Pump

Presented by : Hager Ismail

Mona youssof

Shaimaa Saber

Soha Makhyoun

Contents: Types of pumps used in TPP.

Methods of working.

Sizing of pumps.

Materials of construction.

Application in NPP.

Types of pumps in TPP

Boiler Feedwater pump:

Different shapes of BFW pump

Condensate pumps:

Steam condensate pump

Circulating pump:

Ash Handling pump:

It’s noticed that the most common pumps used in these types are the

positive displacement and the centrifugal pumps:

Positive Displacement pump:

Centrifugal pump:

Volute centrifugal pump axial centrifugal pump

Methods of working

Centrifugal Pumps

Centrifugal Pump – Working

Components of Centrifugal pump

A rotating component comprising of an impeller and a shaft.

A stationery component comprising a volute (casing), suction and delivery pipe.

Working Principle of Centrifugal pump

Principle:

When a certain mass of fluid is rotated by an external source, it is thrown away from the central axis of rotation and a centrifugal head is impressed which enables it to rise to a higher level.

Working:

The delivery valve is closed and the pump is primed, so that no air pocket is left.

Keeping the delivery valve still closed the electric motor is started to rotate the impeller.

The rotation of the impeller is gradually increased till the impeller rotates at its normal speed.

After the impeller attains the normal speed the delivery valve is opened when the liquid is sucked continuously up to the suction pipe.

Volute and Vortex CasingVolute Casing:

In this type of casing the area of flow gradually increases from the impeller outlet to the delivery pipe.

Vortex Casing:

If a circular chamber is provided between the impeller and volute chamber the casing is known as Vortex Chamber.

Priming of a centrifugal Pump The operation of filling the suction pipe,

casing and a portion of delivery pipe with the liquid to be raised, before starting the pump is known as Priming

It is done to remove any air, gas or vapour from these parts of pump.

If a Centrifugal pump is not primed before starting air pockets inside impeller may give rise to vortices and causes discontinuity of flow.

Losses in Centrifugal pumpHydraulic Losses:

Shock or eddy losses at the entrance to and exit from the impeller

Losses due to friction in the impeller

Friction and eddy losses in the guide vanes/diffuser and casing

Mechanical Losses:

Losses due to disc friction between the impeller and the liquid which fills the clearance spaces between the impeller and casing

Losses pertaining to friction of the main bearing and glands.

Sizing

Introduction:pump should be sized so the cavity created in thepump chamber by the pump elements is ofsufficient size to allow satisfactory pumpoperation

Booster pump:

Considerations:Fluid Data

• Viscosity.

• Fluid to be pumped.

• SG/Density.

• Pumping temperature.

• Vapour pressure.

• Solids content (max. size and concentration).

• Fluid behaviour (i.e. Newtonian or Pseudoplastic etc.).

Performance Data:

Capacity (Flow rate).

Discharge head/pressure.

Suction condition (flooded or suction lift).

Site Services Data

Power source ( electric )

Follow these steps:Step 1: Determine flow rate/pump

Step 2: Determine Fluid property information Density, specific gravity, Dynamic or Absolute viscosity, Kinematics viscosity.

Step 3: Design piping systemSelect pipe sizes This is a compromise between installation costs and running costs. Small diameter pipes lead to high line velocities and friction losses.

: Determine System Head Curve4Step Total Head (Hp) Hp = h(d) - h(s)

Total Suction Head h(s)= p(s)/ρ g z(s)+V2s/2g - hL(s) - h(i)

System and pump performance curve

Total Discharge Head

h(d)= p(d)/ρ g + z(s) +V2d/2g+ z(d) + hL(d) + h(e)

Draw System Curve

: Decide on a Duty Point5Step

Duty point: rate of flow at certain head

Pump operating point: intersection of pump curve and system curve

Flow

Head

Statichead

Pump performance curve

System curve

Pump operating point

: Calculate Power required, Efficiency and 6Step Specific Speed

: Hydraulic power is work done by a pump Power in moving the liquid

Pump Efficiency

ηP = Hydraulic Power (W) / Power input to the pump shaft from the motor (W)

Motor Efficiency: ηM

WM is the power from the motor to the shaft = Power supplied to the motor x motor efficiency

Step 7: Calculate NPSH available

Net Positive Suction Head

• NPSH Available: how much pump suction exceeds liquid vapor pressure

• NPSH Required: pump suction needed to avoid cavitation

NPSHA > NPSHR

Otherwise pump will cavitate.

: Develop Pump Specification8Step

list of suitable Pumps from different manufacturers-: Select a short9Step

Step 10: Evaluate Pump Selection

Match Pump and System curve

Determine Efficiency and NPSH margin

Compare efficiency, NPSH margin, and off design performance of different pumps

Determine materials to be used based on fluid properties

Consider vendor technical support and spare parts issues

Consider preferred vendor supply contracts

System Head Curve

For Example 550 G.P.M. the pump head as selected from the system head curve will be 98 ft. T.D.H.

Cavitation Very destructive phenomena that occurs when the

pressure of the fluid drops below vaporization point. The result is the formation of tiny bubles that colapses when pressure increase on the impeller. Those implosions work as small “explosions” on the impeller that will destroy it.

It’ll happen mainly for 3 reasons: Bad system design. Clogging of pre-filters. Valves closed on the suction side.

Cavitation is audible in the form of high pitch screeching

AFFINITY LAWS :All Centrifugal Pumps follow the Affinity Laws which are

given below :

Q N Q D

H N2 and H D2

P N3 P D3

where N is the Speed of the Pump (rpm) &

D is the Diameter of the Impeller