Irrigation System Design

Center Pivot and End Gun Design

BSEN 4210

Simon Gregg

October 13, 2014

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Contents

1 Introduction 3

2 Pivot System Design 4

3 End Gun Design 6

4 Results 8

5 Conclusion 9

6 Appendix 106.1 Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106.2 Pivot Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.3 End Gun Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156.4 Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216.5 Additional Maps & Friction Loss . . . . . . . . . . . . . . . . . . . . . . . . 23

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1 Introduction

Irrigation systems are very important to the production of agriculture products in arid andsemiarid climates, therefore, the design, implementation, and operation of these systemsare crucial to the production of healthy high yield products. Pivot irrigation is a highlyused method of irrigating circular or irregular shaped fields. Proper pivot system designensures adequate pressure throughout the system including the end gun if desired. Thislaboratory exercise gives the student experience in designing pivot irrigation systems andend gun sizing.

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2 Pivot System Design

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3 End Gun Design

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4 Results

Table 1 displays the radius of throw and flow rate calculated with the provided pivot systemand end gun compared to the best match end gun nozzle from Rain Bird. The Rain Birdend gun nozzle chosen is 2000 Series Rain Gun Model GNS-2005T Taper Bore Nozzle.

Table 1: Comparison Calculated Radius and Flow to Rain Bird Specified

Origin Radius of Throw Flow RateFeet GPM

Calculated 213 386

GNS-2005T 179 369

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5 Conclusion

Based on calculations done with specifications of pivot system design and available pres-sures at the last sprinkler the calculated results are comparable to the available nozzlesprovided by Rain Bird 2000 Series. Table 1 displays the calculated results of the systemcompared to the theoretical values given from Rain Bird for Model GNS-2005T. The largerend gun brought to class could be used for this application. It is a similar size to theGNS-2005T and could provide similar results as seen in Table 1. The big gun rotationis set by the trip stops which create the change in rotation by causing the return arm tobe brought into or out of the flow of water. The return arm and the pendulum arm haveguides which direct the force of water in either direction creating moments which spin thegun.

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6 Appendix

6.1 Soils

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6.2 Pivot Design

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6.3 End Gun Design

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2000 Series Rain Guns®

Performance Charts

U.S. Units

SR2005/F2004 - GNS-2005T Taper Bore Nozzles

NOZZLE SIZE .8" .9" 1.0" 1.1" 1.2" 1.3"

(ft.) (gpm) (ft.) (gpm) (ft.) (gpm) (ft.) (gpm) (ft.) (gpm) (ft.) (gpm)PSI @ Nozzle

Rad. Flow Rad. Flow Rad. Flow Rad. Flow Rad. Flow Rad. Flow58 144 141 148 170 153 220 164 256 169 298 177 363 60 146 144 149 173 155 224 166 260 171 303 179 369 70 154 155 157 186 165 242 178 282 184 328 188 398 80 158 166 162 199 169 258 186 301 195 350 193 426 90 162 176 166 212 171 274 193 319 204 372 197 451 100 168 186 169 224 172 289 196 336 212 392 - - 109 172 193 174 233 174 301 198 351 210 409 - -

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SR2005/F2004 - GNS-2005O Ring Orifice Nozzles

NOZZLE SIZE .87" .99" 1.10" 1.20" 1.29" 1.38"

(ft.) (gpm) (ft.) (gpm) (ft.) (gpm) (ft.) (gpm) (ft.) (gpm) (ft.) (gpm)PSI @ Nozzle Rad. Flow Rad. Flow Rad. Flow Rad. Flow Rad. Flow Rad. Flow

60 133 110 143 142 151 181 160 224 167 274 177 326 70 138 120 148 154 157 199 167 245 175 296 184 352 80 143 129 154 165 163 216 174 262 183 318 192 378 90 148 136 159 175 169 227 180 278 189 337 199 401 100 153 143 163 184 174 238 186 293 196 356 205 424 110 157 150 167 193 179 249 191 306 201 371 210 441

Metric Units

SR2005/F2004 - GNS-2005T Taper Bore Nozzles

NOZZLE SIZE 21 mm 23 mm 26 mm 28 mm 30 mm 33 mm

(m) (m3/hr) (m) (m3/hr) (m) (m3/hr) (m) (m3/hr) (m) (m3/hr) (m) (m3/hr)BARS

@ Nozzle Rad. Flow Rad. Flow Rad. Flow Rad. Flow Rad. Flow Rad. Flow

4 44,0 32,1 45,0 38,6 46,5 50,0 50,0 58,1 51,5 67,7 54,0 82,4 4.5 45,8 34,0 46,8 40,9 48,8 53,0 52,5 61,7 54,3 71,8 56,0 87,3 5 47,5 35,9 48,5 43,1 51,0 56,0 55,0 65,3 57,0 75,8 58,0 92,2

5.5 48,3 37,6 49,5 45,2 51,5 58,6 56,8 68,3 59,3 79,4 58,8 96,6 6 49,0 39,3 50,5 47,3 52,0 61,1 58,5 71,3 61,5 83,0 59,5 100,9

