DESIGN FOR SAFETY

1. DESIGN FOR SAFETY HAZARDS ANALYSIS (HAZAN)

2. HAZAN STUDY • STARTS WITH THE SAME INFORMATION AND TEAM AS THE HAZOPS STUDY • EXAMINES THE RESULT OF FAILURE OF EQUIPMENT OR CONTROLS • INDIVIDUAL - SINGLE JEOPARDY • MULTIPLE - DOUBLE JEOPARDY • CAN BE ORGANIZED WITH FAULT TREE ANALYSIS (FTA) • ALSO CALLED QUANTITATIVE RISK ASSESSMENT (QRA)

3. HOW MUCH SHOULD BE SPENT FOR SAFETY? • tx.technion.ac.il/~dlewin/054402/LECTURE_13.pdf -

4. WHAT KIND OF RISKS ARE PRESENT? • tx.technion.ac.il/~dlewin/054402/LECTURE_13.pdf

5. GENERIC FAULT TREE ANALYSIS FOR HAZAN WITH DOUBLE JEOPARDY PRIMARY EVENT CONTROL RESPONSE CONTROL RESPONSE CONTROL SUCCEEDS CONTROL SUCCEEDS CONTROL SUCCEEDS CONTROL SUCCEEDS EVENT OCCURS CONTROL FAILS CONTROL FAILS CONTROL FAILS CONTROL FAILS CONTROL SUCCEEDS EVENT DOES NOT OCCUR EVENT OCCURS EVENT OCCURS CONTROL FAILS EVENT DOES NOT OCCUR SECONDARY EVENT

6. FAULT TREE SYMBOLS • FAULT TREES USE PROGRAMMING SYMBOLS FOR EACH TYPE OF JUNCTION

7. EXAMPLE SHOWING FAULT TREE FOR LOSS OF COOLING WATER SUPPLY DUE TO FAILURE OF ELECTRICAL POWER SUPPLIES. http://www.s-2-s.org/modules.php?name=s2s_wp4&idpart=2&op=v&idp=1476 SEE NEXT PAGE FOR MORE DETAIL.

8. EXAMPLE SHOWING FAULT TREE FOR LOSS OF COOLING WATER SUPPLY DUE TO FAILURE OF ELECTRICAL POWER SUPPLIES. http://www.s-2-s.org/modules.php?name=s2s_wp4&idpart=2&op=v&idp=1476

9. http://www.s-2-s.org/modules.php?name=s2s_wp4&idpart=2&op=v&idp=1476http://www.s-2-s.org/modules.php?name=s2s_wp4&idpart=2&op=v&idp=1476

10. EXAMPLE SHOWING P&ID DIAGRAM FOR COOLING WATERSUPPLY http://www.s-2-s.org/modules.php?name=s2s_wp4&idpart=2&op=v&idp=1476

12. PROBABILITY ANALYSIS FROM HAZAN • PROBABILITIES ARE MULTIPLIED FOR EACH LEVEL OF JEOPARDY • FOR 2 EVENTS IN SERIES, EACH WITH A 0.5 PROBABILITY, PROBABILITY OF BOTH OCCURRING IS 0.25 • SEVERITY MUST ALSO BE CONSIDERED AS A FACTOR IN CONSIDERING DOUBLE JEOPARDY SITUATIONS www.cobalt.chem.ucalgary.ca

13. PRIMARY SOURCES OF CATASTROPHIC EVENTS • HUMAN ERROR • MISLABELING • TRIP FAILURES • STATIC ELECTRICITY • WRONG MATERIAL OF CONSTRUCTION • FAULTY OPERATING PROCEDURES • UNEXPECTED REVERSE FLOW • COMPUTER CONTROL PROBLEMS • IGNORANCE http://www.processforusability.co.uk/safety/images/larsen.jpg

14. INHERENT SAFETY • OBJECTIVES • ELIMINATE HAZARDS • Eliminate the hazardous material • Substitute a non-hazardous material • Discontinue the operation http://www.acusafe.com/Hazard_Analysis/Hazard_Analysis-talks.htm#Talks%20and%20Papers

15. INHERENT SAFETY • REDUCE CONSEQUENCES • Reduce the quantity of the hazardous material • Provide a curbed area with a drain to contain and evacuate a spill • and produce a smaller pool area of a spill • Separate the operation by adequate spacing to reduce exposure to adjacent operations and personnel http://www.acusafe.com/Hazard_Analysis/Hazard_Analysis-talks.htm#Talks%20and%20Papers http://altermondialisme.free.fr/monde/Etats_unis.jpg

