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Lateral Design. Lateral Material/Types. Drip tape Thin wall drip line Heavy wall drip line Polypipe with punch emitters Polypipe with sprays. Typical Layouts. More layouts. SDI. Lateral installation. SDI burial depth. Tape orientation One tape or more per bed Holes upward - PowerPoint PPT Presentation
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Lateral Design
Lateral DesignLateral Material/TypesDrip tape
Thin wall drip line
Heavy wall drip line
Polypipe with punch emitters
Polypipe with sprays
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Typical Layouts
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More layouts
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SDI9
Lateral installation10SDI burial depthCropBurial DepthLine spacingTrees and grapes>16 inches (0.4m)As per row spacingBerries, Vines> 8 inches (0.2m)As per row spacingRow crops corn, cotton 12 inches (0.3m) 24 80in (0.6 -2.03m)Raised beds single rowTomatoes, melons2-4 inches (0.05 0.1m)One line 4- 6 inches (0.1 -0.15m) from center of bedRaised beds double rowOnions, peppers, strawberries2-4 inches (0.05 0.1m)One line down center of bedRaised beds double row> 30 inch (0.75m) bed width3-6 inches (0.075 -0.15m)Two lines spaced the bed width apart11Tape orientationOne tape or more per bedHoles upwardTape thicknessTrend toward thickerTape materialsStretch vs. breakage12Lateral Line DesignImportant lateral characteristicsFlow rateLocation and spacing of manifoldsInlet pressurePressure difference
13Standard requiresPipe sizes for mains, submains, and laterals shall maintain subunit (zone) emission uniformity (EU) within recommended limits
Systems shall be designed to provide discharge to any applicator in an irrigation subunit or zone operated simultaneously such that they will not exceed a total variation of 20 percent of the design discharge rate.Start with average lateral
15Design objectiveLimit the pressure differential to maintain the desired EU and flow variationWhat effects the pressure differentialLateral length and diameterEconomics longer and smallerManifold locationslopeAllowable pressure loss (subunit)This applies to both the lateral and subunit. Most of the friction loss occurs in the first 40% of the lateral or manifold
Ranges from 2 to 3 but generally considered to be 2.5
DPs =allowable pressure loss for subunitPa = average emitter pressurePn = minimum emitter pressure17Emission Uniformity
18EU is related to Friction loss
19ExampleGiven: CV=0.03, 3 emitters per plant, qa = .43gph Pa=15 psi, EU=92, x=0.57
Find: qn, Pn, and P 20Solution
21Practice problem
22Flow rateWhere:l = Length of lateral, ft. (m).Se = spacing of emitters on the lateral, ft. (m).ne = number of emitters along the lateral.qa = average emitter flow rate, gph (L/h)
23Slope and topography
24Biggest mistake generally made by dealers. Why? Same reason NRCS does. It takes time to go out and survey.
Slope creates major problems with efficiency and uniformity ( e.g.. Drainage after shutoff)Four Cases
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Lateral Flow flat slope26
Lateral Flow 2% downhill slope27
Lateral flow 2% uphill slope28
Lateral flow varied slope29Manifold spacingSpacing is a compromise between field geometry and lateral hydraulics Lateral length is based on allowable pressure - head difference.Have the same spacing throughout the field in all crops 30Manifold LocationMore efficient to place in middle
two laterals extend in opposite directions from a common inlet point on a manifold, they are referred to as a pair of laterals. Manifold placed to equalize flow rates on the uphill and downhill laterals31
32Manifold placementzz0.00.51.00.850.10.561.20.890.20.601.40.920.30.651.60.940.40.691.80.960.50.722.00.980.60.752.20.990.70.782.41.000.80.812.61.000.90.832.751.00
33Determine optimum lateral lengthEU SlopeBased on friction loss limited to the allowable pressure difference (Ps)
34HydraulicsLimited lateral losses to 0.5DPsEquation for estimatingDarcy-Weisbach(best)Hazen-WilliamsWatters-Keller (easiest, used in NRCS manuals)35
C factorPipe diameter (in)130 1140< 3150 3130Lay flatHazen-Williams equationhf =friction loss (ft)F = multiple outlet factorQ = flow rate (gpm)C = friction coefficientD = inside diameter of the pipe (in)L = pipe length (ft)36Watters-Keller equation
hf = friction loss (ft)K = constant (.00133 for pipe < 5 .00100 for > 5)F = multiple outlet factorL = pipe length (ft)Q = flow rate (gpm)D = inside pipe diameter (in)37Multiple outlet factorsNumber of outletsFNumber of outletsF1.8511.7521.8511.752123456781.000.640.540.490.460.440.430.421.000.650.550.500.470.450.440.43910-1112-1516-2021-3031-70>700.410.400.390.380.370.360.360.420.410.400.390.380.370.3638Adjust length for barb and other minor losses
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OrOr use equation
Where Fe= equivalent length of lateral, ft)K = 0.711 for English units)B = Barb diameter, inD = Lateral diameter, in40Adjusted length
L = adjusted lateral length (ft)L = lateral length (ft)Se = emitter spacing (ft)fe = barb loss (ft)41Barb lossMore companies are giving a Kd factor now days
42ExampleGiven: lateral 1 diameter 0.50, qave=1.5gpm,Barb diameter 0.10 lateral 2 diameter 0.50, qave=1.5gpm, k=.25 Both laterals are 300 long and emitter spacing is 4 ft
Find: equivalent length for lateral 1 and hetotal for lateral 2 43Solution
Lateral 1Lateral 244Practice problem
45ProcedureStep 1 - Select a length calculate the friction loss
Step 2 adjust length to achieve desired pressure difference ( 0.5DHs)
46Step 3 - adjust length to fit geometric conditions
Step 4 - Calculate final friction loss
Step 5 Find inlet pressure
Step 6 Find minimum pressure
47Next step is to determine hPaired Lateral
Single Lateral Slope conditionsS > 0
S = 0
Slope ConditionsS < 0 and S > friction slope
48Last condition
S < 0 and S < Friction slope
Which ever is greater49Find minimum lateral pressureWhere S > 0 or S=0
Where S < 0 and S < Friction slope
Where S < 0 and S > friction slope
50Inlet pressureEstimate with the following equationSingle Lateral
Paired Lateral
Better to use computer program
51Handout Pressure summaryDesign ConsiderationsSelect emitter/flow rateDetermine required operating pressureCalculate friction lossQuick estimate use multiple outlet factorManufactures softwareBuilt spreadsheetDecide whether to use single or paired lateralsMake adjustments Determine h and hose EU
53 Practice problem
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Class design problem
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