Sprinkler Irrigation Technology Guide

SPRINKLER IRRIGATION
TECHNOLOGY AND APPLICATION
Moshe Sne
Irrigation and Plant Nutrition Consultant
2011

I
FOREWORD
Ten years ago I had composed in cooperation with the late Elimelech Sapir the booklet
“Sprinkler Irrigation”. The publication was used as a textbook in courses on irrigation
organized by the Israeli Ministry of Foreign Affairs, The Centre for International
Cooperation (Mashav), through its agricultural aegis The Centre for International
Agricultural Development Cooperation (CINADCO), of the Israeli Ministry of Agriculture
and Rural Development.
The courses were carried-out in Israel and abroad for farmers, extension workers and
policy makers in the field of irrigation and water management. They were designated for
beginners and first time users of pressurized irrigation. Elucidation of the theoretical
concepts was simplified to correspond with course participants' requirements.
In the last decade, irrigation technologies became more advanced and more sophisicated,
perceptions and attitudes were changed, so updating this publication had been essential.
The booklet covers the technology and theory of sprinkler irrigation. In addition to
conventional sprinkler irrigation, two derivative technologies are dealt – micro-irrigation
and mechanized irrigation. Micro-irrigation employs micro emitters of low volume water
discharge with two patterns of water distribution:
a. Water is distributed through the air.
b. Water is delivered directly to the soil from drippers and bubblers.
The booklet relates only to those emitters that spread the water through the air,
drippers and bubblers are excluded.
The mechanized irrigation stemmed from sprinkler irrigation. In its first generation, the
emitters were solely impact sprinklers. Later-on it shifted to using micro-emitters operating
at low working pressure. This technology is gaining momentum all over the world. For that
reason it is covered with much more detail than in the first edition.
The manuscript emphasizes the practical aspects of sprinkler irrigation. The more
advanced reader may refer to the extensive literature dealing with the subject.
Related publications are listed in the References and Bibliography list at the end of the
booklet.
I have chosen to distribute the new publication by the Scribd network with the hope that
users of the old version can update themselves.
Moshe Sne

II
TABLE OF CONTENTS
TOPIC Page
Forword I
Table of Contents II
List of Tables IX
List of Figures XI
1. INTRODUCTION 1
Overview …………………………………………………………………. 1
Surface Irrigation ………………………………………………………… 2
Surface Irrigation Methods …………………………………………….. 2
Advanced Technologies ………………………………………………... 3
2. SPRINKLER IRRIGATION 4
Introduction ………………………………………………………………. 4
Advantages ……………………………………………………………….. 4
Disadvantages and Limitations …………………………………………... 4
Definitions ………………………………………………………………... 5
Nominal Pipe Diameter ………………………………………………… 6
Sprinkler Types …………………………………………………………... 6
Sprinkler Classification ………………………………………………… 7
The Jet Angle …………………………………………………………... 13
Sprinkler Flow-rate …………………………………………………….. 14
Working Pressure (Head) ………………………………………………. 14
Sprinkler Spacing, Selection and Operation …………………………... 14
3. MICRO-EMITTERS 16
Introduction ………………………………………………………………. 16
Micro-emitter types ………………………………………………………. 17
Static Micro-emitters (Micro-jets) ……………………………………... 17
Micro-sprinklers ………………………………………………………... 18
Micro-sprinkler Types …………………………………………………. 19
Emitter Mounting ………………………………………………………… 20
Water Distribution Patterns ………………………………………………. 21
Pressure Compensation …………………………………………………... 22

III
4. THE IRRIGATION SYSTEM 23
The Pumping Unit ………………………………………………………... 23
Pump Performance Terminology ………………………………………. 24
Pump Types …………………………………………………………….. 25
Suction Lift of a Pipe …………………………………………………... 26
Kinetic Pumps ………………………………………………………….. 27
Installation of Vertical Turbine Pumps ………………………………… 31
Submersible Pumps …………………………………………………….. 31
Pump Stages ……………………………………………………………. 32
Solar water Pumps and Solar Water Pumping Systems ………………... 33
Variable speed drives …………………………………………………... 33
Selecting an Efficient Pumping Plant ………………………………….. 34
Maintaining Irrigation System Efficiency ……………………………… 34
The Pumping Unit Efficiency ………………………………………….. 35
Cavitation ………………………………………………………………. 37
Pump Curves …………………………………………………………… 37
Pump and Well Testing ………………………………………………… 39
5. PIPES AND ACCESSORIES 40
Introduction ………………………………………………………………. 40
Pipe Materials …………………………………………………………….. 40
Iron, Steel and Copper ………………………………………………….. 40
Aluminum ………………………………………………………………. 41
Asbestos-cement ………………………………………………………... 41
Concrete ………………………………………………………………... 41
Plastic Materials ………………………………………………………... 41
External and Internal Pipe Diameter ……………………………………... 45
6. COUPLERS 46
Connectors (Fittings) ……………………………………………………... 46
Aluminum Couplers ……………………………………………………. 46
7. REGULATION AND CONTROL 49
Introduction ………………………………………………………………. 49
Supply Pipelines ………………………………………………………… 49

IV
The Control head …………………………………………………………. 49
Regulation and Control Devices …………………………………………. 50
Valves ………………………………………………………………….. 50
Control Valves – Functioning and Actuation ………………………….. 55
Check-valves …………………………………………………………… 58
Pressure Relief Valves …………………………………………………. 59
Pressure Regulators …………………………………………………….. 60
Air-release Valves ……………………………………………………… 61
Atmospheric Vacuum Breakers ………………………………………... 62
Valve Capacity …………………………………………………………… 62
Automation ……………………………………………………………….. 62
Overview ……………………………………………………………….. 62
Flow-meters …………………………………………………………….. 63
Metering-valves (Hydrometers) ………………………………………... 64
Control Patterns ………………………………………………………… 64
Irrigation Timers ……………………………………………………….. 65
Computer-based Irrigation control Systems ……………………………. 66
Supervisory Control And Data Acquisition (SCADA) ……………….. 68
8. WATER TREATMENT AND FILTRATION 71
Introduction ………………………………………………………………. 71
Particulate Matter ………………………………………………………… 71
Biological Substances ……………………………………………………. 71
Chemical Precipitates …………………………………………………….. 72
Water hardness …………………………………………………………… 72
Iron and Manganese in Water ………………………………………….. 73
Biological Oxidation Demand (BOD)…………………………………….. 73
Filtration ………………………………………………………………….. 73
Screen (Strainer) Filters ………………………………………………... 73
Disc Filters ……………………………………………………………... 75
Media Filters …………………………………………………………… 75
Sand Seperators ………………………………………………………… 76
Filter Characteristics …………………………………………………… 77

V
Flow Direction …………………………………………………………. 78
Filter Cleaning …………………………………………………………. 79
Filter Location ………………………………………………………….. 81
Supplementary Water Treatments ………………………………………... 81
Chlorination …………………………………………………………….. 82
Acidification ……………………………………………………………. 82
9. FERTIGATION 83
Introduction ………………………………………………………………. 83
Advantages of fertigation ………………………………………………. 83
Limitations and Risks in Fertigation …………………………………… 83
Technologies of Fertigation ……………………………………………… 83
Patterns of Injection ……………………………………………………. 83
Fertilizer Tank ………………………………………………………….. 84
Venturi Injector ………………………………………………………… 85
Injection pumps ………………………………………………………… 85
Injecton Site ……………………………………………………………… 88
Injection at the Main Control Head …………………………………….. 88
Injection at Sub-main Heads …………………………………………… 88
Injection at the Control Head of each Block …………………………… 88
Control and Automation ………………………………………………….. 88
Quantitative Dosing ……………………………………………………. 88
Proprtional Dosing ……………………………………………………... 88
Avoiding Corrosion damage ……………………………………………... 89
Back-flow Prevention …………………………………………………….. 89
Back-siphonage ………………………………………………………… 89
Back-pressure …………………………………………………………... 89
Chemical Aspects of fertigation ………………………………………….. 89
Safety ……………………………………………………………………... 90
10. FLOW-RATE – WATER HEAD RELATIONSHIP 91
Water Pressure ……………………………………………………………. 91
Elevation Head (z) ……………………………………………………… 91
Dynemic head ….. ………..……………………………………………. 92

VI
Velocity Head …………………………………………………………... 92
Head Losses ……………………………………………………………… 92
Friction Losses …………………………………………………………. 92
Operating Pressure ……………………………………………………….. 96
Hydraulic Characteristics of Emitters ……………………………………. 97
Calculation of Head Losses ………………………………………………. 98
Technical data ……………………………………………………………. 98
Pressure measurement ………………………………………………….. 98
Calculation of Longitudinal Head Losses ……………………………… 98
11. WATER MOVEMENT AND DISTRIBUTION IN THE SOIL 109
Soil Properties ……………………………………………………………. 109
Soil Texture …………………………………………………………….. 109
Soil – Water relationship …………………………………………………. 111
Introduction …………………………………………………………….. 111
Saturation ………………………………………………………………. 111
Field Capacity 111
Wilting Point …………………………………………………………… 111
Factors affecting the Difference in Water Storage ……………………... 111
Available Water Capacity (AWC) ……………………………………... 112
Water Movement in the Soil …………………………………………… 112
The Determination of the Water Status in the Soil …………………….. 114
Water Intake Rate (WIR) of the Soil …………………………………… 115
Soil Wetting Patterns ……………………………………………………... 120
Water dosage …………………………………………………………… 120
Chemical Composition of the Water …………………………………… 120
Water Distribution Uniformity …………………………………………… 120
Distribution Uniformity in Fully Soil Surface Wetting Irrigation ……... 121
Distribution Uniformity in Localized irrigation ……………………….. 129
12. SPRINKLER IRRIGATION TECHNIQUES 131
Overview …………………………………………………………………. 131
Hand-move ……………………………………………………………….. 131
Aluminum Pipes ………………………………………………………... 131

