Chemical Process Safety

1. Chemical Process Safety Read Chapter 24:Turton’s Design Book (Crowl & Louvar) Chapter 11:HazardIdentification Chapter 12: Risk Assessment Guidelines for Hazard Evaluation Procedures, 3rd Ed., CCPS (John Wiley), 2008: 5.3; 7.0-7.5; ch 9

2. Introduction SAFE PROCESS DEVELOPMENT Synthetic organic chemistry ideas Automated laboratory reactors. Process optimization Desktop screening, databases, calculations Discovery research and multiple experiments Pilot plant studies Scale up and design Industrial production. Debottlenecking. Optimization of mature processes. Retrofits. C H E M I C A L P R O C E S S L I F E C Y C L E HAZOP, HAZAN, HAZID Adiabatic calorimeters Automated Calorimeters and reactors Micro and mini scale reactors Desktop studies Design reappraisal, relief systems, dump and quench tanks Kinetics, modelling, simulation Objective is to move from the earliest phases of research and development through to full scaleproduction in a confident, safe and cost effective manner D. Crowl, notes

3. Figure 11-1 Hazards identification and risk assessment procedure. (Adapted from Guidelines for Hazards Evaluation Procedures (New York: American Institute of Chemical Engineers, 1985), pp. 1–9.)

4. Process Hazard Analysis – Many Options What-If Checklist What-If/Checklist FMEA – Failure Mode & Effects Analysis FTA – Fault Tree Analysis Hazards Surveys HAZOP – Hazards & Operability study

5. Process Hazard Analysis – Many Options What-If Checklist What-If/Checklist FMEA – Failure Mode & Effects Analysis FTA – Fault Tree Analysis Hazards Surveys HAZOP – Hazards & Operability study

6. 1. What-If Analysis • Unstructured method for considering results of unexpected events • Uses questions beginning with "what-if“ • Not concerned with "how" failures occur • Purpose is to identify problems that could lead to accidents • Results in a list of potential problem areas and suggested mitigation methods

7. What-If Example LNG Vaporizer What if: (a) Water flow is stopped? (b) LNG flow is stopped? (c) Natural gas temperature is too low? (d) Water flow is too low? (e) Water pressure is too high? (f) A tube leaks into the shell? (g) Inlet water temperature is too low? D. Crowl, notes

8. What-If Example LNG Vaporizer What-If Consequence/ Hazard Recommendation Automatic interlock to Water flow is stopped? Water in shell freezes and may rupture shell; natural stop LNG flow if water gas temperature too low. flow is stopped. LNG flow is stopped? Not Hazardous None Natural gas temperature is Downstream piping may Monitor gas temperature; too low? become embrittled. low temperature alarm. Natural gas temperature Monitor flow rate; low Water flow is too low? may be too low; water may flow alarm. freeze in tubes. D. Crowl, notes

9. 6. Hazards Surveys Can be simple like inventory of hazardous chemicals More rigorous procedures: - Dow Fire & Explosion Index - Dow Chemical Exposure Index

10. 6. Hazards Surveys: Dow Fire & Explosion Index • Complex and detailed procedure carried out by an individual • Rates relative hazards of storing, handling, processing flammable • and explosive materials • Systematic approach independent of judgmental factors • Break the process down into unitsor sections, e.g. the reactor, • storage tank or a pump • Use experience to select the units or sections that have the highest • likelihood of a significant hazard (too many to cover all); may use • checklist approach to choose • Definethe material factor (what chemicals are being used); in general, higher • the value the more flammable / explosive • Adjust this with various penalties based on conditions such as storage above • normal boiling point, exothermic reaction, etc • Then take credits for safety procedures and safety systems • Finally arrive at a number that rates the hazard; compare with table / • experience

11. Penalty factors General Process Hazards Factor Special Process Hazards Factor 6. Hazards Surveys: Dow Fire & Explosion Index Dow Fire & Explosion Index standard form; C&L Fig 11-3 Penalties Material factor MF F1 F2 D. Crowl, notes

