HAZARD IDENTIFICATION METHODS / Part 2 Antony Thanos Ph.D. Chem. Eng. antony.thanos@gmail

1. This project is funded by the European Union Projekat finansira Evropska Unija HAZARD IDENTIFICATION METHODS / Part 2Antony ThanosPh.D. Chem. Eng.antony.thanos@gmail.com Project implemented by Human Dynamics Consortium Projekat realizuje Human Dynamics Konzorcijum

2. What-if • Setting of questions : “What (will happen) if…?” for the examination of evolution of undesired initial events (deviations from design, normal operation) in small sections of establishment • Areas covered by questions : • Equipment failures • Human errors (sequence of actions etc.) • Operating conditions deviations from normal • External events

3. What-if (cont.) • Examples of questions : • What-if tank level is very high ? (deviation from normal) • What-if gas phase connection valve remains closed during LPG tank loading ? (human error)

4. What-if (cont.) • Examples of questions for piping : • What-if pipe leaks ? • What-if pipe is plugged ? • What-if pipe is subject to pressure surge ? • ……. Please contribute……

5. What-if (cont.) • Examples of questions for piping : (cont.) • What-if pipe is subject to sudden flow interruption (water hammer issues) ? • What-if pipe is subject to vibration ? • What-if pipe supports fail ? • What-if pipe temperature rises ?

6. What-if (cont.) • Examples of questions for heat exchangers : • What-if feed temperature increases ? • What-if flow stops in hot feed ? • ……. Please contribute……

7. What-if (cont.) • Examples of questions for heat exchangers : (cont.) • What-if flow stops in cold feed ? • What-if there is excessive fouling ? • What-if there is tube failure ?

8. What-if (cont.) • Example What-if table for Road tanker movement during loading

9. LC PRV LIT HV FI LCV • What-if (cont.) Please apply What-if in vessel

10. What-if (cont.) • Example What-if table

11. What-if (cont.) • Example What-if table (cont.)

12. What-if (cont.) • Advantages : • Simple • Applicable even in rather early stage of design • Correlates hazards, causes and protection measures • General questions can be applied in every process : e.g. “What will happen if instrument air supply fails?”

13. What-if (cont.) • Advantages : (cont.) • Effectively applied with combination of check lists • Limited time requirements (in the order of 8 days for large processes)

14. What-if (cont.) • Disadvantages : • Not strictly defined • Success heavily depends on experience of work team and questions set • Hazards can be easily overlooked • No evaluation of deviation cause (e.g. why tank level is very low, why tanker moved?) • Can be considered as suitable for Safety Report, but proper judgment for “what-if” questions is necessary

15. FMEA (Failure Mode and Effects Analysis) • Focus on events caused by component failures and not to deviations of operating parameters • Bottom-up approach (initial failure to top event) • Origin from military applications (MIL-P-1629)

16. FMEA (cont.) • FMEA development : • Identification of sub-systems to be examined • Identification of equipment/components per sub-system • Definition of failure type per equipment (failure cause could also be defined) • Definition of outcomes per failure (assuming that protection measures are not in operation) • Identification of safeguards (protection measures) • Proposals

17. FMEA (cont.) • General failure types : • Failure in operation (e.g. unintended stop of agitator) • Failure to operate at prescribed time (e.g. agitator failure to start when required by process) • Failure to cease operation at prescribed time (e.g. feed valve failure to close after necessary time to feed reactor – batch process) • Operation at premature time (e.g. pump starts before discharge valve opens)

18. FMEA (cont.) • Effects (outcomes) types: Local/System • Can be complemented with probability calculations and severity estimation (FMECA variation of method) • Applicable widely also in electronics aviation, space, automobile industry • Indispensable for reliability concept. Essential method in Safety Integrity Level (SIL) evaluation (FMEDA variation of method)

19. FMEA (cont.) Example of simplified results table for LPG road tanker loading hose

20. LC PRV LIT FCV FI LCV • FMEA (cont.) Please apply FMEA to regulating valve (FCV) at reactor inlet

21. FMEA (cont.) • Example FMEA table

22. FMEA (cont.) • Advantages : • Strictly defined and systematic method (IEC 60812) • Direct correlation of hazards and causes and effects • Easily applied in systems with simple and in-series failures

23. FMEA (cont.) • Disadvantages : • Emphasis only to component failures and not to deviations caused by failures in other processes • Only single failures are used • Hard to implement in systems where hazards appear as outcome of failure combinations (undetectable failures must be checked for potential hazards in combination with other failures)

24. FMEA (cont.) • Disadvantages : (cont.) • Human errors are not easily encountered (only indirectly by component failures incurred) • Not focused on system/process behaviour • Experienced personnel required • Time consuming (in the order of 4 weeks for large systems)

25. FMEA (cont.) • Can be considered as suitable for Safety Reports under the condition of human errors taken into account

26. Fault tree • Fault tree development : • Accident (top event) selection • Accident causes identification (all intermediate events contributing to top event, 1st stage) • Identification of all events (2nd stage) contributing to 1st stage events ….. • … down to basic fault events (component faults)

27. Fault tree (cont.) • Top-down approach • Application of Boolean algebra operands (AND, OR) for definition of sequence for failures and errors (incl. human) contributing to accident • Origin from military application (Bell laboratories, 1962, Minuteman I ICBM) Missile) • Applicable in electronics, aviation, space and nuclear industry, robotics • Results presented in logic diagram form

