Vacuum Pump: Type: Liquid Ring Vacuum Pump Make: Nash Model: At-1006e

VACUUM PUMP TYPE : LIQUID RING VACUUM PUMP MAKE: NASH MODEL: AT-1006E

Vacuum • A perfect vacuum is defined as a region in space without any particles. • But perfect vacuum is an idealistic case. It cannot be achieved in a laboratory, although there may be small volumes which, for a brief moment, happen to have no particles of matter in them. Even if all particles of matter were removed, there would still be photons and gravitons, as well as dark energy and other aspects of the quantum vacuum. Pressure ranges of each quality of vacuum in different units Vacuum quality

Torr

Pa

Atmosphere

Atmospheric pressure

760

1.013×105

1

Low vacuum

760 to 25

1×105 to 3×103

9.87×10−1 to 3×10−2

Medium vacuum

25 to 1×10−3

3×103 to 1×10−1

3×10−2 to 9.87×10−7

High vacuum

1×10−3 to 1×10−9

1×10−1 to 1×10−7

9.87×10−7 to 9.87×10−13

Ultra high vacuum

1×10−9 to 1×10−12

1×10−7 to 1×10−10

9.87×10−13 to 9.87×10−16

Extremely high vacuum

< 1×10−12

< 1×10−10

< 9.87×10−16

Outer space

1×10−6 to < 1×10−17

1×10−4 to < 3×10−15

9.87×10−10 to < 2.96×10−20

Perfect vacuum

0

0

0

0.099 atm

Absolute Pressure vs Gauge Pressure

Pabsolute = Patm + Pgauge (Pguage must be positive)

Pressure

Pgauge Pabsolute Atmospheric Pressure

Patm

Measuring Vacuum

Pressure

Most commonly used measurement unit for vacuum is Torr. 1atm= 760mm Hg=29.92” Hg 1 Torr= 1 mm Hg

Atmospheric Pressure Pgauge

Pabsolute

Patm

Pabsolute = Patm + Pgauge (Pgauge must be negative for vacuum)

WHY VACUUM IS MAINTAINED IN CONDENSER Increasing the efficiency by lowering the Condenser Pressure: • To take advantage of the increased efficiencies at low pressures, the condensers of steam power plants usually operate well below the atmospheric pressure Disadvantages : • It creates the possibility of air leakage into the condenser. More importantly, it increases the moisture content of the steam at the final stages of the turbine.

However, there is a lower limit on the condenser pressure that can be used. It cannot be lower than the saturation pressure corresponding to the temperature of the cooling medium.

WHY VACUUM IS MAINTAINED IN CONDENSER • Air and non-condensable gases reduce the heat transfer efficiency in condenser. For example, the thermal conductivity of air is 0.000049, compared with 0.002 for water, 0.20 for iron, and 0.96 for copper. Not removing air and non-condensable gases from the steam system can reduce heat transfer efficiencies by 21% or more depending on the air concentration in the steam system. • The non-condensable gases form a stagnant film on the walls of the heat transfer surface, which creates a resistance. Heat energy transmitting through the heat transfer surface has to pass by conduction through these films of resistance. A film of air or non-condensable gases that is only one thousandth of an inch thick has the resistance of a three-inch wall of iron. • During shutdown of a steam system or its components, the system depressurizes, with the steam condensing and reducing in volume by as much as 1,600 times. This reduction in volume produces a vacuum in the steam system or steam components. Air is drawn into the steam system through steam components, such as air vents, valve packing, and flanges, and the air drawn in fills the vacuum. When energizing a steam system or steam heat transfer components, one of the first goals should be to vent the air out of the steam system or components.

So, the function of vacuum pump to remove air (non-condensate) gas from condenser and to create the vacuum start-up period.

GEAR PUMP

Liquid ring vacuum Pump: Operation Principle • A liquid ring vacuum pump has an impeller with blades attached to a centre hub located in a cylindrical body but off-set from the centre. • The pump requires a liquid (sealant) to create vacuum. Prior to starting the pump, it should be partially filled with the liquid sealant. The liquid can be water (making it a water ring pump), oil or a solvent, depending upon the application.

Operation Principle • When the pump starts, the impeller slings the liquid sealant, by centrifugal force, to the outside walls of the body forming a ring of liquid. • Because the impeller is off-set from the body, some of the blades are fully immersed in liquid, and some are almost out of the liquid

• The area of void space without liquid, is sealed off between the liquid and between the impeller blades, called an impeller cell. • As we follow one impeller cell from the top of the pump, counter-clockwise, we can see the liquid recedes from the centre hub, acting as a liquid piston to create a larger cell. • As we follow one impeller cell from the top of the pump, counter-clockwise, you can see the liquid recedes from the centre hub, acting as a liquid piston to create a larger cell. This is the suction of the pump. • After impeller cell passes the inlet port and travels toward the discharge port, the sealant liquid is forced back toward the centre hub of the impeller, creating the compression step.

