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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001522
EISBN: 978-1-62708-235-8
..., which indicated turbulent filling of the mold. Spherical pores would have indicated the melt had been improperly degassed. Based on these findings, it was recommended that the manufacturer analyze and redesign the gating system to eliminate the turbulent flow problem during the permanent mold casting...
Abstract
In the EMD-2 Joint Directed Attack Munition (JDAM), the A357 aluminum alloy housing had been redesigned and cast via permanent mold casting, but did not meet the design strength requirements of the previous design. Mechanical tests on thick and thin sections of the forward housing assembly revealed tensile properties well below the allowable design values. Radiology and CT evaluations revealed no casting defects. Optical microscopy revealed porosity uniformly distributed throughout the casting on the order of 0.1 mm pore diam. Scanning electron microscopy revealed elongated pores, which indicated turbulent filling of the mold. Spherical pores would have indicated the melt had been improperly degassed. Based on these findings, it was recommended that the manufacturer analyze and redesign the gating system to eliminate the turbulent flow problem during the permanent mold casting process.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001276
EISBN: 978-1-62708-215-0
... the piping, extremely turbulent flow, and/or intrusions (weld backing rings or weld bead protrusions) on the internal surface of the pipes. Increasing the pipe diameter and decreasing the intrusions on the internal surface would help to eliminate the problem. Diameters Leakage Mechanical properties...
Abstract
The carbon steel feedwater piping at a waste-to-energy plant was suffering from wall thinning and leaking after being in service for approximately six years. Metallographic examination of ring sections removed front the piping revealed a normal microstructure consisting of pearlite and ferrite. However, the internal surface on the thicker regions of the rings exhibited significant deposit buildup, where the thinned regions showed none. No significant corrosion or pitting was observed on either the internal or external surface of the piping. The lack of internal deposits on the affected areas and the evidence of flow patterns indicated that the wall thinning and subsequent failure were caused by internal erosion damage. The exact cause of the erosion could not be determined by the appearance of the piping. Probable causes of the erosion include an excessively high velocity flow through the piping, extremely turbulent flow, and/or intrusions (weld backing rings or weld bead protrusions) on the internal surface of the pipes. Increasing the pipe diameter and decreasing the intrusions on the internal surface would help to eliminate the problem.
Image
in Failures of Pressure Vessels and Process Piping
> Analysis and Prevention of Component and Equipment Failures
Published: 30 August 2021
Fig. 69 (a) Schematic representation of the production system. (b) Location of the pit plug and metal loss and transition of laminar fluid flow to turbulent flow
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Image
Published: 01 January 2002
Fig. 8 Elongated surface cavities on the inside surface of a 70-30 cupronickel tube produced by erosion-corrosion. The tube surface is clean, the attack having occurred due to brine flowing through it at 70 °C (158 °F) with turbulent flow and an excessive level of dissolved oxygen.
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Image
in Failure of Copper Alloy 443 Heat-Exchanger Tubes
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
Fig. 1 Copper alloy C44300 heat-exchanger tube that failed by impingement corrosion from turbulent flow of air and condensate along the shell-side surface. (a) Shell-side surface of tube showing damaged area. (b) Damaged surface showing ridges in affected area. 4×. (c) Unetched section through
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Image
in Failure Analysis of Heat Exchangers
> Analysis and Prevention of Component and Equipment Failures
Published: 30 August 2021
Fig. 8 Copper alloy C44300 heat-exchanger tube that failed by impingement corrosion from turbulent flow of air and condensate along the shell-side surface. (a) Shell-side surface of tube showing damaged area. (b) Damaged surface showing ridges in affected area. Original magnification: 4×. (c
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Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001316
EISBN: 978-1-62708-215-0
... is the consequence of turbulent flow eroding the protective oxide scale and base metal during operation. In boiler systems, an oxide scale is established to protect the components from further metal loss due to oxidation. This scale was visible on the outside surfaces of separators 2 and 3. The scale was not present...
Abstract
Three 1006 carbon steels team/water separators failed in a boiler in installation after several years of service. Annual inspection had revealed no evidence of deterioration until the last inspection, when they were removed from service. Metallurgical investigation determined that the separators had deteriorated because of erosion corrosion. Further analysis of the boiler operation revealed that operational changes made in the last year of service caused an increase in velocity of the water/steam mixture. It was recommended that the operating parameters for the boiler be reevaluated and prior levels of operation be reinstituted.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.steel.c9001234
EISBN: 978-1-62708-232-7
... joints Turbulent flow Copper pipe Joining-related failures Erosion - corrosion A general view of the specimen under examination from a copper hot water system is shown in Fig. 1 in the as supplied condition. As can be seen from the photograph, a bent pipe has been soldered into a straight pipe...
