Presentation on theme: "Local Application Total Flooding System: (NFPA 12) A system consisting of a supply of carbon dioxide arranged to discharge into, and fill to the proper."— Presentation transcript:
1Local ApplicationTotal Flooding System: (NFPA 12) A system consisting of a supply of carbon dioxide arranged to discharge into, and fill to the proper concentration, an enclosed space or enclosure around the hazard.Protected volumeIn order to discuss “local application” the concept of “total Flooding” needs to be understood.Total flooding system
2Local ApplicationTotal Flooding: (NFPA 2001) The act and manner of discharging an agent for the purpose of achieving a specified minimum agent concentration thoughout a hazard volume.Uses: for extinguishment of Class A, Class B and Class C type surface and deep seated fires where the hazard is enclosed.Concentration:Specific to the agent and agent manufacturer.
3Local Application: Definitions Local Application system: (NFPA 12) A system consisting of a supply of extinguishing agent arranged to discharge directly on the burning material. (NFPA 2001 ref NFPA 12)Protected objectAt this point in 2013 there are no definitive guidelines to “local App” in NFPA 2001Local application system
4Local Application Uses: Typically used to extinguish surface fires where the enclosure does not conform to the requirements of total flooding OR the hazard is not enclosed. A blanket of CO2 applied directly to the burning material, starving the fuel of oxygen and providing some cooling.
5Local Application Considerations Guidance:Provided by NFPA 12 with expertise provided by “systems” manufacturers and “users”.Limited guidelines provided by NFPA to date.
6Local Application Considerations Protection of entire hazard.:Hazard shall include all areas subject to spillage, leakage, dripping, splashing, or condensation.Hazard shall include all associated materials and equipment including stock, drain boards, hoods, ducts, motors, oil pumps and lines…Inter-exposing hazards may be subdivided (and protected) if approved by the AHJ.
7Local Application Considerations Quantities:Required amount of CO2 is based on the total rate of discharge needed to blanket the area coupled with the time required.Discharge Time:30 seconds of CO2 LIQUID per nozzle, minimumIf the liquid has an auto-ignition temperature BELOW its boiling point, the discharge must be 3 minutes of LIQUID per nozzle, minimumConcentrations:There is no design concentration for these types of systems.
8Rate by Area Method The area method Shall be used where the fire hazard consist primarily of flat surfaces or low-level objects associated with horizontal surfaces.Think: Spkr. system layout: square foot (ft2) area coverage per spkr.
9Rate by Area Open top tanks or vats containing combustible liquids. Suitable for use on:2 Dimensional Class B Flammables, combustible vapors or shallow solid surface coatingsOpen top tanks or vats containing combustible liquids.Vertical Hazards less than 2’-0 in height.Can not be used where the material could support a Deep-Seated fire.
10Rate By Area – Important definitions Discharge Nozzles: Should be directional, listed and approved.Liquid Surface: A surface with a flammable liquid in depth. Splashing of the liquid is possible during dischargeCoated Surface: Area covered with a flammable but not in depth. Splashing is not possible.Side of Square: Length of the longest side of an area that can be protected by a discharge nozzle that is located at a specific height above the hazard.Freeboard: The distance between the top of a tank and the liquid surface inside the tank.Projection Distance: The distance from the bottom or edge of the nozzle to the fuel surface.
13Rate by Area Continued… Number of Nozzles:N1 = Side of Square ÷ Length (Rounded Up)N2 = Side of Square ÷ Width (Rounded Up)Total Number of Nozzles = N1 × N2Calculate System Flow Rate:Quantity of Nozzles × Nozzle Flow Rate
14Rate by Area: Design Summary Define hazard parametersDetermine number of nozzlesCalculate system flow rateAdd 40%: liquid portion onlyHPCO2: Liquid CompensationLPCO2: Initial Vapor CompensationConsult mfg.Discharge TimeQty.CO2 Req’d
16Rate by Area – Open Top Pits Definition: An open pit greater than 4 ft (1.2M) in depth OR a depth equal 25% the width, which ever is greater.Coated / Liquid Surface Rules still applyFlow Rate: 4 lbs/min/ft2; not based on nozzle projection distance / square areaProjection Distance: Nozzles to be mounted at 66% of the pits depth.9ft deep pit would have the nozzles mounted at the 6ft level.Liquid Discharge remains 30 seconds.Common Open Top Pit Hazards:Oil pitsQuench pits
17Rate By VolumeFor Local App. “Rate by Volume” Systems CO2 is discharged onto and surrounds an assumed volume.+2’-0”17
18Rate by Volume Suitable for use on: 2 Dimensional Hazards partially or completely surrounded by permanent walls extending at least 2 ft. above the hazard3 Dimensional hazards
19Rate by Volume Continued… Two methods of protecting a Rate by Volume Hazard:Standard Method: (no permanent walls exist adjacent to the hazard)Partial Enclosure Method: (Permanent walls adjacent to the hazard)Allows for the use of less gasAllows you to be more competitiveCertain criteria must hold true:Walls must NOT be part of the hazardWalls must extended at least 2 ft above the hazardPermanent walls must be relatively close to the hazard (4 ft. to 8 ft.)
20Rate by Volume Continued… Assumed VolumeStandard Method: Add 2 ft to the extreme dimensions for all four sides and the top of the hazard.Partial Enclosure: If permanent walls exist which do not form part of the hazard itself, then use the actual distance to that wall.Discharge RatesStandard Method: 1.0 lbs/min/assumed ft3Partial Enclosure: Permanent walls proportionally reduce the rate down to 0.25 lbs/min/ft3. (Refer to FSSA Guidelines, NFPA 12)
21Rate by Volume Continued… Assumed Volume Guidelines:No assumed dimension may be less than 4’Requires a closed floor orVolume below must be added in and additional nozzle usedThe area below must already be protected with CO2 that discharges at the same timeIf openings are small they can be protected or screened using Rate by Area directed into the Rate by Volume Hazard.
22Rate by Volume Partially Enclosed Determine the Assumed Volume With Perimeter WallsFor sides of the hazard that do not have permanent walls, add 2’ to each side as with the Standard MethodFor sides that do have permanent walls, add the actual distance to the permanent wall.Permanent WallsHAZARDAdd 2’ to the height to get assumed height, unless the top of the hazard is enclosed.