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Lubrication systems
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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.mech.c0009190
EISBN: 978-1-62708-225-9
... Abstract In an industrial application, 24 speed-increaser gearboxes were used to transmit 258 kW (346 hp) and increase speed from 55 to 375 rev/min. The gears were parallel shaft, single helical, carburized, and ground. The splash lubrication system used a mineral oil without antiscuff...
Abstract
In an industrial application, 24 speed-increaser gearboxes were used to transmit 258 kW (346 hp) and increase speed from 55 to 375 rev/min. The gears were parallel shaft, single helical, carburized, and ground. The splash lubrication system used a mineral oil without antiscuff additives with ISO 100 viscosity. After about 250 h of operation, two gearboxes failed by bending fatigue. Investigation showed the primary failure mode was scuffing, and the earlier bending fatigue failures were caused by dynamic loads generated by the worn gear teeth. Testing of a prototype gearbox showed that the failure resulted from several interrelated factors: the lubricant viscosity was too low causing high temperatures; no antiscuff additives were used; a gearbox designed as a speed reducer was used as a speed increaser (the designer selected a long-addendum tooth for the pinion); the gear teeth were not provided with a coating or plating to ease running-in; and the gears were not run-in properly under reduced loads. The case suggests that such gear failures can be avoided if designers and operators recognize that the lubricant is an important component of a gearbox and appreciate that gear design requires the consideration and control of many interrelated factors.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.auto.c0047846
EISBN: 978-1-62708-218-1
... loading. It was revealed by visual examination that the fracture had initiated in the sharp corner at the bottom of a longitudinal hole which was part of a force feed lubricating system. Beach marks were observed on the fracture surfaces. It was revealed by further examination that the slip clutch...
Abstract
An 8640 steel shaft installed in a fuel-injection-pump governor that controlled the speed of a diesel engine used in trucks and tractors broke after few days of operation. The mechanism that drove the shaft was designed to include a slip clutch to protect the governor shaft from shock loading. It was revealed by visual examination that the fracture had initiated in the sharp corner at the bottom of a longitudinal hole which was part of a force feed lubricating system. Beach marks were observed on the fracture surfaces. It was revealed by further examination that the slip clutch was removed in an effort to reduce cost and hence the shaft was subjected to increased vibration and shock loading. Insufficient fatigue limit of the shaft was revealed by fatigue testing of the shafts taken from stock in a rotating-beam machine. As a corrective measure, the fatigue limit of shafts was increased to 760 MPA by nitriding for 10 h at 515 deg C.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006806
EISBN: 978-1-62708-329-4
... (cyclic/steady, unidirectional/reversing) Speed Lubricants and lubrication system characteristics Lubricant cleanliness and filtration Operating temperatures Counterface (shaft) material and finish Alignment It is necessary to understand the bearing geometry (shapes, grooving...
Abstract
A mechanical part, which supports the moving part, is termed a mechanical bearing and can be classified into rolling (ball or roller) bearings and sliding bearings. This article discusses the failures of sliding bearings. It first describes the geometry of sliding bearings, next provides an overview of bearing materials, and then presents the various lubrication mechanisms: hydrostatic, hydrodynamic, boundary lubrication, elastohydrodynamic, and squeeze-film lubrication. The article describes the effect of debris and contaminant particles in bearings. The steps involved in failure analysis of sliding bearings are also covered. Finally, the article discusses wear-damage mechanisms from the standpoint of bearing design.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0001809
EISBN: 978-1-62708-180-1
... pumps) or a specifically applied lubricant. It is usually the case that the more severe the duty of bearings the more precisely they will be made and the more likely there will be a support (lubrication) system to ensure long life and to prevent catastrophic failure. Bearing Materials The lowest...
