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The Situation
2014 NFPA Conference & Expo
• NFPA 13 defines a “sloped ceiling” as one where the slope exceeds 2 in 12 (9.5°)(See Section 3.3.5.3)
• NFPA 13 requires 30% increase to the design area for sloped ceilings (See Section 11.2.3.2.4)
Modeling Storage Occupancies
Under Sloped Ceilings
Presented by:
y
Kenneth E. Isman ‐ NFSA
– Light Hazard
– Ordinary Hazard
– Extra Hazard
Victoria B. Valentine ‐ NFSA
Andre Marshal ‐ CSS
Noah Ryder ‐ CSS
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The Situation
The Situation
• NFPA 13 does not tell you what to do in this circumstance
• NFPA 13 tells you what not to do (don’t use the criteria in the storage chapters)
• NFPA 13 has no criteria for dealing with storage under sloped ceiling
• “12.1.2 Ceiling Slope. The sprinkler system criteria specified in Chapter 12 and Chapters 14 through 20 are intended to apply to buildings with ceiling slopes not exceeding 2 in 12 (16.7%) unless modified by a specific section in Chapter 12 and Chapters 14 through 20.”
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The Concerns
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Concerns (Elevation View)
• How many sprinklers will open if there is a fire?
• Where will those sprinklers be that will open?
– Will those sprinklers be over the fire and have an effect on the fire?
– Will those sprinklers be remote from the fire taking water from the supply, but not helping with fire control?
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Concerns (Plan View)
Options Now Available
1. Don’t design storage buildings with a ceiling slope greater than 2 in 12
2. Install a drop ceiling under the sloped ceiling
– Sprinkler below drop ceiling to protect storage
– Sprinkler above drop ceiling if needed to protect kl
b
d
l
f
d d
concealed space
– Make sure ceiling is substantial and stays in place early in fire
Open sprinklers at peak remote from fire
How big will this fire be when closest sprinklers open?
3. Hire a fire protection engineer who can analyze the situation and develop reasonable answers to the questions asked on earlier slides
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Potential Procedure for FPE Analysis
Potential Procedure for FPE Analysis
3. From discharge criteria in step 2, determine necessary pressure at sprinklers
4. Divide the pressure in step 3 by the cosine of the angle of the slope
pp y
y
5. Apply a safety factor to the number of sprinklers that were calculated to be open in step 1(a)
6. Apply a safety factor to the shape of the design area calculated in step 1(b)
7. Answers to steps 4, 5 and 6 constitute discharge criteria for that specific situation
1. Model specific situation to see:
a) How many sprinklers will open
b) Which sprinklers they will be
c) Heat release rate of fire when sprinklers over fire open
2. Review existing fire tests to see if discharge criteria exists for a fire with the heat release in step 1(c) when sprinklers open
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Step 1 Modeling
Overview
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• NFSA hired Custom Spray Solutions to model a series of conditions
Objective of study
Geometry and slopes of interest
Fire definition
Sprinkler characteristics
– Suppression off
pp
– Potential effects
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Model characteristics
Results of analysis
Conclusions
Future Work
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Objective of Study
Geometry
Does a sloped ceiling significantly affect the activation of the sprinklers in the region of the fire and if so at what slope does this begin to occur?
36m x 50m footprint
Geometry
Sprinklers & Commodity
• 13 Rows of sprinklers, longitudinal spacing constant, latitude spacing adjusted based on slope
• 7 rows of commodities
• Commodities mimic Plastic Commodity HRR C
diti
i i Pl ti C
dit HRR
curve from FMRC‐84‐0056 report
Fire
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•
•
•
30000
25000
HRR (kkW)
• HRR curve taken from freeburn fire test of plastic commodities
• Fire located between commodities and
commodities and centered on 4 sprinklers at ground level
Sprinkler Characteristics
20000
15000
Generic upright standard response sprinkler
RTI’s of 100 and 300 examined
Activation temperature 74° C
No water flowing (i.e. no suppression occurring)
10000
5000
0
0
100
Time (s)
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Model
Results 2:12
• Q* and D* analysis done to aid in grid sizing
• Grid Resolution 0.10m cubes
• Slopes
– 2:12
– 4:12
– 6:12
• Prescribed fire growth rate
– Ramp
– Fire area, 1m2
Results 2:12
2:12 Results, RTI Comparison
Activation Order
Time (s)
HRR
01
96.9 s
5738
02
100.3 s
7337
03
101.5 s
7348
04
103 2 s
103.2 s
7329
05
107.8 s
7899
06
108.9 s
9076
07
113.1 s
9649
08
117.0 s
RTI=300
10540
09
117.1 s
10540
10
118.2 s
11044
11
119.7 s
10644
Results 6:12
RTI=100
Results 6:12
Activation Order
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
Time (s)
97.3
98.2
113.2
115.1
119.5
120.9
122.5
123.8
126.5
134.6
135.3
135.5
136.2
136.6
137.4
139.7
142.8
144.2
145.0
145.5
145.8
HRR (kW)
4801.98
7552.75
8630.82
10036.67
10328.14
11514.61
11827.58
14077.64
12881.48
14697.90
14890.81
14201.05
15623.09
15073.80
15718.76
15776.78
20151.83
22334.08
22820.93
23639.38
22068.50
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6:12 Results, RTI Comparison
RTI=100
Conclusions
• Sloped ceiling up to 4:12 minimal to no change in activation order for given scenario
• 6:12 still produces reasonable results, first two sprinklers to activate are around fire and next three are adjacent or around it
three are adjacent or around it
• RTI has a significant impact on sprinkler activation time, activation order for same scenario is slightly altered
RTI=300
Conclusions
Future Work for Modeling
• Sloped ceiling requirements in NFPA 13 may be able to be revised
• Individual sprinkler response characteristics may be important
• Evaluate impact of:
– X,Y Fire location on activation
– Z Fire location (i.e. initial height) on activation
– Ceiling height vs. commodity storage height
– Suppression on sprinkler activation
Suppression on sprinkler activation
• Generic sprinkler spray characteristics
• Manufacturer/Model specific sprinkler characteristics
Next Steps in Potential Discharge Criteria Determination
• Look at heat release rates of fire when all four sprinklers around fire are open
• Are these comparable to fire size under flat ceiling situations?
2014 NFPA Conference & Expo
Thank You
CEUs:
To receive CEUs for this session, scan your badge at the back of the room before leaving
Evaluation: Complete the session evaluation on the mobile app. (To download, search your app store for ‘NFPA 2014 C&E.’)
– If so, you have your discharge criteria
If so you have your discharge criteria
– If not, need to do more work
Handouts:
Handouts will be available via the mobile app or at nfpa.org/conference
Recordings: Audio recordings will be available. To order, see Fleetwood Media Productions (at Breakers Registration desk) or visit nfpa.org/conference
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