Hyd Calc of in Rack Sprinklers Handout

11/19/2012

AIA CES Program #: NFSATV1512 Provider #: G131 1.5 LU/HSW

Hydraulic Calculation of In‐Rack Sprinklers .

National Fire Sprinkler Association is a Registered Provider with The The American American Institute of Architects Architects Continuing Education Systems (AIA/CES) (AIA/CES).. Credit(s) earned on completion of this of this program will be reported to AIA/CES to AIA/CES for for AIA members. Certificates of Completion of Completion for both AIA members and non‐AIA members are available upon request.

, . . . . . . .

Vice President of Engineering of Engineering

This program is registered with AIA/CES with AIA/CES for for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any of any material of construction of construction or any method or manner of handling, of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this of this presentation 2

Copyright Materials

Program Description The hydraulic calculation procedures for in‐rack sprinklers are very different from the procedures for ceiling sprinklers. Determination of the of the number of sprinklers of sprinklers that might open if there if there is a fire as well as the location of the of the most demanding sprinklers can be a challenge. Next, the user needs to be determine if the if the in‐rack sprinkler demand needs to be added to (and balanced with) the ceiling sprinkler demand. Procedures will be provided for all of these of these steps in the calculation process as well as a discussion of decisions that can be made (sprinkler selection, pipe sizing and pipe location) to make the system as efficient as possible.

This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the of the The National Fire Sprinkler Association is prohibited.

© National Fire Sprinkler Association 2012 3

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Hydraulic Calculation of In of In‐Rack Sprinklers

Learning Objectives At the end of this of this program, participants will be able to:

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1. Calculat Calculate e the correct number of in of in‐rack sprinklers for different commodities being protected. 2. Se ect t e correct ocation o t e in‐rac sprin sprin ers ers to be calculated. 3. Correctly Correctly apply the rules regarding the balancing of in‐rack sprinkler demands with ceiling sprinkler demands. 4. Calculat Calculate e the size the pipe feeding the in‐rack system to be most efficient.

Assumptions/discussion How many sprinklers?

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Where are they?

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Minimum flow and ressure? ressure?

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Calculation technique

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Balance to ceiling sprinklers?

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Making the design most efficient

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Assumptions •

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You’ve already decided to use in‐rack sprinklers to protect the commodity You’ve already decided how many levels of in‐rack sprinklers to install

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You’ve already decided where the piping is going to go

Hydraulic Calculations •

Assumptions

Performed to tell you

How many sprinklers will be open? •

NFPA 13 Class I‐IV Commodity –

What pipe size will be best?

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Will the water supply provide the flow and pressure necessary to con ro suppress a re

We’re using the section numbers from the 2010 edition of NFPA 13 in this program Previous editions have similar , have changed For the 2013 edition (which most people have not seen yet) the rules are similar, but have been clarified where some holes existed

Group A Plastics

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Rubber tires

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NFPA 30 – Flammable and Combustible Liquids

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NFPA 30B – Aerosols

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Will depend on: Number of levels of in‐racks

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Type of sprinklers at the ceiling

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NFPA 13 ‐ 2010 •

Class I‐IV Commodity (Chapter 16) Storage 25 ft and less (16.2)

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Class I‐IV Commodity •

Storage up to 25 ft (16.2.4.3.1) If spray sprinklers or CMSA sprinklers at the ceiling

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Storage over 25 ft (16.3)

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Group A Plastics (Chapter 17) Storage 25 ft and less (17.2)

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Storage over 25 ft (17.3)

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Rubber Tires (18.5) •

1 level protecting Class I, II or III: 6 sprinklers 1 level protecting Class IV: 8 sprinklers 2 or more levels protecting Class I, II or III: 10 sprinklers (5 on the top two levels) 2 or more levels protecting Class IV: 14 sprinklers (7 on the top two levels)

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Example 1 Class III, 2‐Levels of In‐Racks

Example 1 Class III, 2‐Levels of In‐Racks Plan View

Plan View

Elevation View Double Row Racks




Storage over 25 ft (16.3.4.3) If spray sprinklers or CMSA sprinklers at the ceiling

