Safety Considerations in Chemical Industries: 23-Chem-A5 Chemical Plant Design and Economics, May 2017, Q5

Question 5: Safety Considerations in Chemical Industries (20 marks)

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.

Given / Find. A process-safety question. Each of the five hazard categories is answered with the key design and operating considerations that reduce or control that hazard, consistent with Canadian OH&S and process-safety-management practice.

(a) Building and process equipment

Adequate spacing/segregation of units; fire-resistant, non-combustible construction.
Open (well-ventilated) structures to prevent vapour accumulation; explosion venting/blast walls.
Multiple, clearly marked exits and escape routes; safe layout of aisles and access.
Pressure vessels and piping designed to code (ASME/CSA) with relief devices; guarded/shielded hot and high-pressure equipment.

(b) Fire prevention and control

Eliminate ignition sources near flammables; control flammable-vapour release (bonding, purging, inerting).
Fixed and portable fire-fighting: hydrants, sprinklers/deluge, foam, CO₂/dry-chemical suited to the fuel.
Fire and gas detection with alarms; emergency isolation and depressuring/blowdown systems.
Firewater supply and containment (dikes/bunds); trained fire brigade and emergency plan.

(c) Mechanical hazards

Guards on rotating and moving machinery (couplings, belts, shafts); lock-out/tag-out for maintenance.
Protection from falls, falling objects, and moving vehicles; safe access, platforms, and handrails.
Relief of stored mechanical/pressure energy before servicing; proper lifting and materials handling.
Noise and vibration control; personal protective equipment.

(d) Electrical hazards

Proper grounding and bonding of equipment; protection against shock and static discharge.
Explosion-proof / intrinsically-safe electrical equipment in classified (hazardous) areas.
Overcurrent protection, insulation, and guarding of live parts; lock-out of electrical supplies for work.
Emergency and standby power for critical safety systems; compliance with the electrical code.

(e) Chemical hazards

Knowledge of toxicity, flammability, reactivity, and exposure limits (SDS) for every chemical.
Containment of toxic/corrosive materials; ventilation, scrubbing, and gas detection for leaks.
Prevention of runaway/incompatible-chemical reactions; adequate cooling, relief, and segregated storage.
Personal protection, safe handling and disposal procedures, and emergency showers/eyewash and first aid.

Concept & Theory

Topic. Loss prevention and process-safety design across building, fire, mechanical, electrical and chemical hazards.

Why this works. Safety is engineered in through the hierarchy of controls — eliminate or substitute the hazard first, then engineering controls (containment, relief, ventilation, explosion-proofing), then administrative controls and PPE last. Each hazard class calls for the controls that break its specific accident chain: ignition control and firewater for fire, guarding and lock-out for mechanical, grounding and area classification for electrical, containment and SDS-based handling for chemical.

Common pitfall. Relying on PPE or procedures (the weakest controls) in place of inherently safer design, relief, and containment; or omitting area electrical classification where flammable vapours are present.

Source. Peters, Timmerhaus & West, Ch. 3 (general design considerations — safety and loss prevention); CCOHS and provincial OH&S / CSA Z767 process-safety-management guidance.

Question 5 of 6: Safety Considerations in Chemical Industries