This project is funded by the European Union Projekat finansira Evropska Unija

1. This project is funded by the European Union Projekat finansira Evropska Unija HAZARD IDENTIFICATION: PRINCIPLES, METHODOLOGY, EXISTING APPROACHESAntony ThanosPh.D. Chem. Eng.antony.thanos@gmail.com Project implemented by Human Dynamics Consortium Projekat realizuje Human Dynamics Konzorcijum

2. Hazard • State, action or physical-chemical characteristic with potential of harm to equipment, human health or the environment • Examples: • Work at height – Hazard of fall • Toxic material handling (e.g. production of NH3) – Hazard of toxic release and toxic effects to human via dispersion and inhalation of toxic substance

3. Hazard source examples: • Failures of control systems, e.g. instrument failure, controller failure, control valve failure • Mechanical failures, e.g. corrosion, weld defects, human error in design • Operator errors • External sources, e.g. earthquakes, missiles from accidents in other equipment • Management failures, as lack of operating / maintenance procedures

4. Accident : The event that leads to harm to human, environment or equipment • Accident probability : The probability of evolution of a hazard to an accident • Hazard : natural gas equipment (e.g. valve) • Accident : leak with ignition • Probability of accident : 10-4 per year

5. Consequence : The outcome (effects) of an accident • Examples : • Injury from fall from height • Pulmonary damage due to inhalation of released NH3 • Burns from thermal radiation of fire in gasoline tank

6. Hazard Identification : Use of techniques for identifying hazards, causes of accidents and effects • Techniques do not automatically reveal hazards, but facilitate the systematic examination of hazards, taking into advantage of existing knowledge of systems examined • “Few accidents occur because the design team lack knowledge; Most errors in design occur, because the design team fail to apply their knowledge”, Trevor Kletz

7. Not all hazards or causes/effects are guarantied to be found • Results quality are strongly dependent on personnel experience • The prudent application Hazard Identification Techniques can identify important accidents, their causes and effects

8. Safety reviews/audit/inspections • The simplest technique • Not strictly formed technique • Evaluation of information from : • Visits to workplaces • Review of drawings, operation procedures • Interviews with personnel • Records of events

9. Checklists • Written list of questions (usually require answers in YES/NO form). • Level of detail strongly depends on author experience • Extent can be : • Minimal. Too generic, but easily applied in different processes within a company • Very detailed, focusing in a specific process only

10. Checklists (cont.) • Examples : • Are there available and valid test certificates for each safety valve ? • Is every equipment grounded ? • Are there dry-run protection provisions for pumps ? • Can pump shut-off pressure exceed downstream pipe design pressure ?

11. Checklists (cont.) • Advantages • Very useful in compliance checking with standards, legislation requirements etc. • Can be used by non-experience personnel • Adaptable to analysis depth desired • Disadvantage: Hazards not foreseen by questions cannot be identified

12. Preliminary Hazard Analysis • Applied usually in initial design of layout planning • Examines basic characteristics for: • Raw materials, intermediates/final products, wastes • Equipment: high pressure systems, reactors • Factors causing accidents and safety equipment • Procedures for operation, control, maintenance

13. Preliminary Hazard Analysis (cont.) • Hazard attributed to ranking scheme such as : • I, Insignificant • II, Limiting • III, Critical • IV, Catastrophic

14. Preliminary Hazard Analysis (cont.) • Advantage: Applicability even in early stage of design, with rather limited information, permitting interventions for risk control with minimum cost, e.g. identification of intermediate products with special hazards (Bhopal accident), permitting examination of different production process • Disadvantage:Not strictly defined technique. Information collected within discussions without systematic structure.

15. Preliminary Hazard Analysis (cont.) • Results presented usually in sheet form Example of resultsforLPG road tanker HazardCauseEffects Cat. Mitigation/Prevention measures Flammable 1. Hose rupture Uncontrolled leak, III a.Procedures require release due to tanker potential off-site handbrake on movement consequences during loading

16. Relative Ranking • Calculation of qualitative or quantitative index of hazard, based on characteristics of hazardous processes • Examples : DOW F&EI (Fire and Explosion Index), MOND Toxicity index F&EI= MF*(1+GPH)*(1+SPH) • MF: Material factor, based on NFPA flammable and reactivity • ranking, or calculated on physicochemical properties • GPH : General Process Hazard • SPH: Specific Process Hazard • GPH/SPH : Calculated as Sum of penalties of partial • values availablein tables

