1、Designation: D7973 14Standard Guide forMonitoring Failure Mode Progression in Plain Bearings1This standard is issued under the fixed designation D7973; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONOil analysis is a part of condition-based maintenance programs. Despite the wide use for severaldecades, there is no systematic approach
3、to selecting oil tests based on failure mode analysis. Mostusers select tests primarily based on oil degradation criteria, minimizing the potential for detectingsurface damage and limiting the potential benefits of the oil analysis program. This guide provides anexample of justification for oil anal
4、ysis from a failure standpoint to include both component wear andfluid deterioration.1. Scope1.1 This guide covers an oil test selection process for plainbearing applications by applying the principles of FailureMode and Effect Analysis (FMEA) as described in GuideD7874.1.2 This guide approaches oil
5、 analysis from a failure stand-point and includes both the bearing wear and fluid deteriora-tion.1.3 This guide pertains to improving equipment reliability,reducing maintenance costs, and enhancing the condition-based maintenance program primarily for industrial machineryby applying analytical metho
6、dology to an oil analysis programfor the purpose of determining the detection capability ofspecific failure modes.1.4 This guide reinforces the requirements for appropriateassembly and operation within the original design envelope, aswell as the need for condition-based and time-based mainte-nance.1
7、.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro
8、-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D130 Test Method for Corrosiveness to Copper from Petro-leum Products by Copper Strip TestD445 Test Method for Kinematic Viscosity of Transparentand
9、Opaque Liquids (and Calculation of Dynamic Viscos-ity)D664 Test Method for Acid Number of Petroleum Productsby Potentiometric TitrationD665 Test Method for Rust-Preventing Characteristics ofInhibited Mineral Oil in the Presence of WaterD1500 Test Method for ASTM Color of Petroleum Products(ASTM Colo
10、r Scale)D5185 Test Method for Multielement Determination ofUsed and Unused Lubricating Oils and Base Oils byInductively Coupled Plasma Atomic Emission Spectrom-etry (ICP-AES)D6304 Test Method for Determination of Water in Petro-leum Products, Lubricating Oils, and Additives by Cou-lometric Karl Fisc
11、her TitrationD7685 Practice for In-Line, Full Flow, Inductive Sensor forFerromagnetic and Non-ferromagnetic Wear Debris De-termination and Diagnostics for Aero-Derivative and Air-craft Gas Turbine Engine BearingsD7690 Practice for Microscopic Characterization of Par-ticles from In-Service Lubricants
12、 by Analytical Ferrogra-phyD7874 Guide for Applying Failure Mode and Effect Analy-sis (FMEA) to In-Service Lubricant Testing1This guide is under the jurisdiction of ASTM Committee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee D02.96.04 on Gu
13、idelines for In-Services Lubricants Analysis.Current edition approved Dec. 1, 2014. Published February 2015. DOI: 10.1520/D7973-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informa
14、tion, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 Other Documents:3ISO 4407 Hydraulic Fluid PowerFluid ContaminationDetermination of ParticulateISO 11500 Hydrauli
15、c Fluid PowerDetermination of theParticulate Contamination Level of a Liquid Sample byAutomatic Particle Counting Using the Light-extinctionPrinciple3. Terminology3.1 Definitions:3.1.1 bearing failure, nthe termination of the bearingsability to perform its design function.3.1.2 bearing failure initi
16、ation, nthe moment a bearingstarts to perform outside of its design function measured byperformance characteristics.3.1.3 cause(s) of failure, nunderlying source(s) for eachpotential failure mode that can be identified and described byanalytical testing.3.1.4 design function, nfunction or task that
17、the system orcomponents should perform.3.1.5 detection ability number, D, nranking number thatdescribes the ability of a specific fluid test to successfullydetect a failure modes cause or effects.Ascale is used to gradedetection ability numbers.3.1.6 dynamic viscosity (), nthe ratio between the appl
18、iedshear stress and rate of shear of a liquid; commonly known asa fluid resistance to flow.3.1.7 effect(s) of failure, npotential outcome(s) of eachfailure mode on the system or components.3.1.8 failure-developing period (FDP), nperiod fromcomponents incipient failure to functional failure.3.1.9 fai
19、lure mode, nphysical description of the manner inwhich a failure occurs.3.1.10 failure mode and effect analysis (FMEA),nanalytical approach to determine and address methodicallyall possible system or component failure modes and theirassociated causes and effects on system performance.3.1.11 hydrodyn
