1.AIR EVACUATION SYSTEM AND COMPARISON IN ALL STAGES RHITESH KUMAR GUPTA

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. 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. 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. An eccentric rotary vane pump 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. The impeller sits between two end plates (port plates) which haveshaped 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. 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. 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. 1 atm = 1.01 bar = 1.03 ksc = 10 mwc = 760 mmhg = 760 torr 11. Damages done by cavitations (Impeller) 12. Damages done by cavitations (casing) 13. Damages done by cavitations (port plates) 14. Vacuum Pump Specification of St.-2 & 4 Vacuum Pump & Motor: STAGE-2STAGE-4MAKESIEMENS-AGEdwards pump ltd. UKNO. OF PUMPS2* 100%2* 100%RATED SPEED590 RPM590 RPMNO. OF STAGE0102OPERATING LIQ.WATER, 15 CWATER, 15 CSTARTING MOI37 KGM237 KGM2POWER RATING135 KW132 KWVOLTAGE415 V415 VCURRENT255 A267 A 15. R/C Pump: STAGE-2STAGE-4TYPELM 65-200LM 65-200CAPACITY32 m3/hr32 m3/hrDELIVERY HEAD12 m12 mMOTOR MAKESiemensAMTECS LTDTYPERotary Current motorRotary Current motorPOWER2.2 KW1.5 KWVOLTAGE415 V415 VSPEED1400 rpm2715 rpm 16. Single-Stage vs. Two-Stage Pumps: The above describes the cycle of a single-stage pump; so in onerevolution, 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. Two-stage pumps have better efficiency at higher vacuumlevels (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. 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. Single Stage vacuum pump 20. Single Stage vacuum pump (Impeller) 21. Discharge portSuction portSingle Stage vacuum pump (Port plate) 22. Double Stage vacuum pump 23. ejector 24. Problems faced in LRVP: Reduced capacity Low rpm, vacuum leak, high sealant temp., incorrect sealant flow Excessive noiseDefective brg., too much sealant flow, cavitation, misalignment Overheating Defective brg., high sealant temp, suction open to atm. 25. Excessive Vibration Defective brg., too much sealant flow, cavitation, misalignment Motor overloaded Excessive back pressure, too much sealant liquid, pump jamming 26. Thank You