12. 6. Hazards Surveys: Dow Fire & Explosion Index Dow F&EI - Determining the degree of hazard, Table 11-2 F&EI index valueDegree of hazard 1 – 60 Light 61 – 96 Moderate 97 – 127 Intermediate 128 – 158 Heavy > 158 Severe D. Crowl, notes

13. 7. Hazard and Operability (HAZOP) Study • HAZOP is a Structured "What If" Type of Study • Objectives • - Identify Hazards • - Identify Operability Problems • HAZOPs Use Team Approach • Multi-Disciplinary • Guide word based • Structured and Systematic

14. Hazards and Operability Study • Investigative Process • Select study nodes • Major process vessels • Major process lines connected to process vessels • Pumps and compressors • Heat exchangers • Major support systems • Pick a process parameter • - Flow, level, temperature, pressure, volume, pH, concentration, agitation, etc

15. Hazards and Operability Study • Investigative Process (Cont’d) • Apply guide words to process parameters • Determine deviation from design • Determine consequences of deviations • Evaluate consequences • Typical causes of deviations • Hardware failures • Human error • Outside forces • Unanticipated process state

16. Hazards and Operability Study • Investigative Process (Cont’d) • Suggested actions • Change in design • Change in equipment • Alter operating procedures • Improve maintenance • Investigate further • HAZOP Follow-up • Assign responsibility for carrying out recommendations with agreed timetable • Refer recommendations to appropriate managers • Evaluate and review • Record keeping • Copy of all data used • Copy of all working papers • HAZOP worksheets

17. Hazards and Operability Study Guide Words and Their MeaningsSimple words or phrases used to qualify the intention and associated parameters in order to discover deviations.

19. HAZOP Example • Chemistry is such that concentrations of B must not exceed that of A • First Study Node - pipeline from suction side of pump that delivers A to the reaction vessel • First Guide Word - Noto design intent of transfer A • Causes of Deviation • Supply tank is empty • Pumps fail to run • Pipeline is fractured • Isolation valve is closed • Consequences • Excess of B over A could lead to an explosion • Recommendation • Install interlock device on pump B into reactor

20. HAZOP Example Worksheet D. Crowl, notes

21. W. Buck, SDSMT Seminar, 2012

22. Risk Matrix Consequence Frequency Unacceptable Undesirable Risk = F x C Marginal Acceptable B.K. Vaughen, PSM Overview, SACHE, 2012

23. Risk Equation Frequency How often the event may occur - its likelihood is a “probability” Consequence How severe the event may be - an undesired result of the event B.K. Vaughen, PSM Overview, SACHE, 2012

24. Operational Discipline The personal commitment of everyone to ensure theirpersonal and process safety by 1) performing their tasks correctly, and 2) recognizing, responding to and seeking help, as needed, to unanticipated situations or conditions. OD B.K. Vaughen, PSM Overview, SACHE, 2012

25. Operational Discipline “Organizational” OD Leadership Focus Employee Involvement Practice Consistent With Procedures Excellent Housekeeping “Personal” OD Awareness Knowledge Commitment B.K. Vaughen, PSM Overview, SACHE, 2012

26. Risk Reduction F FrequencyEngineering and Administrative Controls Design Phase: the best time to use ISP C ConsequenceInherently Safer Processes Emergency Response B.K. Vaughen, PSM Overview, SACHE, 2012

27. Risk Reduction OD Operational DisciplineSafety Culture Organizational OD Safety Behaviorand Personal OD Commitment Characteristics B.K. Vaughen, PSM Overview, SACHE, 2012

28. Effect of Poor OD on Risk B.K. Vaughen, PSM Overview, SACHE, 2012

29. Risk Matrix W. Buck, SDSMT Seminar, 2012

30. PSM Systems Designed to minimize process safety risk: There is always some level of risk Our PSM-related risk reduction efforts are compared and evaluated against other potential business risks (i.e., environmental, operational, maintenance, quality and financial) B.K. Vaughen, PSM Overview, SACHE, 2012

32. B.K. Vaughen, PSM Overview, SACHE, 2012

33. Questions?