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Published byTrenton Brought Modified about 1 year ago

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Carbon Dioxide Systems 1.Carbon dioxide properties 2.Storage 3.Uses 4.Limitations 5.Types of systems 6.Local Application 7.Total Flood

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1. Carbon Dioxide Properties [.03%] in atmosphere Colourless, odourless Density 1.5 times air Non-conductive Forms dry ice snow Displaces oxygen and cools

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Phase Diagram Fig. 7-1, page 115 Solid phase Vapour phase Liquid phase Triple point Critical temperature

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2. Storage High Pressure Cylinders Low pressure Storage Containers

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High Pressure Cylinders Liquid CO 2 @ 70 0 F, 850 psi, Can range 32 0 F – 120 0 F Capacity, 5- 100 lb Relief valve, 2500-3,000 psi Usually matching reserve Fill density 68% Dip tube

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Low Pressure Storage Containers Constant O 0 F, 300 psi Refrigerated, pressurized Electrical supervision Capacity in tons Insulated Pressure relief multiple discharges possible

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3. Uses Ordinary combustibles, class A Flammable liquids, class B Electrical hazards, class C See examples in text

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4. Limitations Not with Oxidizers Reactive metals Metal hydrides Occupied areas

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Personnel Hazards Ideally unoccupied [CO2] > 34% [O2] < 15% Continuous pre-discharge alarms Breathing apparatus Voice alarm systems Exits

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Personnel Hazards continued Signs Training Time delay Manual activation Manual override Scented gas

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5. Types of Systems Total flooding Local application Hand hose lines Standpipe systems and mobile supply

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6. Local Application Rate-by-volume local application Rate-by-area local application

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Rate-by-volume local application Imaginary volume object flush on solid floor add 2 feet to each open surface V img = (L + 4 ft) x ( W + 4 ft) x (H + 2 ft) R = Vimg x ( 1lb/min/ft 3 ) W = R x D

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Rate-by-area local application Pages 127-131 2D horizontal fires flammable liquids diptanks, drainboards min. discharge 30 sec. If storage is high pressure, add 40%

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Nozzles Square coverage typically 20-30 ft 2 specifications from manufacturer

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1. determine max. width 2. Extend line horizontally to intersect nozzle graph different scales for drainboard and diptank 3. Drop vertical line from point of intersection 4. Extend horizontal line from point of intersection 5. Read flow rate F liquid (lb/min) Steps

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6. Number of nozzles for diptank N liquid 7. FR liquid = N liquid x F liquid 8. Number of nozzles for drainboard N coated 9. FR coated = N coated x F coated 10. FR total = Fr liquid + Fr coated 11. W (lb) = FR (lb/min) x D (min) 12. If storage is HP, increase FR by 1.4

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7. Total Flood Multi-step procedure –Evaluate room –Evaluate fire –calculation

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Evaluate enclosure integrity Acoustical ceiling tiles door closers Windows Other openings Floor openings Wall joints

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Evaluate Enclosure Integrity continued Wall rigidity HVAC –Supply shut-off –Exhaust dampers Fan test

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Evaluate Personnel Hazards Record activity Time to exit Worse case time to exit Door recognition test Warning sign effectiveness Review personnel hazards Don’t increase hazard

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Evaluate fire scenario Control ignition sources –See list pages 133-4 Surface or deep-seated fire?

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Measure room volume L x W x H Can reduce for solid objects Add plenum space

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Determine type of combustible Material Surface or deep-seated fire

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Determine Minimum design concentration See fig. 7-10 Theoretical minimum Minimum design concentration 34-75%

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Determine volume factor See 7-ll and 7-12 Lb CO 2 / ft 3 For design conc. = 34% Varies with room size Minimum values exist

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Determine basic quantity of CO 2 Assumes design conc. = 34 % Q basic (lb) = V(ft 3 ) x volume factor (lb/ft 3 )

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Determine material conversion factor See 7-13 Dimensionless number Increases quantity Materials with design conc. > 34%

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Adjust quantity for temperature 1% increase / 5F 0 > 200 0 F 1% increase / 1F 0 < 0 0 F

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Adjust quantity for unclosable openings Add extra gas See 7-14 Need area of opening Distance center below ceiling

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Other scenarios for loss of gas Supply air Calculate quantity Apply flooding factor Apply material conversion factor Apply temperature compensation

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Consider extended application For other leaks Deep-seated fires Maintain design conc.

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Calculate pressure relief venting Very tight rooms X = Q total / 1.3 P ½ See 7-15 unlikely

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Determine number of nozzles One / 400 ft 2 ceiling area Max 20 ft spacing Max. 10 ft from wall

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Calculation form See page 145

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