17. Relative Ranking (cont.) • MF table values adjusted, if necessary, depending on process conditions (e.g. material used at temperature over flash point) • GPH example : Extremely sensitive exotherm reactions : GPH=1.25 (nitration) • SPH examples : • Quantity of flammable material, graph based on potential heat release • Pressure of temperature cycling, SPH=0.3

18. Relative Ranking (cont.) • F&EI values : • 1-60,Light • 61-96,Moderate • 97-127, Intermediate • 128-158, Heavy • 159, Severe

19. Relative Ranking (cont.) • Advantages : • Strictly defined • Easy to be implemented, due to the rather limited data required • Applied in either Unit or Site level • Very useful in evaluation of alternative processes, comparison of different sites, ranking of hazardous areas within on Site

20. Relative Ranking (cont.) • Disadvantages : • Strong dependence of outcome from penalties/equations used and assumptions used

21. What-if • Setting of questions : “What will happen if…?” for the examination of evolution of undesired initial events (deviations from design ,normal operation. • Examples of questions: • What will happen if gas phase connection valve remains closed during tank loading? • What will happen if tank level is very high?

22. What-if (cont.) Example : LPG road tanker loading station

23. What-if (cont.) • Advantages : • Simple • Correlates hazards, causes and protection measures • General questions can be applied in every process : e.g. “What will happen if instrument air supply fails?” • Effectively applied with combination of check lists

24. What-if (cont.) • Disadvantages : • Not strictly defined • Success heavily depends on experience of work team and questions set • Hazard can be easily overlooked • No evaluation of deviation cause (e.g. why tank level is very low, why tanker moved?)

25. FMEA (Failure Mode and Effects Analysis) • Focus on events caused by component failures and not to deviations of operating parameters • Bottom-up approach • FMEA development : • Identification of equipment/component • 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

26. FI LIT • FMEA (cont.) • Examples of failures : • valves : valve sticks to position, leakage from stem • mixer : unintended stop of operation • cooling network: loss of cooling water supply • Example : Regulating valve (open loop) at reactor inlet

27. FMEA (cont.) • Example : Atmospheric reactor feed valve

28. FMEA (cont.) • Advantages : • Direct correlation of hazards and causes • Easily applied in systems with simple and in-series failures: • Disadvantages : • Emphasis only to component failures and not deviations caused by failures in other processes • Not focused on system/process behaviour • Hard to implement in systems where hazards appear as outcome of failure combinations • Time consuming

29. Fault tree • Technique starts from the expression of hazard (accident) and goes to identification of possible causes (top-down approach) • Application of Boolean algebra operands (AND, OR) for definition of sequence for failures and errors (incl. human) contributing to accident • Results presented in logic diagram form

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

31. Fault tree (cont.) • Advantages : • 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 • Disadvantages : • Strong dependence on final accidents (top events) selected for building trees • High experience and proper software required • Time consuming

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 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, so that all group members understand the basic elements of process examined Ομάδα HAZOP

41. FI LIT • HAZOP (cont.) • Example : Atmospheric reactor Ομάδα HAZOP

42. HAZOP (cont.) • HAZOP Table example : 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. 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

45. HAZOP (cont.) • HAZOP Team. Usual 4-12 members (very small groups lack broad disciplines, very large groups proceed very slow and have limited discussions between members) • HAZOP examination sessions organisation: • Predefined • Participants presence verified • Participants do not leave during meeting (dedicated time) Ομάδα HAZOP

46. HAZOP (cont.) • HAZOP examination sessions : • Usually 2-3 hours, up to 4-6 hours • Longer sessions result to actually slower progress and bad quality of results due to group fatigue • Sessions must not be interrupted • Successive days should be avoided if possible Ομάδα HAZOP

47. HAZOP (cont.) • Necessary support material for examination session to begin : • Updated P&IDs • “Carrying out a HAZOP on a incorrect line diagram is the most useless occupation in the world”,Trevor Kletz • Plot plans • Flow sheets • Operating manuals, control documentation Ομάδα HAZOP

48. HAZOP (cont.) • Necessary support material for examination session to begin : • ESD procedures • Equipment specifications • SDS • Accident reports • Support material available to HAZOP team at least 1 week before sessions to begin Ομάδα HAZOP

49. HAZOP (cont.) • HAZOP examination session room : • Sufficient space, isolate from other activities • Big table available • Laptop for HAZOP table entry during session • Wall/floor stand for drawings • Projector for clarifications presentation (if necessary, especially in large groups) Ομάδα HAZOP

50. HAZOP (cont.) • Advantages : • Widely applied and recognised • Systematic and comprehensive -nevertheless creative- technique • System (process) oriented • Covers both causes and effects of hazards, along with safeguards, in a robust format • Human errors and equipment failures can be identified