Hydraulic EngineeringHydraulic

Engineering

Prof. Zaher Kuhail

Eng. Tamer Eshtawi

Prof. Zaher Kuhail

Eng. Tamer Eshtawi

Lecture 12

Water Pump

Safety systems on pipelines to avoid (water hummer)

• Pump Inertia

• Bypass Reflex Valve

• Surge Tanks

• Discharge Tanks

• Reflex Valve

Water Pump• Water pumps are devices

designed to convert mechanical energy to hydraulic energy. They are used to move water from lower points to higher points with a required discharge and pressure head. This chapter will deal with the basic hydraulic concepts of water pumps.

Pump Classification

• Turbo-hydraulic (kinetic) pumpsCentrifugal pumps (radial-flow pumps)Propeller pumps (axial-flow pumps)Jet pumps (mixed-flow pumps)

• Positive-displacement pumps Screw pumpsReciprocating pumps

Centrifugal pumps (radial-flow pumps)

Propeller pumps (axial-flow pumps)

Centrifugal Pump Impeller; which is the rotating part of

the centrifugal pump .

Casing; which is an air-tight passage surrounding the impeller

Suction Pipe with a Foot-valve and a Strainer

Delivery Pipe

The Shaft

The Motor

Hydraulic Analysis of Pumps and Piping Systems

H t

hd

H s

tat

h s

H m

s

H m

d

Datum pump center line

h fs

h f

d

Case 1

H s

tat

H m

dH

ms

hd

H t

h s

Datum pump center line

h f

d

h f

s

Case 2

• hs (static suction head): it is the difference in elevation between the suction liquid level and the centerline of the pump impeller.

• hd (static discharge head): it is the difference in elevation between the discharge liquid level and the centerline of the pump impeller.

• Hstat (static head): it is the difference (or sum) in elevation between the static discharge and the static suction heads, .

• Hms (manometric suction head): it is the suction gage reading (if a manometer is installed just at the inlet of the pump, then Hms is the height to which the water will rise in the manometer).

• Hmd (manometric discharge head): it is the discharge gage reading (if a manometer is installed just at the outlet of the pump, then Hmd is the height to which the water will rise in the manometer).

• Hm (manometric head): it is the increase of pressure head generated by the pump, .

• Ht (total dynamic head): it is the total head delivered by the pump:

)2

(2

22

g

VH

g

VHH s

msd

mdt

)2

(2

22

g

VH

g

VHH s

msd

mdt

Case 1

Case 2

g

V

g

VHHH sd

msmdt 22

22

2 Case ,2

1 Case ,2

2

2

g

VhhhH

g

VhhhH

hhhH

SmSSfSmS

SmSSfSmS

mddfdmd

HP V

gZ

P V

gZt

d dd

s ss

2 2

2 2Or From Bernoulli

Pump Efficiency

p

o

i

t

i

Power output

Power input

P

P

Q H

P

•Motor which has an the efficiency

PQ H

it

p

•Which is the power input delivered from the motor to the pump

m

im P

P

which is the power input delivered to the motor .

•The overall efficiency of the motor-pump system o p m

Example 1Pump with suction pipe diameter of 100mm and delivery pipe diameter of 75mm, Q in the system is 15L/s. the manometeric suction head is 198 mm of mercury, where the manometeric discharge pressure is 0.95 bar. Motor power is 3.2 KW

S

SSd

ddt Z

g

V

γ

PZ

g

V

γ

PH

22

22

m 69.910.1980.95 bar 95.0γ

Pheadwater

d

m 5.21)(13.6 198.0γ

Ps

m 588.02/V 2d gm/s 39.3Vd

m 186.02/V 2s gm/s 91.1Vs

m...-...H t 9911588052201860699

Solution

3200t

m

o ρgQH

P

Pη

percent ..

...η 55550

23

99110150819

Efficiency