Vapor dispersion water sprays

Water spray systems have been demonstrated to assist in the dispersion of vapor releases. The sprays assist in the dilution of the vapors with the induced air currents created by the velocity of the projected water particles. They cannot guarantee that a gas will reach an ignition source but do improve that probabilities that dispersion mechanisms will be enhanced. 

Activate fixed fire extinguishing systems or vapor dispersion mechanisms (i.e., water sprays). 

There are a variety of nozzles that can be provided to hoses and monitors. They are capable of projecting a solid, spray or fog stream of water depending on the requirements and at varying flow rates. Straight stream nozzles have a greater reach and penetration, while fog and water sprays will absorb more heat because the water droplets absorb more heat due to greater surface area availability. Fog and water spray nozzles are sometimes used to assist in the dispersion of vapor releases. 

Sprinkler - Water deflector spray nozzle devices used to provide distribution of water at specific characteristic patterns and densities for purposes of cooling exposures, suppression of fires and vapor dispersions. 

Vapor Dispersion Vapors from certain materials can be dispersed or moved using water spray or air movement. Reducing the concentration of the material may bring the material into its flammable range. 

Tolson, P., Examination of possible electrostatic hazards arising from the use of water spray barriers to disperse flammable vapors, J. Electrostatics, 23, 89-98, 1989. 

Some toxic chemicals have a strong affinity for water or other liquids. Sprays in the path of the cloud will absorb some of the chemical and will induce more turbulence in the cloud which can lead to enhanced dispersion. Water is used for vapors that have an affinity for water, for example halogen acids, and ammonia. 

Martinsen, Muhlenkamp, and Olson 1977 To test varied spray nozzles and water flow rates to determine their effectiveness in dispersing LNG vapors. Water sprays do affect concentration reduction of LNG vapors... 

Moodie 1981 To study the effectiveness of different nozzle sizes and arrangements in full-scale water-spray barriers to disperse heavy-gas vapor clouds. Amount of air entrained by a water-spray barrier may be dependent on nozzle inclination. Results demonstrated the effectiveness of the basic arrangement tested and the experimental method of assessment. 

Water sprays from monitor nozzles and hose lines can be used for vapor mitigation. Tests have been conducted in which monitor nozzles and hose lines have been used to create a chimney effect through which the gas is forced upward and dispersed at a high elevation (Beresford, 1981). Application techniques and flow rates are facility-, installation-, and material-specific. Careful planning, analyses, and testing should be conducted prior to deciding on the use of a mobile water spray as a proven means of mitigation. Preventive maintenance of this equipment is key to reliable operation. Hose lines, typically, are hydrostatically tested annually. Flow tests should also be conducted periodically. 

In the analysis it was assumed that the water-spray curtain was activated within one minute of the start of the incident and that 86% of the HF vapor from the evaporating pool that reached it was removed. The balance of the HF not removed by the water sprays became the material that formed the reduced hazard zone and the input for the dispersion modeling. For the F/l meteorological conditions the mitigated hazard zone for the centerline concentration of 20 ppm was 750 m. The effectiveness of water spray as postrelease mitigation measure is shown in Table 7.6. 

Water, steam, and air curtains and water sprays are primarily effective in dispersing and/or diluting vapors with air to reduce the severity of effects of a hazardous vapor release. In some cases, vapors can be partially knocked down or absorbed after release. ... 

SPILL CLEAN UP use water spray to cool and disperse vapors dilute spills to form nonflammable mixtures control runoff and isolate discharged material for proper disposal eliminate all ignition sources. 

SPILL CLEAN-UP collect leaking and spilled liquid in sealable containers or absorb as much as possible with inert materials, sueh as dry earth or sand flush remaining liquid with large amounts of water but not into spaces such as sewers due to possibility of explosion use water spray to disperse vapor remove all sources of ignition. 

SPILL CLEAN-UP Stop or control leak if possible use water spray to cool and disperse vapors absorb liquid in noncombustible materials (e.g., dry earth, sand or vermiculite), and place in chemical waste container. 

SPILL CLEAN-UP use water spray or fog to knock down and absorb vapors if in liquid form, absorb in noncombustible material or allow to vaporize, and disperse the gas. 

SPILL CLEAN-UP evacuate danger area ventilate area of leak or spill use fine water spray to disperse vapors water jet should never be directed on liquid remove all sources of ignition. 

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