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A Project on Pressure and temperature analysis of tilted pad thrust bearing using Teflon pads


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An Project on Temperature and pressure analysis of tilted pad thrust bearing using Teflon as pad material

Published in: Engineering
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A Project on Pressure and temperature analysis of tilted pad thrust bearing using Teflon pads

  2. 2. INTRODUCTION:  The term Sliding bearing refers to a type of bearing where two conformal surfaces usually the stationary bearing and a moving shaft slide relative to one another with load distributed directly across the interface. A suitable lubricant may be employed to reduce the friction between these two surfaces. In fluid film bearings, this lubricant builds up a layer of sufficient thickness such that the two surfaces are completely separated.  Tilted Pad Thrust Bearing are designed to transfer high axial load from rotating shaft with minimum power loss. Bearing consist of circumferential pads & each pad is free to tilt to create self lubricating hydrodynamic film .  The number of parameters which affect the bearing are categorized as operating parameter and performance parameters.  Speed of rotation, applied load, surface curvature & type of lubrication are the operating parameter while max. pressure generated ,temperature of bearing , oil viscosity ,minimum film thickness, surface wear are performance parameters.
  3. 3. CONSTRUCTION :  Tilting pad thrust bearing is an assembly of number of tilted pads, Runner, lubricating oil, cooling coils and casing.  Bearing pads are individual plates which are free to tilt about their individual pivots. usually three or more pads are used .  Pads are made up of two layers of materials .Face layer of pad is Babbit or PTFE (Polytetrafluoroethylene) with 2- 3 mm thickness. This layer is supported by MS pad called as backing.  Lubricating oil is provided in housing as a bath or fed either to centre of housing near shaft or to the leading edge of pad with external aid.  Depending upon the method of lubrication, it is also differentiated as Flooded lubrication or Directed lubrication.  Runner of bearing is attached to rotating shaft whose thrust need to support by bearing.
  4. 4. Bearing Runner Tilted pad IMAGES:
  5. 5. WORKING:  In Titling pad thrust bearing, Runner and pads are separated by an oil film during operation.  When the runner is stationary ,the pads are in direct contact with pad .As shaft with runner rotates form an oil film between the pad and runner.  Each Pad will tilt to the some angle which forms converging wedge. The flow constriction due to wedge acts as a bottleneck, which causes slowing down the flow rate across the pad from the inlet edge towards the trailing edge.  The gradual reduction of oil volume in the gap leads to rise in pressure of the oil film which lifts the shaft.
  6. 6. OBJECTIVES:  To acquire detailed understanding of the current system.  To modify old cooling system.  To replace lubricating Oil in the test Rig  To replace defective Direction Control Valve  To develop pressure sensor for pressure measurement  To develop temperature sensor for temperature measurement  To demonstrate the test rig for sake of pressure and temperature readings with different load conditions  To measure frictional power losses  To analyze the obtained readings  To conclude on the basis of observations and readings taken.
  8. 8. DESCRIPTION OF TEST RIG:  It mainly consists of four distinct parts: 1) Driving motor along with driving pulley : A.C induction motor. Capacity 7.5 HP Rated speed 1430 rpm 2) Oil Sump and Runner along with Driven Pulley: Oil sump is a casting body . Inside this a pocket is fitted. Pocket has eight equally placed radial slots and dowel pins. There are eight pads which tilt about an axis passing through its geometric center along a radial slot. Tilting of each pad about the pivot causes formation of wedge shaped oil film along the sliding direction of runner. This wedge shape oil film in turn causes self acting pumping action of oil. The combination of squeeze, stretch and wedge effect generates pressure within oil film. Due to this pressure, load of runner is sustained.
  9. 9. 3) Hydraulic power pack and loading system: Loading system consists of lever, loading piece, brackets, with their base plate. Hydraulic cylinder which is mounted on loading frame provides the load as per requirement through loading lever beam. Loading frame consists of two vertical I columns with four I beams welded together. Loading member is supported in brackets at one end and loaded by hydraulic cylinder at other end. 4) Cooling System : Copper tubing of 1 inch diameter is provided. One end of this copper tubing is connected to a reservoir of water and other end is drained. The cooling effect is provided by circulating water around the oil sump. For better and effective cooling, the rate of water flow is increased by placing reservoir tank at a height of 10 feet from setup foundation.