16. INHERENT SAFETY • REDUCE LIKELIHOOD OF INITIATION • Reduce the potential for human error through simplicity of design • Control ignition sources • Provide redundant alarms http://www.acusafe.com/Hazard_Analysis/Hazard_Analysis-talks.htm#Talks%20and%20Papers

17. INHERENTLY SAFE DESIGN • GUIDELINES TO REVIEW PROCESS DESIGN FOR SAFETY • INTENSIFICATION • SUBSTITUTION • ATTENUATION • LIMITATION OF EFFECTS • SIMPLIFICATION • KLETZ, TREVOR, PLANT DESIGN FOR SAFETY, HEMISPHERE PUBLISHING 1991

18. INTENSIFICATION POLICIES • REDUCE QUANTITIES OF MATERIALS IN THE SYSTEM • REACTORS • TUBE FLOW VS. CSTR • VAPOR PHASE VS. LIQUID PHASE • DISTILLATION • LIMIT INVENTORIES • USE IN-COLUMN HEAT EXCHANGERS • HEAT EXCHANGERS • SHELL & TUBE VS. PLATE • PROCESS FLOW IN TUBES http://www.inl.gov/featurestories/i/scwr.gif

19. INTENSIFICATION POLICIES • STORAGE • MINIMAL VOLUME STORAGE TANKS • PIPELINES • NUMBER OF TRAINS • SINGLE TRAIN HAS SMALLER OVERALL INVENTORY THAN MULTIPLE TRAIN • SINGLE TRAIN HAS FEWER LEAK POINTS • SINGLE TRAIN HAS ECONOMY OF SCALE http://rphrm.curtin.edu.au/2006/issue1/defense05.png

20. SUBSTITUTION POLICIES • USE LESS HAZARDOUS RAW MATERIALS • USE LESS HAZARDOUS NON-REACTIVE COMPONENTS • REPLACEMENT OF CFCs IN REFRIGERATION SYSTEMS AND AEROSOLS WITH HFCs AND N2 • USE OF SUPERCRITICAL CO2 IN PLACE OF METHYLENE CHLORIDE FOR EXTRACTION • USE OF WATER-BASED SOLVENTS FOR SEMI-CONDUCTOR PROCESSING • USE STEAM AND WATER AS HEAT TRANSFER MEDIA INSTEAD OF HYDROCARBONS

21. ATTENUATION POLICIES • USE LESS HAZARDOUS CONDITIONS FOR PROCESSES • LOWER PRESSURES • LOWER TEMPERATURES • MULTIPLE STEPS • NORMALLY COST EFFECTIVE SINCE PROCESS CONDITIONS ARE CLOSER TO AMBIENT

22. ATTENUATION POLICIES • AMMONIA SYNTHESIS (KHARBANDA & STALLWORTHY, SAFETY IN THE CHEMICAL INDUSTRY, HEINMANN PROFESSIONAL PUBLISHING,1988) N2 + 3H2 → 2NH3 • 1930’S CASALE PROCESS AT 450 – 600 atm • 1950’S ICI PROCESS 300 – 350 atm • 1960’S KELLOGG PROCESS 150 atm • 1982 ICI AMV PROCESS 80 - 100 atm http://www.topsoe.com/site.nsf/vIMAGESBYNAME/Ammonia28---PVC-diagram.gif/$file/Ammonia28---PVC-diagram.gif

23. KLETZ, TREVOR, PLANT DESIGN FOR SAFETY, HEMISPHERE PUB, 1991 LIMITATION OF EFFECTS • CHANGE PROCESS SEQUENCE TO LIMIT HAZARDOUS CONDITIONS • SEQUENCE OF PROCESSES • NUMBER OF STEPS IN A SINGLE VESSEL • USE OF SUBMERGED PUMPS TO REDUCE LEAK IMPACTS http://www.savinobarbera.com/images/istallazione-pompa-immersa-bg.gif

24. SIMPLIFICATION POLICIES • STRONGER EQUIPMENT TO REPLACE RELIEF SYSTEMS • MATERIALS OF CONSTRUCTION THAT RETAIN DUCTILITY (LOW TEMPERATURES) • ELIMINATE EXCESS INSTRUMENTATION • MINIMIZE NUMBER OF PIECES OF EQUIPMENT BY COMBINING SERVICES KLETZ, TREVOR, PLANT DESIGN FOR SAFETY, HEMISPHERE PUB, 1991

25. CLASS PROBLEM • GIVEN: Automobile • WANTED: Fault tree analyzing when auto fails to start • BASIS: Engine powered car with remote starting switch • SOLUTION: Present results as fault tree chart. Estimate probability for each component.