Abstract
This article discusses the classification of sliding bearings and describes the major groups of soft metal bearing materials: babbitts, copper-lead bearing alloys, bronze, and aluminum alloys. It provides a discussion on the methods for fluid-film lubrication in bearings. The article presents the variables of interest for a rotating shaft and the load-carrying capacity and surface roughness of bearings. Grooves and depressions are often provided in bearing surfaces to supply or feed lubricant to the load-carrying regions. The article explains the effect of contaminants in bearings and presents the steps for failure analysis of sliding bearings. It also reviews the factors responsible for bearing failure with examples.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001045
EISBN: 978-1-62708-214-3
... a dezincification-resistant alloy was recommended. Cooling systems Dezincification Hydroelectric power generation Lubrication systems Yellow brass, 65% Cu UNS C27000 Dealloying/selective leaching Background Several brass alloy 270 heat exchanger tubes began to leak after approximately 5.5 years...
Abstract
A failure analysis was conducted on brass alloy 270 heat exchanger tubes that were pulled from a unit used to cool oil for the speed regulators and thrust bearings of a hydroelectric power plant. The tubes began to leak after approximately 5.5 years of service. Macrophotography and scanning electron microscopy were used to examine samples from the tubes. An energy-dispersive electron microprobe analysis was carried out to evaluate the zinc distribution. Results showed that the failure was due to dezincification. Replacement of the tubes with new tubes fabricated from a dezincification-resistant alloy was recommended.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003556
EISBN: 978-1-62708-180-1
... the degradation of various protective systems, such as corrosion inhibitors and lubricants. The article describes the failure analysis of steel, iron, copper, aluminum, and their alloys. It also discusses the probes available to monitor conditions relevant to MIC in industrial systems and the sampling...
Abstract
This article focuses on the mechanisms of microbially induced or influenced corrosion (MIC) of metallic materials as an introduction to the recognition, management, and prevention of microbiological corrosion failures in piping, tanks, heat exchangers, and cooling towers. It discusses the degradation of various protective systems, such as corrosion inhibitors and lubricants. The article describes the failure analysis of steel, iron, copper, aluminum, and their alloys. It also discusses the probes available to monitor conditions relevant to MIC in industrial systems and the sampling and analysis of conditions usually achieved by the installation of removable coupons in the target system. The article also explains the prevention and control strategies of MIC in industrial systems.
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006911
EISBN: 978-1-62708-395-9
... and lubrication technologies, the percentage of global GDP, energy consumption, and CO 2 emission can be significantly reduced. Friction and Wear of Polymers In order to reduce wear and energy consumption, it is imperative to address appropriate material selection in mechanical systems. The usual metrics...
Abstract
Tribology is the study of contacting materials in relative motion and more specifically the study of friction, wear, and lubrication. This article discusses the classification and the mechanisms of friction, wear, and lubrication of polymers. It describes the tribological applications of polymers and the tribometers and instrumentation used to measure the tribological properties of polymers. The article discusses the processes involved in calculating the wear rate of polymers and the methods of characterization of the sliding interface. It provides information on the pressure and velocity limit of polymer composites and polymer testing best practices.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001356
EISBN: 978-1-62708-215-0
... and the presence of moist hydrogen used to cool the ring. Factors which promoted the failure were higher than normal strength levels in the ring material, lower than normal ring operating temperatures, possible moisture in the lubrication oil system, periodic poor performance of the hydrogen dryers, and a ring...
Abstract
A shrunk-fit 18 Mn-5Cr steel retaining ring failed without warning during normal unit operation of a 380 MW electrical generator. The cause of the ring failure was determined to be intergranular stress-corrosion cracking (IGSCC) because of the high strength of the ring material and the presence of moist hydrogen used to cool the ring. Factors which promoted the failure were higher than normal strength levels in the ring material, lower than normal ring operating temperatures, possible moisture in the lubrication oil system, periodic poor performance of the hydrogen dryers, and a ring design which allowed water to become trapped in a relief groove. These factors caused pitting in the ring in an estimated 100 hours of operation. The ring had been inspected previously 18 months prior to the failure and no defects or pitting were found. Calculations showed that a 0.127-cm (0.050-in.) deep pit could grow to a critical size in 3000 to 4000 hours of operation. To prevent further failures, it was recommended that the ring be replaced with an 18 Mn-18Cr alloy with superior resistance to IGSCC. A program of periodic inspection and replacement of other retaining rings in the system was also recommended.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.conag.c9001248
EISBN: 978-1-62708-221-1
... of the transmission system showed there might arise possibilities of choking in the line lubricating oil. Such eventualities would, of course, cause seizure of the gears and damage. The incidence of such defects stopped after corrective measures were taken. In this particular instance, corrective measures could...
