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PUMPS SANDAL SHASHANK ANSHU 41013768
46

boiler feed pump

Oct 28, 2014

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Page 1: boiler feed pump

PUMPS

SANDAL SHASHANK ANSHU 41013768

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FLOW OF THE PRESENTATION

• Definition• Terminologies• Classification• Centrifugal Pump & classification• Vane Pump• Cavitation, NPSH & Specific speed• Technical and functional details of BFP• Technical and functional details of CEP• Technical and functional details of Vacuum Pump

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DEFINITION

Pumps is a machine which adds energy to a fluid, resulting in an increase in fluid pressure.

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TERMINOLOGY

Discharge Head is the verticle distance between the pump datum point and the liquid surface in the receiving tank.

Suction Head - If the water to be pumped has its surface above the center of the pump, then this relationship is called a "suction head". More technically, it is the positive verticle distance between the pump datum and the liquid surface in the suction well.

Static Head Static head is the distance that the water is to be lifted.

Static Head = Discharge Head - Suction Head

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Friction Head This is the pressure drop on both inlet and discharge sides of the pump due to frictional losses in fluid flow.

Total Head or Total Dynamic Head: The Total Head, also called the Total Dynamic Head (TDH), is the sum of the Static Head and the Friction Head. The Total Head, or TDH, is the value used in the horsepower calculations.

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CLASSIFICATION

PUMPS

POSITIVE DISPLACEMENT

ROTARY RECIPROCATING

ROTODYNAMIC

CENTRIFUGAL

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POSITIVE DISPLACEMENT PUMPS

In this type of pumps fluid is directed in to a closed volume and energy transfer to the fluid is accomplished by movement of the boundary of the closed volume causing the volume to expand or contract thereby sucking in or squeezing out the fluid.

ROTODYNAMIC PUMPS

In this type of pumps fluid is displaced and transferred using the inertia of the fluid in motion.

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CENTRIFUGAL PUMP

In this type of pumps fluid encounters the rotating blades ( impeller) and acquires tangential and radial velocity by so-called centrifugal forces (which are actually the lack of centripetal forces to sustain circular motion), and after gaining the speed and pressure, fluid gets decelerated by diffuser thereby further increase in fluid pressure takes place.

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CENTRIFUGAL PUMP CONSTRUCTION

• IMPELLERS The impeller is mounted on a shaft with bearings so that it can be rotated

inside the casing. • SHAFTS Pump shafts are designed to support the impeller on one end,overhung from

the bearings or between the bearings. The overhung design allows straight liquid flow into the impeller, but results in greater radial load on the bearings. The overhung design eliminates one seal around the shaft and simplifies the constructionof the casing.

• SEAL In order to seal rotating shafts against leakage of the pumped liquid, soft

packing is often used.• CASING Pump casings collect the liquid from the pump impeller, convert the velocity

energy to pressure energy, and guide the liquid to the pump discharge nozzle.

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MULTISTAGE CENTRIFUGAL PUMP

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CENRIFUGAL PUMPS

AXIAL FLOW MIXED FLOW RADIAL FLOW

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RADIAL FLOW PUMP

A centrifugal pump in which the pressure is developed wholly by centrifugal force. Often simply referred to as centrifugal pumps. The fluid enters along the axial plane, is accelerated by the impeller and exits at right angles to the shaft (radially). Radial flow pumps operate at higher pressures and lower flow rates than axial and mixed flow pumps.

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AXIAL FLOW PUMP

A centrifugal pump in which the pressure is developed by the propelling or lifting action of the vanes of the impeller on the liquid. Axial flow pumps differ from radial flow in that the fluid enters and exits along the same direction parallel to the rotating shaft. The fluid is not accelerated but instead "lifted" by the action of the impeller. They may be likened to a propeller spinning in a length of tube. Axial flow pumps operate at much lower pressures and higher flow rates than radial flow pumps.

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MIXED FLOW PUMP

A centrifugal pump in which the pressure is developed partly by centrifugal force and partly by the lift of the vanes of the impeller on the liquid , between radial and axial flow pumps, the fluid experiences both radial acceleration and lift and exits the impeller somewhere between 0–90 degrees from the axial direction. As a consequence mixed flow pumps operate at higher pressures than axial flow pumps while delivering higher discharges than radial flow pumps. The exit angle of the flow dictates the pressure head-discharge characteristic in relation to radial and mixed flow

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Positive displacement

Rotary

Gear Vane

Reciprocating

Plunger

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VANE PUMPS

In this type of pumps rotor axis is positioned eccentric to the circular ring inside which is rotates. Since the vanes are free to slide in their slots , they move outward due to centrifugal force and as the vanes make contact with the inner ring walls , a positive seal takes place between the vane tip and the cam ring. Thus a number of chambers are formed between the vanes and cam ring. The chamber changes their volume continuously because the vanes follow the inner contour of the ring.

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PUMP CAVITATION

During pumping action it is possible for the local pressure inside the pump to fall below the vapor pressure of the liquid ( also called saturation pressure), typically on the suction side of the pump where the pressure is lowest and hence liquid boils locally causes the appearance of vapor-filled bubbles called cavitation bubbles. After the bubble formation they are transported though the pump to region where the pressure is higher, causing rapid collapse of the bubbles. This collapse of bubbles causes pitting of the blades which may lead to blade failure.

