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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001526
EISBN: 978-1-62708-229-7
... Abstract In Nov. 1998, the west superheater outlet header at an electricity generating plant began to leak steam. Subsequent investigation revealed the presence of a crack that extended for 360 deg around the full circumference of the header and through the full cross-sectional thickness...
Abstract
In Nov. 1998, the west superheater outlet header at an electricity generating plant began to leak steam. Subsequent investigation revealed the presence of a crack that extended for 360 deg around the full circumference of the header and through the full cross-sectional thickness. The subsequent inspection of this header and the east superheater header revealed the presence of extremely severe ligament cracking. They operated at 2400 psi (16.5 MPa) and a temperature of 540deg C (1005 deg F). Both were fabricated from seamless pipe produced in accordance with ASME Specification SA-335, and the steel was Grade P22, a 2.25Cr-1Mo alloy steel. Visual and metallurgical evaluations showed the cracking in the west superheater outlet header was caused by thermal fatigue. Tube holes had served as a preferential site for thermal fatigue cracking.
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in Failure Analysis of Superheater Outlet Header
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
Fig. 1 This is the 5-ft. long section cut from the west superheater outlet header in tube rows number 4 through 7. Subsegments of row 4 are referred to as A1, A2, A3, etc.
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in Preventive Analyses of Croloy 1 Pressure Parts
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
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in Failure Investigation of Longitudinal Seam Welded Elevated Temperature Header
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
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in Failure Investigation of Longitudinal Seam Welded Elevated Temperature Header
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
Fig. 2 Schematic diagram of Shawville 3 SH outlet header, with boat sample locations indicated.
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in Failures of Pressure Vessels and Process Piping
> Analysis and Prevention of Component and Equipment Failures
Published: 30 August 2021
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c0048845
EISBN: 978-1-62708-229-7
... welds in the secondary superheater outlet headers (constructed of SA335-P11 material) of a major boiler were described as an example. The OD of the header was measured to detect the amount of swelling and found to have increased 1.6% since its installation. Ligament cracks extending from tube seat...
Abstract
The maximum life of base-loaded headers and piping is not possible to be predicted until they develop microcracking. The typical elements of a periodic inspection program after the occurrence of the crack was described extensively. Cracks caused by creep swelling in the stub-to-header welds in the secondary superheater outlet headers (constructed of SA335-P11 material) of a major boiler were described as an example. The OD of the header was measured to detect the amount of swelling and found to have increased 1.6% since its installation. Ligament cracks extending from tube seat to tube seat were revealed by surface inspection. Cracks were found to originate from inside the header, extend axially in the tube penetrations and radially from those holes into the ligaments. Cracks in 94 locations, ranging from small radial cracks to full 360Ý cracks were revealed by dye-penetrant inspection. The unit was operated under reduced-temperature conditions and with less load cycling than previously until a redesigned SA335-P22 header was installed.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c0060154
EISBN: 978-1-62708-234-1
... Abstract One of the coils in the radiant section of a primary reformer furnace used in an ammonia plant was found leaking. The bottom of one of seven outlet headers (made of ASME SA-452, grade TP316H, stainless steel) was revealed during examination to be ruptured. It was revealed...
Abstract
One of the coils in the radiant section of a primary reformer furnace used in an ammonia plant was found leaking. The bottom of one of seven outlet headers (made of ASME SA-452, grade TP316H, stainless steel) was revealed during examination to be ruptured. It was revealed by metallurgical examination that it had failed as a result of intergranular fissuring and oxidation (creep rupture). The ruptured area revealed that the header had failed by conventional long-time creep rupture as a result of exposure to operating temperatures probably between 900 and 955 deg C. Three samples from different sections (ruptured area, slightly bulged but nonruptured area and visually sound metal) were inspected. The presence of pinhead-size intergranular fissures throughout the cross sections of the latter two samples was observed. An ultrasonic attenuation method was employed to investigate the remaining headers. All headers were revealed by ultrasonic readings to be in an advanced stage of creep rupture and no areas were found to be fissured to a degree that they needed immediate replacement. As a conclusion, the furnace was deemed serviceable and it was established that in the absence of local hot spots, the headers would survive for a reasonable period of time.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c0048318
EISBN: 978-1-62708-234-1
... Abstract A resistance-welded carbon steel superheater tube made to ASME SA-276 specifications failed by pitting corrosion and subsequent perforation, which caused the tube to leak. The perforation was found to have occurred at a low point in a bend near the superheater outlet header...
