Storage Occupancies Under Sloped Ceilings. Victoria B. Valen.ne, P.E. IFSA Technical Director 6 November 2014

Transcription

1 Storage Occupancies Under Sloped Ceilings Victoria B. Valen.ne, P.E. IFSA Technical Director 6 November 2014

2 The Situa.on NFPA 13 defines a sloped ceiling as one where the slope exceeds 2 in 12 (9.5 )(See Sec.on ) NFPA 13 requires 30% increase to the design area for sloped ceilings (See Sec.on ) Light Hazard Ordinary Hazard Extra Hazard 2

3 The Concerns 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? 3

4 Sprinkler Layout Eleva6on View Plan View 4

5 Op.ons Now Available Do not design storage buildings with a ceiling slope greater than 2 in 12 Install a drop ceiling under the sloped ceiling Sprinkler below drop ceiling to protect storage Sprinkler above drop ceiling if needed to protect concealed space Make sure ceiling is substan.al and stays in place early in fire Hire a fire protec.on engineer who can analyze the situa.on and develop reasonable answers to the ques.ons asked on earlier slides 5

6 Procedure for FPE Analysis 1. Model specific situa.on to see: How many sprinklers will open Which sprinklers they will be Heat release rate of fire when sprinklers over fire open 2. Review exis.ng fire tests to see if discharge criteria exists for a fire with the heat release in step 1(c) when sprinklers open. 3. From discharge criteria in step 2, determine necessary pressure at sprinklers. 6

7 Procedure for FPE Analysis 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 cons.tute discharge criteria for that specific situa.on. 7

8 Modeling Stepped Ceiling Small frac.on of T T T = 0.1H or T = 0.2H H Step should be between 0.01H and 0.04H 8

9 Modeling Spray Paeern Under Sloped Ceiling Custom Spray Solu.ons February 2013 Modeled double- row racks, 20 h high Looked at spray on ceiling and weing of surfaces on storage loads 9

10 Graphic Output of Spray Modeling 10

11 Conclusions from Spray Modeling Orien.ng the sprinkler parallel to the ceiling Reduces the quan.ty of water that strikes the ceiling The ceiling is less of an obstruc.on Increases the quan.ty of water delivered to the protected commodi.es This modeling was done without fire tes.ng or fire plume interac.on 11

12 Fire Modeling NFSA hired Custom Spray Solu.ons to model a series of condi.ons Modeled 20 h high rack storage At the low end of pile heights that qualifies as storage Allowed us to keep the size of the building smaller to minimize modeling.me We had free- burn heat release data for rack storage of 20 h high Class II and Group A plas.cs 12

13 Geometry 36m x 50m footprint

14 Fire HRR curve taken from FM report for Plas.c & Class II commodi.es Fire located centered on 4 sprinklers at ground level Generic upright standard response sprinkler RTI s of 100 and 300 examined Ac.va.on temperature 74 C No water flowing (i.e. no suppression occurring) HRR (kw) HRR (kw) Time (sec) Time (s)

15 Results 2:12 Group A Plas.cs Ac6va6on Order Time (s) HRR (kw) Up Slope s s s s s s s s s s s 10644

16 2:12 Results, RTI Comparison RTI=100 RTI=300 RTI=100 RTI= s s s s s s s s s s

17 Up Slope Results 6:12 Ac6va6on Order Time (s) HRR (kw)

18 6:12 Results, RTI Comparison RTI=100 RTI=300

19 Conclusions Up to 4:12 minimal to no change in ac.va.on order for given scenario 6:12 s.ll produces reasonable results First 2 sprinklers to ac.vate are around fire and next 3 are adjacent or around it RTI has a significant impact on sprinkler ac.va.on.me Ac.va.on order for same scenario is slightly altered Sloped ceiling requirements in NFPA 13 may be able to be revised Individual sprinkler response characteris.cs may be important

20 Next Steps in Poten6al Discharge Criteria Determina6on Look at heat release rates of fire when all four sprinklers around fire are open Are these comparable to fire size under flat ceiling situa.ons? If so, you have your discharge criteria If not, need to do more work 20

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