Maintenance of Condenser Vacuum Pump & Seal Water

SystemBy:

Ganesh KumarSr. Engineer (O&M), APNRL

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Two Stage Vacuum Pump (AT-Series)

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Major Components of Two Stage

Vacuum Pump

1. IE Head2. 2nd Stage Rotor3. 2nd Stage Lobe4. 2nd Stage Manifold5. Manifold Cover6. Gas Discharge

7. Interstage check valve

8. 2nd Stage Cone9. IE Bracket10. 1st Stage IE Cone11. 1st Stage Body

12. 1st Stage Rotor13. 1st Stage DE Cone14. Shaft15. DE Head16. Vacuum Pump 1st

Stage Inlet

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Internals of Vacuum Pump

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• The vacuum pump has two-stage rotor which is turned by an external motor. One portion of the rotor lies within a first - double flow stage chamber that is formed by the casing, the other portion of the rotor lies within the second - single flow stage chamber.

• Both pump stages function identically. • The axis of the casing is offset from the axis of the

rotor. • Water is admitted to the first stage chamber through

a passage in the cone, and acts as a seal liquid. Additional seal water is fed directly to the vacuum pump from the heat exchanger to seal clearances in the vacuum pump.

• The Air/water vapor mixture from the condenser is drawn in through the air inlet. A spray nozzle in the cone forms the seal water into a spray pattern through which the air/water vapor mixture must pass. At the point, most of the water vapor condenses.

Operating Principle

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• Then, the pumped gasses and seal water are discharged through the first stage discharge passage to the second stage at increased pressure. Finally the air and seal water is ejected at atmospheric pressure through the air discharge to the separator.

• In the separator, the seal water drops from the air stream to the bottom, and the air vents out the top. An automatic float switch and make-up solenoid valve, and an overflow loop maintain the proper level of seal water.

• After it passes through the pump and separator, the seal water is circulated through a heat exchanger, and then back to the pump.

Operating Principle

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Operating PrincipleVacuum Pump Comprises of Three Major Stages in one cycle.

1. Intake2. Compression3. Discharge

Note: It uses water or any other suitable liquid which acts as “liquid piston”. Hence it is also called as Liquid Ring Vacuum Pump.

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STAGE-1 : INTAKE

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STAGE-2 : COMPRESSION

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STAGE-3 : DISCHARGE

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Operating Principle

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Operating Principle3

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Maintenance PlanWeekly

1. Carry out external cleaning of equipment.

2. Check all valves for gland leakage if leakage is to be observed, same to be attended either by replacing the glands or by tightening it.

3. Check the foundation bolt tightness and take corrective action if required.

4. Check for pump gland leakage, if leakage is observed, same to be attended either by replacing the glands or by tightening it.

5. Clean strainer for makeup water & seal liquid line.

6. Bearing greasing to be done if found necessary.

7. Attend all leakages either by welding / replacement of gland / gaskets.

8. Checking of alignment of Pump with Motor and do the necessary correction if required.

9. Spill over oil / water / grease / cotton waste / etc. in surrounding area and floor to be cleaned up to the satisfaction of EIC.

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Maintenance PlanHalf Yearly

1. Inspection of bearings of Pump & lubricate, if necessary.

2. Cleaning of seal water coolers i.e. PHE.3. Inspection of motor-pump coupling & lubricate, if

necessary.

Yearly1. Overall maintenance of the vacuum pump.2. Remove any scale deposition on pump impeller.3. Replace the Pump gland packing.

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Major BreakdownBearing Failure

Possible Causes Check coupling alignment. Check for soft foot - pump properly shimmed. Check for equal seal flow to each side of pump. Eliminate piping stress – when inlet is disconnected -no

misalignment.

Could be eliminated via Monitor bearing temperatures/vibration weekly. Use recommended grease. Do not mix different greases. Do not over-grease. Check grease at 6 month intervals. Monitor packing leakage. Be sure refill grease is same as existing grease.

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Trouble ShootingHigh Vibration

Possible Causes Excess Seal water – overload the pump. Deteriorated base or foundation. Equal seal flow to each side of pump. Scale buildup on the impeller

Could be eliminated via Monitor pump vibration weekly. Proper seal water flow to the pump. Check for tightness of the foundation bolt.

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THANK YOU