Explosion Risk Analysis (ERA)

Fire & Explosion Risk Assessment (FERA) is a structured and systematic process to identify and assess risks from fire and explosion hazards. The results of this assessment are used to ensure safe facility layouts, specify passive and active fire protection requirements, and provide input for Escape and Evacuation Risk Assessment (EERA), Emergency Systems Survival Assessment (ESSA), Building Risk Assessment (BRA) and Quantitative Risk Assessment (QRA) studies.

The objectives of a FERA include:
⦁ Identifying potential fire and explosion hazards in a facility or during an activity;
⦁ Identifying the impact of fires and explosions on plant equipment, and facilities;
⦁ Providing recommendations to minimize the severity of fires and explosions;
⦁ Defining the required protection measures which control or mitigate the effects of fires and explosions; and
⦁ Assessing opportunities to reduce risks further from fire and explosion hazards.

In a typical ERA, a statistical analysis of occurrence of all aspects of the event sequence leading up to an explosion is required, in order to establish a probabilistic representation of the blast loads. This will include the following aspects:
⦁ leak frequency analysis
⦁ flammable gas dispersion
⦁ ignition probability modelling
⦁ flammable gas explosion

The flowchart provided in Figure 1 shows how the different tasks interrelate.

Frequency Assessment
Since the ERA is a risk based approach it is not limited to a single worst case nor a limited number of credible scenarios but it considers all the potential losses of containment (e.g. small, medium, large and even full bore leak) that can arise in the facility and attributes a probability to each event. The likelihood of loss of containment of a given isolatable section of the process is determined using historical failure rate data for standard plant components (e.g. pumps, valves, flanges, etc.). The frequency assessment involves the quantification of failure frequencies by combining the component failure rate data with a component ‘parts count’ of a given isolatable section. This parts count is done for all the isolatable sections that have been identified in order to cover the risks of the entire facility. This frequency assessment is the first step of any risk based approach. The HSE hydrocarbon release database (HCRD) has become the standard source of release frequencies for offshore facilities (OGP, 2010).

⦁ Dropped Object Study
⦁ Ship Collision Study
⦁ SSIV Requirement Study
⦁ Flare Radiation, Dispersion & Noise
⦁ AIV & FIV Analysis
⦁ Deflagration Study