Through This Module District Collectors Will Be in a Position to Understand The

Module - 10

Contents

District Collectors (DCs) are officers of the Indian Administrative Services and are the most powerful government officials of the districts. They are entrusted the task of handling laws and orders, revenue collection, taxation, the land use planning permissions and the handling of natural and man-made emergencies.

Looking into the recent development in the area of disaster management the district collector is the boss of all types of Disaster Management. What is his/her duty and how he/she takes action are described in the present module. The module 15 also provides guidance to manage disasters.

Through this module District Collectors will be in a position to understand the

·  Existing Acts and regulations

·  Disaster management cycle

·  Types of industrial hazards

·  Their roles and responsibilities in prevention and response mechanism

1. Prevailing laws and regulations

After Bhopal Gas Tragedy of Union Carbide India Ltd., Govt. of India enacted and amended some laws to prevent and manage the Chemical (industrial) Disaster Management.

The important laws are:

Manufacture, Storage and Import of Hazardous Chemical (MS and IHC) Rules, 1989;

·  Factories Act 1948 and subsequent amendments;

·  Central Motor Vehicles Rules (CMVR) 1989 and amendments;

·  Chemical Accidents (Emergency Planning, Preparedness and Response) Rules, 1996;

·  Public Liability Insurance (PLI) ACTct, 1991; and

·  Disaster Management (DM) Act 2005.

In addition to the above, the following guideline has also been made to prevent and manage the referred disasters

·  NDMA Guidelines on Chemical (Industrial) Disaster Management 2007, the guidelines are available at www.ndma.gov.in

The other related laws and regulations are listed in appendix I.

2. Chemical Disasters or Accidents

The following definitions have been adopted in various existing Indian laws.

“Chemical Accident” means an accident involving a fortuitous, or sudden or unintended occurrence while handling any hazardous chemicals resulting in continuous, intermittent or repeated exposure to death, or injury to, any person or damage to any property but does not include an accident by reason only of war or radio-activity;

“Major Chemical Accident” means an occurrence including any particular major emission, fire or explosion involving one or more hazardous chemicals and resulting from uncontrolled developments in the course of industrial activity or transportation or due to natural events leading to serious effects both immediate or delayed, inside or outside the installation likely to cause substantial loss of life and property including adverse effects on the environment;

“Major Accident Hazards (MAH) Installations” means an isolated storage and industrial activity at a site, handling (including transport through carrier or pipeline) of hazardous chemicals equal to or, in excess of the threshold quantities specified in column 3 of Schedule 2 and 3 respectively of MS and IHC rules 1989.

3. Sources of the above disasters and accidents

The accidents as defined above in point 2. may happen to any one of the following “industrial activity”

i.  carried out in an industrial installation referred to in Schedule 4, of MS and IHC rules 1989, involving or likely to involve one or more hazardous chemicals;

ii.  on-site storage or on-site transport which is associated with that operation or process as the case may be;

iii.  isolated storage;

iv.  pipelines;

v. 

vi.  tTransportation of hazardous chemicals also cause the disasters due to accidents on road and rail, the road accidents are important for him/her to take care as DC of the district, while rail accidents need support of railways authorities.

4. Types of major chemical/industrial hazards

In addition to loss of life, the major consequences of chemical disasters include impact on livestock, flora/fauna, the environment (air, soil and water) and losses to industry as shown in Figure Fig. 1. Chemical accidents may be categorised as a major accident or a disaster depending upon the number of casualties, injuries, damage to the property or environment. A ‘major accident’ is defined in the Manufacture, Storage and Import of Hazardous Chemicals (MS and IHC) Rules, 1989, issued under the Environment (Protection) Act, 1986, whereas 'disaster' is defined in the DM Act, 2005. Fig-1

Major industrial hazards are generally associated with the potential for fire, explosion or dispersion of toxic chemicals and usually involve the accidentally release of chemicals from containment. Accidents involving major hazards could include:

·  Leakage of flammable material, mixing of material with air, formation of flammable vapour cloud to a source of ignition, leading to a fire or an explosion affecting the site and possibly a populated area.