Abstract
Failure occurred in the teeth of a case-hardening Ni-Cr-Mo alloy steel spur gear in the transmission system of heavy duty tracked vehicles. The defects were in the nature of seizure on the involute profile. Scrutiny of the transmission system showed there might be choking in the lubricating oil line. Such would cause seizure of the gears and damage. The incidence of such defects stopped after corrective measures were taken.
Book Chapter
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003524
EISBN: 978-1-62708-180-1
... mechanics fracture modes fracture surface lubricants macroscopic examination mechanical testing microscopic examination nondestructive inspection sampling simulated-service testing stress analysis wear failure ANALYZING the inevitable failures that occur during testing, manufacturing...
Abstract
This article describes the preliminary stages and general procedures, techniques, and precautions employed in the investigation and analysis of metallurgical failures that occur in service. The most common causes of failure characteristics are described for fracture, corrosion, and wear failures. The article provides information on the synthesis and interpretation of results from the investigation. Finally, it presents key guidelines for conducting a failure analysis.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001118
EISBN: 978-1-62708-214-3
... the minimum tolerable defect size was also recommended. Aircraft components Commercial planes Lubrication systems Springs (elastic) Wire 321 UNS S32100 Metalworking-related failures Fatigue fracture Background Two stainless steel springs in oil ring lip seals failed. Applications...
Abstract
Failure of AISI type 321 stainless steel internal springs from newly manufactured lip seals on a shaft between a turbine power unit and a pump in a commercial aircraft secondary unit was investigated. Examination of the coils from two failed springs showed that both had failed by fatigue. The springs contained drawing defects that served as the fatigue crack initiation sites. It was recommended that the wire drawing process be investigated for various levels of steel cleanliness to predict the incidence of drawing defects at the wire surface. Stress analysis to determine the minimum tolerable defect size was also recommended.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001382
EISBN: 978-1-62708-215-0
.... It was recommended that proper lubrication procedures be maintained to allow free rotation of the bolts while in service. Axles Couplings Lubrication Railroads 1045 UNS G10450 Fatigue fracture Background A trunnion bolt that was part of a coupling system in a train failed in service, causing cars...
Abstract
A trunnion bolt that was part of a coupling in a metropolitan railway system failed in service, causing cars to separate. The bolt had been in service for more than ten years prior to failure. Visual examination showed that the failure resulted from complete fracture at the grease port and surface groove located at midspan. Drillings machined from the bolt underwent chemical analysis, which confirmed that the material was AISI 1045 carbon steel, in accordance with specifications. Two sections cut from the bolt were subjected to metallographic examination and hardness testing. The fracture origin was typical of fatigue. The ultimate tensile strength of the bolt was in excess of requirements. Wear patterns indicated that the bolt had been frozen in position for a protracted period and subjected to repeated bending stresses, which resulted in fatigue cracking and final complete fracture. It was recommended that proper lubrication procedures be maintained to allow free rotation of the bolts while in service.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.usage.c0046242
EISBN: 978-1-62708-236-5
... be checked for residual magnetism and should be demagnetized if any is present. The lubrication oil should be changed or filtered to remove any debris from previous damage to the gears. The oil-circulation system should be put into operating conditions. Selected References Selected References...