VII
Flexible laterals in Orchards …………………………………………… 133
Permanent Installations …………………………………………………... 134
Solid-set in Orchards …………………………………………………… 134
Mini-sprinklers Solid-set Systems in Vegetables ……………………… 135
Mechanized Irrigation ……………………………………………………. 137
Introduction …………………………………………………………….. 137
Towline ………………………………………………………………… 137
Wheel Move ……………………………………………………………. 138
Traveling Gun (Traveler) ………………………………………………. 141
Continuous-move Sprinkler System ……………………………………… 147
The Water Emitters …………………………………………………….. 147
Center-Pivots …………………………………………………………… 157
Lineat-Move Systems …………………………………………………... 182
Control and Automation ………………………………………………... 187
13. PLANNING AND DESIGN OF SPRINKLER IRRIGATION 192
Introduction ………………………………………………………………. 192
Planning …………………………………………………………………... 192
Soil Properties ………………………………………………………….. 192
Climate Data ……………………………………………………………. 194
Cropping Data ………………………………………………………….. 194
Water Resources ………………………………………………………... 194
Data Manipulation ………………………………………………………... 195
Soil Wetting Pattern ……………………………………………………. 195
Manipulation Steps ……………………………………………………... 196
Existing Equipment ………………………………………………………. 198
Calculation Formulae …………………………………………………….. 200
The Design Procedure ……………………………………………………. 201
Overview ……………………………………………………………….. 201
System Layout ………………………………………………………….. 201
Water Flow Velocity …………………………………………………… 203
Spacing …………………………………………………………………. 203
Choosing Emitters and Laterals ………………………………………... 204

VIII
Fxample of the Design Process …………………………………………... 204
Additional Examples of System Design Schemes ……………………….. 209
14. IRRIGATION SCHEDULING 212
Introduction ………………………………………………………………. 212
Calculation of the Water Amount in Sprinkler Irrigation ………………... 213
Calculation of the Precipitation Rate …………………………………... 213
Calculation of the Irrigation Duration ………………………………….. 213
The Total Flow-rate of the Irrigated Area ……………………………… 213
Scheduling with the water Budget Concept ……………………………. 214
Scheduling Software and On-line Calculators …………………………. 216
15. MONITORING AND CONTROL 219
Monitoring ………………………………………………………………... 219
Soil Water Monitoring …………………………………………………. 219
Plant Water Status Monitoring …………………………………………. 220
Plant Organs Elongation and Expansion ……………………………….. 221
Irrigation Control ………………………………………………………… 221
Manual Control ………………………………………………………… 221
Quantitative Automatic Water Shutdown ……………………………… 221
Fully Controlled Irrigation ……………………………………………... 221
Integrated Irrigation and Fertigation Control …………………………... 221
Integrated monitoring and Control ……………………………………... 222
16. MAINTENANCE 223
Introduction ………………………………………………………………. 223
Installation ………………………………………………………………... 223
Mains and Sub-mains …………………………………………………... 223
Laterals …………………………………………………………………. 223
Routine Inspection ……………………………………………………….. 224
Pump Inspection ………………………………………………………... 224
System Performance ……………………………………………………. 224
Routine Maintenance ……………………………………………………... 225
System Flushing and Cleaning …………………………………………. 225
The Control Head ………………………………………………………. 225

IX
The Irrigation Network …………………………………………………. 226
Micro-irrigation Systems ………………………………………………. 228
Mintenance of Accessories ……………………………………………... 228
Maintenance of Fertigation Systems …………………………………… 230
Chemical Water Treatments ……………………………………………… 230
Acidification ……………………………………………………………. 230
Oxidation ……………………………………………………………….. 231
Overwintering of the Irrigation System ………………………………….. 231
Entire System …………………………………………………………... 231
Filtration Equipment …………………………………………………… 231
Valves …………………………………………………………………... 231
Controllers and Sensors ………………………………………………… 231
Chemical Injection Equipment …………………………………………. 231
Pumps …………………………………………………………………... 232
Electric Motors …………………………………………………………. 232
17. GLOSSARY 233
18. REFERENCES AND BIBLIOGRAPHY 262
LIST OF TABLES
No. PAGE
2.1. Wind Velocity Definitions ……………………………………………. 15
2.2. Recommended Spacing between Sprimklers …………………………. 15
5.1. PE (Polyethylene) Pipes for Agriculture ……………………………... 42
5.2. LDPE Pipes Internal (Inner) Diameter and Wall Thickness …………. 43
5.3.
HDPE
HDPE Pipes Internal (Inner) Diameter and Wall Thickness …………. 43
5.4. PVC Pipes for Agriculture ……………………………………………. 44
5.5. Internal Diameter and Wall Thickness of PVC Pipes ………………… 44
7.1. Flow-rate of Spring Actuated Pressure Regulators …………………… 61
8.1. Relative Clogging Potential of Micro-emitters by Water Contaminants 72
8.2. Screen Perforation Examples …………………………………………. 74
8.3. Sand Particle Size and Mesh Equivalent ……………………………... 76

X
8.4. Nominal Filter Capacity – examples ………………………………… 78
9.1. Electric Charges of Nutrients ………………………………………… 90
10.1. Pressure and Water Potential Units …………………………………... 91
10.2. Friction Coefficients ………………………………………………… 93
10.3. Multiple Outlets factor F ……………………………………………… 97
10.4. Effect of the Emitter Exponent on Pressure – Flow-rate Relationship . 97
10.5. Head Losses in Non-Distributing Aluminum Pipes, m. Head per 100-
m. Pipe Length (without Outlets) ……………………………………..
99
10.6. F Coefficient in Laterals ……………………………………………… 100
11.1. Soil Classification According to Particle Diameter …………………... 109
11.2. Available Water in Different Soil Textures ………………………….. 112
11.3. Average values of Water States in Different Soil Textures – W/W …. 112
11.4. Calculating Christiansen's Coefficient of Uniformity with Experimental
Data (example) …………………………………………………………
127
12.1. Recommended Hose Size for Traveler Sprinklers …………………… 147
12.2. Characteristics and Performance of the Emitters …………………….. 165
12.3. Wetting Diameter of Emitters at 1.8 m3
/h Flow-rate ………………… 171
12.4. Recommended Spacing – m. for Emitters at 2 m. Height at Different
Working Pressures …………………………………………………….
177
13.1. Sprinkler Performance (example) ……………………………………. 199
13.2. Maximum Allowed Number of Sprinklers on Lateral on Level Ground 201
13.3. The Chosen Emitter …………………………………………………... 206
13.4. Allowed Length of Laterals …………………………………………... 206
13.5. Basic data …………………………………………………………….. 207
13.6. Head-loss Calculation ………………………………………………… 208
13.7. Total Requested Dynamic Head ……………………………………… 208
14.1. Annual Crops Irrigation Scheduling Form …………………………… 212
14.2. The Estimated Available Water per Unit of Rooting Depth for Soils of
Various Textures and the Intake Rate for Various Soil Textures …….
214
14.3. Active Root-zone Depth of Fruit Trees ………………………………. 215

XI
LIST OF FIGURES
No. PAGE
1.1. Level Border Strip Flooding ………………………………………… 2
1.2. Leveled Beds between Contour Lines ……………………………….. 3
1.3. Furrow Irrigation …………………………………………………….. 3
2.1. Sprinkler Spacing Positions …………………………………………. 5
2.2. Irrigation Intensity …………………………………………………… 5
2.3. The Influence of Wind on the Uniformity of Water Distribution …… 6
2.4. Outdated Pressurized Irrigation Systems ……………………….. 6
2.5. Impact-Hammer Sprinkler …………………………………………… 8
2.6. Turbo-Hammer Sprinkler ……………………………………………. 8
2.7. Gun Sprinkler (Rain-gun) ……………………………………………. 8
2.8. Stand-alone Gun-sprinkler with Stabilizer in the Field ……………… 9
2.9. Pop-up Sprinklers ……………………………………………………. 10
2.10. Part-circle Static Sprinklers ………………………………………….. 10
2.11. Impact Sprinkler Components …………………………………… 11
2.12. Configurations of Impact Sprinklers ………………………………… 12
2.13. Nozzle Types ………………………………………………………… 13
2.14. Jet Angles ……………………………………………………………. 13
2.15. Low-volume Under-canopy Sprinklers ……………………………… 14
3.1. Diverse Micro-emitters …………………………………………….. 16
3.2. Static Micro-jets ……………………………………………………... 17
3.3. Vortex Sprayer ………………………………………………………. 18
3.4. Vibrating Micro-jet ………………………………………………….. 18
3.5. Modular Micro-emitter – Water Spreading Pattern …………………. 18
3.6. Rotating Micro-sprinklers …………………………………………… 19
3.7. Micro-sprinklers Configurations …………………………………….. 19
3.8. Modular Micro-sprinkler …………………………………………….. 19

XII
3.9. Mounting Alternatives of Micro-emitters …………………………... 21
3.10. Water Distribution by Micro-sprinkler at Different Flow-rates ……...
(example)
22
3.11. Multiple-jet (Fan-jet) Emitter's Distribution Patterns ……………….. 22
4.1. Schematic Plot Irrigation System ……………………………………. 23
4.2. Electric Water Pumps ……………………………………………… 23
4.3. Pump Type Classification …………………………………………… 25
4.4. Centrifugal Pump ……………………………………………………. 27
4.5. Different Flow Patterns in Centrifugal Pumps ………………………. 28
4.6. Water Flow in Volute Pump ………………………………………… 29
4.7. Deep-well Verical Turbine Pumps …………………………………... 30
4.8. Pump Impellers ……………………………………………………… 31
4.9. Single-stage Pump …………………………………………………… 32
4.10. Multi-stage Pump ……………………………………………………. 32
4.11. Solar Pumping System ………………………………………………. 33
4.12. A Variable-frequency Drive Controlls a Set of 3 Pumps …………... 33
4.13. Pump Efficiency Curve ……………………………………………… 36
4.14. A Scheme of Pump Curves ………………………………………….. 37
4.15. An Example of Pump Curves Plotted on One sheet …………………. 38
4.16. Horse-power Curves …………………………………………………. 38
4.17. Critical Points on the Pump Curve …………………………………... 39
6.1. Hermetic and Detached Band Couplers …………………………….. 46
6.2. Single Latch Couplers ………………………………………………. 46
6.3. Valve Adapters ………………………………………………………. 47
6.4. Adapter Made of Al-Pb Metal Alloy ………………………………... 47
6.5. Aluminum Lateral Assembly ………………………………………... 47
6.6. Plastic and Metal Connectors ………………………………………... 47
6.7. Lock Fastened PolyPropylene Connectors
………………………………..
48
6.8. On-line Saddles ……………………………………………………… 48
7.1. Water Supply Network .…………………………………………… 49