Abstract
A resistance-welded carbon steel superheater tube made to ASME SA-276 specifications failed by pitting corrosion and subsequent perforation, which caused the tube to leak. The perforation was found to have occurred at a low point in a bend near the superheater outlet header. It was found that the low points of the superheater tubes could not be completely drained during idle periods. Water-level marks were noticed on the inside surface above the area of pitting. It was revealed by microscopic examination that localized pitting had resulted from oxidation. It was concluded that water contained in the tube during shutdowns had accumulated and cumulative damage due to oxygen pitting resulted in perforation of one of the tubes. Filling the system with condensate or with treated boiler water was suggested as a corrective action. Alkalinity was suggested to be maintained at a pH of 9.0 and 200 ppm of sodium sulfite should be added to the water.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001669
EISBN: 978-1-62708-229-7
... outlet temperature of 566 deg C, the 11.4 cm thick header had operated for approximately 187,000 h at the time of the failure. Discussion focuses on the results of a metallographic examination of boat samples removed from the longitudinal seam weldment in the vicinity of the failure and at other areas...
Abstract
As the result of a leak detected in a plate-formed header at PENELEC'S Shawville Unit No. 3, an extensive failure investigation was initiated to determine the origin of cracking visible along the longitudinal weld seam. Fabricated from SA387-D material and designed for a superheater outlet temperature of 566 deg C, the 11.4 cm thick header had operated for approximately 187,000 h at the time of the failure. Discussion focuses on the results of a metallographic examination of boat samples removed from the longitudinal seam weldment in the vicinity of the failure and at other areas of the header where peak temperatures were believed to have been reached. The long-term mechanical properties of the service-exposed base metal and creep-damaged weld metal were determined by creep testing. Based on the utility's decision to replace the header within one to three years, an isostress overtemperature lead specimen approach was taken, whereby failure of a test specimen in the laboratory would precede failures in the plant. These tests revealed approximately a 2:1 difference in life for the base metal as compared to weld metal.
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in Preventive Analyses of Croloy 1 Pressure Parts
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
Fig. 2 Microstructure, linked voids, and split grain boundaries in the failed outlet header shown in Fig. 1 . 400x
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in Failures of Pressure Vessels and Process Piping
> Analysis and Prevention of Component and Equipment Failures
Published: 30 August 2021
Fig. 54 Microstructure, linked voids, and split grain boundaries in the failed outlet header shown in Fig. 53 . Original magnification: 400×
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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001590
EISBN: 978-1-62708-228-0
... close to the outlet header. The location is indicated on Fig. 1 . Fig. 3 Skid-mounted hydrogen production units, Belgium The crack was in the heat-affected zone of the weld and had developed parallel to the weld (along the fusion line). The crack appeared to be brittle. A micrograph...
Abstract
This case study demonstrates that Alloy 601 (UNS N06601) is susceptible to strain-age cracking. The observation illustrates the potential importance of post weld heat treatment to the successful utilization of this alloy in certain applications.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001688
EISBN: 978-1-62708-234-1
... the design called for ( 2 ). Superheater Header Stub Failures Failures had occurred in the stubs connecting the outlet header to the superheater tubes in a steam generator. The steam temperature at outlet was nominally 515°C and they had been in service for some 175,000 h. Because there was extensive...
Abstract
Some examples of equipment failures involving high temperature operation are presented. They include some steam generator superheater components and a pump shaft that should not have been at high temperature. Metallographic analysis is used to determine the causes of failure in each case.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001341
EISBN: 978-1-62708-215-0
..., and two tube rows were changed to SB 407 alloy 800H from alloy 800. The superheater ( Fig. 1 ) includes inlet and outlet headers at the top, with tubes suspended from these headers. The assembly is one of several exchangers suspended in an exhaust flue downstream of a methanol reformer. The internal coil...
Abstract
An SB407 alloy 800H tube failed at a 100 deg bend shortly after startup of a new steam superheater. Three bends failed and one bend remote from the failure area was examined. Visual examination showed that the fracture started on the outside surface along the inside radius of the bend and propagated in a brittle, intergranular fashion. Chemical analysis revealed that lead contamination was a significant factor in the failure and phosphorus may have contributed. The localized nature of the cracks and minimum secondary cracking suggested a distinct, synergistic effect of applied tensile stress with the contamination. Stress analysis found that stress alone was not enough to cause failure; however the operating stresses in the 100 deg bends were higher than at most other locations in the superheater Reduced creep ductility may be another possible cause of failure. Remedial actions included reducing the tube temperature, replacing the Schedule 40 100 deg bends with Schedule 80 pipe, and solution annealing the pipe after bending.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001609
EISBN: 978-1-62708-229-7
... a bypass system or a recirculation system that partially redirects water from its outlet back to its inlet. This helps maintain the CT exhaust gas temperature flowing over the harps and maintains temperatures above the acid dewpoint temperature. The addition of a recirculation system causes a minor...