Abstract
In a copper hot water system, a bent pipe was soldered into a straight pipe with twice the diameter. The neighborhood of the soldered joint was covered with corrosion product predominantly blue-green in color, presumably carbonates. When these corrosion products were scratched off it was seen that the copper beneath this layer had not suffered noticeable attack. The object of the examination was the localized deep cavities located almost symmetrically to both sides of the inserted end of the narrower tube on the internal wall of the wider tube which had in one place been eaten right through. The symmetrical location on each side of the point of insertion of the narrower pipe and the localized sharp delineation of the attack indicated erosion due to the formation of turbulence. By avoiding sharp transitions and abrupt changes in cross section it is possible to design the pipe work so that localized turbulence is obviated. Degassing and cleansing of the water also would reduce the danger of erosion particularly in the case of softened water, which takes up oxygen and carbon dioxide very readily thus becoming particularly aggressive.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c0048714
EISBN: 978-1-62708-229-7
... analysis of the tube confirmed that the material was copper alloy C44300 (arsenical admiralty metal). Fig. 1 Copper alloy C44300 heat-exchanger tube that failed by impingement corrosion from turbulent flow of air and condensate along the shell-side surface. (a) Shell-side surface of tube showing...
Abstract
Tubes in heat exchangers, made of copper alloy C44300 and used for cooling air failed after 5 to six years of service. Air passed over the shell-side surface of the tubes and was cooled by water flowing through the tubes. Water vapor in the air was condensed (pH 4.5) on the tube surfaces during the cooling process. Air flow over the tubes reversed direction every 585 mm as a result of baffling placed in the heat exchangers. An uneven ridgelike thinning and perforation of the tube wall on the leeward side of the tube was revealed by visual examination. Undercut pits on the outer surface of the tube were revealed by metallographic examination of a cross section of the failed area. Impingement attack which led to perforation was revealed by both the ridgelike appearance of the damaged area and the undercut pitting. The heat exchanger was retubed with tubes made of aluminum bronze (copper alloy C61400).
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c0046414
EISBN: 978-1-62708-234-1
..., severely eroded surfaces of the impellers are characteristic of cavitation damage. In this instance, cavitation damage could have been the result either of a turbulent flow pattern caused by the movement of the impellers in the liquid or of excessive air in the system because the water in the supply tank...
Abstract
Two water pumps were taken out of service because of reduced output. Visual inspection revealed considerable material loss in both impellers, which were 25.4 cm (10 in.) in diam x 1.3 cm (0.5 in.) wide and made from a cast bronze alloy. Several similar water pumps operating under nearly identical conditions, drawing water from an open tank through a standpipe, had no observable failures. Etched micrographs 100x of samples taken from the impellers showed clean, pockmarked, severely eroded surfaces, characteristic of cavitation damage. Investigation also revealed that considerable quantities of air were being drawn into the system when water in the supply tank dropped below a certain level. It was concluded that cavitation erosion (due to the uptake of air) caused metal removal and microstructural damage in the impellers. Recommendations included adding a water-level control to the piping system and excluding air from the pump inlet.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.chem.c9001718
EISBN: 978-1-62708-220-4
.... This appearance is consistent with cavitation damage, the degradation of a metal surface due to the hammer-like blows created by the formation and rapid collapse of vapor bubbles within a liquid undergoing severe turbulent flow. Vapor bubbles form when the local pressure is reduced below the vapor pressure...
Abstract
Post-service destructive evaluation was performed on two commercially pure zirconium pump impellers. One impeller failed after short service in an aqueous hydrochloric acid environment. Its exposed surfaces are bright and shiny, covered with pockmarks, and peppered with pitting. Uniform corrosion is evident and two deep linear defects are present on impeller blade tips. In contrast, the undamaged impeller surfaces are covered with a dark oxide film. This and many other impellers in seemingly identical service conditions survive long lives with little or no apparent damage. No material or manufacturing defects were found to explain the different service performance of the two impellers. Microstructure, microhardness and material chemistry are consistent with the specified material. Examination reveals the damage mechanism to be corrosion-enhanced cavitation erosion, the most severe form of erosion corrosion. Cavitation damage to the protective oxide film caused the zirconium to lose its normally outstanding corrosion resistance. The root cause of the impeller failure is most likely the introduction of excessive air into the pump due to low liquid level, a bad seal or inadequate head. Corrosion pitting, crevice corrosion, and solidification cracks (casting defect) also contributed to the failure.