XIII
7.2. Typical Control Head ..…………………………………………….. 49
7.3. Valve Types …………………………………………………………. 50
7.4. Manual Actuators ……………………………………………………. 50
7.5. Globe Valve …………………………………………………………. 51
7.6. Angular Valve ……………………………………………………….. 51
7.7. Single-seat Globe Valve ……………………………………………... 52
7.8. Double-seat Globe Valve ……………………………………………. 52
7.9. Gate Valve …………………………………………………………… 53
7.10. Ball Valve Cutaway …………………………………………………. 53
7.11. Butterfly Valve ………………………………………………………. 54
7.12. Piston Valve …………………………………………………………. 54
7.13. Diaphragm Valve Components ……………………………………… 55
7.14. Diaphragm Valves …………………………………………………… 55
7.15. Diaphragm Valve Working Pattern ………………………………….. 55
7.16. Control Valve Actuators ………………………………….………… 56
7.17. Cutaway of Solenoid Valve …………………………….…………… 56
7.18. Scheme of Solenoid Operation ……………………………………… 57
7.19. Fail Closed (NC) Solenoid Valve – Components and Working
Pattern ………………………………………………………………..
57
7.20. Hydraulic Control Valve …………………………………………….. 58
7.21. Check Valves ………………………………………………………… 59
7.22. Pilot Controlled Hydraulic Pressure Relief Valves ………………….. 59
7.23. Pilot Valves ………………………………………………………….. 60
7.24. Pressure Regulators ………………………………………………….. 60
7.25. Cross Section of Air-release Valves ……………………………… 61
7.26. Atmospheric Vacuum Breakers ……………………………………... 62
7.27. Flow-meters …………………………………………………………. 63
7.28. Hydrometers – Cross-section ………………………………………... 64
7.29. Hydrometer – Manual and Remote-controlled Dial ………………... 64

XIV
7.30. Local Irrigation Controller …………………………………….. 67
7.31. SCADA Control System ……………………………………………. 68
7.32. RTUs Connected to Field-unit (FU) by Cable ………………………. 69
7.33. Internet Mediated SCADA Network ………………………………… 70
8.1. Screen Filter …………………………………………………………. 73
8.2. Screen Patterns ………………………………………………………. 74
8.3. Head Losses in Clean Screen Filters ………………………………… 75
8.4. Disc Filter ……………………………………………………………. 75
8.5. Media Filters ………………………………………………………… 76
8.6. Sand Separator - Working Pattern …………………………………… 76
8.7. Hydro-cyclone Sand Separator – Head Losses and Optimal Flow-
rates …………………………………………………………………..
77
8.8. Manual Cleaning of Screen filters …………………………………… 79
8.9. Hose Flushing of a Disc-filter ……………………………………….. 79
8.10. Continuous Flushed Circulating-filter ………………………………. 79
8.11. Automatic Screen Filters with Scanning Nozzles …………………… 80
8.12. Automatic Flushing of Disc-filter …………………………………… 80
8.13. High-capacity Media-filter Array ……………………………………. 81
8.14. Back-flushing of Media-filters ………………………………………. 81
9.1. Fertilizer Tank ……………………………………………………….. 84
9.2. Venturi Injector ……………………………………………………… 85
9.3. By-pass Venturi Installation …………………………………………. 85
9.4. Piston and Diaphragm Hydraulic Pumps ……………………………. 86
9.5. No-drain Hydraulic Pump …………………………………………… 86
9.6. Piston Pump Installation in Control Head …………………………… 87
9.7. Fertilizer Solution Flow-meter with Pulse Transmitter
…………………….
87
9.8. Mixer Array ………………………………………………………….. 87
9.9. Electric Pump ………………………………………………………... 88
9.10. Tandem Back-flow Preventer ………………………………………... 89

XV
10.1. Graphic Presentation of Friction Head ……………………………….. 94
10.2. Feeding Micro-tube Connection ……………………………………... 95
10.3. Head-losses in Hydraulic Valves ……………………………………. 95
10.4. Pressure Measurement ……………………………………………... 98
10.5. Slide-ruler for Head-loss Calculation in Pipes ………………………. 101
10.6. Nomogram for Hazen-Williams Formula ………………………….. 103
10.7. Nomograms for Head-loss Determination In Polyethylene Pipes ………. 104
10.8. Nomogram for Local Hydraulic Gradient Determination in
Accessories ……………………………………………………………
105
10.9. Nomogram for Calculation of Head-losses in LDPE Pipes …………. 106
.10.10 Nomogram for Calculation of Head-losses in HDPE Pipes …………. 107
10.11. Nomogram for Calculation of Head-losses in PVC Pipes …………... 108
11.1. Visual Illustration of Soil Particle Diameter ………………………… 109
11.2. Soil Texture Triangle ………………………………………………...
…………………………………………………
110
11.3. Illustration of the Water States in the Soil …………………………...
..11111111111111111111111
111
11.4. Water-air Ratio in Two Soil Types, 12 Hours After Irrigation ……… 111
11.5. Illustration of the Available Water in the Soil ………………………. 112
11.6. Water Potential Values in the Different Water States in the Soil …… 113
11.7. Water Retention Curves in Different Soil Textures …………………. 114
.11.8 The Sequence of Soil Moisture Determination by the Gravimetric
(Oven Drying) Method ……………………………………………….
115
11.9. Edelman Dutch Auger ………………………………………………..
11.10. Water Infiltration into the Soil – Curve ……………………………... 115
11.11. Soil Texture Triangle – Infiltration Rate Contours ………………….. 116
11.12. Typical Infiltration Curves in Different Soil Textures ………………. 116
11.13. The Basin Infiltrometer ……………………………………………… 117
11.14. Double Ring Infiltrometer …………………………………………… 118
11.15. The “Sprinkler Method” ……………………………………………... 119
11.16. Single Sprinkler Test ………………………………………………… 122

XVI
11.17. Single Lateral Test …………………………………………………... 123
11.18. Simultaneously Operated Laterals Test ……………………………… 123
11.19. Open-air Test Plot and Covered Distribution Test Facility …………. 123
11.20. Grid of Catch Cans …………………………………………………... 124
11.21. Recording Form for Measurement of the Uniformity of Water
Distribution …………………………………………………………..
125
11.22. Measured Water Amounts in One Quarter of the Wetted Area in
Single-sprinkler Test ………………………………………………….
126
11.23. Single Sprinkler Distribution Pattern in Wind-less Conditions ……... 126
11.24. Wind Effect on the Distribution Pattern on Both Sides of a Single
Lateral ………………………………………………………………...
128
11.25. Unilateral Presentation of the Distribution Pattern of a Mini-emitter …. 128
12.1. Hand-move Lateral ………………………………………………….. 131
12.2. Hand-move Layout: 2” Aluminum Pipes, Spacing 6 X 12 m. 4
Laterals X 4 Positions…………………………………………………
………………………………………………………….
132
12.3. Coupling of Aluminum Pipe …………………………………………. 132
12.4. Ten-shift Manual Drag Under-canopy Sprinkler Array ……………. 133
12.5. Orchard Under-canopy Micro-sprinkler Irrigation ………………
……….……………….
134
12.6. Solid-set System in Orchard. Spacing 6 X 4 m. Sprinkler Flow-rate …
100 l/h
134
12.7. Orchard Overhead Irrigation ………………………………………… 135
12.8. Solid-set Mini-sprinkler Irrigation of Vegetables …………………… 136
12.9. Towline ……………………………………………………………... 137
12.10. Towline Accessories …………………………………………………. 137
12.11. Linear Towline System: 2 Sets, 8 Laterals Each, Six Positions per
Lateral, Spacing 12X18 m …………………………………………..
138
12.12. Sprinkler Vertically Stabilized by a Swivel and a Ballast …………... 139
12.13. Side-roll Operating Scheme …………………………………………. 140
12.14. Side-roll in the Field …………………………………………………. 140
12.15. Manually Moved Big Gun ………………………………………. 142
12.16. Hose-reel Traveler …………………………………………………… 143

XVII
12.17. Cable-tow Traveler ………………………………………………….. 143
12.18. Hose-reel Traveler Operating Scheme ………………………….. 144
12.19. Water-driven Cable-tow Traveler Scheme ………………………….. 145
12.20. Cable-tow Traveler Operating Scheme ……………………………… 145
12.21. Linear-Move System with On-top High-pressure Impact Sprinklers
and End-gun ………………………………………………………….
148
12.22. Impact Sprinkler – Nozzle Options ………………………………….. 148
12.23. Stationary Deflection-pad Emitters ………………………………….. 150
12.24. Nozzle and Deflection-pad Options for Stationary Spray …………… 150
12.25. Micro-emitters On-drops in Work
………………………………………………..
151
12.26. Nozzle and Pad Options in Rotators …..…………………………….. 151
12.27. Up-right Spinner ……………..…….………………………………… 151
12.28. Rotators and Spinner ………………………………………………… 152
12.29. Distinctive Emitters ………………………………………………….. 152
12.30. LDN Emitters at Work ………………………………………………. 153
12.31. LDN (Low Drift Nozzle) Emitter Configurations …………………… 154
12.32. Oscillating Deflection Pad Options ………………………………….. 155
12.33. Components of Oscillating Emitters ………………………………… 155
12.34. Inverted Wobbler on Drops ………………………………………….. 155
12.35. Diverse Configurations of Inverted Wobblers ……………………… 156
12.36. Quad-spray and its Water Application Modes ……………………… 156
12.37. Aerial View of Center-Pivot Irrigated Area …………………………. 157
12.38. Center-Pivot Operation Scheme ……………………………………... 157
12.39. Net Irrigated Area …………………………………………………… 157
12.40. Components of Center-Pivot / Linear-Move Lateral System ……….. 158
12.41. Universal System (Can Be Used as Linear-Move or Center-Pivot) …. 159
12.42. Center-Pivot Main Tower …………………………………………. 160
12.43. Corner Arm ………………………………………………………….. 160
12.44. Options of Sprinkler Position and Dicharge ………………………… 161