·  -Leakage of toxic material, formation of a toxic vapour cloud and drifting of the cloud, affecting directly the site and possibly populated area.

Depending upon the state of released chemical, cause and on its consequences, the major hazards in chemical process industry are classified as:

·  Fire

·  Explosion

·  Toxic release

For more details see ThemeModule-12 “Consequence Analysis: A Vital Need for Emergency Planning”

4.1 Fire

The Fire is a process of burning that produces heat, light and often smoke and flame.

The effect of fire on the people takes the form of skin burn due to the exposure to thermal radiation. The severity of the burns depends upon the intensity of the heat and exposure time. In general terms the skin withstands heat energy of 10kW/m for approximately 8 seconds and that of 30kW/m for 0.4 seconds before pain is felt. The effect of various heat radiation levels is given in Table-1.

Table-1

Fire can takes several different forms i.e.

·  Flash Fire

·  Jet fire

·  Pool Fire

·  Secondary fire

a. Flash fire

A flash fire occurs when a cloud of flammable gas and air is ignited. The speed of burning is function of the concentration of the flammable component in the cloud and also the wind speed. Within a few second of ignition the flame spreads both upwind and downwind of the ignition source. Initially the flame is contained with in the cloud due to premixed burning of the regions within the flammable limits. Subsequently the flame extends in the form of a fire plume above the cloud. The downwind edge of the flame starts to move towards the spill point after consuming the flammable vapour downwind of the ignition source. The duration of this fire is very short and the damage is caused by thermal radiation and oxygen depletion. Photo-1 shows the flash fire.

b. Jet Fire

A jet fire occurs when a flammable liquid or gas is ignited after its release from a pressurised, punctured vessel or pipe. The pressure of release generates a long flame, which is stable under most conditions. A flash flame may take the form of jet flame on reaching the spill point. The duration of the jet fire is determined by the release rate and the capacity of the source. Flame length increases directly with flow rate. Typically a pressurised release of 8kg/s would have a length of 35m. The cross winds also affects the flame length. It is shown in Photo-2.

c. Pool fire

A pool fire occurs on ignition of an accumulation of liquid as a pool on the ground or on water or on other liquid. A steadily burning fire is rapidly achieved as the flame sustain due to vapour provided by evaporation of liquid by heat from the flames.

The maximum burning rate is function of the net heat of combustion and heat required for its vaporisation. Generally heat radiation depends on the burning rate of flame and its diameters. Photos 3a-3c show the pool fire.

Big pool fire is very hazardous and disastrous to control. This type of fire is prominent in tank farm areas and in bulk depots of petroleum products where petrol, and diesel are stored. Jaipur fire of the 2009 is the worst example of pool fire in Indian history where we lost petroleum products of worth crores and human lives and property. District collectors have to audits such bulk depots from disaster prevention angle and should be in the priority list of their administration.

d. Secondary Fire

The secondary fire involves the combustion of flammable materials those are not directly concerned with the process, and are some time present unnecessarily. For example:

·  Stored raw material and products, including packaging materials;

·  Combustible insulation of vessels, pipelines and electrical cables;

·  Combustible building material and linings.

Protection is by elimination or segregation of combustible materials, use of incombustible materials of construction and insulation, and control of ignition sources. Careless or deliberate actions may defeat in-built precautions.

4.2 Explosion

An explosion involves the production of a pressure discontinuity or blast wave resulting from a rapid release of energy. A pressure disturbance is generated in to the surrounding medium. Air becomes heated due to its compressibility and this leads to an increase in the velocity of sound, causing the front of disturbance to steepen as it travels through the air. The loading and hence the damage to the nearby targets are governed by the magnitude of and duration of pressure waves. Missiles may be generated by an explosion and are capable of causing severe damage to adjacent plant structures and people.

The explosion mainly occurs due to the rapid combustion of a flammable material but can be brought about from the chemical reactions other than combustion, provided they release large amount of energy (heat). Examples of these chemical reactions are Polymerisations, the decomposition of unstable substances and exothermic interactions of many kinds.

