air evacuation system and lrpv (liquid ring vacuum pump)


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air evacuation system and lrpv (liquid ring vacuum pump)

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air evacuation system and lrpv (liquid ring vacuum pump)

  2. 2. Air Zone:  Inside the shell, a central or side portion longitudinally is separated by an outer shield except at the bottom. This partition is called the Air zone. All the gases released in the condenser due to cooling are taken out via these air zone tubes. From a suitable portion of this air zone inside the shell an air vent pipe is taken out and brought out of the shell for connection to an air extraction device.
  3. 3. Air Ejector: Two types of ejector: Starting Ejector Main Ejector (two in no.) Steam is used as motive medium in air ejector. All ejectors have its steam source from Aux PRDS Header.
  4. 4. VACUUM PUMP AND WORKING PRINCIPLE Positive displacement pump: A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side
  5. 5. An eccentric rotary vane pump
  6. 6.  The Liquid Ring Vacuum Pump: A Liquid Ring Vacuum Pump consists of a multi bladed, rotating element (impeller), electricity positioned within a cylindrical casing. The compression of the gas occurs in one or two impeller stages . Incompressible fluid, called service liquid, is introduced to the LRVP. Its heat capacity (specific that) and the boiling point (vapour pressure) being two of the most important specific characteristics service liquid. Other factors such as the solubility of process components into the service liquid and service liquid viscosity is also important.
  7. 7. The impeller sits between two end plates (port plates) which have shaped holes cut into them called ports. As the impeller rotates, a ring of liquid is formed inside the pump casing from centrifugal force. This action draws the gaseous stream into the pump through the inlet port. In two stage LRPV, the second stage is volumetrically smaller doing the final compression of the gas. The gas then exits the pump usually at atmospheric pressure along with the service liquid.
  8. 8. Working Principle: The gas enters the pump chamber A-B via suction port. The gas is trapped between two impeller vane. The impeller rotate eccentrically in relation to the centre line of the liquid ring that, by centrifugal force, assumes the shape of impeller casing. The progressive change of volume between the two vanes, the impeller hub and the liquid ring first creates a vacuum and then a compression of the gas in the B-C area till the gas is discharged, together with a portion of the liquid, through the discharge port C-D. The lost liquid must be replenished.
  9. 9. Cavitation:  Cavitations is a phenomenon which occurs in specific fluid environments and is an important factor when using this type of vacuum equipment. The vaporization of the service liquid sets up the structures of cavitation in the LRVP, but the damage is caused when the vapour bubbles collapse, not when they form. When the collapse occurs, a high velocity micro-jet of water tears away at the metallic surfaces of the pump internals. The damage is recognized as a series of craters or holes in a continuous pattern on an LRVP impeller. Also, damage can occur on the suction and discharge ports in either stage of the LRVP.
  10. 10. 1 atm = 1.01 bar = 1.03 ksc = 10 mwc = 760 mmhg = 760 torr
  11. 11. Damages done by cavitations (Impeller)
  12. 12. Damages done by cavitations (casing)
  13. 13. Damages done by cavitations (port plates)
  14. 14. Vacuum Pump Specification of St.-2 & 4 Vacuum Pump & Motor: STAGE-2 STAGE-4 MAKE SIEMENS-AG Edwards pump ltd. UK NO. OF PUMPS 2* 100% 2* 100% RATED SPEED 590 RPM 590 RPM NO. OF STAGE 01 02 OPERATING LIQ. WATER, 15° C WATER, 15° C STARTING MOI 37 KGM2 37 KGM2 POWER RATING 135 KW 132 KW VOLTAGE 415 V 415 V CURRENT 255 A 267 A
  15. 15. R/C Pump: STAGE-2 STAGE-4 TYPE LM 65-200 LM 65-200 CAPACITY 32 m3/hr 32 m3/hr DELIVERY HEAD 12 m 12 m MOTOR MAKE Siemens AMTECS LTD TYPE Rotary Current motor Rotary Current motor POWER 2.2 KW 1.5 KW VOLTAGE 415 V 415 V SPEED 1400 rpm 2715 rpm
  16. 16. Single-Stage vs. Two-Stage Pumps: The above describes the cycle of a single-stage pump; so in one revolution, we have suction (pulling a vacuum), and compression (back to atmosphere). Some manufacturers single stage pumps can operate up to -0.89 ksc, A two-stage pump is just two of these operating in series, so the discharge of the 1st stage goes into the suction port of the 2nd stage.
  17. 17. Two-stage pumps have better efficiency at higher vacuum levels (higher than -0.79 ksc) than a single stage pump. A two-stage pump is also a much better choice if you are handling solvents at higher vacuum levels (higher than -0.79 ksc). This has to do with the effect of sealant temperature rise being spread across two stages and its relationship to the sealant vapor pressure.
  18. 18. Major Difference: No. of stages Use of vacuum ejector Used in single stage vacuum P/P Comes in operation when (gas temp. –sealant temp) < 7 c Sucks gas form separator tank and supply it to vacuum P/P I/L port to prevent cavitations without affecting the air I/L line vacuum. Use of Anti - Cavitation line Used in two stage vacuum P/P. Connected to second stage second stage I/L (first stage dish.) to prevent cavitation.
  19. 19. Single Stage vacuum pump
  20. 20. Single Stage vacuum pump (Impeller)
  21. 21. Discharge port Suction port Single Stage vacuum pump (Port plate)
  22. 22. Double Stage vacuum pump
  23. 23. ejector
  24. 24. Problems faced in LRVP: Reduced capacity Low rpm, vacuum leak, high sealant temp., incorrect sealant flow Excessive noise Defective brg., too much sealant flow, cavitation, misalignment Overheating Defective brg., high sealant temp, suction open to atm.
  25. 25. Excessive Vibration Defective brg., too much sealant flow, cavitation, misalignment Motor overloaded Excessive back pressure, too much sealant liquid, pump jamming
  26. 26. Thank You