XVIII
12.45. Towable Center-Pivot ……………………………………………….. 163
12.46. Goosenecks on Top of lateral ………………………………………... 166
12.47. Positioning Options of Low-pressure Emitters on Drops …………… 167
12.48. Furrow Dikes ………………………………………………………… 168
12.49. Boom-backs behind Center-Pivot Towers …………………………... 169
12.50. Bi-lateral Boom Appendage with end-gun on a Center-Pivot ………. 170
12.51. Emitter Spacing Patterns in Center-Pivot ……………………….. 173
12.52. An Example of Water Logging by Spray Emitters - Close-up ……… 174
12.53. The Effect of Using Pressure Regulators in Slopy Terrain …………. 174
12.54. Small-diameter Pressure Regulators Installed for Single Emitters ..…
.and on Drops
175
12.55. Relationship between Width of the Wetted Coverage (W) and
Application Intensity for the Same Flow-rate ………………………..
176
12.56. Relationship between Required Application Intensity and Time of
Application for the Same Depth of Application ……………………..
177
12.57. Center-Pivot End-gun Installations ………………………………….. 178
12.58. Irrigation of Orchards by Center-Pivot
……………………………….
179
12.59. Linear-Move Lateral ………………………………………………… 182
12.60. On-lateral Trip Switch ………………………………………………. 183
12.61. Linear-Move System with Spray Emitters on Drops ………………... 184
12.62. Linear-Move System with Rotators on Drops ………………………. 185
12.63. Linear-Move – Main-line in Field Margin …………………............... 186
12.64. Linear-Move System Pumping Water from Ditch …………………... 186
12.65. Operation Scemes of Ditch-fed Linear-Move Systems ……………… 186
12.66. VRI with Individual Emitter Control ………………………………... 188
12.67. VRI – Partially Irrigating Lateral ……………………………………. 189
12.68. Individually Controlled Node ……………………………………….. 189
12.69. Control Panel Positioned in the Pivot point …………………………. 189
12.70. On-screen Operation Presentation …………………………………... 191
13.1. Topographic Map ……………………………………………………. 192

XIX
13.2. Irrigation Planning Form …………………………………………….. 193
13.3. Different Design Alternatives ……………………………………….. 202
13.4. Manifolds Save in Cost of Accessories ……………………………… 202
13.5. Citrus Grove - 11.5 Ha. ……………………………………………… 204
13.6. The Design Sceme …………………………………………………… 207
13.7. Hand-move Design Scheme …………………………………………. 209
13.8. Gun Traveler Design Scheme ……………………………………….. 210
13.9. Solid-set in Orchard …………………………………………………. 211
14.1. Typical Root Systems of Field Crops ……………………………….. 215
14.2. Irrigation Design Software Screenshot ……………….……………... 216
14.3. Visual Presention of Designed System ……………………………… 217
14.4. Scheduling Software Screen-shot …………………………………… 217
14.5. On-line Calculator …………………………………………………… 218
15.1. Tensiometers ………………………………………………………… 219
15.2. Watermark Granular Sensor …………………………………………. 219
15.3. Time Domain Transmissometry Sensor ……………………………... 219
15.4. The Pressure Bomb ………………………………………………….. 220
15.5. Fertilizer and Water Controller ……………………………………… 221
15.6. Integrated Monitoring and Control ………………………………….. 222
16.1. Punch and Holder ……………………………………………………. 223
16.2. Automatic Lateral End Flushing Valve ……………………………… 225
16.3. Control Head ………………………………………………………… 225
16.4. Coupling of PE Pipes ……………………………………………….. 226
16.5. Replacing Seal ………………………………………………………. 226
16.6. Insertion of Emitters In Small-diameter Soft PE Lateral ….………. 227
16.7. Components of Hydraulic and Metering Valves. The Wear-
sensitive Components ………………………………………………
227
16.8. Sprinkler Tools ……………………………………………………… 227
16.9. Sprinkler components ………………………………………………. 227

XX
16.10. Micro-jets and Mini-sprinklers Components ……………………….. 228
16.11. Vertical Stake ………………………………………………………... 229
16.12. Flow Regulator ……………………………………………………… 229

1
1. INTRODUCTION
1.1 Overview
Water scarcity, soaring energy costs, deterioration of agricultural land and
desertification, threaten agricultural development and food production for the fast
growing world population.
Irrigated agriculture increases twice to ten-fold the yield per land unit, compared with
non-irrigated farming.
Irrigation has its roots in the history of mankind and is even mentioned in the Bible:
“A stream flows from Eden to irrigate the garden...” (Genesis, 10). The
prosperous ancient civilizations developed fresh water sources and delivery systems
that were used for irrigation. In years of drought, people were forced to migrate in
search of water. Unfortunately, innumerable wars were triggered by water scarcity.
Rivers and streams are natural water conveyors. Natural and artificial lakes are used
as water reservoirs. The construction of dams converts segments of rivers' courses
into reservoirs and increases their water storage capacity. Following the introduction
of pumps, pipelines were installed as water conduits. The pipes are made of steel,
aluminum, concrete and plastic materials. Population growth triggered long distance
conveyance of water and promoted the development of water engineering and the
derived science of hydraulics. Irrigation can be regarded as the science of survival.
Gigantic irrigation water supply projects were built throughout the ancient world.
Among them: The 1,200 km long Grand Canal in China. Water supply and irrigation
systems were constructed thousands of years ago in India and Sri Lanka. Today,
engineers are still impressed by the sophistication of ancient water delivery systems
and the irrigation techniques employed. The Romans constructed sophisticated
aqueducts, dozens of km long to deliver water to the new built cities. In Egypt, food
production is fully dependent on the Aswan dam that stores water for irrigation of the
Nile valley and some of the adjoining desert and guarantees food supply to the
population.
Prior to the harnessing of electricity, water had to be conveyed by gravity, along
natural slopes that required the construction of canal networks, for the water flow and
excavating the water path accordingly. This practice had its limitation, since water
could not be conveyed to the lands lying above the water sources. A remarkable
revolution in irrigation technology commenced with the development of pumps that
enabled lifting water above the height of the water source.
Irrigation technologies are classified into two main categories:
a. Surface (non-pressurized) irrigation - furrow, borders, flooding, basins, etc.
b. Pressurized irrigation - sprinkler, spray and drip irrigation (including mechanized
irrigation).
Surface irrigation is regarded as the most wasteful irrigation technology. Irrigation
efficiency is mostly below 40%. In sprinkler and mechanized irrigation, the efficiency
ranges from 60% to 85%. In micro-irrigation, the efficiency can attain 90% - 95%.
Salinization of irrigated lands is the most prevalent trigger of desertification
(conversion of cultivated land to desert). More than one million hectares of arable
land on the globe is lost annually due to salinization.

2
Careful water application in optimal timing and dosage with timely salt leaching when
needed, is a prerequisite for long-run sustainable agriculture and inhibition of
salinization.
Sprinkler irrigation, facilitates the elimination of salinization by leaching the
accumulating salts out of the active root-zone by precise application of the required
water amount.
There are significant differences between surface and sprinkler irrigation in the
pattern of water movement and distribution in the soil. Ponding of water on the soil
surface, in furrows and small basins is common in surface irrigation while water
ponding in sprinkler irrigation indicates the existence of non-permeable soil layers or
exessive water application rate, above the percolation capacity of the soil.
In today's raised standards of living, more attention is given to irrigation of residential
and recreational facilities like home gardens, lawns, sports and golf courses. The
equipment used is partially adapted from agricultural appliances and partially
dedicated gear that is designed specifically for these facilities.
1.2. Surface Irrigation
Surface irrigation is the most widespread irrigation technique used on the globe.
More than 90% of the 280 million irrigated hectares in the world are irrigated by
surface irrigation. Surface irrigation methods can be classified into a number of
techniques. The selection of the method depends on factors such as cropping
technology, climate, soil type, topography, water availability and distribution facilities,
farmers mentality and tradition. The most significant soil factors are the structure and
the physical properties of the soil: soil texture, soil permeability; water flow on the soil
surface and its movement in the soil; field capacity and wilting point; soil aeration. The
most relevant climate factors are precipitation and evaporation rates during the
growing season. Thorough consideration of the above-mentioned factors and
incorporation of advanced techniques as zero slope leveling, SCADA (Supervisory
Control And Data Acquisition) and surge (intermittent, pulsating application of water
flow) irrigation, may facilitate achieving, by this “ancient technology”, efficient water
use, high yields and good produce quality.
1.2.1. Surface Irrigation Methods
Fig. 1.1. Level Border Strip Flooding
1.2.1.1. Level Border Strip Flooding
The level border bed (broad-bed, or paddy) resembles a broad furrow (4 - 18 m
wide), bordered by levees, with zero slope across its width and a longitudinal slope
not greater than 1%. By opening the floodgate at the head of the bed, or by activating
siphons, the bed is filled with water from a ditch or a furrow. This method, which is fit

3
for appropriately leveled topographic structures only, requires some land leveling and
a high water flow-rate. Wetting the bed during a short period of time prevents water
losses beneath the root zone depth. The performance of the system should be
examined by field tests (advance and retreat of water as a function of time). Rice,
banana, alfalfa and other field crops are usually irrigated by this method.
1.2.1.2. Leveled Beds between
Contour Lines
This method is similar to border
strip flooding, however the bed
walls are contour lines as shown
in the illustration to the right.
1.2.1.3. Furrows
The water is distributed in the
field by means of narrow ditches,
each of them delivering water to
one or two rows of plants.
Obtaining good irrigation
efficiency necessitates two
stages of watering. In the first
stage a high flow-rate is sent to
wet promptly the soil surface
along the entire furrow. Then a
second lower flow-rate is
delivered in a longer time period.
1.2.2. Advanced Technologies
Zero slope leveling and surge
irrigation are two procedures
that increase irrigation efficiency
in surface irrigation. These
procedures can be applied with
both flood and furrow irrigation.
1.2.2.1. Dead Level Layout
When high precision land
leveling, supported by laser
sensors is applied, zero slope, dead level layout can be practical. Irrigation efficiency
in this layout can be much higher than in the traditional layouts. Width of area
between borders is limited to 100 – 150 m.
1.2.2.2 Surge Irrigation
The principle of surge irrigation is the splitting of water application to several pulses.
The first pulse is of high volume of water. It is aimed to wet as fast as possible the
entire length of the irrigated bed or furrow without inducing erosion. That first flow
partially seals the upper layer of the soil and enables the next pulses to be of smaller
volumes for longer time periods, rendering even depth percolation along the flow
path. Modern surge irrigation layouts employ automatic surge valves that direct water
in alternating pulses to different sectors of the plot according to pre-planned
timetable.
Fig. 1.2. Leveled Beds between Contour Lines
Fig. 1.3. Furrow Irrigation