6.5 50,3 40,9 51,0 49,3 52,3 63,6 59,3 74,1 63,3 86,4 60,5 104,57 51,5 42,5 51,5 51,2 52,5 66,1 60,0 76,9 65,0 89,8 - -

7.5 52,5 43,9 53,0 53,0 53,0 68,4 60,5 79,8 64,0 92,8 - -

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SR2005/F2004 - GNS-2005O Ring Orifice Nozzles

NOZZLE SIZE 20.32 mm 22.86 mm 25.4 mm 27.94 mm 30.78 mm 33.02 mm (m) (m3/hr) (m) (m3/hr) (m) (m3/hr) (m) (m3/hr) (m) (m3/hr) (m) (m3/hr)

BARS @

Nozzle Rad. Flow Rad. Flow Rad. Flow Rad. Flow Rad. Flow Rad. Flow 4 43,5 32,5 46,2 42,4 49,4 51,8 51,5 62,2 53,6 73,5 - -

4.5 45,5 33,6 48,6 43,6 51,5 53,4 54,2 64,5 57,0 77,4 59,9 91,7 5 46,8 35,7 50,1 46,2 53,0 56,7 55,9 68,6 58,8 82,1 61,6 92,7

5.5 48,1 37,6 51,3 48,6 54,4 59,6 57,4 72,2 60,3 86,3 63,2 102,26 49,2 39,4 52,5 50,7 55,6 62,3 58,8 75,5 61,7 90,2 64,7 106,8

6.5 50,2 41,0 53,3 52,7 56,7 64,8 60,1 78,5 63,1 93,7 66,0 111,17 51,2 42,4 54,6 54,6 57,7 67,0 61,2 81,4 64,3 97,0 67,2 114,9

7.5 52,1 43,8 55,6 56,3 58,7 69,2 62,3 84,0 65,4 100,0 - -

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BSEN 4210 End Gun Design for Pivot Irrigation

Hydraulic calculations for end gun nozzle:

3” diam. (.0491 ft2) 6” length 1.35” diam. (.0099 ft2) 60 psi

Given: End gun nozzle above supplied with 60 psi pressure. Required: What is the estimated velocity and flow from the nozzle outlet? Solution: Using Bernoulli equation, elev 3” + press 3” + vel hd 3” – head loss 3”-1.35” = elev 1.35” + press 1.35” + vel hd 1.35” (eq 1) 60psi + vel hd 3” - head loss 3”-1.35” = vel hd 1.35” Write velocity of 3” inlet in terms of velocity of 1.35” outlet (from continuity equation). V3” = (1.35/3)2 V1.35” therefore, V3” = .2025 V1.35”

Solve for velocity at the nozzle outlet. 138.6 ft + (.2025 V1.35”)2 / 2g – 5.5 (.2025 V1.35”)2 /2g = (V1.35”)2 / 2g (eq 2) 138.6 ft - .0029 V 1.35” 2 = V 1.35” 2 (.0155) 138.6 ft = 0.0184 V 1.35” 2

V 1.35” = 86.8 fps Solve for flow out the nozzle. Q = VA = 86.8 ft/sec x .0099 ft2

Q = .859 cfs = 386 gpm (very close to flow of Rainbird 1.3” nozzle)

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Minor Loss Coefficients 443

Sluice gate in rectangular conduit

where n = hiH.

Measuring nozzle @

M 1 = 0.3 D.p for d = 0.8D

M 1 = 0.95 D.p for d = 0.2D

where D.p is the measured pressure drop.

T1Z:--Venturi meter@

to 0.2 D.p where D.p is the measured pressure drop.

Measuring orifice, square edged

where D.p is the measured pressure drop.

Confusor outlet

diD = k =

@ . Exit from pipe into reservoir

.. k = 1.0

Diffusor outlet for Did> 2

Source: A. L. Simon, Practical Hydraulics (1976)• .fohn Wiley & Sons, Inc., New York.

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6.4 Assignment

BSEN 4210 Lab 6 Center Pivot and End Gun Design (50 points)

Introduction: You have completed your pivot irrigation specifications for a field on the Sanders farm in Coffee County, Alabama. Your hydraulic analysis and design resulted in a specified system design capacity (maximum flow rate), length of lateral, and pressure requirement at the last nozzle. You also specified the required radius of the end gun (i.e., end gun throw). Your job now is to determine if either of the end guns brought to lab will fit your design specifications and if not, what modifications or alternate end guns will work. Assignment:

1. Determine if the Rainbird 205G (2000 Series Rain Gun) or 103DL (1005 Series Rain Gun) end gun assemblies brought to lab have sufficient flow capacity and radius of throw to handle design requirements for the specified corn/peanut field at the Sanders farm. If not, what modifications (eg., different nozzle) or alternate end guns (Rainbird, Zimmatic, Valley, Lockwood, Reinke, etc.) might be used. Support your decision with engineering analysis, described below. You may visit Rainbird or other manufacturer websites.