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Plan View •

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1 level protecting Class I, II or III: 6 sprinklers 1 level protecting Class IV: 8 sprinklers 2 or more levels protecting Class I, II or III: 10 sprinklers (5 on the top two levels) 2 or more levels protecting Class IV: 14 sprinklers (7 on the top two levels)

Calculate 10 sprinklers: 5 on the top two levels


Any storage height (16.3.3.5) If ESFR sprinklers at the ceiling

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Calculate 8 sprinklers on one level

Group A Plastics •

Storage of any height (17.2.4.3 for up to 25 ft; 17.3.4.3 for over 25 ft) If spray sprinklers or CMSA

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1 level: 8 sprinklers 2 or more levels: 14 sprinklers (7 on the top two levels)

If ESFR sprinklers at the ceiling: calculate 8 sprinklers (on one level)

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Rubber Tire Storage •

18.5.3 and 18.5.1 If 1 level of in‐rack sprinklers,

What if you don’t have enough in‐rack sprinklers on a level? •

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calculate 12 sprinklers If more than 1 level, calculate like lastics Cha ter 17

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14 sprinklers (7 on the top two levels)

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Calculate all of the sprinklers within a rack, including sprinklers on other levels, but you are not required to jump the aisle See Example 2 Same as Example 1 Supposed to calculate 10 sprinklers, 5 on each level Only 7 sprinklers in each rack

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Minimum Flow and Pressure? •

NFPA 13 Class I‐IV Commodity –

Group A Plastics

Calculate 7 Sprinklers

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Rubber tires

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Aisle

NFPA 30 – Flammable and Combustible Liquids

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NFPA 30B – Aerosols

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Will depend on: Type of sprinklers at the ceiling

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Storage up to 25 ft (16.2.4.4) If spray sprinklers or CMSA sprinklers at the ceiling

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Plan View

15 psi minimum

21.7 gpm at 15 psi

21.7 gpm for k‐5.6 sprinkler

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Which would you choose?



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Storage over 25 ft (16.3.4.3.1) If spray sprinklers or CMSA sprinklers at the ceiling

Class I‐IV Commodity Any storage height (16.3.3.5)

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If ESFR sprinklers at the ceiling

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50 psi, must use k‐8.0 sprinklers

Minimum 30 gpm •

. gpm a

ps

28.7 psi for k‐5.6 sprinkler

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Which sprinkler would you choose?

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Group A Plastics Spray Sprinklers at Ceiling •

For storage up to 25 ft, depends on the in‐rack configuration selected from the Figures: Figure 17.2.1.2.1(b) & (f): 15 psi

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Group A Plastics ESFR Sprinklers at Ceiling •

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Must use k‐8.0 60 gpm (17.3.3.4.1) 56.3 psi

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15 psi when sprinklers are at every other flue intersection 15 psi for k‐8 and 30 psi for k‐5.6 when sprinklers are at every flue

For storage over 25 ft: 30 gpm regardless of situation

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Hydraulic Calculation of In‐Rack Sprinklers

Rubber Tire Storage •

18.5.4 30 psi

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. gpm or ‐ . spr n er


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How many sprinklers?

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Where are they?

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Minimum flow and ressure?

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Assumptions/discussion

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Calculation Technique •

Just like with ceiling sprinklers Start at most remote sprinkler with flow and pressure

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Plan View 21.7 gpm at 15 psi

Work backwards to the water supp y a ng pressure increases due to friction loss

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C

B

Add flows from other open sprinklers encountered on the way

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Adjust for elevation changes

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In‐Rack Calculation

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Assumptions Class III Commodity – Encapsulated 4 ft aisles High Temperature k‐8.0 sprinklers

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4 10

3 9

2 8

1 7

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In‐Rack Demand

1.2 15.4

Ceiling Sprinkler Demand

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At Point “C”

