Safe design has long been a priority in the process industries. It is a design that effectively minimizes the likelihood of process hazards and mitigates their potential consequences to achieve tolerable risk.
Today, the process industries need to be certain that their stakeholders have confidence in how they manage the environmental, health, security, and safety implications of industrial activities. A safe and documented design basis, together with a formal safety management system and safety practices, procedures, and training, are critical for providing that level of confidence required for risk management.
Risks (see Figure 1) cannot be completely eliminated from the handling, use, processing, transportation, and storage of hazardous materials. Instead, the goal of process safety management is to consistently reduce risk to a level that can be tolerated (see Figure 2) by all concerned including facility staff, company management, surrounding communities, the public at large, industry, and government agencies. A systematic, risk-based approach to safe design can help eliminate hazards that pose high risk from the process and mitigate the potential consequences of hazards.
To achieve a consistent, effective approach to risk reduction, design engineers must be able to define “tolerable” and “intolerable” risks. To meet the expectations of shareholders, employees, regulators, and the communities that surround process facilities, design engineers need to be able to document how risk and safety are addressed in the design process.
At the same time, to meet business needs of the company, process safety design solutions must be cost-effective. A risk-based approach to safe design enables design engineers to answer the needs of all process safety stakeholders without compromising on safety and without excessive prevention and mitigation measures. Risks are typically reduced to a level that is as low as reasonably practicable (ALARP) as shown in Figure 3.
For chemical processing safe design, risk is understood in terms of the likelihood and consequences of hazard scenarios that could expose people, property, or the environment to the harmful effects of a hazard. Hazards, as defined by the Center for Chemical Process Safety (CCPS) of the American Institute of Chemical Engineers (AIChE), include chemical or physical conditions or characteristics that can harm people, property, or the environment. Incident likelihood encompasses frequency and probability; consequences refer to outcomes and impacts.
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