4
2. SPRINKLER IRRIGATION
2.1. Introduction
Sprinklers were first introduced at the beginning of the twentieth century as
pressurized irrigation emitters for the irrigation of flower gardens. Later-on they were
adapted to the irrigation of field crops, plantations and greenhouses.
Sprinkler irrigation was extensively expanded after the Second World War when
aluminum became a cheap and widely available commodity and flat land, suitable
for non-pressurized irrigation became scarce. Sprinkler irrigation enables
simultaneous operation of many laterals of sprinklers, facilitates accurate water
measurement and regulation of the water application rate to the water intake rate of
the soil.
2.2. Advantages
a. Sprinkler irrigation is suitable to diverse topographic conditions like
uneven lands and steep slopes that cannot be irrigated by surface
irrigation.
b. A vast selection of emitters and nozzles facilitates the matching of the
water application rate to the intake rate of the soil.
c. Uniform distribution of water in the field renders high water use efficiency.
d. Easy and simple operation, only short training of the operators is required.
e. Capability of accurate measurement of the applied water amount.
f. Prospective high mobility of the irrigation equipment from one field to another.
g. The operation of solid-set and mechaniized systems, minimizes labor
requirement.
h. Feasibility of frequent - small water dosage applications for germination,
cooling, frost protection, etc.
i. The closed water delivery system prevents contamination of the flowing
water, decreasing the occurrence of emitter clogging.
j. Convenient blending of fertilizers with the irrigation water.
k. Handy integration with automation and computerized irrigation control devices.
2.3. Disadvantages and Limitations
a. High initial investment.
b. Extra cost of the energy consumed for creation of water pressure.
c. Sensitivity to wind conditions.
d. Water losses by evaporation from soil surface, the atmosphere and plant
canopy.
e. Induction of leaf-diseases in overhead irrigation.
f. Hazard of salt burns on wetted foliage in overhead irrigation.
g. Washout of pesticides from the foliage in overhead irrigation.
h. Interference of irrigation with diverse farm activities like tillage, spraying,
harvesting, etc.
i. Hazard of soil surface encrustation and enhancement of runoff from soil
surface.
j. Water losses in plot margins.

5
2.4. Definitions
2.4.1. Pressure: a force acting on an area, expressed in units of kg/cm2
, bars,
atmospheres or PSI (Pounds per Square Inch).
2.4.2. Water head: the pressure at the base of a water column, expressed in meter
units. The head in the bottom of a water column 10 m. high, is 10 m. = 1 bar. ≈ 1 atm.
2.4.3. Water amount: measured in volume units. In the metric system the common
units are liter (l) and cubic meter (m3
) (1,000 l = 1 m3
).
2.4.4. Water flow-rate (discharge): the amount of water flowing through a certain
cross-section per time unit. In the metric system the units are: m3
/h or liter/h (l/h).
2.4.5. Wetting diameter: the diameter of a circle of soil surface, wetted by a
certain sprinkler = twice the wetting radius of the sprinkler. Measured in meters.
2.4.6. Sprinkler spacing: the spacing between the sprinklers along and between
the sprinkler laterals. For example: 12 m x 18 m.
a. Rectangular Position b. Diagonal Position
Fig. 2.1. Sprinkler Spacing Positions
2.4.7. Irrigation Intensity: the force of the water drops exerted on the soil surface
during precipitation. The intensity depends on the number of drops, their size, their
velocity and the impact angle at which they hit the soil surface. The intensity is
expressed in qualitative terms: high, medium, low.
a. High Intensity – Rough Droplets b. Low Intensity – Fine Droplets
Fig. 2.2. Irrigation Intensity

6
2.4.8. Application (precipitation) rate: the amount of water applied to an area
unit per a unit of time: 1 mm/h = 1 m3
per 0.1 Ha/h = 10 m3
per Ha per hour.
2.4.8. Irrigation interval: The time interval between two water applications = the
period between the start of one irrigation cycle and the start of the following one.
2.4.9. Irrigation cycle: The period between the beginning and the termination of
one irrigation event of a certain area.
2.4.10. Wind velocity: expressed in meters per second (m/sec.) or km/h units.
Fig. 2.3. The Influence of Wind on the Uniformity of Water Distribution
2.4.11. Nominal pipe diameter: The nominal diameter of steel and asbestos-
cement pipes, up to 10" is the internal diameter, measured in inches (1 inch = 25.4
mm.) In wider diameters, as well as in aluminum, plastic pipes and tubes the nominal
diameter is the external diameter, measured in inches in aluminum pipes and in mm.
in pipes made of plastic materials.
2.5. Sprinkler Types
In the early years, water under pressure had been applied by nozzles
mounted along oscillating galvanized cast iron pipes. The oscillating
movement was driven by the inherent water pressure in the irrigation
system. Another means for water distribution was perforated tin pipes laid on
the soil surface.
a. Skinner Oscillating Pipe System b. Perforated Pipe (Perf-O-Rain)
Fig. 2.4. Outdated Pressurized Irrigation Systems After Benami & Ofen 1993
Contemporary sprinklers are made of metal and plastic materials. The sprinklers are
mounted on metallic or plastic risers of various heights, corresponding to the
irrigation technique and the crop canopy height.

7
2.5.1. Sprinkler Classification
Sprinklers are classified according to their function, pattern of operation, working
pressure, flow-rate, materials from whom they are made, etc.
2.5.1.1. Sprinkler Function
Sprinkler function classification is based on the crop and growing technologies, for
whom the sprinkler type is designated.
2.5.1.1.1. General use: Impact sprinklers with jet angle of 300
, one or two nozzles, are
used for overhead irrigation in field crops, forage and vegetables, as well as in
overhead irrigation in orchards, in hand move, solid-set and towed laterals.
2.5.1.1.2. Under-canopy sprinklers: used for irrigation in orchards. The jet angle is 40
-
70
. This group is comprised of under-canopy impact-hammers, turbo-hammers,
whirling sprinklers, mini-sprinklers, microsprinklers and microjets – rotors, spinners,
sprayers and ray-jets (multiple jets). These emitters are used also for solid-set
irrigation in vegetables and flowers in the open field and greenhouses and in
mechanized irrigation.
2.5.1.1.3. Gun sprinklers: Used for irrigation of wide-scale field crops and forage
areas, may be used as stand-alone units, in laterals, moved by hand or installed on
self-propelled travelers and in center pivots and lateral move machines, as end-
guns.
2.5.1.1.4. Part circle sprinklers: These sprinklers are installed at lateral ends, plot
margins and in specific situations in mechanized laterals in order to avoid water
losses beyond plot borders and wetting of roads and sidewalks.
2.5.1.1.5. Regulated sprinklers: May be pressure-compensated or flow-regulated.
Simplifies design and operation in harsh topography conditions.
2.5.1.1.6. Pop-up sprinklers: Used in irrigation of lawns, golf courses and residential
areas.
2.5.1.1.7. Small-size impact and turbo-sprinklers: are used for under canopy irrigation
in orchards, and overhead irrigation in open field and protected vegetables and
flowers.
2.5.1.1.8. Static sprinklers are used in small residental gardens.
2.5.1.2. Pattern of Operation
Sprinklers are operated by water pressure. A water jet that is ejected from a nozzle
activates the moveable component of the sprinkler.
2.5.1.2.1. Rotating impact sprinkler: The water jet, emitted from the nozzle, hits the
hammer arm, pushing it in counter-clockwise direction. A spring returns the arm
back. Its strike on the sprinkler body results in rotary movement of the body in the
opposite direction. The impact sprinklers are fitted with one, two or three nozzles.
This sprinkler type is manufactured in diverse configurations. With a 300
ejection
angle it is used for overhead irrigation of field crops and orchards. For under-canopy
irrigation of orchards the recommended jet angles are 40
-70
. Initially. the sprinklers
were made of metal, but later-on, plastic materials were also used. The wear of
moving parts and nozzles made of reinforced plastic, is much lower than that of
metallic ones. Although impact sprinklers are highly reliable, they require strict
routine maintenance to guarantee consistent operation along time.
2.5.1.2.2. Turbo-hammer sprinkler: The water jet stirs a grooved wheel that hits the

8
hammer. The impact of the hammer rotates the sprinkler. The turbo-hammer
sprinklers are made of plastic material and are used for the irrigation of orchards,
vegetables and gardens at low flow-rates.
Fig. 2.5. Impact-Hammer Sprinkler Fig. 2.6. Turbo-Hammer Sprinkler
From "Naan" Brochure
2.5.1.2.3. Gun Sprinklers
Fig. 2.7. Gun Sprinkler (Rain-gun)
Big size hammer sprinklers are made of brass with two or three nozzles. The working
pressure is high (4 - 8 bars). The sprinkler flow-rate range is 6 - 60 m3
/h. Gun

9
sprinklers are used for irrigation of forage and field crops in solid-set schemes, in
Center-Pivot and Lateral-Move irrigation machines and as a traveling gun in "stand-
alone" configuration.
Fig. 2.8. Stand-alone Gun-sprinkler with Stabilizer in the Field
2.5.1.2.4. Pop-up sprinklers - commonly used for lawn and golf courses irrigation. The
sprinkler pops upwards at the beginning of the irrigation and falls back after shut-
down into its underground housing, where it remains in stand-by position until the
next irrigation. In the underground stand-by position it allows the undisturbed use of
lawns, parks or golf courses, and does not interfere with lawn mowers' operation.
There is a wide-range of pop-up sprinkler types, including part-circle sprinklers, as
well as rise-ups of various heights.
2.5.1.2.5. Gear-driven sprinklers are used mostly in residential and public lawns
irrigation. Some gun sprinklers are also driven by a turbine and velocity reduction
gear.
2.5.1.2.6. Rotor and rotary stream sprinklers often incorporate a small water turbine
which, by means of reducing gears, provides for slow, continuous nozzle or nozzle
head rotation. Gear-drive mechanisms require clean water to prevent clogging and
wear.

