30 August 2021
Fig. 8 Microstructure of a carbon steel boiler tube subjected to prolonged overheating below Ac 1 showing (a) decomposition of pearlite into ferrite and spheroidal carbides (original magnification: 400×) and (b) spheroidization of carbide and grain-boundary voids characteristic of tertiary More