Abstract
Alloy 430 stainless steel tube-to-header welds failed in a heat recovery steam generator (HRSG) within one year of commissioning. The HRSG was in a combined cycle, gas-fired, combustion turbine electric power plant. Alloy 430, a 17% Cr ferritic stainless steel, was selected because of its resistance to chloride and sulfuric acid dewpoint corrosion under conditions potentially present in the HRSG low-pressure feedwater economizer. Intergranular corrosion and cracking were found in the weld metal and heat-affected zones. The hardness in these regions was up to 35 HRC, and the weld had received a postweld heat treatment (PWHT). Metallographic examination revealed that the corroded areas contained undertempered martensite. Fully tempered weld areas with a hardness of 93 HRB were not attacked. No evidence of corrosion fatigue was found. Uneven temperature control during PWHT was the most likely cause of failure.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001328
EISBN: 978-1-62708-215-0
... Intergranular oxidation Mechanical properties Thermal stresses Tubing Weldments Incoloy 800H UNS N08810 Intergranular fracture Background Maintenance shutdown inspections regularly showed cracks in the welded outlet pigtail connections of a steam-methane reformer furnace. Applications...
Abstract
During 5.7 years of service, dye penetrant inspection of Inconel 800H pigtail connections regularly showed cracks at weld toes. Weld repairs were not able to prevent reoccurrence but often aggravated the condition. Samples containing small, but detectable, reducer-to-pigtail cracks showed intergranular cracks originating at weld toes and filled with oxidation product, which precluded determination of the cracking mechanism. All weldments exhibited high degrees of secondary precipitates, with original fabrication welds exhibiting higher apparent levels than repair welds. SEM/EDS analysis showed base metal grain boundary precipitates to be primarily chromium carbides, but some titanium carbides were also observed. Failure was believed to result from the synergism of thermally driven tube distortion, which resulted in over-stress, and from the intergranular oxidation products and intergranular carbides which contributed to cracking. It was recommended that stresses be reduced and /or that materials and components be changed. Refinements in welding procedures and implementation of preweld/postweld heat treatments were recommended also.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001638
EISBN: 978-1-62708-228-0
... not as strong as the cast alloys, possessed greater ductility and thermal shock resistance and became the alloy of choice for furnace outlet connections, transfer lines, and headers. It is widely used for these components in ethylene plants throughout the world. 4 While materials that are more resistant...
Abstract
An Incoloy 800H (UNS N08810) transfer line on the outlet of an ethane-cracking furnace failed during decoking of the furnace tubes after nine years in service. A metallographic examination using optical and scanning electron microscopy as well as energy-dispersive x-ray spectroscopy revealed that the failure was due to sulfidation. The source of the sulfur in the furnace effluent was either dimethyl disulfide, injected into the furnace feed to prevent coke formation and carburization of the furnace tubes, or contamination of the feed with sulfur bearing oil.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.chem.c9001686
EISBN: 978-1-62708-220-4
... was wound in a right-hand helix with a coil centerline diameter of approximately two meters. There were 24 3 4 total loops in the coil with the majority of the loops being tight wound and final three loops at the outlet end of the vaporizer being loose wound. The coil was design to ASME Code...
Abstract
A root cause failure analysis was performed on a vaporizer coil removed from a horizontal forced circulation vaporizer. The carbon steel coil was wound in a right-hand helix with a coil centerline diameter of about 2 m. The vaporizer was gas fired and used Dowtherm A as the heat transfer fluid. Design conditions are based on annular fluid flow to cool the coil wall. NDE, metallographic and fractographic examinations were performed. Numerous, circumferentially oriented, OD initiating cracks were found near the crown for two coils near the non-fired end of the vaporizer. The cracking was confined to the inner diameter of the vaporizer coil at positions from 4:00 to 7:00. The cracking was characterized as transgranular and the fracture surface had beach marks. The failure mechanism was thermal fatigue. The heat transfer calculation predicted that dryout of the coil would occur for coils at the non-fired end of the vaporizer during low flow transients. Dryout results in rapid increase in the tube wall temperature. Thermal cycling of the coil is completed by liquid quenching resulting from resumption of normal flow rates and the return to annular flow. The probable root cause of failure was low flow transient operation.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0001818
EISBN: 978-1-62708-180-1
... Hydrotesting A 150-cm (60-in.) inside-diameter boiler drum fabricated of 18-cm (7-in.) thick ASTM A515, grade 70, steel failed during final hydrotesting at a pressure of approximately 26 MPa (3.8 ksi). The shock wave from the vessel rupture also damaged several connected headers and piping runs...
Abstract
This article discusses the effect of using unsuitable alloys, metallurgical discontinuities, fabrication practices, and stress raisers on the failure of a pressure vessel. It provides information on pressure vessels made of composite materials and their welding practices. The article explains the failure of pressure vessels with emphasis on stress-corrosion cracking, hydrogen embrittlement, brittle and ductile fractures, creep and stress rupture, and fatigue with examples.