Control of risk is a pervasive issue in engineered processes. All Engineer-it strategies contibute to minimising the risk of unsatisfactory outcomes, i.e. to risk mitigation.
A common defininition of risk is: the combination of the likelihood of occurrence and the consequences of a negative event i.e. of the occurrce a hazard.
A process for controlling risk is: First, identify the hazard; then use mitigation measures in this order of preference:
- Take action to eliminate it
- Seek to reduce the likelihood of the event
- Seek to reduce the consequences should the event occur.
For example, in construction site safety, the hazard of people falling from a scaffold may be mitigated by:
- Eliminate: Avoid using a scaffold; work from secure platforms on the inside of the building.
- Reduce likelihood: Provide a barrier on the outside of the scaffold.
- Reduce consequences: personnel are attached by a safety line.
What-if analysis is commonly used to identify hazards. The risk analysis team ask questions such as 'What if the control system fails?'
Formal approaches to risk control include:
- Use of a risk register where the hazards are identified, quantified and mitigated
- Hazard and operability analysis (HAZOP) - typically used for the design and operation of chemical plant.
The failure of a safety-critical system could result in loss of life, significant financial loss, damage to the environment, etc. Safety-critical contexts arise, for example, in the development of drugs, in the flight control of aircraft, in buildng processes. Especial attention to safety issues is needed in the design and development of such systems; in particular, the adoption of a safety culture is advised.
A safety culture is where all involved in the enterprise constantly think about safety, act safely and suggest actions to improve safety. Collaborative leadership is essential in a safety culture. A suggestion to improve safety made by any employee must be considered by management and, if appropriate, acted on. The concept of whistleblowing is discarded. Those who make useful suggestions for improvement may be rewarded rather than vilified.
If you visit a nuclear power plant, you will be introduced to the safety culture and be expected to act safely. This situation also pertains if you visit a well managed construction site.
The diagram below shows the dramatic reduction in accidents after a safety culture was adopted in the construction of the 2012 London Olympic Park.