Book Chapter
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003567
EISBN: 978-1-62708-180-1
... to localized wear, but careful monitoring is necessary to prevent failure of the worn parts because of corrosion ( Ref 2 ). Turbulence and eddies are promoted either where fittings or valves project into the mainstream flow or where the diameter of a pipe changes. The momentum of the particles is sufficient...
Abstract
This article focuses on the corrosion-wear synergism in aqueous slurry and grinding environments. It describes the effects of environmental factors on corrosive wear and provides information on the impact and three-body abrasive-corrosive wear. The article also discusses the various means for combating corrosive wear, namely, materials selection, surface treatments, and handling-environment modifications.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.steel.c9001714
EISBN: 978-1-62708-232-7
..., carburization as an initiation condition for metal dusting was found. The welding protrusion will change laminar flow of the gas, to turbulent flow. The solid particles in the turbulent gas, will remove the chromia layer behind the welding protrusion and weaken the resistance of the pipe surface...
Abstract
In a HyL III heat exchanger's radiant pipes, metal dusting reduced the pipe thickness from 8.5 to 3 mm in just nine months, leaving craters on the inner surface. The pipes are fabricated from HK 40 alloy. The heated gas (400 to 800 deg C) consisted of CO, CO2, and H2, with a 4:1 CO/CO2 ratio. Metallographic investigations revealed that the surface of the attacked pipes consisted of (Cr, Fe) carbide. The metal dusting was the result of a decomposition process (CO to CO2 + C) that deposited C on the pipe surface. Because of the high temperature, the C subsequently diffused through the surface oxide layer (Cr2O3), triggering a succession of reactions that led to pitting and the formation of craters.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003568
EISBN: 978-1-62708-180-1
..., and exposing new reactive surfaces that are anodic to uneroded neighboring areas on the surface. This results in rapid localized corrosion of the exposed areas in the form of smooth-bottomed shallow recesses. Nearly all flowing or turbulent corrosive media can cause erosion-corrosion. The attack may...
Abstract
Erosion occurs as the result of a number of different mechanisms, depending on the composition, size, and shape of the eroding particles; their velocity and angle of impact; and the composition of the surface being eroded. This article describes the erosion of ductile and brittle materials with the aid of models and equations. It presents three examples of erosive wear failures, namely, abrasive erosion, erosion-corrosion, and cavitation erosion.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c0091293
EISBN: 978-1-62708-234-1
.... Figure 1 shows the microbes that were cultured from the corrosion product. They were found to be sulfur-reducing bacteria. Uniform thinning occurred when the resultant oxide on the copper pipe surface eroded in low flow rates. The threshold for erosion by turbulent waters is much lower with this type...
Abstract
Copper piping in a closed-loop water heater system was found to be corroded with MIC and erosion of the weak oxide layer. Investigation (visual inspection, bacterial corrosion cultures, and 20x/400x micrographs) supported the conclusion that the corrosion was caused by microbiological attack, specifically sulfur-reducing bacteria. No recommendations were made.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006795
EISBN: 978-1-62708-295-2
... shallow recesses. Nearly all flowing and turbulent corrosive media can cause erosion-corrosion. The attack can exhibit a directional pattern related to the path taken by the corrodent as it moves over the surface of the metal. Figure 10 shows the interior of a 50 mm (2 in.) copper river waterline...
Abstract
Erosion is the progressive loss of original material from a solid surface due to mechanical interaction between that surface and a fluid, a multicomponent fluid, an impinging liquid, or impinging solid particles. The detrimental effects of erosion have caused problems in a number of industries. This article describes the processes involved in erosion of ductile materials, brittle materials, and elastomers. Some examples of erosive wear failures are given on abrasive erosion, liquid impingement erosion, cavitation, and erosion-corrosion. In addition, the article provides information on the selection of materials for applications in which erosive wear failures can occur.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001592
EISBN: 978-1-62708-228-0
... containing H 2 S and CO 2 at a down-hole temperature greater than 50 °C. In a wet environment, CO 2 becomes aggressive. CO 2 corrosion can be distinguished as one of three types, depending on the flow: Pitting in moderate flow, mesa-type attack in medium flow, or flow induced localized corrosion (FILC...
