When discussing risk, we typically consider two key aspects: frequency and severity. The higher the frequency and severity, the greater the risk. But what are the factors that influence the frequency and severity of risks?
In process safety, we analyse risks by considering factors related to nature, objects and humans. These factors can be summarized by the acronym TIMEX: Time, Inventory, Material, Energy and eXposure. (Tracey, 2024) For nature related risks, we assess time, including day, weather, season or other time related elements. When evaluating objects, we focus on inventory, material and energy to identify the types and quantities of substances involved. One of the primary goals of process safety is to protect people, so we also analyse exposure to person.
Now that we understand the factors affecting risk, the next step is to control hazards in order to reduce the risk. This can be done by eliminating hazards and implementing preventive and control measures. Hazard Elimination is most effective during the design stage by addressing ‘time, inventory, material, energy and exposure’ related to hazards throughout the entire lifecycle of a manufacturing process. Tools such as HAZOP (Hazard and Operability Study) and PHA (Process Hazard Analysis) are commonly used for this purpose. It is quicker and easier to make changes at the design stage because only design documents need to be modified- there is no need to build, move or install equipment or machines. However, during the production stage, equipment and machines are already installed, so eliminating hazard might require equipment modifications, which can be time consuming. As a result, preventive measures and control measures are typically employed during this stage.
Preventive measures include detectors (e.g., gas detectors, smoke detectors, fire detectors), ventilation systems, EX rated equipment, training programs. Control measures include emergency response plans, fire extinguishers, sprinklers systems.
Elimination, prevention and control measure are all aimed at reducing risk and protecting both people and the environment. Only by understanding the factors that influence risks that we can apply appropriate measure to reduce risk effectively, protect human and the environment.
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Reference: Tracey Kelly, 2024, IOSH Process Safety training, Dublin.