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As you can see from Figure the pressure available at the pump inlet, which is the pressure that we would measure if we put a gauge at that point, can be reasonably high but still drop considerably as it makes it’s way into the pump. The pressure may be lowered enough that the fluid will vaporize and will then produce cavitation.

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NPSH

NPSH (net positive suction head) is defined as the difference between the net inlet head and head corresponding to vapor pressure of the liquid.

This value is required to avoid cavitation. Cavitation will be avoided if the head at the suction is higher than the vapor pressure head of the fluid.

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SPECIFIC SPEED

Specific speed Ns is a quasi non-dimensional number used to classify pump impellers as to their type and proportions. In Imperial units it is defined as the speed in revolutions per minute at which a geometrically similar impeller would operate if it were of such a size as to deliver one liter per second against one meter of hydraulic head.

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where:Ns is specific speed (unitless)

n is pump rotational speed (revolutions per seconds)Q is flowrate (m³/s) at the point of best efficiencyH is total head (m) per stage at the point of best efficiencyg is acceleration due to gravity (m/s²)

where:Nss = net suction specific speed

N = rotational speed of pump in rpmQ = flow of pump in US gallons per minuteNPSHR = Net positive suction head (NPSH) required

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Specific speed (Ns) identifies the approximate acceptable ration of the impeller eye diameter (D1) to the impeller maximum diameter (D2) in designing an impeller:

• Ns 500 to 5000 D1/D2 > 1.5 - Radial flow pump • Ns 5000 to 10000 D1/D2 < 1.5 - Mixed flow pump • Ns 10000 to 15000 D1/D2 = 1 - Axial flow pump

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BOILER FEED PUMP

• BFP is the most power consuming auxilliary of the power plant placed at the ground floor.

• BFP is located in the feed water cycle and pumps the demineralised feed water from deaerator to economiser inlet header.

• This system also supplies desuperheating water to boiler superheater and HP bypass system.

• Feedwater from 2nd stage of BFP is supplied to reheaters as desuperheating water.

• One branch is fed into feedwater pipe at the inlet economizer for boiler initial filling up .

• Each unit has three motor-driven variable speed feed-water pump with 50% capacity with hydraulic coupling.

• Two pumps work in normal operation and third one is standby.• All three pumps are preceded by a booster pump respectively.

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TECHNICAL DETAILS OF BFP

• Manufactured by KSB.• It is a centrifugal pump.• Temp. of the feedwater at the inlet of booster pump is 180

deg. C.• Suction flow is 600 cubic meter/hr . • Total dynamic head of the pump is 218.5 kg.• Rated RPM of the pump is 5118.• Power input to pump is 3866.2 kw• Efficiency of the pump is 81.3%• NPSH required is 2.55 kg.

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• Shut off head is 269.935kg.• No of stages in pump is 5• Impeller’s material is ASTM A743 CA15 which is an alloy of

carbon(<=0.15%), chromium(11.5% - 14%), iron(81% - 88%), manganese(<=1%), molybdenum(<=0.50%), nickel(<=1%), phosphorous(<=0.04%), silicon(<=1.5%), sulphur(<=.04%).

• Pump is coupled with motor through hydraulic coupling.• Motor is with rated power 5600 KW ,RPM 1500 and 6.6 KV

voltage is used to operate a BFP and booster pump.• Booster pump model no. YNKN300/200 with rated RPM of

1480.• It develops head of 6.25 kg. with required NPSH of 0.324 kg.

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Inlet of BFPOutlet of BFP

Recirculation line

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HYDAULIC COUPLING

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Recirculation line

Supply to reheater spray

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CONDENSATE EXTRACTION PUMP• CEP is also located at ground Floor.• CEP convey condensate water from condenser hotwell to deaerator.• Chemical dosing is done just after the CEP.• Then taping of cooling water to gen stator is provided also

condensate water to vacuum pump and vacuum breaker is supplied.• After that there are tapings to –1. closed circuit cooling water expansion tank2. HP flash tank3. LP bypass desuperheating water 4. Gland steam desuperheating water5. Desuperheating water to FOSH, coal mill steam, APRDS 6. To surge tank is also provided to ensure water level of hot well

under all kinds of condition.

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TECHNICAL DETAILS OF CEP

• There are two CEPs here in each unit with 100% capacity.

• CEP is the centrifugal pump manufactured by KSB.• Designed capacity of the CEP is 750 cubic meter/hr.• Discharge pressure at designed capacity is 29.8kg.• Suction pressure of the CEP is 0.1013 kg.• NPSH required for CEP is 0.343 kg.• Shut off head of the CEP is 33.5 kg.• It consumes 761 KW at 6.6 KV voltage.

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VACUUM PUMP

• It is located at ground floor.• It’s function is to establish and maintain the

vacuum in condenser.• It brakes the condenser vacuum during to

protect turbine during emergency.• There are two vacuum pumps in each unit one

is operating and another is standby.

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FUNCTONAL ELEMENTS OF VACUUM PUMP

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TECHINICAL DETAILS OF VACUUM PUMP

• It can extract 86 kg/hr. of dry air at max.• It requires 35 min. to establish the initial vacuum.• It is driven by 132 KW motor.• Vacuum pump outlet pressure is 0.90 kg.• Inlet and outlet temp. of vacuum pump are 36 and 33

deg. C. • Separator air outlet flow is 14 kg/hr.

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QUERIES ???

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REFERENCES

• RPSCL Tech diary.• google.com• Fluid Mechanics by Yunus Cengel and John Cimbala.

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THANK YOU