The Situation. Modeling Storage Occupancies Under Sloped Ceilings. Concerns (Elevation View) The Concerns 4/29/ NFPA Conference & Expo

Transcription

1 2014 NFPA Conference & Expo Modeling Storage Occupancies Under Sloped Ceilings Presented by: Kenneth E. Isman NFSA Victoria B. Valentine NFSA Andre Marshal CSS NFPA 13 defines a sloped ceiling as one where the slope exceeds 2 in 12 (9.5 )(See Section ) NFPA 13 requires 30% increase to the design area for sloped ceilings (See Section ) Light Hazard Ordinary Hazard Extra Hazard Noah Ryder CSS 2 NFPA 13 has no criteria for dealing with storage under sloped ceiling 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. 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) 3 4 The Concerns 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? 5 6 1

2 Concerns (Plan View) Options Now Available How big will this fire be when closest sprinklers open? Open sprinklers at peak remote from fire 7 1. Don t design storage buildings with a ceiling slope greater than 2 in Install a drop ceiling under the sloped ceiling Sprinkler below drop ceiling to protect storage Sprinkler above drop ceiling if needed ddto protect concealed space Make sure ceiling is substantial and stays in place early in fire 3. Hire a fire protection engineer who can analyze the situation and develop reasonable answers to the questions asked on earlier slides 8 Potential Procedure for FPE Analysis 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 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 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 9 10 Step 1 Modeling NFSA hired Custom Spray Solutions to model a series of conditions Overview Objective of study Geometry and slopes of interest Fire definition Sprinkler characteristics Suppression off Potential effects Model characteristics Results of analysis Conclusions Future Work 11 2

3 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 i Plastic Commodity HRR curve from FMRC report HRR curve taken from freeburn fire test of plastic commodities Fire located between commodities and centered on 4 sprinklers at ground level Fire kw) HRR (k Sprinkler Characteristics Generic upright standard response sprinkler RTI s of 100 and 300 examined Activation temperature 74 C No water flowing (i.e. no suppression occurring) Time (s) 3

4 Model 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, 1m 2 Results 2:12 Results 2:12 2:12 Results, RTI Comparison Activation Order Time (s) HRR s s s s s s s s s s s RTI=100 RTI=300 Results 6:12 Results 6:12 Activation Order Time (s) HRR (kw)

5 6:12 Results, RTI Comparison RTI=100 RTI=300 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 RTI has a significant impact on sprinkler activation time, activation order for same scenario is slightly altered Conclusions Sloped ceiling requirements in NFPA 13 may be able to be revised Individual sprinkler response characteristics may be important Future Work for Modeling Evaluate impact of: X,Y Fire location on activation Z Fire location (i.e. initial height) on activation Ceiling height vs. commodity storage height Suppressionon 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? If so, you have your discharge criteria If not, need to do more work 2014 NFPA Conference & Expo CEUs: Thank You 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. ) Handouts: Handouts will be available via the mobile app or at nfpa.org/conference 29 Recordings: Audio recordings will be available. To order, see Fleetwood Media Productions (at Breakers Registration desk) or visit nfpa.org/conference 5