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235 gpm at 71 psi

22.0

Ceiling Sprinkler Demand •

After calculation, ceiling sprinkler demand at Point “C” is: 665 gpm at 84 psi

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Figure 16.2.1.3.2(f); Curve “C” 0.345 gpm per sq ft over 2000 sq ft Reduce by 20% due to extra level of in‐rack sprinklers (see 16.2.1.3.4.4) Final density/area: 0.276 gpm/sq ft over 2000 sq ft

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Put Demands Together •

Ceiling

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665 gpm at 84 psi

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In‐Rack 235 gpm at 71 psi

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Balancing the Flows

Can’t add flows unless the pressure is the same Adjusting the lower pressure situation to the higher pressure is called “Balancing the Flows”

Basic Procedure 1. Calculate the two demands separately from the most remote point to the node where they connect 2. Get the k‐factor for the lower Q pressure situation:

K



P

3. Apply the k‐factor to the higher pressure to get the new flow: Q K P 4. Add the two flows together 

Example 1

Node C

1. Calculate the two demands separately a. In‐Racks: 235 gpm at 71 psi

To Ceiling Sprinklers To In‐Rack Sprinklers

b. Ceiling: 665 gpm at 84 psi

2. Get the K‐factor for the lower pressure situation –

665 gpm at 84 psi

Which is the lower pressure situation?

C

Example 1 1. Calculate the two demands separately a. In‐Racks: 235 gpm at 71 psi

Example 1 3. Apply the K‐factor to the higher pressure

b. Ceiling: 665 gpm at 84 psi

2. Get the K‐factor for the lower pressure situation –

K

In‐Racks: 235 gpm at 71 psi

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Q

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K P

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27.89 84

256

In Racks are the lower situation in this case 235

Q 

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P

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27.89

71

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Adding Flows From In‐Rack Sprinklers to Ceiling Sprinklers

Example 1 4. Add the flows together In‐Racks: 256 gpm at 84 psi

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Ceiling: 665 gpm at 84 psi

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Total: 921 gpm at 84 psi

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Always do it unless the standard specifically says not to Happens for some flammable and combustible liquids (NFPA 30) and aerosol (NFPA 30B) arrangements Many in‐rack sprinklers –

Many barriers in the racks

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Ceiling sprinklers don’t become involved in fighting the fire unless the very top of the rack is burning

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Making the Design Most Efficient

Hydraulic Calculation of In‐Rack Sprinklers •

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Where are they?

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Systems with in‐rack and ceiling sprinklers are most efficient when the in‐rack demand matches the ceiling s rinkler demand at the oint of connection Issues that effect efficiency Sprinkler selected Piping sizes Distances pipe needs to be run

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Can we make Example 1 more efficient? •

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Individual Demands In‐Racks: 235 gpm at 71 psi

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Can we Make Example 1 More Efficient? •

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Individual Demands In‐Racks: 235 gpm at 71 psi –


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Could increase pipe size in the ceiling sprinkler system to get the demand down to 71 psi Could decrease the pipe size in the in‐rack system to get the demand up to 84 psi

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Friction Loss

In‐Rack Sprinkler System •

10 ft of 2‐inch pipe

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196 ft of 2½-inch pipe and fittings

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More 2‐inch and less 2½-inch will make the system more efficient

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Friction Loss

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49

Re lace 49 ft of 2½‐inch pipe with 2‐inch pipe and the pressure demand for both will be 84 psi

0.264 psi/ft difference

Need to make up a difference of 13 psi (84 – 71 = 13)

Flow Comparison •

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0.192 psi/ft

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0.264

Friction Loss in 2‐inch: 0.456 psi/ft

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But how much more?

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Flow to in‐rack sprinklers: 235 gpm

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Total demand with 10 ft of 2‐inch: 921 gpm at 84 psi Total demand with 59 ft of 2‐inch: 665 + 235 = 900 gpm at 84 psi Saved 21 gpm by changing 49 ft of 2½‐inch pipe to 2‐inch

Hydraulic Calculation of In‐Rack Sprinklers •

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Where are they?

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Hyd Calc of in Rack Sprinklers Handout

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