Abstract
Sucker-rod pumps are operating in very aggressive environments in oil well production. The combined effect of a corrosive environment and significant mechanical loads contribute to frequent cases of failure of the rod string during operation. Standards and recommendations have been developed to control and avoid those failures. This study presents various failure cases of sucker rods in different applications. The heat treatment of the steel material and the resulting microstructure are an important factor in the behavior of the sucker rod. A spheroidized microstructure presents a weaker resistance to corrosion affecting the rod life. Non-metallic inclusions are a pitting preferential site leading to fatigue crack initiation. Heterogeneous microstructure as banded martensite and ferrite/pearlite decreases the ductility of the material affecting the fatigue propagation resistance.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.mech.c9001222
EISBN: 978-1-62708-225-9
.... This is because more frequent changes in the flow direction cause the liquid metal stream to become more turbulent and to include more air bubbles and oxides. For this reason usually only components which are not subjected to very great demands with regard to soundness under pressure are die cast 1...
Abstract
A full lift disk, made of die cast brass, which served as a lifting aid in a safety valve, had cracked in service at a number of locations in the vicinity of the threaded hole. During microscopic examination, agglomeration of oxide inclusions were noted in the region of the cracks. Because the die cast brass was alloyed with aluminum, these inclusions consisted predominantly of aluminum oxide. The tolerable limit in pores and oxide inclusions was greatly exceeded in the lift disk under examination. Above all, the numerous oxide skins disrupted the cohesion of the microstructure and were primarily responsible for the failure of the lift disk.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.chem.c0091362
EISBN: 978-1-62708-220-4
... will result in a flow condition that is turbulent enough to aspirate air into the gas stream, thus contaminating the weld and destroying its mechanical and corrosion properties. The manifold gas system also contributed to this failure. When this system is first used, it is necessary to purge the contents...
Abstract
A nozzle in a wastewater vaporizer began leaking after approximately three years of service with acetic and formic acid wastewaters at 105 deg C (225 deg F) and 414 kPa (60 psig). The shell of the vessel was weld fabricated from 6.4 mm (0.25 in.) E-Brite stainless steel plate and measured 1.5 m (58 in.) in diameter and 8.5 m (28 ft) in length. Investigation (visual inspection, chemical analysis, radiography, dye-penetrant inspection, and hydrostatic testing of all E-Brite welds, 4x images, 100x/200x images electrolytically etched with 10% oxalic acid, and V-notch Charpy testing) supported the conclusion that failure of the nozzle weld was the result of intergranular corrosion caused by the pickup of interstitial elements and subsequent precipitation of chromium carbides and nitrides. Carbon pickup was believed to have been caused by inadequate joint cleaning prior to welding. The increase in the weld nitrogen level was a direct result of inadequate argon gas shielding of the molten weld puddle. Two areas of inadequate shielding were identified: improper gas flow rate for a 19 mm (0.75 in.) diam gas lens nozzle, and contamination of the manifold gas system. Recommendations included changes in the cleaning and welding process.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c0091402
EISBN: 978-1-62708-234-1
... heating and cooling cycles per hour for at least 16 h/day, or a minimum of 224 cycles/day. Steam and water pressure were 1035 kPa (150 psi) and 895 kPa (130 psi) respectively, and water-flow rate was estimated to be 1325 L/min (350 gal/min) based on pump capacity. Water-inlet temperature was 10 to 15 deg...
Abstract
Leakage was detected in a malleable iron elbow (ASTM A 47, grade 35018) after only three months in service. Life expectancy for the elbow was 12 to 24 months. The piping alternately supplied steam and cooling water to a tire-curing press. The supply line and elbow were subjected to 14 heating and cooling cycles per hour for at least 16 h/day, or a minimum of 224 cycles/day. Steam and water pressure were 1035 kPa (150 psi) and 895 kPa (130 psi) respectively, and water-flow rate was estimated to be 1325 L/min (350 gal/min) based on pump capacity. Water-inlet temperature was 10 to 15 deg C (50 to 60 deg F) and outlet temperature was 50 to 60 deg C (120 to 140 deg F). The pH of the water was 6.9. Investigation (visual inspection, chemical analysis, and 67x nital etched micrographs) supported the conclusion that the elbows had been given the usual annealing and normalizing treatment for ferritizing malleable iron. This resulted in lower resistance to erosion and corrosion than pearlitic malleable iron. Recommendations included replacing the elbows with heat-treated fittings with a pearlitic malleable microstructure.