Question 5 of 7: Risk Management and Chemical Risk Assessment

Question 5: Risk Management and Chemical Risk Assessment (20 marks: 6/7/7)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(i) Components of the Risk-Management Process

• Establish the context — scope, objectives, criteria.
• Risk identification — identify hazards and risk events.
• Risk analysis — estimate likelihood and consequences.
• Risk evaluation — compare against criteria; decide what is acceptable/tolerable.
• Risk treatment/control — apply the hierarchy of controls; may also transfer (insurance) or avoid the risk.
• Monitoring and review; communication and consultation throughout.

(ii) Steps in Chemical Risk Assessment

1. Identify the chemicals and their hazards — inventory, SDS, hazard classification.
2. Identify exposure scenarios — who is exposed, tasks, routes (inhalation/skin/ingestion), frequency and duration.
3. Assess exposure — measure or estimate airborne concentrations/skin contact and compare against occupational exposure limits (TWA/STEL/ceiling).
4. Characterize the risk — combine hazard severity with exposure likelihood; determine whether risk is acceptable.
5. Determine controls (hierarchy) and re-assess residual risk.
6. Document, communicate and review (after change or periodically).

(iii) Risk Reduction in Chemical Processing Plants

• Inherent safety (most fundamental) — minimize inventory of hazardous material, substitute safer chemicals, moderate conditions (lower T/P), simplify the process.
• Engineering controls — containment/closed systems, ventilation, pressure relief (relief valves/rupture discs), interlocks and trips, automation/remote operation, gas detection and alarms, bunding/containment for spills.
• Process hazard analysis — HAZOP, what-if, layers-of-protection analysis to identify and add safeguards.
• Administrative — safe operating procedures, permits (hot work, confined space), management of change, training, maintenance.
• PPE and emergency preparedness — spill response, emergency shutdown, evacuation, mutual aid. Multiple independent layers of protection ("defence in depth").