10
a. Gear-driven b. Part-circle Impact c. Pop-up Sprinkler Irrigating A Lawn
Fig. 2.9. Pop-up Sprinklers
2.5.1.2.7. Static sprinklers – are
made of brass or rigid plastic
materials, without moving parts.
These sprinklers are used
mainly in residential gardens.
They irrigate a full or partial
circle. The wetting range is
smaller as compared to rotating
sprinklers.
Manufacturers' catalogs provide
the essential data about the
specifications and performance
of the sprinklers. Information is
given about flow-rate (Q), and
the effective wetting diameter (D), in the range of the allowed working pressure (P).
Additional data relate to the recommended spacing between sprinklers, the
precipitation rate and distribution uniformity.
a. Fixed Angle b. Adjustable Angle
Fig. 2.10. Part-circle Static Sprinklers

11
2.5.2. Components of Impact Sprinklers
2.5.2.1. Base: It is the connection to
the riser. It has internal or external
thread, manufactured in diameters of
0.5” - 3".
2.5.2.2. Tube: It is inserted in the base
and fixed to the body of the sprinkler.
Between the base and the tube there
are located 1 - 3 seals that function as
bearings to smooth the rotation of the
sprinkler and minimize wear from the
friction of the tube with the base.
2.5.2.3. Sand protection mechanism:
Consists of a thrust spring and an
external plastic sleeve that prevents
the intrusion of sand and grit from the
outside.
2.5.2.4. Body: Accommodates the
housings in which the nozzles are
fitted and carries the moving parts of
the sprinkler. The body can be of one
of the configurations:
2.5.2.4.1 Bridge: In some sprinkler
types, the hammer is connected to the
body by means of a shaft fixed to a
bridge between two vertical supports.
The sprinkler rotation is activated by
the impact of the hammer on one of
the supports. The reverting spring
surrounds the shaft.
2.5.2.4.2. Crown: Other types of sprinklers are bridge-less. The spring is connected
above the hammer by a plastic or metallic crown. Under frost or dusty conditions, an
external plastic cover protects the spring.
2.5.2.5. Spring: Stimulates the rotation of the sprinkler by returning the hammer arm
that was activated by the water jet that was emitted from the nozzle. In the Bridge
Sprinkler, the spring is fixed within a fastening frame while in the Crown Sprinkler
the spring is not fixed within the frame.
In a Crown Sprinkler, the spring tension can be adjusted to the size of the nozzle and
the water head. Springs are commonly made of copper, however when using
reclaimed water, stainless steel springs are recommended.
2.5.2.6. Hammer arm: Activates the sprinkler rotation. Wetting range and distribution
are determined by the number of strikes per minutes (30-60). There are two types of
hammer arms:
2.5.2.6.1. Spoon drive: a rigid arm without moving parts, used in medium and high
pressure conditions.
2.5.2.6.2. Wedge (dual action) drive: a plastic wedge is fitted on a shaft at the edge of
Fig. 2.11. Impact Sprinkler Components

12
the arm. Used in low-pressure conditions prone to malfunction for small diameter
wetting.
2.5.2.7. Buffer: Absorbs partially the energy of the hammer impact to Minimize the
wear of the body by the strikes and acts as a guide to the arm.
a. Spoon Drive b. Wedge (Dual Action)
Drive
c. Part-circle Sprinkler
d. Bridge Sprinkler e. Crown Sprinkler f. Protected Crown Sprinkler
Fig. 2.12. Configurations of Impact Sprinklers
2.5.2.8. Nozzles
Each sprinkler is fitted with one, two or three nozzles. The nozzle type and size
determine the flow-rate, the distribution pattern and uniformity and the droplets size.
Nozzles are prone to wear and change of the flow-rate as well as the water
distribution pattern. Irrigation water containing sand is abrasive and may expand the
nozzle aperture and increase the flow-rate, as well as change the distribution pattern.
Plastic nozzles are more resistant to abrasion than metallic ones.
There are different types of nozzles. A circular cross-section of the nozzle's aperture,
indicates a long range jet while an elliptic or half-crescent cross-section indicates a
short-range wetting diameter. Maximum range is achieved by a jet angle of 300
related to the soil surface while in under-canopy sprinklers, 40
and 70
angles are
dominant. Nozzle size is expressed as its diameter in mm. Since the nozzle cross-
section is not always circular, size definition may be quoted as the nominal size that
is equivalent to a nozzle of circular cross-section with an identical flow-rate.
Ordinarily, the nozzle size is stamped on the nozzles. In plastic nozzles it is common

13
to distinguish between different sizes by different colors.
Fig. 2.13. Nozzle Types After S. Elhanani, 1961
The nozzle flow-rate (Q) depends on the water pressure head, the diameter of the
nozzle's aperture and its friction coefficient.
(Eq. 2.1)
Where:
Q = Nozzle flow-rate (discharge), expressed as liters per hour (l/h)
P = Water pressure head, expressed in m (meters)
D = Nozzle nominal diameter, expressed in mm
C = Friction coefficient. Its value for small nozzles, up to 5.5 mm. = 0.95.
For medium size nozzles, 5.5-8 mm. = 0.9
For large nozzles, over 8 mm. = 0.85.
The pressure dependent flow-rate for a certain nozzle is:
(Eq. 2.2)
Where:
Q1 = The flow-rate at the P1 head.
Q2 = The flow-rate at the P2 head.
2.5.3. The Jet Angle
The angle of the water stream ejected from the nozzle determines the range, the
sensitivity to wind and the water distribution pattern. Larger angles, up to 450
, render
longer range but higher sensitivity to wind. For the irrigation of field crops a 300
angle
is common, while for under-canopy irrigation in orchards, the prevalent angles are 40
- 70
.
Fig. 2.14. Jet Angles

14
a. Impact Sprinklers b. Turbo Sprinkler
Fig. 2.15. Low-volume Under-canopy Sprinklers
2.5.4 Sprinkler Flow-rate
Sprinklers are classified into three groups in respect to their flow-rate.
2.5.4.1. Low flow-rate: 20 - 500 l/h. Used in orchards, greenhouses and gardens.
2.5.4.2. Medium flow-rate: 500 - 5000 l/h. Used mainly for overhead irrigation in
field crops, orchards, fodder and vegetables.
2.5.4.3. High flow-rate: Above 5 m3
/h. Used in wide-spacing positioning and
mechanized irrigating machines.
2.5.5. Working Pressure (Head)
2.5.5.1. Low pressure: Up to 2 bar (20 m.). Microjets, microsprinklers, mini-
sprinklers, whirling sprinklers and turbo-hammer sprinklers.
2.5.5.2. Medium pressure: 2 - 5 bar (20 - 50 m.). Impact sprinklers.
2.5.5.3. High pressure: Above 5 bar (50 m.). Gun sprinklers and large impact
sprinklers.
2.5.6. Sprinkler Spacing, Selection And Operation
There are a number of elementary factors that have to be considered in the selection
of sprinklers according to distinct operating conditions:
a. The flow-rate and wetting diameter at different degrees of pressure.
b. Crop spacing.
c. The desired range of the pressure and the recommended spacing between
emitters.
d. Soil intake rate. The application rate has to be lower than the soil intake rate.
e. Wind conditions during the irrigation season.
f. Water quality.
(Eq. 2.3)
g. Wind velocities in the plot have to be considered in the selection of the sprinkler
type as well as the spacing between the sprinklers. As the wind velocity is higher, the

15
spacing will be smaller.
Table 2.1. Wind Velocity Definitions:
No wind 0 - 1.0 m/sec.
Medium wind velocity 1.0 - 2.5 m/sec.
Strong wind 2.5 - 4.0 m/sec.
Very strong wind above 4.0 m/sec. Sprinkler overhead irrigation is
not recommended.
Table 2.2. Recommended Spacing between Sprinklers
Positioning Wind velocity m/sec Spacing
No wind 60% of wetting diameter
2 50% of wetting diameter
3.5 40% of wetting diameter
Rectangular
More than 3.5 30% of wetting diameter
No wind 65% of wetting diameter
2 55% of wetting diameter
3.5 45% of wetting diameter
Diagonal
More than 3.5 30% of wetting diameter
The diagonal (staggered) position allows for wider spacing between sprinklers under
windy conditions.

16
3. MICRO-EMITTERS
3.1. Introduction
The term micro-irrigation relates to
pressurized irrigation technologies
employing water emitters with tiny
apertures that deliver water at a low flow-
rate. The micro-emitters are classified into
two principal groups:
a. Emitters that distribute water through
the air: micro-sprinklers, rotors, spinners,
wortex emitters, vibrating emitters,
microjets, sprayers, rayjets and foggers.
There is no definite difference between
sprinklers for irrigation and the micro-
emitters that distribute water through the
air in micro-irrigation. There is a
controversy about the distinction between
macro and micro emitters – the common
division boundary is 60 – 120 l/h.
b. Emitters that deliver the water directly
to the soil – drippers and bubblers. These
emitters are not covered in this booklet.
The primary use of non-drip micro-
irrigation technology is for the irrigation of
orchards and greenhouses. Unlike sprinkler irrigation of field crops and vegetables, in
which the desired result is rain-like uniform distribution over the entire irrigated area,
in orchard irrigation, full cover and even distribution of water, is unattainable and is
not necessary. The objective of orchard irrigation is to deliver a uniform amount of
water to each tree and to distribute it in compliance with the distribution of the root
system in the soil.
There are still orchards that are irrigated by overhead sprinklers, particularly for frost
and hot spell protection. In these orchards, the sprinklers employed are of the same
types that are used for irrigation of field crops. Obviously, because of the interference
of the canopy in orchards, an even distribution of water on the soil surface cannot be
achieved. Overhead irrigation in orchards is favored when frost protection is a
significant factor in the selection of the irrigation technology. However there are many
drawbacks in the use of overhead sprinkler irrigation in orchards. It interferes with
pest management by leaching the pesticides from the canopy and enhances leaf and
fruit diseases. The energy consumption in overhead irrigation is higher than in under-
canopy irrigation.
The dominant technology in orchard pressurized irrigation, therefore, is under-canopy
irrigation by low-volume, low-angle sprinklers, mini and micro-sprinklers, as well as
microjets, sprayers and drippers.
Recently, the use of micro-sprinklers had been extended to irrigation of vegetables
and field crops.
Micro-sprinklers are commonly built of rigid plastic materials. They are much smaller
Fig. 3.1. Diverse Micro-emitters

