Troubleshooting in vacuum Pump

Presented by : Nisarg J.Rana

Guided by : Nitin V. Bhate

Introduction Vacuum pumps and system are one of the widely

used equipment in process plant. Hence, it is very important to correctly analyse

common problem that occurs in the process plant and to deal with it.

This presentation highlights working and various troubleshooting guidelines for some of the most commonly use vacuum machines likes Liquid ring , rotary piston , rotary vane, dry screw & steam ejector .

Overview of Presentation Introduction

Working of Various Vacuum pumps Problem & Troubleshooting Conclusions

Working of vacuum pump

Liquid ring vacuum pump : The aspirated gas enters the pump

chambers via the pump suction flange. The gas is trapped between 2 impeller vanes. The impeller rotates eccentrically in relation to the centre line of the liquid ring that by centrifugal force. Assuming the shape of the impeller casing. The progressive change of the volume between the 2 vanes. The impeller hub and the liquid ring creates a vacuum and the compression of the gas till the gas is discharge with the portion of liquid through discharge port.

Chemical industry digest vol-xx.9/september 2007

1)Air or fluid move through the inlet.

2) vane can rotate either clock wise or anti clock wise & seal the media between vanes and the hosing wall. Due to the fluid this volume should remains constants through out the entire cycling process.

3)Then in is move to the outlet. The rotor blades are positioned to enable them to contain a specific volume of air or fluid. Due to the vane having a cylindrical movement it creates a smooth flow as the fluid is transferred to the pumping chamber.

Rotary vane vacuum pump

BY Daniel pascoe/fluid power journal

Rotary piston vacuum pump1) Rotary piston vacuum pump

doesn’t spin on its axis. It moves in circular path within the pumping chamber.

2) As it passes top dead centre, it creates constantly increasing internal space on the suction side.

3) And constantly decreasing internal space on the pressure or discharge side.

4) A high integrity seal is maintained between the suction & pressure side by a film of oil that is capture between the piston and cylinder.

5) There is no contact between piston and cylinder.

6) The oil film is maintained by all dragged into the clearance by the moving piston which creates hydrodynamic wedge.

7) At the end of compression cycle, the clearance volume is completely filled with oil

Tuthill vacuum system/kinney single stage rotary piston vacuum pump/page

no.5

Dry screw vacuum pump

Screw pumps carry gas in the spaces between the screw threads.  The gas is displaced axially as the screws mesh.

Single screw pumps are commonly called progressive cavity pumps.  They have a rotor with external threads and a stator with internal threads.  The rotor threads are eccentric to the axis of rotation.

Multiple screw pumps have multiple external screw threads. 

KINNEY/ KDPH-120 DRY SCREW VACUUM PUMP

Steam jet ejector Steam jet ejectors are often used

to pull vacuum on surface condensers, evaporators, etc. A high pressure, motive, fluid (usually steam) enters the ejector chest through a nozzle and then expands. This converts its pressure energy to velocity.

The increased velocity causes reduced pressure, which sucks in and entrains gas from the suction. The diffuser section then recompresses the mixed steam/gas stream to some intermediate pressure.

The exhaust is then sent to a condenser which quickly condenses the steam at a low pressure and temperature so that the volume quickly decreases.

cheresources/questions/thermodynamics-182

chemical industry digest vol-xx.9/september 2007

Problems occuring in vacuum pumps

Liquid ring vacuum pump Problems : Leakage : leakage could be occur in 4 area 1) Gland packing area 2) Leakage at body gasket 3)

Leakage at the body plugs 4) Leakage through castings

Noisy Pump Operation : 1)Foreign object trapped into the pump 2) Pump

severely overloaded with water 3) Cavitations 4) Bearing noise

Vibration Problems : classified into two categories 1) Intermittent vibration 2) Continuous chronic

Vibration Vacuum problem Continuous chronic Vibration

Rotary vane vacuum pump

Problems : Pump does not start

Pump does not Reach Ultimate Pressure

Pumping Speed is too Low

After Switching off Pump under Vacuum, Pressure in System Rises too Fast

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Rotary piston vacuum pumpsProblems :

Excessively High System/Pump Ultimate Pressure Excessive Pump Noise at Low Pressure Pump Stalls Pumps does not Start Oil Discharged from Oil Mist Eliminator

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Dry screw vacuum pumpProblems : Insufficient Pumping Capacity Overload on Electric Motor Overheat Knocking Damaged Bearing or Gear

Graham corporation /2010

Steam Ejector

Problems : Poor ejector performance, unstable operation, pressure

swings Reduced ejector capacity and an increase in suction

pressure Poor ejector performance, unstable operation, pressure

swings Low ejector discharge temperature Higher than design discharge pressure Higher than design suction pressure (assuming motive

steam pressure and quality are normal and discharge pressure is equal to or less than design)

Conclusions

A step by step procedure, adopted in troubleshooting vacuum pump and ejectors helps in easily locating the problem and in finding appropriate solution. In general, the first step is to compare the original design condition with the existing conditions.

Any change in design conditions including utilities may have a direct impact on the performance of the unit. Once it is ascertained that external factors are not responsible for malfunctioning of vacuum system, troubleshooting of the equipment should be done .

Thank You