2. All supporting calculations (on engineering paper) and documentation must be attached and referenced to receive full credit.

Specific requirements of this assignment:

a. Lab report to include a title page, table of contents, and all required design calculations. b. Specify the pivot design spreadsheet). c. Estimate the approximate flow, in gpm, at the end gun similar to the gpm/ac average

application rate of the gross irrigated area from the pivot design spreadsheet. d. Measure end gun assembly and nozzle dimensions in class and develop an engineering

sketch of relevant hydraulic fixtures for each end gun (exclude moving impact diffusers). e. Using Rain Bird specifications provided, select one of the two end guns brought to class

and from part d that fits closest to design requirements for radius (part b) or flow (part c). f. Using ONLY nozzle dimensions (from part d) and design pressure available at last nozzle

(from pivot design spreadsheet), determine the velocity and flow of water exiting the nozzle you select in part e.

g. Estimate the theoretical radius of throw at the velocity determined from part f, above (Hint: use projectile equations learned in previous engineering and physics classes, ignore wind resistance, and assume the end gun nozzle is located10 ft. above the ground).

h. Compare your answers from parts f and g with Rain Bird specifications (radius and flow) for an end gun nozzle of similar size and configuration.

i. Report whether either of the two end guns brought to class would be recommended for your end gun design.

j. If neither is acceptable, propose alternate design or nozzle configuration. Extra credit (5 points each):

1. By observing the end gun assemblies brought to class, describe how the end gun, under only water power, rotates a prescribed arc, reverses itself and starts over.

2. Go to Berkeley Pumps website (BEC2) on Canvas web page under Web resources and find a suitable pump curve for the center pivot (based on determined flow and TDH).

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GRADING: Lab 6 End gun design - 50 points Presentation (25 pts.): ____ neatness and organization Content (25 pts.): ____ specify the center pivot gpm and pressure requirement at the pump (i.e., the pump

specifications needed to operate the center pivot system as designed). ____ specify the gpm/ac average application rate of the pivot ____ provide an engineering sketch of the end gun nozzle showing relevant hydraulic features ____ determine the theoretical radius of throw of the nozzle in class at design pressure ____ select the Rainbird end nozzle (highlight that will work for your design Extra credit (5 points each): ____ describe how end gun rotates a prescribed arc, reverses itself and starts over ____ select a pump curve and print pump curve suitable for specified operating conditions

(GPM and TDH) of the center pivot at the Sander s Farm. HINTS: End Gun Design for Pivot Irrigation General requirement Provide your recommendation for nozzle / end gun design, including a recommended nozzle size and trajectory angle. c compare average gpm/ac to acreage irrigated with end gun to estimate comparable flow rate needed e Large Rainbird 205 G Rain Gun performance charts; use Rain Bird 2000 Series Performance Charts provided. Small 103 DL DH Rain Gun performance charts; use Rain Bird 1005M-DC Series Performance Charts provided. f use minor loss coefficient for a confusor outlet (attached) g x = Vx0 t z = Vz0 t ! gt2 Use 30º trajectory for existing gun.

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BSEN 4210 Center pivot design (in-class)

Introduction: An irregular-shaped field on the Sanders farm in Coffee County, Alabama needs rainfall on a guaranteed basis for the growing of corn and peanuts. Since we cannot guarantee this atmospheric phenomenon for the Sanders family, we have taken matters into our own hands. How? With sprinkler irrigation of course! Procedures and objectives: Using materials presented in lab, you will complete the analysis and design of a pivot irrigation system on the Sanders farm, including but not limited to design depth of irrigation, irrigation period, system design capacity (maximum flow rate), location of pivot, length of lateral, pressure requirement at the last nozzle, and required distance of the end gun throw. You will specify the supply pump and location, size the main supply pipe, and analyze the system for pressure reduction and/or flow control. You will utilize aerial photography and soils and topographic mapping to determine design parameters for the center pivot system. Your design will be turned over to a center pivot manufacturer who will develop a sprinkler package for the system you specify. Adequate surface water is available adjacent to the irrigated field specified in lab. Materials provided for assignment:

1. Blank spreadsheet for pivot irrigation system design (from Mr. Ted Tyson, Auburn University Cooperative Extension).

2. Aerial mapping, topographic mapping, and soils polygons for the Sanders farm (from Terra Server, USGS).

3. Soil overlays, including soil map units and associated tables of engineering, chemical, and physical soil properties in the vicinity (from Coffee County Soil Survey, NRCS).

4. Nelson sprinkler specifications, ranging from 25-100psi. 5. Table of maximum irrigation application rates for soils in Alabama. 6. Table of pipe sizes for center pivot design.

Deliverables:

1. Lab report to include a title page, table of contents, sketch of pivot and pump on the aerial photograph, and all required design specifications (fill out all blanks on the design spreadsheet). Retain a copy of your design spreadsheet for end gun design..

2. Supporting calculations and assumptions must be shown and referenced in order to receive credit. Retain a copy of your design calculations for end gun design.

6.5 Additional Maps & Friction Loss

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