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### Transcript of PumpTech Customer Education - PNWS- Sessions... · PDF file Bernoulli’s theorem...

• PumpTech Customer Education

Bellevue Moses Lake Canby

http://www.Pumptechnw.com

Joe Evans, Ph.D

• Pump Ed 101

Centrifugal Pump Hydraulics

Three Reasons BEP Operation is Important

Joe Evans, Ph.D

http://www.PumpEd101.com

Pump ED 101

• Centrifugal Pumps

Animated Software Company

Pump ED 101

*

Displacement

• Impellers

Pump ED 101 Dynamics

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• Centrifugal Pump Dynamics

Discharge

Volute

Impeller

Suction

What Type of Energy is Added by the Impeller ?

Pump ED 101

Hint *

Dynamics

Centrifugal

Cutwater

• Centrifugal Force

 It is defined as “center fleeing”

Pump ED 101 Dynamics

*

../../PP Presentations/PP's under construction/Centrifugal training/car.html

• Centrifugal Force

 When an object is traveling in a circle, it is actually moving in a straight line at any single point in time.

 Instead it actually moves in the same direction it was traveling at the exact instant it is released.

Farce

Pump ED 101

*

Dynamics

cforce.gif

• So, How Does It Work ?

1 Rotation of the impeller forces water from its entry point, at the eye, into its vanes.

2 Water moving through the vanes creates a partial vacuum at the eye allowing atmospheric, or some other outside pressure, to force more water into the eye.

3 As water travels through the vanes, it gains rotational velocity (kinetic energy) and reaches its maximum velocity just as it exits the vanes.

4 Upon exiting the vanes, water enters the volute where most of its kinetic energy of motion is transformed into pressure energy.

Pump ED 101

*

Dynamics

• The Volute and its Function

The volute houses the impeller and is the “receptacle” for the water exiting its vanes.

Its smooth, nearly circular, geometry guides the flow from the impeller towards its discharge. During this trip, the flow encounters an ever increasing volume.

The volute converts the kinetic energy (velocity) imparted by the impeller into pressure.

Pump ED 101

*

Dynamics

• The Performance Curve

 Pump Information

 Flow and Pressure at Several Points

 Hydraulic Efficiency

 Horsepower

 Net Positive Suction Head Required (NPSHr)

Pump ED 101

*

Curve

• Pump ED 101

The Performance Curve

• Pump ED 101

The Performance Curve

BEP

11.5”

• Pump ED 101

The Performance Curve

BEBOP

• The Performance Curve

Pump ED 101

*

Curve

BEBOP

• BEBOP & The Cost of Pump Operation

 Power consumption is at its lowest

 Maintenance costs are their lowest

 Useful life is at its maximum

Pump ED 101

When a centrifugal pump is operated at BEBOP

../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls ../../PP Presentations/PP's under construction/Centrifugal training/series parallel.xls

• 0

20

40

60

80

100

120

140

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

H e a d (

ft )

Gallons Per Minute

System Curve Design Flow

300' 6" Steel Pipe

Pump ED 101

The System Curve

• 121

105

95

87

79

72

65

57

49

121

105

95

87

79

72

65

57

49

0

20

40

60

80

100

120

140

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

H e a d (

ft )

Gallons Per Minute

Simplex Duplex

System Curve Design Flow

H4HX 1750 RPM, Trim 10", 71% eff

300' 6" Steel Pipe

Pump ED 101

The System Curve

13.8 HP

24.4 HP

• 109

93

83

74

66

60

52

45

37

109

93

83

74

66

60

52

45

37

0

20

40

60

80

100

120

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

H e

a d

( ft

)

Gallons Per Minute

Simplex Duplex System Curve Design Flow

H4HX 1750 RPM, Trim 9.5", 71% eff

300' 8" Steel Pipe

Pump ED 101

The System Curve

11.5 HP

22.2 HP

../../../../../../Program Files/Hydromatic Pumps/H2Optimize Hydromatic/h2opt.exe

• System Hydraulics – Radial Thrust

 Ideally a pump should operate between 90% and 110% of its BEBOP.

 If it does not, the radial forces that act upon a centrifugal pump’s impeller can account for a large percentage of premature failures.

 The increased shaft deflection will decrease mechanical seal, wear ring, and bearing life.

 Worse case - shaft breakage

19 Pump Ed 101

• • Forms about the periphery of the impeller due to uneven volute geometry

• A function of total head, width and diameter of the impeller

• Usually reaches a maximum at or near shut off head

Pump Ed 101

• Pump ED 101

../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls radial thrust calculator.xls

• Pump ED 101

Cavitation

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

Types of Cavitation

Normal Cavitation – Low NPSHa

Wear Ring Recirculation – Low Flow

Discharge Recirculation – Low Flow

Suction Recirculation – Low Flow

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

Types of Cavitation

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

Wear Ring Recirculation

Cavitation

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

Discharge Recirculation Cavitation

Occurs on the high pressure side of the vane

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

Discharge Recirculation Cavitation Two Vane

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

Suction Recirculation Cavitation

Occurs on the high pressure side of the vane

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

Suction Recirculation Cavitation

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Pump ED 101

Suction & Discharge Recirculation Cavitation

../../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls

• Conservation of Energy

50 PSI 50 PSI 48 PSI

100 GPM

Pump ED 101

Bernoulli’s theorem states that, during steady flow, the energy at any point in a conduit is the sum of the velocity head, pressure head, and elevation head. It also states that this sum will remain constant if there are no losses. Daniel Bernoulli 1700-1782

H = v + p + z = Constant

*

Dynamics

• Pump ED 101 Total Head

Total Suction Head hs = ± hgs + hvs ± Zs

Total Discharge Head hd = hgd + hvd ± Zd

Total Dynamic Head H = hd - hs

Where:

Z = gauge distance above or below datum

Where:

../../../../Program Files/America Online 7.0/pumped101.com files/series parallel.xls Field Test.xlsx

• Pump ED 101

*

Dynamics