  10. 10. DEVELOPMENTS IN CURRENT PROJECT SET-UP: The following developments are done :  DC valve replacement.  Forced cooling.  Oil replacement.  Modified calibration fixture.
  11. 11. Cooling tower Calibration fixture
  12. 12. JUSTIFICATION FOR SELECTION OF PTFE AS PAD MATERIAL: Available Grades :  Virgin PTFE  15% Peek PTFE  15 To 25% Glass Filled PTFE  25 To 35% Carbon Filled PTFE  15% Graphite Filled PTFE  40 to 60% Bronzed Filled PTFE  5 to 15% Aluminum Oxide Filled PTFE  5 to 10% Stainless Steel Filled PTFE  5 to 10% Mica Filled PTFE  55% + 5% Bronzed + Molybdenum Disulphide Filled PTFE  15% + 5% Glass + MOS2 Filled PTFE  Pigmented PTFE
  13. 13. INHERENT TEFLON PROPERTIES:  PTFE against steel has one of the lowest coefficients of friction  The load bearing capacity of the PTFE sheet is in the range of 130-140Kg/  The PV values are found to be in excess of 10,000 Pressure (P) is the load placed on a bearing assembly. Velocity (V) is the surface speed at which an object, such as a shaft, moves. P-V is defined as the combination effect of the pressure of the object and the velocity at which it moves on the bearing surface.  Service temperatures of -250 to +250°C are possible.
  14. 14. CALIBRATION OF DIAPHARGMS: The material of diaphragm is Brass. Strain gauges are stacked on diaphragm and such a diaphragms are mounted in a fixture for pressure measurement. Diaphragm specification – 2 mm thick and 16 mm dia.  Procedure Of Calibration : 1) The strain gauges to be used for calibration is fitted in a fixture and mounted on dead weight calibration apparatus. 2) The strain gauge connecting wires are attached to strain guage indicator. 3) The pressure variation is done by varying the dead weights. 4) For different loads the indicator gives different reading and these readings are noted down.
  15. 15. INSTRUMENTATION FOR EFFECTIVE TEMPERATURE MEASUREMENT For effective temperature measurement, locations for mounting of temperature sensors are very necessary. It is found that following methods are used for temperature measurement 1) Temperature Grid. 2) T 50/75 or 75/75 3) Oil Film Tapping. From the above methods mentioned, temperature grid method is used. Advantages –  It gives variation of temperature over pad surface  It gives temperature grid on pad surface.  It is best for laboratory testing.
  16. 16. SR.NO LOCATION NO. LOCATION 1 1 25/75 2 2 75/75 3 3 25/25 4 4 75/25 5 5 50/50 LOCATION OF TEMPERATURE SENSORS:
  17. 17. Location of Thermocouple
  18. 18. INSTRUMENTATION FOR EFFECTIVE PRESSURE MEASUREMENT  Pressure on pad varies along length and width of pad.  We are interested to know maximum pressure carried by pad.  According to previous studies following locations were chosen for pressure sensor mounting Sr. No. Pressure points Angular position from leading edge of pad (degree) Radial Position from Centre of bearing Pad(mm) 1 Pp1 14.07 133.10 2 Pp2 38.20 120.5 3 Pp3 34.30 105.76 • Point 1 is near leading edge and at upper side of pad • Point 2 is near 75/75 location. Maximum pressure varies nearby this point. • Point 3 is near trailing edge and at lower side of pad.
  21. 21. OBSERVATIONS, RESULTS AND CONCLUSIONS :  Pressure Readings.  Temperature Readings.  Heat Gained By Water / Frictional Loss.
  24. 24. POWER LOSS: PARTICULARS LOAD(KG) 175 1055 1936 2641 WATER INITIAL TEMPERATURE (0C) 29.1 29.57 30 30.1 WATER FINAL TEMPERATURE (0C) 34.1 36.8 39.8 42.4 TEMPERATURE GAINED BY WATER(0C) 5 7.23 9.8 12.3 OIL INITIAL TEMPERATURE (0C) 32.4 33.2 30.7 30.9 OIL FINAL TEMPERATURE (0C) 38.5 41.6 41.7 44 TEMPERATURE GAINED BY OIL(0C) 6.1 8.4 11 13.1 MASS FLOW RATE OF WATER MW (KG/SEC) 3.25 X 10- 2 3.25 X 10- 2 3.25 X 10- 2 3.25 X 10- 2 HEAT GAINED BY WATER(KWATTS) 0.68 0.98 1.33 1.67
  25. 25. CONCLUSION:  By referring to graph no.1, it can be concluded that pressure carried by pad increases as load on pad increases  By referring to graph no.2, it can be concluded that temperature of pad increases as load on pad increases.  Maximum temperature of pad is observed at 75/75 location.  By referring to graph no.3, it can be concluded that frictional loss increases as load on pad increases  Maximum pressure on pad is observed near 75/75 location.  Maximum pressure on pad is observed near to maximum temperature location.
  26. 26. EXISTING TRENDS:  LEG trademark coined by KINGSBURY  LEG slim-line low profile bearings  Thinner profiles  Each pad equally loaded  Leveling plates on back of pad  Leveling plates located in carrier ring ensures equal loading.
  27. 27. FUTURE SCOPE:  Effects of different surface coatings on wear resistance of sector shaped pads and bearing performance can be studied.  Use of various pivot position rather than central pivot and its effect on performance.  Implementation of various pad materials and assuring their sustainability.  Use of different lubricating oil. E.g. Bio-lubricants.  Use of different pad profiles can be implemented
  28. 28. GALLERY:
  29. 29. GALLERY:
  30. 30. GALLERY:
  31. 31. Thank you !!!!!