Oil Flushing Visual Inspection Media and Criteria
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Oil Flushing - Visual Inspection Media and Criteria By Larry B Jordan Throughout my career in the flushing industry I have been asked countless time about the criteria and materials used for deeming a system clean. When it comes time to perform oil flushing on your equipment it is important to build the criteria into your flushing plan or procedure. There are two aspects to keep in mind when deeming a flush clean. First is the materials you cannot see with a naked eye. An average human hair width is around 40-micron but particulate can cause damage to your system as small as 2-micron. So how can you judge your system clean if you cannot see the material. There are a few options for you at this point. • Option 1 – Use a laboratory to test your oil and verify results. The pros for using a lab are controlled, certified results. Cons for utilization of a laboratory are time and control. For example, the flush has become the controlling factor of your outage and you are ready to move forward with final testing to verify the flush. If this happens to be at 5pm on a Friday, does your lab run over the weekend? Where is the closest lab? Do you have to wait for shipping, processing, then posting of results? Having worked in some rural areas the timing can be anywhere from 2-4 days waiting for expedited results. • Option 2 – Using a patch kit. While patch kits have come a long way from the old microscope and counting particles, (Newer versions allow for attachment to computer and measurement of actual particles) Patch kits still allow for human error. They are more of a quick “down and dirty” method and should always be backed by sending a sample to a laboratory. • Option 3 – Portable Particle Counters. Using a particle counter on site is the quickest most reliable method for verification of microscopic particles. There are multiple types and should be researched based on application. Where light refracting units are great for turbine and hydraulic fluids they can give false readings with darker oils and oils with moisture contamination. Pore blockage units will work with darker oils and moisture but will require more care with handling and calibration. The preferred units will give you particle counts in both ISO and NAS based on manufacturer requirements. Always verify calibration on unit before staking the success of the flush on the readings. So, what about material you can see? The material should show up on the particle count….right? Not always. Picture the following. You have a verified oil sample at an ISO Code of 18/16/14. You take a ball bearing the size of a marble, clean it off with denatured alcohol and drop it into the sample. You then run the sample through your portable particle counter. The sample comes back at 18/16/14. Why? Simple, the bearing is too large to run through the particle counter. That is why it is vital to have both particle count and visual inspection as part of your cleanliness criteria. This bring me to the second part around inspection media. The most common media used is 100 mesh screen. This can come in different forms required by equipment manufacturers.
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Transcript of Oil Flushing Visual Inspection Media and Criteria
OilFlushing-VisualInspectionMediaandCriteriaByLarryBJordanThroughoutmycareerintheflushingindustryIhavebeenaskedcountlesstimeaboutthecriteriaandmaterialsusedfordeemingasystemclean.Whenitcomestimetoperformoilflushingonyourequipmentitisimportanttobuildthecriteriaintoyourflushingplanorprocedure.Therearetwoaspectstokeepinmindwhendeemingaflushclean.Firstisthematerialsyoucannotseewithanakedeye.Anaveragehumanhairwidthisaround40-micronbutparticulatecancausedamagetoyoursystemassmallas2-micron.Sohowcanyoujudgeyoursystemcleanifyoucannotseethematerial.Thereareafewoptionsforyouatthispoint.
• Option1–Usealaboratorytotestyouroilandverifyresults.Theprosforusingalabarecontrolled,certifiedresults.Consforutilizationofalaboratoryaretimeandcontrol.Forexample,theflushhasbecomethecontrollingfactorofyouroutageandyouarereadytomoveforwardwithfinaltestingtoverifytheflush.Ifthishappenstobeat5pmonaFriday,doesyourlabrunovertheweekend?Whereistheclosestlab?Doyouhavetowaitforshipping,processing,thenpostingofresults?Havingworkedinsomeruralareasthetimingcanbeanywherefrom2-4dayswaitingforexpeditedresults.
• Option2–Usingapatchkit.Whilepatchkitshavecomealongwayfromtheoldmicroscopeandcountingparticles,(Newerversionsallowforattachmenttocomputerandmeasurementofactualparticles)Patchkitsstillallowforhumanerror.Theyaremoreofaquick“downanddirty”methodandshouldalwaysbebackedbysendingasampletoalaboratory.
• Option3–PortableParticleCounters.Usingaparticlecounteronsiteisthequickestmostreliablemethodforverificationofmicroscopicparticles.Therearemultipletypesandshouldberesearchedbasedonapplication.Wherelightrefractingunitsaregreatforturbineandhydraulicfluidstheycangivefalsereadingswithdarkeroilsandoilswithmoisturecontamination.Poreblockageunitswillworkwithdarkeroilsandmoisturebutwillrequiremorecarewithhandlingandcalibration.ThepreferredunitswillgiveyouparticlecountsinbothISOandNASbasedonmanufacturerrequirements.Alwaysverifycalibrationonunitbeforestakingthesuccessoftheflushonthereadings.
