Lesson-12-Centrifugal-Pumps-Maintenance-Operational-Problems.docx

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1、1.esson12CentrifugalPumps-MaintenanccOperationalProblems&Remedies第12课离心泵的难妒操作问SS&补救措施Duringtheoperationofthecentrifugalpumps(seeFig.12-1).severalproblemsarefacedwhichhavetobe100kedinloduringtheiroperationinordertogettrouble-freeservicefromthesepumps.Themainproblem,typicaltocentrifugalpumps,facedbyth

2、esepumpsiscavitation,whichiscausedbythefactthatthesepumpsoperatewithsuctionpressuremuchbelowtheatmosphericpressure.Thisoccursmainlyinthepumpsusedfortransferringwater.OtherproblemsfacedbythesePUmPSaremainlyduetonormalwearandtearofthematerialsoveraperiodoflime.在离心泵(见图12-D运转期间，要了解岗心泵运转期间会面临的若干问遨以使使其无故障

3、地工作。离心系面彼的典型的主要何题是气蚀，造成这-T实的缘由是这些泵是在吸入压力大大低于大气压力下工作的。这主要发生在用于输送水的泵中。这泵面临的其他问题主要是在一段时间内材料的正常磨根.图2-l单级诲心泵OperationalProblems操作何也Duringthepumpoperation,asthewatermasspassesfromeyeoftheimpellertowardsitsperiphery,itcreatesvacuumattheeyeoftheimpellerandinsidethesuctionpipe.Ifthetemperatureofthewaterpassi

4、ngthroughthesuctionpipeandtheeyeoftheimpellerhappenstobehigherthanthesaturationtemperatureofthewaterattheprevailingvacuum,someofthewatermayevaporatetoformlinyvaporbubbles,whichtravelthroughtheimpeller.Asthewatermasspassesfromeyeoftheimpellertowardsitsperiphery,itspressurerisesandthevaporinthetinybub

5、blesbecomesunstableandcondensesbacktoliquidcausingsmallimplosionsinthesebubbles.Theseimplosionsinthetinyvaporbubblesinthewatermasshaveenoughenergytocausepittingintheadjoiningmaterialoftheimpelleraswellasthepumpcasing.Thisprocessofimpellerandthecasingmaterialwastageiscalledcavitation.在泉操作过程中，当聚集的水从叶轮

6、中心向外相传递时，在叶粒中心和吸入管内产生了直空。假如通过吸入管和叶轮孔的水湿高于在当前的真空下水的饱和湿度，一的水可能会蒸发形成做小的水蒸气泡,流过叶轮.当聚集的水从叶轮中心向外国传递时,其压力增加.而且在小气泡中的蒸汽变得不稳定并凝聚为液体.导致在小气泡中内爆.这些水中小气泡的内爆具有足泌的能状而造成叶轮Itt印的材料以及茉克的凹陷。叶轮和泵壳材料损耗的过程被称为气蚀。Asthepumpoperatesataparticularavailablenetpositivesuctionhead,IhCcavitationisfoundoccurringataparticularlocation

7、onthepumpimpelleranditscasing.Thelocationmayvarj,frompumptopumpasdifferentpumpsOPerateatdifferentnetpositivesuctionheads.Afterseveralyearsofuse,thepittingcausesthewastageintheimpellerandthecasingmaterialsufficientIomakeitweakrequiringreplacement.随着泵在一个特定可用的冲压买下运行，气蚀是在泵叶轮及其外壳的特定位也发生的.发生的位附.可能因系的净压头不同

8、而不同。经过数年的运用，点状腐蚀引起的叶轮和套管材料的消耗足以使它性能弱化从而须要更换。TheonlyremedytopreventcavitationinanypumpistoensurethattheIcmperaturcofthewaterpassingthroughthesuctionpipeandtheeyeoftheimpellerismaintainedbelowthesaturationtemperatureattheprevailingvacuum,artfromthat,theinnersurfaceofthecasingmaybecoatedwithhardepoxyla

9、yertominimizetheeffectofcavitation.防止泵气蚀的唯一补救拈脩是确保通过吸人管和叶轮中心的水温保持低于在一股真空下的饱和温度。此外，泵壳的内表面可以涂硬的环氧树质层将气蚀的影响减到嫉小。Otherproblemsrelatedtothecentrifugalpumpoperationaremainlyduetowearandtearinthemovingprtsduetofriction.Thiswillresultin其他关于离心泵操作的问S8主要是由于运动部件摩擦而造成的磨损，这将导致：Increaseintheclearancebetweentheimpellerneckandthewearringsresultinginreductioninvolumetricefficiency.Replacementofwearringsistheonlyreneearofgreaseongaskct/faccs.)IO拆除上曲板的螺栓并取下装板，利去旧蛰片，井检查协作面，成对更换垫片,(光的油脂涂抹在集片/面)11. Theputnpshaftwithimpellercanbeliftedoutofcasing.11柒轴与叶轮可以从里面抽Hk12. Dismantletheimpeller,andremovethewearring.12拆卸