Question 5 of 6: Startup and Shutdown Safety

Question 5: Startup and Shutdown Safety (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 qualitative safety-review question drawn from process-safety-management practice: the pre-startup safety review (PSSR) checklist and the controlled-shutdown checklist. The answer is a checklist of the key questions, each tied to the hazard it guards against.

(a) Ten startup safety questions

1. Purging — Have all vessels and lines been purged of air (or of process gas) so that no flammable air/fuel mixture can form when hydrocarbons are admitted?
2. Leak/pressure test — Has the system been pressure-tested and confirmed leak-tight at operating pressure before introducing hazardous fluids?
3. Blinds and isolation — Have all blinds/spades used for maintenance been removed (and any required blinds installed), and are isolation valves lined up correctly?
4. Relief and venting — Are all relief valves, rupture discs and vent systems in service, correctly set and not isolated?
5. Instrumentation and interlocks — Are all instruments, alarms, trips and safety interlocks calibrated, functional and enabled (not bypassed)?
6. Utilities — Are all utilities (cooling water, steam, instrument air, inert gas, electrical power) available and stable before startup?
7. Drains and low points — Are drains and low-point valves closed, and has accumulated water/liquid been removed to avoid slugging or thermal shock?
8. Materials and inventory — Are the correct feedstocks and catalysts loaded, and is the initial inventory within safe limits (no overfill)?
9. Rate of change — Are heat-up/pressurisation rates controlled within metallurgical and thermal-stress limits, avoiding rapid transients?
10. Personnel and procedures — Are operators trained on the startup procedure, is the work-permit/lockout cleared, and are emergency-response provisions (fire water, PPE, evacuation) in place?

(b) Five shutdown safety questions

1. Depressurisation — Is the plant being depressurised and cooled in the correct controlled sequence to prevent thermal shock or vacuum collapse?
2. Inventory removal — Has hazardous inventory been drained, pumped out or routed to safe disposal/flare before equipment is opened?
3. Purging and inerting — Have vessels been purged/inerted to remove flammables (and to prevent an air ingress that could form an explosive mixture)?
4. Isolation and lockout — Are energy sources and process connections positively isolated (blinded, locked out/tagged out) before hand-over to maintenance?
5. Cooling and reactive hazards — Are exothermic/reactive materials safely quenched or removed, and is residual heat dissipated so no runaway or auto-ignition can occur while the plant is down?