17
and cheaper than conventional sprinklers.
3.2. Micro-emitter Types
There are four emitter types:
a. Static Micro-emitters
b. Vortex Emitters
c. Vibrating Micro-jets
d. Micro-sprinklers
3.2.1. Static Micro-emitters (Micro-jets)
Static micro-jets have no moving components and are classified into three groups:
3.2.1.1. Sprayers – the water stream is fragmented into tiny droplets by means of a
static deflector. Water is distributed in a relatively short range and the tiny drops are
wind-sensitive.
In sprayers, the deflectors form a fine spray, providing uniform coverage that is
essential in sandy soils. They are particularly useful for frost protection. However,
they are susceptible to wind and bring about relatively high evaporation losses.
The deflectors are produced in diverse styles that allow sector coverage from 450
to
3600
.
3.2.1.2. Misters and Foggers – water droplets are smaller than in sprayers. Spread
range is shorter. Wind sensitivity and evaporation losses are higher than in sprayers.
This type is mostly used to increase the humidity in greenhouses and poultry coops,
as well as for frost protection in orchards.
3.2.1.3. Multi-jet Emitters (Ray-jets, Fan-jets) – the water stream is splitted into 4 –
20 discrete jets. The wetting range is extended and wind sensitivity is reduced.
Absence of moving parts increases its reliability compared with rotating micro-
sprinklers.
a. Static Sprayer b. Ray-jet c. Mister d. Fogger
Fig. 3.2. Static Micro-jets

18
3.2.1.4. Vortex Emitters
These emitters have no moving parts.
The water whirls in a circular vortex
chamber that delivers a low flow-rate
through a relatively large opening that
reduces clogging hazard. The area
wetted by this emitter is smaller than the
wetted area by micro-sprinklers.
3.2.1.5. Vibrating Micro-jets
Water ejected from a circular orifice
strikes a deflector and triggers it to
vibrate. The vibration of the deflector
creates larger drops than those of
sprayers, increases the distribution
range and reduces evaporation and
sensitivity to wind. The emitter is simple
and reliable.
3.2.2. Micro-sprinklers
Micro-sprinklers are manufactured in different configurations. Their distinctive
characteristic is the rotation of the deflector or the nozzle around a central shaft. This
facilitates wetting of larger area, compared with micro-sprayers. However, the
inclusion of moving parts increases the susceptibility to the interference of external
factors, as well as wear, tear and breakage of its components. During harvest
operations, fruit pickers sometimes step on and break micro-sprinkler emitters and
stakes. Herbicide spray booms and other tillage equipment can also damage the
emitters.
Most types of micro-sprinklers are modular. Many components are interchangeable
and enable the modification of flow-rate, range, distribution pattern and droplet size,
matching to specific requirements, at low cost.
Fig. 3.5. Modular Micro-emitter – Water Spreading Pattern
Deflectors in diverse configurations allow sectorial coverage from 450
to 3600
.
Fig. 3.3. Vortex Sprayer Fig. 3.4. Vibrating
Micro-jet

19
3.2.3. Micro-sprinkler Types
3.2.3.1. Rotors are manufactured in
different configurations. The central
shaft with the nozzle is static. The
water jet hits a rotating deflector that
distributes water in larger area than
the vibrating emitters.
3.2.3.2. Spinners - the nozzle rotates
and further increases the jet range,
that is bigger than that of the
rotators.
The movement of components in
micro-sprinklers increases their
sensitivity to the interference of
factors like weeds, precipitates and
splashed soil particles. It also
accelerates wear and tear. The
damage danger from herbicide
sprayer booms and other tillage
equipment increases during harvest
operations.
Rotors' and spinners' configuration
affects their sturdiness. There are two
principal forms: unilateral and bi-
lateral supports that hold the
rotor/spinner swivel. Bi-lateral
support provides improved holding to
the rotating spinner or deflector, but
the two vertical supports create dry
sectors behind them.
a. Micro-sprinkler Components b. Interchangeable Components
Fig. 3.8. Modular Micro-sprinkler
a. rotor b. spinner
Fig. 3.6. Rotating Micro-sprinklers
a. Unilateral Support b. Bi-lateral Support
Fig. 3.7. Micro-sprinklers Configurations

20
Pressure compensating and flow regulated micro-emitters are particularly suitable for
irrigation of steep sloping plots.
Micro-sprinkler systems require a higher volume of water supply compared with on-
surface or buried drip systems.
Dedicated micro-emitters had been developed for use on laterals in mechanized
irrigation. They will be related in the chapter on mechanized irrigation.
3.3. Emitter Mounting
Emitters can be mounted directly on the lateral, attached by a barbed or threaded
protrusion. The most prevailing connection to the lateral is by means of a small
diameter micro-tube. The vertical position of the emitter is secured by a stake,
stabilizing rod or a weight (in upside-down positioning In greenhouses and
mechanized irrigation). The emitter is raised 10 – 25 cm above soil surface to prevent
water blockong and disturbance in the rotation of the moving parts of micro-sprinklers
by weed interference and splashed soil particles. The micro-tubes are 50 – 100 cm
long and 4 – 8 mm in diameter. To prevent excessive head losses, tube diameter of
at least 6 - 8 mm is required for emitter flow-rates over 60 l/h and when the micro-
tube length is over 60 cm.
In greenhouses, micro-sprinklers, misters and foggers are frequently used to
increase the relative humidity and lower the temperature of the ambient atmosphere.
The misters and the foggers emit tiny droplets and are operated intermittently in
pulses. These emitters are often mounted upside-down with the trajectory angle
slanted downwards, in order to avoid hitting the glass or plastic ceiling.
Threaded micro-emitters are installed on 1
/2
"
– 3
/4" rigid PVC risers. Barb micro-
emitters can be mounted directly on the lateral. In greenhouses, micro-emitters may
be installed upside down for overhead irrigation and misting. Weights are hung to
stabilize them vertically.
Micro-sprinklers are prone to clogging, but when clogging occurs it is quickly visually
noticed and easily cleaned. Some emitters are equipped with a small integral valve to
enable local water shut-down during the cleaning process.
Some types of micro-sprinklers are prone to clogging by the eggs and excretions of
spiders, ants and other insects. Insect-proof devices have been developed to prevent
these obstructions. Spiders are capable of tying up spinners and halt their rotation.
Micro-sprinkler operation can also be disturbed by sand that is splashed upward from
the soil surface when hit by droplets from adjacent emitter.
Blockage that is not removed on time in orchards that employ one emitter per tree
may result in lower yields and reduced produce quality.

21
3.4. Water Distribution Patterns
The emitter’s water distribution pattern is determined by its outlet (nozzle) and
deflector geometry, trajectory angle, droplet size, pressure and flow-rate. The higher
the trajectory angle (up to 300
) and the larger the droplet size and flow-rate, the larger
will be the wetting diameter in the range of the designed working pressure. The
patterns of water distribution and wetting depth in the wetted area vary with the
emitter type. In some emitters the wetting pattern is triangular. These emitters are
suitable for overlapping and full wetting of the soil surface. In some emitters the
deeper wetting depth is adjacent to the emitter while in others the water is distributed
more evenly in most of the wetted area.
a. Sprayer on
Stake
b. Upside-down Misters
with Stabilizing Weights
c. Micro-sprinkler on Rod d. Upside-down
Micro-sprinkler
Fig. 3.9. Mounting Alternatives of Micro-emitters

22
Fig. 3.10. Water Distribution by Micro-sprinkler at Different Flow-rates (example)
Fig. 3.11. Multiple-jet (Fan-jet) Emitter's Distribution Patterns From "Bowsmith" Brochure
3.5. Pressure Compensation
Micro-sprinklers and micro-jets can be pressure compensating. That facilitates longer
laterals and uniform application in harsh topographic conditions.

23
4. THE IRRIGATION SYSTEM
4.1. Introduction
The performance of a pressurized
irrigation system depends on the
available water sources, reservoirs and
pumping facilities. The efficiency of
energy use and water application is
determines by the properties of the
pumping unit and the water delivery and
distribution network.
4.1.1. The Main Components of the
Irrigation System
a. The pumping unit
b. Supply pipeline
c. Control head
d. Mains and sub-mains
e. Manifolds
f. Laterals
g. Risers
h. Emitters
i. Accessories: Valves, check-valves (backflow preventers), air release
valves, vacuum valves, filters, couplers, risers, pressure and flow
regulators, fertigation devices, etc.
4.1. The Pumping Unit
While the water emitters are the core of the pressurized
irrigation system, the pump is its priming element. The
pump lifts water from the source (well, river, lake,
reservoir, canal, etc.,), increases its energy and
governs the capacity and the working pressure in the
system.
Pumps are activated by electric motors or internal
conbustion engines and deliver water under pressure
to the irrigation system. Water supply can be attained
also from external water suppliers that are responsible
for the appropriate pressure head in the connection
point with the irrigation system. In some cases, the
pressure in the supply connection point is too low and
the farmer has to boost the water pressure by means of
a booster pump.
The energy use efficiency of electric motors is much
higher than that of combustion engines. Hence, If
electricity is available, it will be the preferred choice. If
there is no electricity source, pumps can be operated by
a diesel, kerosene or gas motor.
The efficiency of the pumping unit is an important factor
in water discharge, pressure head and energy costs.
Fig. 4.1. Schematic Plot Irrigation System
Layout After NDSU Extension Publication
Fig. 4.2. Electric Water
Pumps

24
The pumping unit is composed of three major components: The power unit, the
transmission to the pump (drive or gear head) and the pump itself.
4.1.1. Pump Performance Terminology
4.1.1.1 Pump performance - Capacity is expressed as volume per time unit, e.g.:
cubic meters per hour (m3
/h) and the pressure as meters (m.) of head. In the
imperial unit system it is designated as gallons per minute (gpm) and feets of
head. In general, in a specific pump, a trade-off occurs between head and capacity.
Increase in head brings about the decrease in capacity and vice versa.
4.1.1.2. Head refers to gains or losses in pressure due to change in topography and
friction in the network.
The following terms are used when referring to lift or head:
4.1.1.3. Static Suction Lift - The vertical distance from the water surface in the
reservoir/well to the centerline of the pump's impeller.
4.1.1.4. Maximum suction lift - Pumps lift water with the support of atmospheric
pressure. The practical suction lift, at sea level, is ~10 m. Later on, the pump imparts
additional pressure to the water and discharges it from the casing.
4.1.1.5. Static Discharge Head — the vertical distance from the discharge outlet to
the point of discharge or liquid level when discharging into the bottom of a tank.
4.1.1.6. Dynamic Suction Head — the static suction lifts plus the friction in the
suction line. Also referred to as Total Suction Head.
4.1.1.7. Dynamic Discharge Head — the static discharge head plus the friction
in the discharge line. Also referred to as Total Discharge Head.
4.1.1.8. Total Dynamic Head — the Dynamic Suction Head plus the Dynamic
Discharge Head. Also referred to as Total Head.
4.1.1.9. Net Positive Suction Head (NPSH) – the head measured in the suction
point.
4.1.1.10. Net Positive Suction Head required (NPSHr) - The minimum head
requirement in the pump inlet. It takes into consideration head losses in the suction
piping and connections, the elevation and absolute pressure of the fluid in the suction
piping, the velocity of the fluid and the temperature, including what goes on in the eye
of the pump's impeller. Some of these factors add energy to the fluid as it moves into
the pump, and others subtract energy from the fluid. There must be sufficient energy
in the fluid for the impeller to convert this energy into pressure and flow. If the energy
is inadequate we say that the pump suffers inadequate NPSH. The NPSHr is actually
the minimum suction pressure necessary to keep the pumped fluid in a liquid state
and avoid cavitation in the pump.
4.1.1.11. Net Positive Suction Head available (NPSHa) The head available at the
pump inlet. It has to exceed the NPSH required.