Abstract
An integral coupling and gear (Cr-Mo steel), used on a turbine-driven main boiler-feed pump, was removed from service after one year of operation because of excessive vibration. Spectrographic analysis and metallographic examination revealed the fact that gritty material in the gear teeth (found at visual inspection) was composed of the same material as the metal in the coupling. Beach marks and evidence of cold work, typical of fatigue failure, were found on the fracture surface. Chips remaining in the analysis cut were difficult to remove, indicating a strong magnetic field in the part. Evidence found supports the conclusions that failure of the coupling was by fatigue and that incomplete demagnetization of the coupling following magnetic-particle inspection caused retention of metal chips in the roots of the teeth. Improper lubrication caused gear teeth to overheat and spall, producing chips that eventually overstressed the gear, causing failure. Because the oil circulation system was not operating properly, metal chips were not removed from the coupling. Recommendations included checking the replacement coupling for residual magnetism and changing or filtering the pump oil to remove any debris.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c0006424
EISBN: 978-1-62708-217-4
... Abstract An external tank pressure/vent valve regulates the external tank fuel feed system, which transfers fuel under pressure to the internal tanks of the aircraft. A dual-position valve was found to be sticking at the intermediate positions. Also, service air check valves located...
Abstract
An external tank pressure/vent valve regulates the external tank fuel feed system, which transfers fuel under pressure to the internal tanks of the aircraft. A dual-position valve was found to be sticking at the intermediate positions. Also, service air check valves located on the incoming lines contained poppets that were being stuck in a closed or partially closed position because of suspected corrosion product. Residue taken from the check valve poppet and from the dual-position valve was chemically analyzed. Chloride was present in both samples. It was suspected that moisture entering the service air lines left a chloride-containing compound upon evaporation within the air check valves and pressure/vent assembly. This compound subsequently reacted with the anodized, dichromate sealed check valve housing to lock the check valve poppets in a closed or partially closed position, decreasing the actual pressure being supplied to the pressure/vent valve. It was recommended that an inspection be conducted to ensure that the service air check valves are operating properly prior to removal and servicing of the pressure/vent valve assembly. It was also recommended that dry-film lubricant be checked to ensure that it meets specifications for the pressure/vent valve assembly.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c9001706
EISBN: 978-1-62708-217-4
.... The crack reached the critical size and caused failure by stress-corrosion cracking (SCC) under static loading conditions in service. The failed beam was protected by a well adhering paint system. However, the presence of adequate amounts of corrosion preventive compound films (CPC) on the surfaces...
Abstract
The truck beam of the left main landing gear (MGL) of a Boeing 707 airplane collapsed on the ground just after the aircraft was unloaded and refueled. The investigation revealed that failure was caused by the propagation of an intergranular crack originating from the bottom of the pit. The crack reached the critical size and caused failure by stress-corrosion cracking (SCC) under static loading conditions in service. The failed beam was protected by a well adhering paint system. However, the presence of adequate amounts of corrosion preventive compound films (CPC) on the surfaces of the failed beam could not be conclusively established because of the long term service exposure and presence of lubricants.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.mech.c0047998
EISBN: 978-1-62708-225-9
... Abstract The drive-shaft hanger bearings failed after 300 to 400 h in service. The shaft, supported by labyrinth-sealed single row radial ball bearings of ABEC-1 tolerances, was made of aluminum 2024-T3 tubing (2.5 cm diam and 1.2 mm wall thickness). The bearings were lubricated with a paste...
Abstract
The drive-shaft hanger bearings failed after 300 to 400 h in service. The shaft, supported by labyrinth-sealed single row radial ball bearings of ABEC-1 tolerances, was made of aluminum 2024-T3 tubing (2.5 cm diam and 1.2 mm wall thickness). The bearings were lubricated with a paste-type mineral-oil lubricant (containing molybdenum disulfide and polytetrafluoroethylene particles) or grease conforming to MIL-G-81322 (containing thickening agent and synthetic hydrocarbons) and had two-piece spot-welded retainers. On visual examination, the balls were observed to be embedded in the inner-ring raceway which had been softened by the elevated temperatures reached during the failure. Broken retainers and worn and bent out of shape seals were found. Penetration of gritty particles, water and other corrosive agents and leakage of lubricant out of the bearing permitted by the worn seals was observed. It was concluded that overheating was caused by lubricant flow was permitted by wear of the labyrinth seals. Positive rubbing seals and MIL-G-81322 grease lubricant were found to have longer life than those with the labyrinth seals and mineral-oil-paste lubricant on testing under simulated environmental conditions and were installed as a corrective measure. Importance of dirt free supply and drainage of oil was discussed.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001783
EISBN: 978-1-62708-241-9
... the dimensions and enlarging the square bearing by 0.015 in. The previous lubricant was also changed to something more suitable for the process. Lab tests conducted by the manufacturer of the system measured improvements in crimp performance of approximately 300%. Data was extrapolated from testing...
