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

2. Release Mitigation

3. 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.

4. 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.

5. 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

6. 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.

7. 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.

8. 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.