LIT194-Handbook of TII.pdf - Diamond Head Sprinkler Supply

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Friction Factor Pipe SizingThis Friction Factor is used to determine the maximum flow in gallons per minute through anysection of lateral line pipe while not exceeding a predetermined pressure loss (pressure variation).In order to minimize uneven distribution, sprinklers should operate with pressure variation betweensprinklers of not more than ± 10 to ± 20% of the desired sprinkler operating pressure.F f = P o x P vL cWhere:F f = Friction Factor, the allowable pressure loss per 100 feet of pipe, in psiP o = sprinkler operating pressure in psiP v = Pressure Variation allowed between the valve and the last sprinkler on the circuitbeing sized, usually 10% or 20% of the desired sprinkler operating pressureL c = Critical Length of pipe from control valve to farthest head in hundreds of feetExample:A) You must determine the amount of pressure variation you can allow between the valveand the last sprinkler head. This is usually 10% to 20% of the operating pressure of thesprinklers on that particular section. For this example we will use 10% (0.10) variation.If a control valve operates a group of sprinklers which require 30 psi to operate (operatingpressure = P o ) the 10% pressure variation (pressure variation = P v ) would allow a totalvariation of 3.0 psi from the valve to the farthest head. (.10 x 30 psi = 3.0 psi)B) Determine the Critical Length (L c )Next you must determine the distance the water travels from the control valve to the farthesthead. That is not necessarily the total length of pipe in the section but just the length of thepipe through which the water flows from the valve to the farthest head. Divide this numberby 100 to determine the hundreds of feet from the valve to the farthest head. This is calledthe Critical Length and represents the hundreds of feet of pipe in which you can afford tolose the pressure you determined was acceptable for pressure variation in step “A” above.20 ft.= Control Valve for these sprinklers= Sprinkler Head requiring 30 psiand delivering 2.0 gpm at that pressure40 ft.80 ft. 40 ft. 60 ft.Fig.1In this diagram you must decide the path the water flows from the valve to the farthest head andcalculate that distance in feet. The water flow path is shown below (Fig. 2) and is represented bythe pipe with the check pattern. Notice the distance of the branch line is NOT included in thedistance. This is because the water flowing to the farthest head does not travel down that length ofpipe and therefore any pressure losses occurring in the branch does not affect the pressure in theCritical Length.6FORMULAS - Hydraulics
20 ft.FarthestHead180 ft.Fig. 2In Fig. 2 the water traveling from the valve to the farthest head must pass through 200 feet ofpipe. This divided by 100 gives a Critical Length (L c ) in hundreds of feet, of 2.0.C) Determine the rate at which you can lose pressure in the pipe. This is called the FrictionFactor (F f ) which is the allowable psi loss per one hundred feet of pipe. We can determinethis allowable rate of loss by dividing the allowable pressure loss (in psi) by the criticallength (in hundreds of feet) by using the formula below.The sprinklers mentioned above (Fig. 1) require 30 psi to operate and a distance from the valveto the farthest head of 200 feet. Using the formula below we can determine the Friction Factor.F f = P o x P vL cF f = 30 x 0.10200/100F f = 32F f = 1.5 allowable psi loss per 100 feet of pipe.The Friction Factor indicates that the pipe is to be sized so that no section of pipe exceeds apressure loss of 1.5 psi per 100 ft. This insures that over the 200 feet from the valve to the farthesthead the total psi loss will not exceed the 3.0 psi allowable loss (10% of the sprinkler operatingpressure). The Friction Factor can be used like a budget. It gives us a guideline by which we cansize the pipe without having excessive pressure loss in any section.For the lateral pipes (those downstream of the control valve) use Class 315 PVC for Z\x inchpipe and Class 200 PVC for all larger sizes. Although this requirement for Class 315 and Class 200is not mandatory and may vary on many larger installations, it is typical for landscape projectsfrom residential through medium commercial projects in the South and Western United States.At this point turn to the Friction Factor Short Cut charts in the Tables section, page 54.Find the Chart for the Friction Factor closest to the one calculated for your sprinkler systemsection. (In this case there is a chart for a Friction Factor of 1.5 psi allowable loss per 100 ft. Whenthere is no chart for the exact Friction Factor calculated, round off the Friction Factor to thenearest chart value.)®Handbook of Technical Irrigation Information7
Page 1: THE HANDBOOK OFTECHNICAL IRRIGATION
Page 9: FORMULAS®Handbook of Technical Irr
Page 12 and 13: Slope (continued)C) The degree of s
Page 16 and 17: Figure 3 represents a portion of th
Page 18 and 19: Static Pressure DeterminationStatic
Page 20 and 21: Water HammerThis formula is used to
Page 22 and 23: AB 325, California Calculation of M
Page 24 and 25: Maximum System Capacity Requirement
Page 26 and 27: Brake HorsepowerThis formula determ
Page 28 and 29: Net Positive Suction Head Available
Page 30 and 31: Water Horsepower RequirementsThis f
Page 32 and 33: Distribution UniformityThis formula
Page 34 and 35: Precipitation Rate - Minimum Rate R
Page 36 and 37: Scheduling CoefficientA scheduling
Page 39: CONVERSIONS®Handbook of Technical
Page 42 and 43: Hunter Industries Conversion TableN
Page 44 and 45: Convert From Into Multiply ByFlow (
Page 46 and 47: Convert From Into Multiply ByPowerB
Page 48 and 49: Convert From Into Multiply ByPressu
Page 50 and 51: Convert From Into Multiply ByVolume
Page 52 and 53: Convert From Into Multiply ByVolume
Page 54 and 55: Decimal and Metric Equivalents of C
Page 57 and 58: Slope ComparisonAmount of Rise in P
Page 59 and 60: Maximum Precipitation Rates for Slo
Page 61 and 62: Water Supply RequirementsAvailable
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Friction Factor Short Cuts for Clas
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Friction Factor Short Cuts for Clas
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Friction Factor Short Cuts for Poly
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Average Number of Sprinklers per Ac
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Approximate Cost of Pump OperationP
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Wire Data: Standard Annealed Copper
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Reference ChartApproximate Number o
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PVC Schedule 40 and Schedule 80 Pip
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FRICTION LOSSCHARTS®Handbook of Te
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Friction Loss CharacteristicsClass
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Friction Loss CharacteristicsNomina
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Friction Loss CharacteristicsSchedu
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Friction Loss CharacteristicsPolyet
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Friction Loss CharacteristicsPepco
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Friction Loss CharacteristicsAWWA S
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Friction Loss CharacteristicsCast I
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Friction Loss CharacteristicsType
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Friction Loss CharacteristicsPortab
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Friction Loss CharacteristicsAustra
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Pressure Loss Through Water MetersP
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Roughness Coefficient C Values forH
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Pressure Loss Through Swing Check V
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®The Irrigation InnovatorsDesign a
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