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Slide 1
Lateral Design
Slide 2
Lateral Material/Types Drip tape Thin wall drip line Heavy wall
drip line Polypipe with punch emitters Polypipe with sprays
Slide 3
Typical Layouts
Slide 4
Slide 5
Slide 6
More layouts
Slide 7
Slide 8
Slide 9
SDI
Slide 10
Lateral installation
Slide 11
SDI burial depth CropBurial DepthLine spacing Trees and
grapes>16 inches (0.4m)As per row spacing Berries, Vines> 8
inches (0.2m)As per row spacing Row crops corn, cotton 12 inches
(0.3m) 24 80in (0.6 -2.03m) Raised beds single row Tomatoes, melons
2-4 inches (0.05 0.1m)One line 4- 6 inches (0.1 - 0.15m) from
center of bed Raised beds double row Onions, peppers, strawberries
2-4 inches (0.05 0.1m)One line down center of bed Raised beds
double row > 30 inch (0.75m) bed width 3-6 inches (0.075
-0.15m)Two lines spaced the bed width apart
Slide 12
Tape orientation One tape or more per bed Holes upward Tape
thickness Trend toward thicker Tape materials Stretch vs.
breakage
Slide 13
Lateral Line Design Important lateral characteristics Flow rate
Location and spacing of manifolds Inlet pressure Pressure
difference
Slide 14
Standard requires Pipe 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.
Slide 15
Start with average lateral
Slide 16
Design objective Limit the pressure differential to maintain
the desired EU and flow variation What effects the pressure
differential Lateral length and diameter Economics longer and
smaller Manifold location slope
Slide 17
Allowable 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 D P s =allowable pressure loss for subunit P a
= average emitter pressure P n = minimum emitter pressure
Slide 18
Emission Uniformity
Slide 19
EU is related to Friction loss
Slide 20
Example Given: CV=0.03, 3 emitters per plant, qa =.43gph P a
=15 psi, EU=92, x=0.57 Find: q n, P n, and P
Slide 21
Solution
Slide 22
Practice problem
Slide 23
Flow rate Where: 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)
Slide 24
Slope and topography
Slide 25
Four Cases
Slide 26
Lateral Flow flat slope
Slide 27
Lateral Flow 2% downhill slope
Slide 28
Lateral flow 2% uphill slope
Slide 29
Lateral flow varied slope
Slide 30
Manifold spacing Spacing 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
Slide 31
Manifold Location More 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
laterals
Determine optimum lateral length EU Slope Based on friction
loss limited to the allowable pressure difference ( P s )
Slide 35
Hydraulics Limited lateral losses to 0.5 D P s Equation for
estimating Darcy-Weisbach(best) Hazen-Williams Watters-Keller (
easiest, used in NRCS manuals )
Slide 36
C factorPipe diameter (in) 130 1 140< 3 150 3 130Lay flat
Hazen-Williams equation hf =friction loss (ft) F = multiple outlet
factor Q = flow rate (gpm) C = friction coefficient D = inside
diameter of the pipe (in) L = pipe length (ft)
Slide 37
Watters-Keller equation hf = friction loss (ft) K = constant
(.00133 for pipe 5) F = multiple outlet factor L = pipe length (ft)
Q = flow rate (gpm) D = inside pipe diameter (in)
Or Or use equation Where Fe= equivalent length of lateral, ft)
K = 0.711 for English units) B = Barb diameter, in D = Lateral
diameter, in
Slide 41
Adjusted length L = adjusted lateral length (ft) L = lateral
length (ft) Se = emitter spacing (ft) fe = barb loss (ft)
Slide 42
Barb loss More companies are giving a K d factor now days
Slide 43
Example Given: lateral 1 diameter 0.50, qave=1.5gpm,Barb
diameter 0.10 lateral 2 diameter 0.50, q ave =1.5gpm, k=.25 Both
laterals are 300 long and emitter spacing is 4 ft Find: equivalent
length for lateral 1 and h etotal for lateral 2
Slide 44
Solution Lateral 1Lateral 2
Slide 45
Practice problem
Slide 46
Procedure Step 1 - Select a length calculate the friction loss
Step 2 adjust length to achieve desired pressure difference ( 0.5 D
H s )
Slide 47
Step 3 - adjust length to fit geometric conditions Step 4 -
Calculate final friction loss Step 5 Find inlet pressure Step 6
Find minimum pressure
Slide 48
Next step is to determine h Paired Lateral Single Lateral Slope
conditions S > 0 S = 0 Slope Conditions S friction slope
Slide 49
Last condition S < 0 and S < Friction slope Which ever is
greater
Slide 50
Find minimum lateral pressure Where S > 0 or S=0 Where S
< 0 and S < Friction slope Where S friction slope
Slide 51
Inlet pressure Estimate with the following equation Single
Lateral Paired Lateral Better to use computer program
Slide 52
Handout Pressure summary
Slide 53
Design Considerations Select emitter/flow rate Determine
required operating pressure Calculate friction loss Quick estimate
use multiple outlet factor Manufactures software Built spreadsheet
Decide whether to use single or paired laterals Make adjustments
Determine h and hose EU