Risk Management and Mitigation Dr. AA Department of Chemical Engineering University Teknology Malaysia

Release Mitigation

Release Mitigation The purpose of the consequence modelling is to provide a tool for performing release mitigation. Release mitigation is defined as “lessening” the risk of a release incident by acting on the source (at the point of release) either - 1. in a preventive way by reducing the likelihood of an event which could generate a hazardous vapour cloud; or 2. in a protective way by reducing the magnitude of the release and/or the exposure of local persons or property.

Release Mitigation Preventing release is the best way to prevent accidents Release mitigation involves (see figure 1) Detecting the release as quickly as possible; Stopping the release as quickly as possible; and Invoking a mitigation procedure to reduce the impact of the release on the surroundings. Reduce amount of vapour formed/release Once a release is in vapour form, the resulting cloud is nearly impossible to control. Table 1 provides additional methods and detail on release mitigation techniques.

Figure 1 – Release Mitigation Procedure Design Basis Source Model Dispersion Model Prediction of Release Impact Is Hazard Acceptable ? Toxic Release Model Revise Process or plant Process operation Emergency response Operate plant yes No Figure 1 – Release Mitigation Procedure

Table 1 Release mitigation approaches Major Area Examples Counter-measures Water sprays. Water curtains. Steam curtains. Air curtains. Deliberate ignition of explosive cloud. Dilution. Foams. Emergency Response On-site communications. Emergency shutdown equipment and procedures. Site evacuation. Safe havens. Personal protective equipment. Medical treatment. On-site emergency plans, procedures, training and drills.

Table 1 Release mitigation approaches Major Area Examples Inherent Safety Inventory reduction : Less chemicals inventoried or less in process vessels. Chemical substitution : Substitute a less hazardous chemical for one more hazardous. Process attenuation : Use lower temperatures and pressures. Engineering Design Plant physical integrity : Use better seals or materials of construction. Process integrity : Ensure proper operating conditions and material purity. Process design features for emergency control : Emergency relief systems. Spill containment : Dikes and spill vessels.

Table 1 Release mitigation approaches Major Area Examples Management Operating policies and procedures. Training for vapor release prevention and control. Audits and inspections. Equipment testing. Maintenance program. Management of modifications and changes to prevent new hazards. Security. Early Vapor Detection and Warning Detection by sensors. Detection by personnel.