20、amic lubrication (HD), nlubrication re-gime where the load carrying surfaces are separated by arelatively thick film of lubricant formed by a combination ofsurface geometry, surface relative motion, and fluid viscosity.3.1.12 kinematic viscosity (), nthe ratio of the dynamicviscosity () to the densi
21、ty () of a fluid.3.1.13 occurrence number, O, nranking number that de-scribes the probability of occurrence of a failure modes causesand effects over a predetermined period of time based on pastoperating experience in similar applications.3.1.14 P-F interval, nperiod from the point in time inwhich a
22、 change in performance characteristics or condition canfirst be detected (P) to the point in time in which functionalfailure (F) will occur.3.1.15 risk priority number, RPN, na numeric assessmentof risk assigned to FMEA process quantifying failureoccurrence, severity of impact, and likelihood detect
23、ion.3.1.16 severity number, S, nranking number that describesthe seriousness of the consequences of each failures modes,causes and effects on potential injury, component or equipmentdamage, and system availability.3.1.17 white metal bearing alloys, nMetal alloys typicallyconsisting of lead (Pb), tin
24、 (Sn) or zinc (Zn) with antimony(Sb) (some known as Babbitt) that are applied as a relativelythin surface to hydrodynamic bearings. These relatively softmaterials are used to ensure embeddability of hard particlecontaminants entrained in the lubricant and to ensure journalprotection should oil suppl
25、y be interrupted.4. Summary of Guide4.1 This guide assists users in the condition assessment ofplain bearing applications by selecting oil tests associated withspecific failure modes, causes, or effects for the purpose ofdetecting the earliest stage of failure development.4.2 There are a number of d
26、ifferent industrial systems withplain bearings. For the purpose of demonstrating the applica-tions of this methodology, a simple horizontal bearing housingutilizing a journal type plain bearing lubricated by an oil ringwill be discussed. This example is a typical application formany industrial pumps
27、 and motors (1).44.3 The focus of this example is to select oil tests capable ofdetecting and monitoring the progression of specific plainbearing failure modes, their causes and effects, as well aslubricating oil deterioration.4.4 The expectation is that similar approaches will beapplied to other sy
28、stem components lubricated under hydrody-namic condition to detect their specific failure modes.5. Significance and Use5.1 This standard is intended as a guideline for the justifi-cation of oil test selection for monitoring plain bearingconditions. One should employ a continuous benchmarkingagainst
29、similar applications to ensure lessons learned arecontinuously being implemented.5.2 Selection of oil tests for the purpose of detecting plainbearing failure modes requires good understanding of equip-ment design, operating requirements, and surrounding condi-tions. Specifically, detailed knowledge
30、is required of bearingdesign configuration, dimensional tolerances, load directions,design limitations, lubrication mechanisms, lubricantcharacteristics, and metallurgy of lubricated surfaces. Equip-ment criticality and accessibility as well as application of othermonitoring techniques (for example,
31、 vibration, ultrasound, orthermal images) are also critical information in this analysisprocess. In addition, detailed knowledge of the lubricating oilis paramount.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4The bold
32、face numbers in parentheses refer to the list of references at the end ofthis standard.D7973 1425.3 To properly apply the FMEA methodology, users mustunderstand the changes encountered in the system during alloperating modes, their impact on design functions, and avail-able monitoring techniques cap
33、able of detecting these changes.To demonstrate this approach, Section 6 will provide extensivedescriptions of the plain bearing failure modes, their causes,and effects.6. Failure Modes and their Effects for Plain BearingApplications6.1 During steady state operation, plain bearings operateprimarily u
34、nder the hydrodynamic (HD) lubrication regime.6.2 The main failure modes of plain bearings include rapidbreakdown or slow deterioration of the HD oil film.6.3 The rapid breakdown of HD oil film can be caused by asudden loss of lubricating oil, rapid change in bearing operat-ing conditions being outs