25
4.1.2. Pump Types
There is an extensive selection of pump types. Only a few of them are used in water
pumping.
Fig. 4.3. Pump Type Classification According to the Hydraulic Institute (HI) Standards
All pumps may be divided into two major categories, based on the pattern in which
they transmit energy to the pumped fluid:
a. Kinetic (dynamic) pumps
b. Positive displacement pumps
1) In kinetic pumps, continuously added energy increases the velocity of the
fluid. Later on, this velocity is converted into pressure. In centrifugal pumps, energy is
imparted to the fluid by centrifugal action, by impeller or lifting action of a screw within
a close-clearance bore.
2) In positive displacement pumps, intermittently added energy directly
increases the pressure of the fluid. The reciprocating action of one or several pistons,
or a squeezing action of diaphragms, meshing gears, lobes, or other moving
elements, displaces the pumped fluid from the suction point to the discharge outlet.
These pumps have limited capacities and are not suitable for pumping when large
volume of water is required for irrigation or drainage. They are used mainly for
injection of chemicals into irrigation systems and will be related in the chapter on
fertigation.
4.1.2.1. Comparison of the Main Features between Kinetic and Positive
Displacement Pumps
4.1.2.1.1. Flow-rate and Pressure Head
The two types of pumps behave differently regarding pressure head and flow-rate:

26
a. The Centrifugal Pump's flow varies, dependending on the system pressure
(head).
b. The Positive Displacement Pump's flow is constant, regardless of the system
pressure (head). Generally, Positive Displacement Pumps are capable to
generate higher pressure than Centrifugal Pumps.
4.1.2.1.2. Capacity and Viscosity
Another significant difference between these two pump types is the effect of viscosity
on the capacity:
a. In Centrifugal Pumps the flow decreases when the viscosity is increased.
Centrifugal Pumps are inefficient at even modest viscosity.
b. In Positive Displacement Pumps the flow increases when viscosity is
increased. Liquids with high viscosity fill the clearances of a Positive
Displacement Pump causing a higher volumetric efficiency. The Positive
Displacement Pump is better suited for high viscosity applications. That
property is irrelevant to pumping of water, since water viscosity changes only
slightly as a function of temperature change.
4.1.2.1.3. Mechanical Efficiency
The pumps behave in different patterns considering mechanical efficiency.
a. In Centrifugal Pumps changes in system pressure (head), affects significantly
the flow-rate.
b. In Positive Displacement Pumps changes in system pressure have little or no
effect on the flow-rate.
4.1.2.1.4. Net Positive Suction Head - NPSH
Another difference relates to the Net Positive Suction Head (NPSH).
a. In a Centrifugal Pump, NPSH varies as a function of flow determined by
pressure.
b. In a Positive Displacement Pump, NPSH varies as a function of flow
determined by speed. Reducing the speed of the Positive Displacement Pump
reduces the NPSH.
4.1.2.1.5. Pump Velocity
a. Since in centrifugal pumps the energy is imparted to the liquid by means of
centrifugal force, the pressure generated is proportional to the square of the
speed of the impeller.
b. A positive displacement pump is simply pushing the liquid against whatever
resistance that is put on its way. The speed at which it runs is irrelevant – the
pressure it can generate is only a function of how mechanically strong the
machine is.
4.1.3. Suction Lift of a Pump
The theoretical suction lift or suction head is equal to atmospheric pressure divided
by the density of the fluid being pumped. In case of plain water (cold) it is 10.33
meters or 33.9 feet. Hence for other fluids maximum suction lift is:

27
(Eq. 4.1)
4.1.4. Kinetic Pumps
Kinetic pumps are dynamic devices that impart the energy of motion (kinetic energy)
to a liquid by use of a rotating impeller, propeller, or similar devices.
Kinetic pumps are classified into two main groups:
a. Centrifugal / Turbine pumps
b. Special pump types: centrifugal screw, rotating case, viscous drag and vortex
action.
4.1.4.1. Centrifugal Pumps
The advantages of centrifugal pumps brought about that they became the pump of
choice in water delivery.
Compared with positive displacement pumps, the main benefits are smaller size and
lower weight. Centrifugal pumps attain much larger flows in a compact device,
without pressure and flow pulsations. They are much easier to control, unlike
positive displacement pumps in which flow-rate can only be controlled by varying the
speed, the flow-rate of a centrifugal pump can be adjusted simply by means of
discharge throttling.
Centrifugal pumps can be classified by impeller shape and characteristics. Impellers
are grouped according to the major direction of flow with respect to the axis of
rotation.
a. Cutaway b. Pump Components
Fig. 4.4. Centrifugal Pump
With respect to type of impeller, all centrifugal pumps can be classified into three
groups:
a. Radial-flow pumps
b. Axial-flow pumps
c. Mixed-flow pumps
Centrifugal pumps can also be classified into four major groups depending on their
design and application.

28
a. Volute pumps
b. Turbine pumps
c. Diffuser pumps
d. Propeller pumps
Centrifugal pumps
employ a rotating
impeller to move water
through a piping system.
The rotating impeller
increases water pressure
by transformation of kinetic energy. As water is drawn into the pump, the rotating
impeller releases kinetic energy into the water. When the water exits outward through
the impeller vanes, the kinetic energy (velocity) is converted into pressure.
Centrifugal pumps must be primed by filling them with water before they can be
activated. Water has to flow into the pump when pressure at the center (eye) of the
impeller is reduced below atmospheric pressure.
Volute pumps and Turbine pumps are the two main centrifugal pump categories
that control and maintain water pressure differently.
4.1.4.1.1 Volute Centrifugal Pumps
The primary difference between volute pumps and turbine pumps is the presence or
lack of diffusion vanes. In volute pumps there are no diffusion vanes, but the outer
casing is a spiral. This shape reduces water velocity (and eventual pressure) by
creating an equal flow of water as it moves around the spiral toward the discharge
nozzle. The spiral is called a volute.
Volute centrifugal pumps are used to pump from reservoirs, lakes, streams and
shallow wells. They are also used as booster pumps in supply and irrigation
pipelines. The impeller converts energy from the motor to the water by centrifugal
force. The rotation of the impeller develops centrifugal forces that drive the water
towards the impeller's external edge. The impeller is surrounded by a volute casing.
The volute or stationary diffuser ring converts the kinetic energy into pressure energy
and delivers the fluid to the pump discharge outlet. The horsepower input is
proportional to the pumping water discharge and the pressure level.
As the resistance of a system increases, the head will also increase. This in turn
causes the flow-rate to decrease and will eventually reach zero. A zero flow-rate is
only acceptable for a short period without causing to the pump to burn-out.
Centrifugal pumps are designed for either horizontal or vertical operation. The
horizontal configuration employs a vertical impeller connected to horizontal drive
shaft. Horizontal centrifugal pumps are the most common in irrigation systems. They
are relatively cheap, require less maintenance, easier to install and more accessible
for inspection and maintenance than the vertical pumps.
Since centrifugal pumps must be "primed" - completely filled with water, before they
can operate, the suction line and the pump have to be filled with water and freed of
air.
Air tight joints and connections are particularly important on the suction pipe. Priming
a pump can be done by hand operated secondary vacuum pumps, internal
combustion engine or motor powered secondary vacuum pumps.
Fig. 4.5. Different Flow Patterns in Centrifugal Pumps
From Grundfos Pump Handbook

29
Vertical centrifugal pumps may be
mounted so that the impeller is
immersed continuously in the water. In
this case, priming is unnecessary.
There are self-priming horizontal
centrifugal pumps for special purpose
use. Self priming is particularly
essential where there are frequent
electrical power outages. Self priming
is requested also with the new
generation of control panels for center
pivots, where automatic restart is a
programmable function.
4.1.4.1.2. Turbine Pumps
In a turbine pump, multiple diffusion
vanes surround the rotating impeller.
As water is released from the center
(eye) of the impeller, it spins outwards
as the impeller rotates. Around the impeller’s circumference are constructed diffusion
vanes - passages that widen gradually and open into a circular or spiral casing. The
main role of the diffusion vanes is to gradually reduce the velocity of water. The
velocity is transformed into pressure. Once in the outer casing, the water circles
around toward the outlet (nozzle), where it exits the pump. Heads over 300 m. are
readily developed in a two-stage turbine pump.
Vertical turbines have vertical drive shafts and are used to pump water from wells.
The impeller has tight axial clearance and pump channel rings that decrease
recirculation head losses.
The channel rings create a circular channel around the impeller's blades from the
inlet to the outlet. The liquid entering the channel from the inlet is picked up
immediately by the vanes on both sides of the impeller and pushed through the
channel by the shearing action. The repeating process continuously increases the
water energy.
4.1.4.1.2.1. Deep Well Turbine Pumps
Deep well turbine pumps are used in cased wells or where the water surface is
deeper than the practical limits of a volute centrifugal pump. Turbine pumps are also
used with surface water systems. Since in this case, the water intake is continuously
below the water surface, priming is not needed. Turbine pump efficiencies are
comparable to or greater than most volute centrifugal pumps. They are usually more
expensive than volute centrifugal pumps and more complicated to inspect and repair.
There are two configurations:
a. The pump is connected with a vertical gear shaft to a motor on top
b. Submersible motor in water-proof case
The turbine pump has three main parts:
a. Head assembly
b. Shaft and column assembly
c. Pump bowl assembly
Fig. 4.6. Water Flow in Volute Pump

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