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For All Design Problems

Remember to

Begin with the End in Mind

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Cover Sheetfor Plans

andCalculations

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Plan of the Piping Configuration

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Calculations

for the Sizesof the PipingSelected andthe Pressure

Available at

the Sourcesof the Fire

ProtectionWater

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A Hydraulic

Graph toShow theWaterSupply andthe Design

OperatingPoint for theFlow and

Pressure ofthe FireProtection

System

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Water Supply to Sprinkler System

includes Total Demand RequirementsFire Sprinkler Water Requirement

Area of Operation in Hazard times DensityDemand PLUS Overage Factor due to Laws ofFluid Mechanics (usually 10 percent as a rule of

thumb)Hose Stream Requirement Based on Occupancy Hazard Classification

Duration of Fire Event in minutes

= Total Water Demand in Gallons

Very important for sizing water storage tanks orcalculating the size of a pond.

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Water Supply to Sprinkler System

includes Total Demand RequirementsArea and Density are determined from

Graph on next page from NFPA-13

Hose Stream Demand and Duration are

determined from NFPA TablesLight Hazard 100 gpm for 30 minutes

Ordinary Hazard 250 gpm for 60-90 minutes

Extra Hazard 500 gpm for 90-120 minutes

Factor for Overage is 10 Percent unless

directed by AHJ to use a different factor.

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Water Flow from Sprinkler

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Orifice Discharge Formula

The orifice discharge formula is simplified for sprinkler heads

because of the uniform diameter.The discharge in GPM (Q) = the orifice coefficient (k) timesthe square root of the pressure (p) at the orifice.

Q = k p^.5 See text page 1098K for sprinkler heads are shown in the text, page 1093

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Orifice Discharge Formula The orifice discharge formula is simplified for sprinkler

heads because of the uniform diameter.

Q = k p^.5 Because k will be constant for all calculations, the

quantity of flow (Q) at each sprinkler head will be

different due to change in pressure in the pipingsystem due to friction loss based on the diameterand roughness of the piping.

From the water supply end toward the most remoteopening the flow rate will decrease.

From the most remote opening toward the water supply

the flow rate will increase.

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Number of Spklrs to be Calculated

A very important element not included inthis Textbook

It must be a whole number, round up

Number of sprinklers per branch

1.2 * A^.5 SA = Design Area

S = Distance between sprinklers on branch line

1st Total sprinklers to be calculated Design Area Area per Sprinkler

It must be a whole number, round up

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Heads in Design Area

OH1 2000sf

2000108=18.5 or 19

1.2*2000^.5

12 = 4.47or 5 hds perbranch

(14 * 108) +(5 * 90 =

1962 sf + 1more head

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System Design Approaches

Hydraulic Method in an Engineered System

Best because

it fits the piping layout

Maybe for economics

Maybe for conservation of pressure available

Maybe because of the way the building will be used

it fits the piping materials specified, many options

it fits the height of the building, elevation head is a big concern

it fits types of sprinklers heads used or required it fits the density of water required for the hazard more

accurately

it can be used to control the velocity of flow in the piping.

(32 fps maximum, some AHJ use 20 fps max.)

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Hydraulic Design Procedure

Determine the Design Conditions

Determine the Water Demand based on Conditions

Determine the Water Supply Static & Residual Pres.

Layout the piping with relation to the building

structure and building usage.Determine the Flow Rate and the Residual Pressurerequired at the Most Remote Sprinkler Head

Determine the difference in the Residual Pressurefrom the Water Supply and the OperatingSprinklers including the Changes in Elevation

Finally, size the piping.

An Example Water Supply

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An Example Water Supply

Graph with Design Limits

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Testing the Water Supply

Flow Test

- usually local water department - contractors

- insurance underwriters

- routine for fire insurance rating

Static pressure - no flow, theoretical, done whilemains are being used

Residual pressure - with a flow rate

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Flow Test Diagram

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Pitot Tube to Measure Pressure

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Pitot Reading Conversion

Log Graph

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Log Graph

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An Example Water Supply

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Water Supply to Sprinkler SystemFire Sprinkler Water Requirement

Area of Operation in Hazard times Density Demand PLUSOverage Factor due to Laws of Fluid Mechanics (usually10 percent as a rule of thumb)

Plus required Hose Stream

Pressure Requirement

Minimum Pressure required at most remote sprinkler

head to produce the flow rate required. Plus Elevation Head, the height of the most remote

sprinkler head.

Plus Friction Loss due flow through the piping.

l ll

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Example Illustration

An Example Water Supply

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An Example Water Supply

Graph with Design Limits

D t i i th Q tit f W t R d i

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Determining the Quantity of Water Reqd is

based on the Protected Hazard

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Set-up for CalculationsHead layout 1st step variable Follow the Rules

Piping arrangement 2nd step variable Tree Configuration

Branches perpendicular to supporting structure

Area of sprinkler operation - 3rd variable Set Formula to Determine the Shape

Calculations 4th step extremely variable Simple, IF you keep track of where flow is going

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Example of Process

Starting Flow Rate Density times Area of Head Coverage

Starting Pressure Calculation p = (Q/k)^2, but not less than 7 psi

If less than 7 psi, then use 7 psi to start

Pressure Required at 2

nd

Head H-W pressure loss calculation

Calculating New Flow Rate for 2nd

Head Q = k(p^.5) Use the p required at that point

f h h l

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An Overview of the Whole

Hydraulic Calculation Process

It is an Iterative Process.

That is, making repetitions or beingrepetitious to achieve solutions.

And, that is what it takes to achieve themost suitable and economical solutions in

engineering any part of any building.

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Tag theNodes to

KeepOrder

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Tag the Nodes to Keep Order

A 1st Branch toRiser Nipple

B 1st BranchRiser Nipple toCross Main

C 2nd BranchRiser Nipple to

Cross MainD 3rd BranchRiser Nipple toCross Main

E 4th BranchRiser Nipple toCross Main

F Cross Main to

Feed Main

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Example ofCalculation

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Example ofCalculation