Defining the parameters Suppose volume of one impeller is V RPM= N Then, theoretical capacity of the pump = (V X N) m3/min If volumetric efficiency is ɳ, capacity will be = ɳ X V X N CAPACITY (C) = ɳ X V X N

P1,T1 Dry Air + Sat Vapour Volume V2

P1,T1 Dry Air Volume V1 P1=Pdryair

P1=Pdryair + Psat Vapour

P1 X V1 = n1RT1

P1 X V2 = nRT1 V2 = V1 X

(P1) P1-Pvap

One Impeller Cell

Major Components of LRVP system To atmosphere

Suction (Air+ Sat Vapour)

Packing gland Assembly

2nd Stage Rotor Separator

Motor

1st

Interstage Manifold

stage Rotor

Grid Coupling

Free end Bearing

Fixed end Bearing Gland Packing with lantern ring

Discharge from 1st stage

Gland Packing with lantern ring

Interstage Check valve Inlet to manifold

Major Components of LRVP system

Manifold

2ndstage Rotor

Separator

1st stage Rotor

Motor

Cooling water Inlet

Shell & Tube type heat exchanger Recirculation Pump

SEPARATOR PUMP INLET

DISCHARGE TO ATMOSPHERE

SPRAY NOZZLES

INLET TO SEPARATOR INTERSTAGE MAIFOLD INLET

LEVEL GAUGE

DRIVING MOTOR FIRST STAGE OUTLET

FIRST STAGE BODY

SECOND STAGE BODY

LEVEL TRANSMITTER CONNECTON

DISCHARGE TO ATMOSPHERE CONNECTION FOR ROTAMETER INLET PNEUMATIC BUTTERFLY VALVE

DUPLEX FILTER

COOLING WATER OUTLET TO HEAT EXCHANGER COOLING WATER INLET TO HEAT EXCHNGER

HEAT EXCHANGER

FLOWMETER (SEALANT LIQUID INLET)

Low Vacuum vs High Vacuum operation

Specification of NASH AT-1006E Performance of the liquid ring vacuum pump is specified by following parameters: • Capacity of free dry air saturated with water vapour at 1” Hg suction pressure (absolute) & subcooled by 7.5 C = 10 SCFM • Hogging Capacity at 10” Hg suction pressure at design condenser CW temperature 33 C = 200 SCFM • Blank off suction pressure at design condenser cooling temperature 33 C = 2” Hg (Absolute • Pump Down time (volume to be evacuated=180 m3 from 1 atm to 10” Hg with two pumps) = 6 min • Recirculation pump design capacity= 7.9kg/cm2 • Heat Exchanger terminal temperatures (counter flow type) Cooling water Inlet

Sealant water

Design Cond

Operating Cond

Design Cond

Operating Cond

13.08

33

15.6

41

_

22.2

49.1

Outlet _

Performance Curve:

60 F sealing water & 7.5 subcooled.

Defining the parameters Blank off Suction Pressure: • The limiting pressure approached in a vacuum system after a sufficient pumping time has elapsed to establish that further reduction in pressure will be negligible. • Blank off suction pressure is measured as close as to suction connection of the pump after isolating the condenser. • For AT 1006E vacuum pump BSP= 2.04 inhg ( 0.070 kg/cm2)

Defining the parameters Cooling Tower

Steam

Vacuum Pump

Condenser Pressure= 0.103 kg/cm2 Temperature=46 C

Suction line of pump

Cooling water Inlet Temperature=33 C

Condensate Design Consideration of condenser:

Condenser Pressure =Saturation Pressure at (Cooling water inlet temperature + 10-15 C) = Saturation Pressure at 33 + 13 = 46 C = 0.103 kg/cm2 (absolute)

Design Consideration: Pressure should be lower than 0.103 kg/cm2. So maximum sealant liquid inlet temperature 46 C in the system otherwise there will be chances cavitation inside pump. To ensure condensation of incoming (liquid + vapour mixture) Maximum sealant liquid temperature is 41 C (designed CW temperature temperature at 33 C of cooling water)

SEPARATOR Discharge to atmosphere Check Valve Rotameter

• • Overflow loop connection Connection to differential level transmitter

Make up water line solenoid valve operated

Connection to drain Check Valve Level Gauge

Connection to drain

Drain Ball Valve

• • •

Connection to drain

Level transmitter signal opens the solenoid valve when the water level drops below 80mm and closes at water level above 120 mm. Overflow loop drains the excess water through the drain pipe. Normal Water level=120mm If the level remains low for 5 sec: DCS alarm If the level remains low for 10sec: DCS interlock

Instruments in the system Cooling Tower

Condenser

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Pneumatically operated butterfly valve

Condenser

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Condenser

Pressure Transmitter (4 nos.)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Condenser

Temperature Transmitter(2 nos.)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Condenser

Flow Transmitter(2 nos.)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Condenser

Temperature Transmitter (2 nos.)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Condenser

Pressure Gauge (4 nos.)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Condenser

Temperature Indicator(4 nos.)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Condenser

Temperature Indicator(2 nos.)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

Instruments in the system Cooling Tower

Condenser

Differential Pressure Transmitter(2 nos.)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Motor

Recirculation Pump

Duplex Filter

PUMP OPERATION Hogging Operation mode

Cooling Tower

Both the butterfly valve will be opened after switching on the vacuum pump

Condenser

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Running Pump

Duplex Filter

PUMP OPERATION Cooling Tower

Hogging Operation mode Condenser

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Running Pump

Duplex Filter

PUMP OPERATION Hogging Operation mode

Cooling Tower

Condenser

When the pressure falls below 0.305 kg/cm2 (300mbar), the system goes to holding mode by shutting down the other pump.