Abstract
An aluminum bronze bushing that serves as a guide in a crimping machine began to fail after 50,000 cycles or approximately two weeks of operation. Until then, typical run times had been on the order of months. Although the bushings are replaceable and relatively inexpensive, the cost of downtime adds up quickly while operators troubleshoot and swap out worn components. Initially, the quality of the bushings came into question, but after a detailed analysis of the entire crimping mechanism, several other issues emerged that were not previously considered. As a result, the investigation provides information on not only better materials, but also design changes intended to reduce wear and increase service life.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006791
EISBN: 978-1-62708-295-2
... in Fig. 7 and of a piston in Fig. 8 . The causes of seizure, which is mainly governed by excessive loading and heating, include ( Ref 15 ): Poor heat dissipation, mainly related to material properties, such as thermal conductivity Poor lubrication system or improper lubrication Excessive...
Abstract
Friction and wear are important when considering the operation and efficiency of components and mechanical systems. Among the different types and mechanisms of wear, adhesive wear is very serious. Adhesion results in a high coefficient of friction as well as in serious damage to the contacting surfaces. In extreme cases, it may lead to complete prevention of sliding; as such, adhesive wear represents one of the fundamental causes of failure for most metal sliding contacts, accounting for approximately 70% of typical component failures. This article discusses the mechanism and failure modes of adhesive wear including scoring, scuffing, seizure, and galling, and describes the processes involved in classic laboratory-type and standardized tests for the evaluation of adhesive wear. It includes information on standardized galling tests, twist compression, slider-on-flat-surface, load-scanning, and scratch tests. After a discussion on gear scuffing, information on the material-dependent adhesive wear and factors preventing adhesive wear is provided.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006789
EISBN: 978-1-62708-295-2
... in engineering systems. They are quite important in dry conditions, that is, when no lubricant is present between the mating surfaces. In this case, the mechanism may be either tribo-oxidative or adhesive wear, depending on the operating parameters (i.e., nominal contact pressure, p , and sliding velocity, v...
Abstract
This article considers the main characteristics of wear mechanisms and how they can be identified. Some identification examples are reported, with the warning that this task can be difficult because of the presence of disturbing factors such as contaminants or possible additional damage of the worn products after the tribological process. Then, the article describes some examples of wear processes, considering possible transitions and/or interactions of the mechanism of fretting wear, rolling-sliding wear, abrasive wear, and solid-particle erosion wear. The role of tribological parameters on the material response is presented using the wear map concept, which is very useful and informative in several respects. The article concludes with guidelines for the selection of suitable surface treatments to avoid wear failures.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001028
EISBN: 978-1-62708-214-3
... fracture was caused by engine vibrations during operation of the aircraft. Fracture characteristics indicated that the fatigue would not have occurred if the initial damage had not taken place. Aerospace engines Engine components Gas turbine engines Lubrication systems Tanks Tearing 321 UNS...
Abstract
Several AISI type 321 stainless steel welded oil tank assemblies used on helicopter engine systems began to leak in service. One failure, a fracture on the aft side of a spot weld, was submitted for analysis. SEM fractography examination revealed fatigue failure. The failure initiated at an overload fracture near the root of the weld and was followed by mode III fatigue crack propagation (tearing) around the periphery of the weld. The initial overload fracture was caused by a high external load, which produced a concentrated stress and fracture at the weld root. The subsequent fatigue fracture was caused by engine vibrations during operation of the aircraft. Fracture characteristics indicated that the fatigue would not have occurred if the initial damage had not taken place.
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