Presentation on theme: "Local Application 1 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:
Local Application 1 Total 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. Total flooding system Protected volume
Local Application 2 Total 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.
Local Application: Definitions 3 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) Local application system Protected object
Local Application 4 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.
Local Application Considerations 5 Guidance: Provided by NFPA 12 with expertise provided by “systems” manufacturers and “users”. Limited guidelines provided by NFPA 2001 to date.
Local Application Considerations 6 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.
Local Application Considerations 7 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, minimum If the liquid has an auto-ignition temperature BELOW its boiling point, the discharge must be 3 minutes of LIQUID per nozzle, minimum Concentrations: There is no design concentration for these types of systems.
Rate 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 (ft 2 ) area coverage per spkr.
Rate by Area 9 Suitable for use on: 2 Dimensional Class B Flammables, combustible vapors or shallow solid surface coatings Open 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.
10 Rate 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 discharge Coated 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.
11 Rate by Area Basic Design Continued... 1’ 3’
12 Rate by Area Basic Design Continued... 1’ 3’
13 Rate by Area Continued… Number of Nozzles: N 1 = Side of Square ÷ Length (Rounded Up) N 2 = Side of Square ÷ Width (Rounded Up) Total Number of Nozzles = N 1 × N 2 Calculate System Flow Rate: Quantity of Nozzles × Nozzle Flow Rate
Rate by Area: Design Summary 14 Determine number of nozzles Calculate system flow rate HPCO2: Liquid Compensation LPCO2: Initial Vapor Compensation Discharge Time Define hazard parameters Add 40%: liquid portion only Consult mfg. Qty.CO 2 Req’d
Rate by Area – Open Top Pits 16 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 apply Flow Rate: 4 lbs/min/ft 2 ; not based on nozzle projection distance / square area Projection 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 pits Quench pits
Rate By Volume For Local App. “Rate by Volume” Systems CO 2 is discharged onto and surrounds an assumed volume. +2’-0” 17
Rate by Volume 18 Suitable for use on: 2 Dimensional Hazards partially or completely surrounded by permanent walls extending at least 2 ft. above the hazard 3 Dimensional hazards
Rate by Volume Continued… 19 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 gas Allows you to be more competitive Certain criteria must hold true: Walls must NOT be part of the hazard Walls must extended at least 2 ft above the hazard Permanent walls must be relatively close to the hazard (4 ft. to 8 ft.)
Rate by Volume Continued… 20 Assumed Volume Standard 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 Rates Standard Method: 1.0 lbs/min/assumed ft 3 Partial Enclosure: Permanent walls proportionally reduce the rate down to 0.25 lbs/min/ft 3. (Refer to FSSA Guidelines, NFPA 12)
Rate by Volume Continued… 21 Assumed Volume Guidelines: No assumed dimension may be less than 4’ Requires a closed floor or Volume below must be added in and additional nozzle used The area below must already be protected with CO2 that discharges at the same time If openings are small they can be protected or screened using Rate by Area directed into the Rate by Volume Hazard.
Rate by Volume Partially Enclosed Determine the Assumed Volume With Perimeter Walls For sides of the hazard that do not have permanent walls, add 2’ to each side as with the Standard Method For sides that do have permanent walls, add the actual distance to the permanent wall. HAZARD Add 2’ to the height to get assumed height, unless the top of the hazard is enclosed. Permanent Walls