So,whataboutmaterialyoucansee?Thematerialshouldshowupontheparticlecount….right?Notalways.Picturethefollowing.YouhaveaverifiedoilsampleatanISOCodeof18/16/14.Youtakeaballbearingthesizeofamarble,cleanitoffwithdenaturedalcoholanddropitintothesample.Youthenrunthesamplethroughyourportableparticlecounter.Thesamplecomesbackat18/16/14.Why?Simple,thebearingistoolargetorunthroughtheparticlecounter.Thatiswhyitisvitaltohavebothparticlecountandvisualinspectionaspartofyourcleanlinesscriteria.Thisbringmetothesecondpartaroundinspectionmedia.Themostcommonmediausedis100meshscreen.Thiscancomeindifferentformsrequiredbyequipmentmanufacturers.
• WyeStrainer- TheWyestrainerusesacylindricalor“barrel”screenforinspections.Whilethescreensarequicktochangeandfairlycommontheyarenotapreferredmethodbymostflushingexperts.Thescreenshaveatendencytogetcrushedfromrepeatedremovalandinstallation.Nottomentioncontaminationcandropoutintothescreencoverandgivefalsepositive.
• BasketStrainer- Basketstrainerareutilizedinmanyflushestoday.Theyacceptfullflowandhasasealedbottomtocatchallmaterialsduringtheinspection.Ifutilizingbasketstrainers,itisadvisabletopurchaseunitswithquickreleasehandlesontopandadrainvalveonbottom.Thisallowsforeaseofinspection.Downsidetobasketstrainersareavailabilityandcost.Thereisno1standardbasketorhousing.Ifabasketisdamagedduringyourflushingactivityyoushouldalwaysstockspares.Thiswillkeepyourflushfromhavingneedlessdelays.
• WitchesHat- Thewitcheshatstrainerisnotcommonlyusedfromflushingexperts,howevertherearemanufacturerswhorequirethestrainertobeplacesinthereturnheaderpreventingcontaminationfromgettingbackintothereservoir.Thewitcheshatshouldonlybeusedforgrosscontaminationandinspectedoften.Thesurfaceareaofthescreenleavestheunitwithatendencytotearorblowout.Otheritemstoconsiderareaccessibility.Thewitcheshatrequiresapipespoolpiecetoallowremovalandinstallation.
• BagFilters- Bagfiltersarecommonlyusedinmanyturbineandcompressorflushestoday.Theprosofbagfiltersarecostandavailability.Bagfilterscanbepurchasesinmanymicronsizestomeetyourneedsaswellasbeingproducedanddistributedglobally.A36”1-micronbagfiltercanbepurchasedforaslittleas$3U.S.Theconswithbagfiltersarethatthehousingtoutilizethebagfilterscanbecostly,bulkyandthefiltersarenominal.Whichistosaytheydonotcaptureallofthecontamination.Bagfiltercanbedifficulttoinspectaswell.Mosttimesnecessitatingcuttingthefilteropenandcountingparticles.
• FlangeScreens- Flangescreensor“slipscreens”astheyarebetterknowninthefieldareapreferredmethodtooilflushsubjectmatterexperts,myselfincluded.Theslipscreencanbeeasilydroppedbetweentwoflangesinplaceoftheexistinggasketmaterial.Thisallowsforeaseofplacementwithoutdisturbingthelubeoilpipinganymorethannecessary.Thescreenscanbecleanedandusedmultipletimesthroughoutaflushifbuiltcorrectly.Itisbestpracticetoutilizealayeredapproachwhenusingslipscreens.Meaning,usinggasketmaterial,a40-meshscreenforarigidback,100-meshscreenontopof40-mesh,thenanotherlayerofgasketmaterial.Allgluedtogetherwithasilicone.Asseeninthepictureabove,ahandleforeasyinstallationandremovalcanbeadded.Theslipscreenallowsforfullflowcaptureofparticulateduringinspectionphase.Theconsofusingtheslipscreencomeintoplayiftheyarenotproperlybuiltorbecomefullycoatedwithdebris.Thiscouldcauseeitheraback-upoffluidupstreamofthescreenorthescreentotear.
Withalloftheinspectionmediaitisrecommendedtoinsertvalvesonbothsidesoftheinspectionlocation.Thisallowsforsegregatingthemediafromthesystem.Preventingoilspillsastheinspectionisexecuted.Alwaysuseatwo-partinspectioncriteria.Particlecountforthematerialsyoucannotseeandinspectionmediaforthematerialyoucan.
