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Capillary compensated hydrostatic thrust pad bearing report

Capillary compensated hydrostatic thrust pad bearing report

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Capillary compensated hydrostatic thrust pad bearing report

  1. 1. Capillary compensated hydrostatic thrust pad bearing Commonlyusedcompensating devices(Flowrestrictor) 1. Capillary(Flowisproportional topressure drop) 2. Sharp edge orifice (flowisproportional tosquare rootof pressure drop.) 3. Flowcontrol valve (constantflow) 4. Pressure sensingvalve (mostaccurate) Requirementof using capillarycontrol device: The bearingstiffnessdependsmainlyonthe nature of the flow control stiffness.Indiscussing circuitdesign,itwillbe therefore necessarytoconsider the relatedeffectsonbearingstiffnessaswell as the more practical aspects of control valve. A simple wayto control the flow of fluidflow to bearingis to introduce a resistance intothe supply line. For example a capillary may be used which produces a pressure drop proportional to follow. A fixeddisplacementpumpdrawsliquidfromatankthroughastraineranddeliversitthrough a line filter to the capillary at a pressure Ps, determined by a pressure relief valve. It is importantto take care that no blockage occur inthe capillarywhichmayleadto a bearingfailure.If the capillaryis easily removable, this will make occasional cleaning convenient. Fig. Capillary compensated hydrostatic thrust pad bearing Four possible methodof manufacturingcapillary restrictor:- 1. Hypodermictubing(commerciallyavailable) 2. Glasscapillary(Commerciallyavailable) 3. Drilling 4. Spark machining
  2. 2. Flowrate and pressure characteristic for various compensatingdevices Fig.Flowrate vs pressure characteristic Fig.Stiffnessfactorvs.Ratioof supplypressure torecesspressure Advantages of Usingcapillary:-  The major advantage of laminarflow restrictorsuchas capillariesisthattheyendow the bearingwiththe greatesttolerance tomanufacturingvariationonbearingclearance.  Capillaryrestrictorismade bycuttinga tube of knownbore toa suitable length. Sothere is manufacturingsimplicity.
  3. 3. Limitationof capillary:-  Capillariesgivesleaststiffnessandpressure sensingvalvegiveshigheststiffness.  Highstiffnesscanonlyachievedbyprovidingmoderatepressureandbearingarea. Hydrostatic thrust pad bearing:-  Designedtoprovide axial loadsupport  PressurizedFluidfilmisgeneratedtobalance the appliedthrustloadwithsufficient separationof stationary(thrustpad) androtatingsurface (Shaftmachinedcollar) toavoid wear,to provide lowfrictioncoefficientandtoavoidexcessive temperature. Mathematical expressionforcapillarycompensatedHydrostatic thrust pad bearing:- Stiffnessof capillarycompensatedhydrostaticthrustpadbearing:-

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