EMERGENCY SITUATION

► Emergency situation for a facility and its operations may be described as a hazardous situation which requires action to control, correct and return the site to a safe condition and also requires timely action to protect people, property and the environment from harm.

► Examples of types of emergencies are:

    - fire (including generation of toxic combustion products)

   - explosion (including BLEVE)

   - spill (of hazardous solids & liquids)

   - gas leak (flammable, toxic, asphyxiant, pressurized or refrigerated liquid)

   - structural failure

   - natural event (including earth quake, storms, tides etc)

► Products impact events (road vehicles, railways, aircraft, ships ), eg: release of gases/hazardous

substances due to impact/collision of vehicles on the storage facility or during transport of such substances

► subversive activities(bomb threat, vandalism, sabotage)

Factors contributing to the emergency situation

·         Characteristics of the chemicals used

·         Storage conditions of the  raw materials

·         Equipment failure

·         Lack of awareness on the msds &emergency preparedness plans

·         Lack of involvement on the periodical testing of emergency

·         Preparedness plan

LEVEL OF EMERGENCY

► There is no direct correlation between the size of a release & scale of emergency

► Eg: A small release of chlorine gas may affect the people outside the boundary of the facility and can be categorized as an external emergency

► A large release of an alkali that  is contained within a bunded area could be classified as a local

► LOCAL EMERGENCY : is an emergency where the impacts on people, property &environment are expected to be confined to a specific location within the facility and no escalation is expected  eg: ruptured drum in ware house, leaking flange or seal, small fire in a bag store .

► SITE EMERGENCY: is an emergency where the impacts on people, property & environment are expected to be confined to spread or affect all parts of the facility but not off site

► EXTERNAL EMERGENCY: An emergency where the impacts on people, property & environment are expected to impact within the facility & beyond the boundary of the facility eg: bomb threat, a large tank bund fire, BLEVE of a large liquefied gas storage, toxic gas release, transport incident

Terminologies

► Vapour Cloud Explosion: An explosion occurring outdoors beginning with the unplanned release of a large quantity of flammable gas or vapourising liquid which ignites following the formation of a cloud or plume of pre-mixed fuel and air. The speed of flame travelling through the cloud may approach detonation velocity

► Unconfined Vapor Cloud Explosion (UVCE): When a flammable vapor is released, its mixture with air will form a flammable vapor cloud. If ignited, the flame speed may accelerate to high velocities and produce significant blast overpressure.

► Flash Fire: Flash fire is a sudden, intense fire caused by ignition of a mixture of air and a dispersed flammable substance such as a solid (including dust), flammable or combustible liquid (such as an aerosol or fine mist), or a flammable gas. It is a fire that spreads with unusual speed, as one that races over flammable liquid or through combustible gases

► A pool fire is a turbulent diffusion fire burning above a horizontal pool of vaporising hydrocarbon fuel where the fuel has zero or low initial momentum. Fires in the open will be well ventilated (fuel- controlled), but fires within enclosures may become under-ventilated (ventilation-controlled). Pool fires may be static (e.g. where the pool is contained) or 'running' fires.

Consequences

► The possible consequences of an emergency situation could be any one of the following or combination depending on the characteristics/properties of the chemical involved & the type &extent of the disaster that has occurred.

► Toxic emissions eg: if caused by leakage of pipeline/flanges would result in release of emissions within the premises ,or even beyond the premises, can cause flammable explosion(depending on its flammability) or confined or unconfined vapour cloud explosion.

► In case of rupturee of a storage tank, discharge of the hazardous substance may cause a pool of fire with or without a BLEVE

BLEVE: Boiling Liquid Expanding Vapour Explosion refers to the sudden rupture (due to fire impingement) of a vessel /systemcontaining liquified flammable gas under pressure. This immediate ignition of the expanding fuel –air mixture leads to intense combustion creating a fireball, blast wave & potential missile damage

CONSEQUENCE: The expected physical result of an incident (eg: gas or liquid release, fire explosion, overpressuring of vessel, discharge of contaminant into a water way) can cause harm to people, property and the environment (eg: heat radiation, explosion, overpressure, concentration of toxic gas, contamination of habitat).

An incident is a deviation from the intended operating conditions at a hazardous facility that has the potential to result in an emergency (eg: hole in pipe work or vessel, runaway reaction, overfilling of pressure vessel)

The triggerring of secondary events (such as toxic releases) by a primary event (such as an explosion) such that the result is an increase in consequence or in the area of an impact zone.

The forth coming slides are pictorial representations of the various events /consequences….of a toxic release for 8 minutes which has led to disastrous consequences.