Handbook for Process Safety in Laboratories and Pilot Plants

Part 4 – Managing Risk: Engineered Controls

The hierarchy of controls for process safety hazards was described in Section 4.2. Engineered safeguards are preferred over administrative safeguards. Thus, the engineered controls described in Part 4 would be preferred over administrative controls described in Part 5.

An engineered control is a specific hardware or software system designed to maintain a process within safe operating limits, to safely shut it down in the event of a process upset, or to reduce human exposure to the effects of an upset [1]. Part 4 includes chapters that present engineered safeguards for specific hazards and one chapter on selection of automated controls.

An integrated strategy with both prevention measures and mitigation measures is typically adopted to address most hazards. The concept of preventive and mitigative safeguards was introduced in Section 4.7. The definitions are repeated here for reference:

• Preventive safeguards lower the likelihood that a loss of control or containment incident will occur. They typically prevent the cause of an incident.
• Mitigative safeguards lower the severity of the consequences should the incident occur. They typically reduce the consequence of an incident.