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Running Pump

Duplex Filter

PUMP OPERATION Hogging Operation mode to Holding mode

Cooling Tower

Condenser

Butterfly valve closed

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Stand by pump

Duplex Filter

PUMP OPERATION Holding Operation mode

Cooling Tower

Pressure of sealant liquid inlet=1.72 bar

Condenser

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Stand by pump

Duplex Filter

PUMP OPERATION Holding Operation mode

Cooling Tower

Condenser

When pressure goes above 0.173352 kg/cm2 (170mbar), signals to start the pump

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Stand by Pump

Duplex Filter

PUMP OPERATION Holding Operation mode

Cooling Tower

Condenser

Vacuum pump motor is turned on, but the butterfly valve will be in closed condition.

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Stand by Pump

Duplex Filter

PUMP OPERATION Holding Operation mode

Cooling Tower

Condenser

When pressure fall below 0.102 kg/cm2 (100mbar), signals to open the butterfly valve. (delay 5sec)

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Stand by Pump

Duplex Filter

PUMP OPERATION Holding Operation mode

Cooling Tower

Condenser

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Running Pump

Duplex Filter

PUMP OPERATION Holding Operation mode

Cooling Tower

When pressure drops to 0.102 kg/cm2 (100mbar), signals to stop the pump (delay 3 Sec)

Condenser

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Running Pump

Duplex Filter

PUMP OPERATION Holding Operation mode

Cooling Tower

Condenser

Manifold

1st stage Rotor

Motor

Manifold

2ndstage Rotor

Separator

Separator

2ndstage Rotor

Return Line to CT

Discharge to atmosphere

1st stage Rotor

Cooling water Inlet

Cooling water Inlet

Shell & Tube type heat exchanger

Shell & Tube type heat exchanger Recirculation Pump

Running Pump

Motor

Recirculation Pump

Stand by pump

Duplex Filter

Control & Trip Conditions Vacuum Pump Starting Conditions: • Cooling water supply to heat exchanger. • Separator level is not low. (below 80mm) • Vacuum pump motor is ready to run. Vacuum Pump Trip Conditions: • Vacuum pump motor trip on overload relay. • Vacuum pump trip on emergency trip from field. • Recirculation pump motor trip on motor overload relay operates or emergency trip from field. • Pneumatic butterfly valve does not open within 30 sec after vacuum pump starts. Recirculation Pump start conditions: • Separator level is not low. • Recirculation pump motor is ready to run.

Recirculation Pump trip conditions: • Recirculation pump motor trip on motor overload relay operates or emergency trip from field. • Separator level trip conditions.

Maintenance Schedule 6 months

12 months

Drive coupling should be lubricated with grease in accordance with the OEM instructions

Replace the stuffing box packing.

Check for bearing conditions & lubricate if required.

Inspect the interstate check valve. Make sure that elastomer on the clapper is intact.

Lubricate drive motor bearing according to motor manufacturer instructions.

Check that shroud vent valve operate freely.

Clean the seal liquid line strainer. Clean it more often if required.

CAUTIONS • The seal liquid must be provided to the unit and both stages primed before the unit is started, even if the pump is only being operated to check the shaft rotation or any other test purposes. • Never operate the pump without sufficient operating liquid and sufficient stream of sealing liquid. During start up, liquid level should be at higher level than shaft. • Feed pressure of the sealant liquid must not be greater than 0.3 bar of discharge pressure. It should be maintained around 1.7 bar. • Continuously check for housing temperature during start up. If the temperature quickly increases or more than 22 C that of operating liquid, switch off the motor immediately. • If the bearing bracket temperature is more than 28 C that of housing, immediately switch off the pump. • After starting the pump monitor the bearing temperature until it it is stable for 30 mins. • Ensure the pump and system for sufficient operating liquid, then turn on vacuum pump & then recirculation pump with in 5sec, other wise vacuum pump motor should be turned off.

• It is advisable to flush the pump with water soluble preserving oil cortec VCI-379E or equivalent after shut down.

TROUBLESHOOTING Check for proper sealant liquid flow rate. Check the correct direction of vacuum pump rotation

Check for obstruction in air discharge line

TROUBLESHOOTING Check for restriction in inlet suction

Check for bearing lubrication, coupling alignment and bearing condition.

Check the operation of solenoid valve in the seal water supply line.

Check the operation of interstage check valve clapper

(Clockwise from DE)

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