1

CXS490 Carbon Dioxide Systems

2

CO2 recognized as a fire extinguishing agent for many years

Used in fixed systems since before World War I.

History

3

Hazards and equipment satisfactorily protected include:

• Flammable liquid materials• Electrical hazards (transformers, switches, circuit breakers,rotating equipment, and electronic equipment)• Engines utilizing gasoline & other flammable liquid fuels.• Ordinary combustibles (paper, wood, and textiles)• Hazardous solids

CO2 Applications

4

When used to protect areas where explosive atmospheres could exist• metal nozzles must be used, and• entire system must be properly grounded.

In addition, objects exposed to discharge from CO2 nozzles• must be grounded to dissipate electrostatic charges.

Static Electricity

5

Carbon dioxide• colorless• odorless• electrically nonconductive• inert gasSuitable medium for extinguishing fires.

Carbon dioxide gas is 1.5 times heavier than air.

Liquid forms solid dry ice (“snow”) when released directly into the atmosphere.

It can be easily liquified by compression and cooling.

Properties

6

Properties

7

• Non Combustible

• Does not react with most substances

• Provides its own pressure for discharge

• Does not produce residues

Additional Properties

8

Physical Properties

HP 850 psi

LP 300 psi

Gas

Gas

Triple Point}Liquid/Gas

} Solid/Gas

Solid

9

At normal temperature and pressure, CO2 is a gas.

Above critical temperature (87.8° F), CO2 is a gas, regardless of the pressure.

Between 87.8° F and - 69° F (Triple point), carbon dioxide is partly a liquid and partly a gas.

Below the triple point (- 69° F, and 75 psi), it is either a solid or a gas depending on pressure and temperature.

Solid carbon dioxide is obtained below - 110° F.

Physical Properties

10

•At extinguishing concentrations, CO2 has a:• suffocating effect that can produces• unconsciousness and• death.

Toxicity

11

Carbon dioxide fire-extinguishing systems are useful within limits of NFPA 12 standard in extinguishing fires involving specific hazards or equipment in the following occupancies where:

• an inert electrically nonconductive medium is

essential or desirable

• cleanup of other media presents a problem

• they are more economical to install than other media

Use

12

Use

13

Carbon dioxide cannot be used on chemicals• containing their own supply of oxygen (such as cellulose nitrate)• reactive materials (sodium, potassium, etc.) and• metal hydrides.

Carbon dioxide's low cooling effect limits its use fordeep-seated fires.

Deep-seated fires require higher concentrations to be maintained for longer periods

Limitations

14

ComponentsStorageHigh Pressure Containers:

• designed to store carbon dioxide at room temperature• 850 psi at 70° F• Pressure rises rapidly with temperature• maximum temperature for storage container limited to 130° F• limitation of filling density to 68 %.• single hazard - discharges all agent • 35, 50, 75, 100 & 120 lb or 16, 23, 34, 45 & 54 kg cylinders

15

ComponentsStorage - High Pressure

16

ComponentsStorage

Low Pressure Containers:

• 1,000 lbs up to many tons• Vessels maintained at 0° F, 300 psi• by means of insulation and mechanical refrigeration• Filling densities can be as high as 95 %• Relief valves on container prevent pressure exceeding• safe limits due to refrigeration failure.• Multiple hazards - can be operated for a discharge time

17

ComponentsStorage - Low Pressure

18

Components - Pipes & Fittings

Piping and fittings shall be able to withstand high pressure developed in system.

Carbon dioxide enters piping as a liquid.

Due to friction, the pressure drops, and consequently part of liquid boils, creating a mixture of liquid and gas in piping (two phase).

19

Components - Pipes & Fittings

Piping must be designed and dimensioned so that pressure never drops under 75 psi (triple point) to avoid formation of solid ("snow") which could block the nozzles' orifices.

In practice, systems are calculated so that pressure never drops under:• 150 psi for low pressure systems, and• 300 psi for high pressure systems.

20

• Must be used within listing's limits• Mainly two types: low or high velocity

• For local application• must cover entire surface involved in fire.

Components - Nozzles

21

Fixed supply of carbon dioxide supplying hose lines

Hand Hose Line System

22

Mobile supply of carbon dioxide capable of being quickly moved to position and connected to a system of fixed piping supplying fixed nozzles and /or hose lines.

Standpipe System & Mobile Supply