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Total Flooding Systems

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Presentation on theme: "Total Flooding Systems"— Presentation transcript:

1 Total Flooding Systems
CXS490 CO2 Total Flooding Systems 1

2 Application Creation of an inert atmosphere in rooms or other enclosure (oven, ducts, etc.). Examples of application: Drying ovens, Switch-gear rooms, Fume exhaust systems, Storage rooms, etc. 2

3 Total Flooding Design Calculated volume may be reduced for space occupied by fixed impermeable objects. Type combustible (fuel) and possibility of potential deep-seated fire Minimum design concentration. Range 34% to 75% from table found in NFPA 12. Volume factor (assumes 34% design concentration) & surface fire. Minimum quantity require adjustments based on possibility deep seated fire could result, temperature & uncloseable openings. 3

4 Deduction Deduction allowance for fixed objects
In figuring the net cubic capacity to be protected, due allowance permitted to be made for permanent, non-removable, impermeable structures materially reducing volume. 4

5 Volume Factor Can use factors in two ways (multiply by smaller or divide by larger factor). 2000 ft3 ---> 20 ft3/lb or 0.05 lb/ft3 W = V x FV = 2000 x or 2000 20 Volume factor used to determine the basic quantity of carbon dioxide to protect an enclosure containing a material requiring a design concentration of 34 percent in accordance with the following Tables: 5

6 Volume Factor - Metric 6

7 Volume Factor - Imperial

8 Deduction As average small space has proportionately more boundary area per enclosed volume than a larger space, greater proportionate leakages are anticipated and accounted for by graded volume factors in the tables. 8

9 Formula W = V x FV x FC where: V = Volume (m3 or ft3)
FV = volume factor (kg/m3 or lb/ft3) FC = concentration factor 9

10 Material Conversion Factor
For materials requiring a design concentration over 34 percent, basic quantity of carbon dioxide calculated from the volume factor given in the tables and increased by multiplying quantity by appropriate conversion factor given in the following figure: 10

11 Minimum Design Concentration

12 Material Conversion Factor

13 Interconnected Volumes
In two or more interconnected volumes where “free flow” of carbon dioxide can take place, the carbon dioxide quantity shall be sum of the quantities calculated for each volume, using its respective volume factor from the tables. If one volume requires greater than normal concentration, higher concentration shall be used in all interconnected volumes. 13

14 CO2 Calculation Space with dimensions of 11.43 m long by 10.69 m wide
by 2.72 m high is to be protected by CO2. The operating temperature range is 10 to 40OC. The room contains a process that generates significant amounts of Methyl Ethyl Ketone (MEK) & Carbon Disulfide (CS2). Determine the required amount of agent and the number of Cylinders. 14

15 CO2 Calculation Review the fuels & Determine which Minimum Design
Concentration (MDC)to use: MEK is 40 % & CS2 is 72 %. Use MDC of 72 % - meets more stringent requirements. FV = from Chart 2-3.3(b) FC = from Figure 2-3.4 Cylinder sizes 34, 45 (most common) & 54 kg - Use largest cylinders 15

16 Special Conditions Additional quantities of carbon dioxide shall be provided to compensate for any special condition that can adversely affect extinguishing efficiency. 16

17 Openings Openings that cannot be closed at time of extinguishment shall be compensated for by addition of a quantity of carbon dioxide equal to anticipated loss at design concentration during a 1-minute period. This amount of carbon dioxide shall be applied through the regular distribution system. 17

18 Losses Room 9 ft ceiling 7 ft Door open Centre above 5.5’ To MDC Line
17 lb/min-ft2 21 ft2 x 17 Loss = 357lb/min 18

19 Ventilation Systems For ventilating systems that cannot be shut down, additional carbon dioxide shall be added to space through the regular distribution system in an amount computed by dividing/multiplying volume moved during the liquid discharge period by flooding factor. This shall be multiplied by material conversion factor when design concentration is greater than 34 percent. 19

20 High Temperature For applications where the normal temperature of the enclosure is above 200°F (93.3 °C): 1% increase in calculated total quantity of CO2 provided for each additional 5°F (2.77°C) above 200°F (93.3 °C) 20

21 Low Temperature For applications where the normal temperature of the enclosure is below 0°F (-17.8 °C) 1% increase in calculated total quantity of CO2 for each 1 °F (0.55 °C) below 0°F (-17.8°C). 21

22 Surface Firew Under normal conditions, surface fires are usually extinguished during the discharge period. Except for unusual conditions, it will not be necessary to provide extra carbon dioxide to maintain the concentration. 22

23 Hazard Cooling If a hazard contains a liquid having an auto-ignition temperature below its boiling point, then CO2 concentration shall be maintained for a period sufficient for liquid temperature to cool below its auto-ignition temperature. 23

24 Ducts & Trenches A minimum flooding factor of 8 ft3/lb (0.22 m3/kg) is used in ducts and covered trenches. If combustibles represent a deep-seated fire more CO2 will be required to meet deep seated fire requirements. 24

25 CO2 Requirements Deep-Seated Fires 25

26 Maintain Concentration
Quantity of carbon dioxide for deep-seated-type fires is based on fairly tight enclosures. After the design concentration is reached, concentration shall be maintained for a substantial period of time, but not less than 20 minutes. Any possible leakage shall be given special consideration because no allowance included in basic flooding factors. 26

27 Flooding Factors For combustible materials capable of producing
Outline only For combustible materials capable of producing deep-seated fires, required CO2 concentrations cannot be determined with the same accuracy possible with surface burning materials. Extinguishing concentration varies with mass of material present because of thermal insulating effects. Flooding factors determined on basis of practical test conditions. 27

28 Flooding Factors Outline only 28

29 Design Rate Outline only Minimum design rate of application based on quantity of carbon dioxide & maximum time to achieve design concentration For surface fires, design concentration shall be achieved within 1 minute from start of discharge. 29

30 Venting Outline only For very tight enclosures, necessary area of free venting calculated from following: 30

31 Acceptable Results Outline Satisfactory results will usually be achieved by assuming expansion of CO2 at 9 ft3/lb (0.56 m3/kg). 31

32 Strength & Pressure Outline / Overview 32

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