Classification of Explosions:

·  Chemical Explosions

·  Physical Explosions

·  Boiling Liquid Expanding Vapour Explosion (BLEVE)

a. Chemical Explosion

Chemical explosions in plant or in vessel can arise due to exothermic reactions occurring internally. Such reactions may involve decomposition of unstable substances, polymerisation of monomers, or combustion of fuel oxidant mixtures. Heating and increase of molecular number can result in a rise in pressure to the bursting point of the vessel, and explosives decompose so quickly that confinement and the development of pressure are self-imposed.

b. Physical Explosion

It occurs simply due to over pressure as in the case of steam boiler and air receiver explosions. Fire is not necessarily a consequence. But fire involving stock, buildings and plant ancillaries can cause physical explosions due to overheating followed by the overpressure in vessels and also the fireballs if contents are flammable. One such case is termed as Boiling Liquid Expanding Vapour Explosion (BLEVE). BELEVE is discussed in detail. It happens in LPG/Propane storage facilities.

The effect of various pressure waves is given in Table-2.

Table-2

c. Boiling Liquid Expanding Vapour Explosion (BLEVE)

The BLEVE occurs when the catastrophic failure of a vessel containing flammable liquid material in pressurized condition takes place. The visual effects of the BLEVE is shown in Photo-4.

Photo-4

For a BLEVE situation following four conditions must be present:

i.  There must be a substance in liquid form. Most of the destructive BLEVEs that have occurred have involved flammable liquids and liquefied flammable gases. BLEVE can occur with any liquid, even with water. The only difference is that with non flammable liquids there is no fireball. However, there will still be damaging effect including the propagating of creaks in the structure of the container together with possibility of subsequent failure and propulsion.

ii.  The liquid must be in a container like sphere, bullet, and or road/rail tanker.

iii.  The contained liquid must be at a temperature above its normal boiling point at atmospheric pressure at the time container allows the pressure inside to build up above atmospheric pressure, the fluid, in the container is able to remain in the liquid state, even though its temperature is above of its normal boiling point. This increase in pressure raises the boiling point of the contained liquid above its boiling point.

iv.  There must be a failure of the container in order to have BLEVE. This container failure can be due to following causes:

o  Flame impingement.

o  Internal structural weakness of the container

o  Failure of improperly designed SRV (safety relieve valve)

o  Impact from a mechanical cause such as a road accident, tanker derailment allowing flammable liquid to flow out.

The physical force that causes the BLEVE is because of the large vapour expansion from the liquid in the container. LPG will expand 250 times its volume when changing from liquid to vapour and water will expand 1700 times its original volume.

BLEVE accounts for the following processes:

·  heat transfer from flame to tank, from tank to the liquid and vapour phases, and between liquid and vapour phases

·  thermodynamics transformation within tank

·  activation of pressure relief valve

·  tank failure

·  -depressurisation of liquid on tank failure and missiles formation

The Hazards of BLEVE

A BLEVE poses the following hazards:

·  Fireball with thermal radiation with some rainout forming pool fires.

·  Hazard zone much larger as in pool fires

·  Missiles and major fragmentation.

·  Rocketing vessel parts.

·  Overpressure from minor shock waves.

The past experience has shown that whenever there is BLEVE; it is only the heat radiation of the fireball and the over pressure, which do the offsite damages. The effects of both can be well understood by the zones of the heat and over pressure generated by the BLEVE. BLEVE is causing damage due to heat and pressure both so, it is most dangerous.

4.3 Toxic release

The prevailing wind speed and the weather conditions play the important role in determining the dimensions of the toxic plume. To understand exposure limits and their respective effects we can divide the affected area in to three zones of various concentration levels. Table 3 describes the limits and effects.

Table-3

5. Impact zones

The impact due to fire, blast and toxicity is important for emergency management. The highest, medium and low vulnerable zones need to be demarcated to assess the areas of probable damages as described above in Tables 1-3. In general the highest vulnerable zone, medium and low vulnerable zones are depicted as red, orange and blue zones respectively.