35、ide the original design basis, oraccidental bearing material disintegration. Wear sensors andother monitoring techniques (for example, bearing surfacetemperature or vibration sensors) would provide better moni-toring capability for this failure mode.6.4 The slow deterioration of HD oil film can be m
36、onitoredby in-line oil sensors or off-line oil sample analysis. Based onoperating experience, several causes are linked to this failuremode.6.5 Causes of Plain Bearing Failures:6.5.1 Change in Dynamic Viscosity of the LubricatingOilDynamic viscosity at operating temperature is the onlyproperty repre
37、senting the lubricant in the HD oil film thicknesscalculation. In general, reduction in dynamic viscosity willreduce the oil film thickness. Under severe transient conditionsreduction of the oil film thickness may change the HDlubrication condition to a mixed lubrication regime and in-crease the ris
38、k of bearing surface contact and wear. If notcorrected, it will cause bearing failure. In opposite conditionswhen the dynamic viscosity is too high, an increase in drag andfriction will result in local heat generation, which may increasethe rate of chemical reaction within the oil film. In condition
39、-based maintenance programs, kinematic viscosity at 40 C (oroccasionally at 100 C) is used to measure this property. Theassumption is that in most industrial applications, lubricantdensity is not significantly changed in the measured tempera-ture of interest (for example, 40 C or 100 C) and trending
40、kinematic viscosity can provide adequate prediction of thelubricants ability to form a reliable and sustainable HD oilfilm. Newer methods exist or are being developed that willmeasure dynamic viscosity directly. These methods may intime become commonly used in this application.6.5.2 Deterioration of
41、 Lubricating Oil ChemistryThe HDlubrication will also depend on the complex relationshipbetween properties of oil-to-metal adhesion and oil-to-oilcohesion. Applying a constant shear stress on the lubricatingoil film may lead to physical damage to the lubricant mol-ecules. The presence of atmospheric
42、 oxygen may initiatechemical reactions such as oxidation. High temperature andpressure will accelerate these reactions and lubricant moleculesthermal breakdown. Finally, lubricating oil will also deteriorateby the additive depletion process (for example, due to expectedperformance). The depletion ra
43、te would depend on the additivetype, applications, and operating conditions. The consequencesof these chemical changes will influence several criticalproperties such as cohesion, adhesion, surface tension, etc.Some visible changes will include an increase in foamingcharacteristics, air release, slud
44、ge and varnish formation, orreduce oil solubility characteristics.6.5.3 Increase in Gaseous, Liquid, and Solid ParticleContaminationAll three contaminants types will affect theHD oil film but in different mechanisms.6.5.3.1 An excessive amount of undissolved gas bubbles inthe oil weakens the load ca
45、rrying capacity of the lubricatingfilm. If the gas is reactive, it can promote chemical degradationof the lubricant which may change the physical characteristicsof the oil.6.5.3.2 A large amount of liquid contaminants, particularlythose having significantly different viscosity or density, mayinfluen
46、ce the dynamic viscosity. If this liquid has chemicalreactivity with the lubricant, it could affect its performancecharacteristics. An example is free water which may notsupport the external load acting on the bearing. It could alsohydrolyze some of the additives, affecting their performance.6.5.3.3
47、 The presence of a moderate concentration of smallsolid particle contamination is of less concern in HDlubrication, assuming the particle sizes are smaller than the oilfilm thickness. However, the presence of solid particles is moreharmful in boundary and mixed lubrication conditions. Thepresence of
48、 solid particles may increase the risk of someparticles being imbedded in soft bearing surfaces and generateabrasive wear to the mating hard surfaces. In applications witha hydrostatic lift system, large solid particles may scratchsurfaces around oil grooves, reducing bearing capability togenerate t
49、he required hydrostatic lift during start up or shutdown operations.6.5.4 Change in Bearing Surface Profile or MaterialPropertiesChanges in the relative speed of bearing surfacesor to the wedge profile will also influence the HD oil film.During start up or shut down operations, plain bearings mostlikely will operate for a short period under mixed or evenboundary lubrication. At these conditions there is an increasedrisk of bearing surface contact resulting in surface wear, whichmay temper the profile of the lubricating oil wedge, thusaffecting th