28. TOXIC RELEASE FROM SAFETY VALVE 4x10-4 per year AND OVERFILLING LOADINGS 200 per year OR 2x10-6 per year AND 1x10-6 per year LEVEL INDICATOR (LI) FAILURE OPERATOR ABSENT DURING LOADING OPER.FAILS TO IDENTIFY LI FAILURE 10-6 per year 10-3 per year 10-3 per year • Fault tree (cont.) • Example : Overfilling of NH3 road tanker

29. Fault tree (cont.) • Advantages : • Well defined (IEC 61025) • Correlation of hazards and causes • Combinations of human errors and equipment failures can be identified • Accident probability calculations possible, if failure/error database is available • Supplement to other techniques (e.g. what-if, HAZOP) for more detailed examination of causes for significant accidents

30. Fault tree (cont.) • Disadvantages : • Complete dependence on final accidents (top events) selected for building trees • Not all top events guarantied to be identified • Sequence errors not easily taken into account • High experienced personnel and proper software required • Time consuming (in the order of 2 months for large processes)

31. Fault tree (cont.) • Can be considered as suitable for Safety Report, but judgment is necessary on completion of top events considered

32. HAZOP (HAZard and OPerability) Study • Hazards and malfunctions are expressed via deviation of operating parameters from normal values, or due to human errors, equipment failures • Usual parameters to be examined : • Pressure • Temperature • Flow • Level

33. HAZOP (cont.) • Usual deviation keywords : Ομάδα HAZOP

34. HAZOP (cont.) • Usual deviation keywords (cont.) : Ομάδα HAZOP

35. HAZOP (cont.) • Usual deviation keywords (cont.) : Ομάδα HAZOP

36. COMMENTS / PROPOSALS Nr CONSEQUENCES DEVIATION CAUSES SAFEGUARDS P-1 P-2 • HAZOP (cont.) • HAZOP examination sessions overview Step 1 Design comprehension Step 2 Systematic examination of deviations Step 3 Comments, proposals Keyword Parameter • NO• LOW• HIGH• AS WELL AS • Flow•Pressure •Temperature HAZOP Table HAZOP Team Ομάδα HAZOP

37. Next section Unit Section (P&ID) Design comprehension Next parameter Key-words application Identification of deviation causes Consequences, safeguards identification Discussion, comments, proposals • HAZOP (cont.) • HAZOP steps Ομάδα HAZOP

38. HAZOP (cont.) • Unit/Sections (Nodes) identification based on main activities. Definition of Section borderlines and related drawings • Sections identification examples : • Pipeline from port to tank • Tank • Tank pump-house • Road tanker loading station Ομάδα HAZOP

39. HAZOP (cont.) • Main equipment definition per Section • Equipment example for Road Tanker loading station : • Liquid phase piping from pump-house • Gas phase return piping to tank • Hoses/loading arms • Road tanker Ομάδα HAZOP

40. HAZOP (cont.) • Before each session, Leader defines Section to be examined • An outline of operation for Section has to be given (appr. 15 min), so that all group members understand the basic elements of process examined Ομάδα HAZOP

41. LC PRV LIT FCV FI LCV • HAZOP (cont.) • Example case Ομάδα HAZOP

42. HAZOP (cont.) • HAZOP Table example for feed line : • Please apply HAZOP for high level and high pressure in reactor HAZARD AND OPERABILITY STUDY   Company :ABC S.A. Drawing: S-9871 (31/12/03) Site :XYZ Site HAZOP Date :01/10/13 Unit : U-1234 Workgroup : See attendance list Section: Reactor feed lineRev.: 5 Ομάδα HAZOP

43. HAZOP (cont.) • HAZOP Table example (cont.): HAZARD AND OPERABILITY STUDY   Company :ABC S.A. Drawing: S-9871 (31/12/03) Site :XYZ Site HAZOP Date :04/10/13 Unit : U-1234 Workgroup : See attendance list Section: Reactor vesselRev.: 5 Ομάδα HAZOP

44. HAZOP (cont.) • HAZOP Table example (cont.): HAZARD AND OPERABILITY STUDY   Company :ABC S.A. Drawing: S-9871 (31/12/03) Site :XYZ Site HAZOP Date :04/10/13 Unit : U-1234 Workgroup : See attendance list Section: Reactor vesselRev.: 5 Ομάδα HAZOP

45. HAZOP (cont.) • HAZOP Table example (cont.): HAZARD AND OPERABILITY STUDY   Company :ABC S.A. Drawing: S-9871 (31/12/03) Site :XYZ Site HAZOP Date :04/10/13 Unit : U-1234 Workgroup : See attendance list Section: Reactor vesselRev.: 5 Ομάδα HAZOP

46. Team formation P&IDs study Examination sessions • HAZOP (cont.) • HAZOP Study organisation • HAZOP team structure • Leader/facilitator • Recorder (Scribe) • Members (design, operator, maintenance, H&S, I&C, inspection) Ομάδα HAZOP

47. HAZOP (cont.) • HAZOP Team • Usually 4-12 members • Very small groups lack broad disciplines, • Very large groups proceed very slowly and have limited discussions between members Ομάδα HAZOP

48. HAZOP (cont.) • HAZOP leader • Facilitator of team operation • Keeps team on track • Avoid unnecessary delays (e.g. unclear issues which need additional information to be provided in later stage) • Follows up pending issues • Experienced in HAZOP method application • Not necessarily a technical expert on the process Ομάδα HAZOP

49. HAZOP (cont.) • HAZOP Members disciplines : • Design • Operator • Maintenance • Health and Safety (H&S) • Instrumentation and Control (I&C) • Inspection • …. Ομάδα HAZOP

50. HAZOP (cont.) • HAZOP examination sessions organisation: • Predefined • Participants presence verified • Participants do not leave during meeting (dedicated time) Ομάδα HAZOP