Process Safety

1.0 Safety and Hazard

Safety is an issue of utmost importance and should at no time be taken lightly. Fire, explosion, toxic release and collapses of structures such as buildings and bridges had all taken too many lives and incurred tremendous amount of losses. Businesses, workers and environment have all been seriously affected. Some of these incidences have very long effects that spanned over many years. For example, Bhopal and Chernobyl incidents that happened in the 1980’s are still collecting tolls on various illness and environmental damages, if not fatality.

1.1 Hazards in Process Industries

There are three main hazards in chemical industries. These are Fire, explosion and toxic release.In many instances, more than one of these hazards occur either simultaneously or in tandem of each other. For example, a fire may lead to explosion which subsequently cause more fire and toxic release.

1.1.1 Fire and Explosion

Fire Triangle

a. Fire Triangle

In order for a fuel to burn, heat, fuel and oxygen must be present.

These three elements form what is called the fire triangle.

To control the fire, at least one of them must be removed.

b. Fuel

c. Oxygen

d. Heat/Ignition

e. Fire Fighting

Removal of any one of the sides of this Fire Triangle will extinguish the fire.

– If fuel is removed, the fire will starve and be extinguished.

– If air is removed, the fire will suffocate – because of a lack of oxygen – and go out.

– The removal of heat is the most common form of fire suppression. There are methods of suppression, however, that work on the basis of suffocating the fire. In most cases water is used to essentially soak up the heat generated by the fire. Without energy in the form of heat the fire cannot heat unburnt fuels to ignition temperature and the fire will eventually go out. Chemicals can be added to water to improve the heat removal properties of water, or to improve the ability of the water to stick to unburnt fuel.

Combustible Dusts

Any combustible material (and some materials normally considered noncombustible) can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, it can become explosive. The force from such an explosion can cause employee deaths, injuries, and destruction of entire buildings. Such incidents have killed scores of employees and injured hundreds over the past few decades.

Materials that may form combustible dust include metals (such as aluminum and magnesium), wood, coal, plastics, biosolids, sugar, paper, soap, dried blood, and certain textiles. In many accidents, employers and employees were unaware that a hazard even existed.

A combustible dust explosion hazard may exist in a variety of industries, including: food (e.g., candy, sugar, spice, starch, flour, feed), grain, tobacco, plastics, wood, paper, pulp, rubber, furniture, textiles, pesticides, pharmaceuticals, dyes, coal, metals (e.g., aluminum, chromium, iron, magnesium, and zinc), and fossil fuel power generation.

1.1.2 Toxic Release

1.2 Causes of Industrial Incidents

Industrial incidents happen due to two major factors :

1. Substandard Design (Unsafe Conditions)

2. Substandard Practice (unsafe Acts)

Of course there are always the third factor such as natural disasters, sabotage etc. Nevertheless, most previous incidents were the results of the two factors mentioned.

While substandard practices can be dealt with through proper safety management system that include safe operating procedures, training and retraining and motivating workers to increase the work place morale, substandard design must first be overcome. Decisions on design approaches and/or techniques/technology utilised should be taken carefully following proper hazard identification and Risk Assessment techniques.

Many techniques have been proposed by the industry, responding from various incidences and disasters. Two classes of important techniques widely used by both industries and authorities are:  Hazard and Operability (HAZOP) Study and Risk Assessment . In this page, these classes of tools are summarized.


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