1. HAZARDS ANALYSIS (HAZAN)
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
EVENT OCCURS
CONTROL SUCCEEDS
CONTROL FAILS
EVENT DOES NOT OCCUR
GENERIC FAULT TREE ANALYSIS FOR HAZAN WITH DOUBLE JEOPARDY
PRIMARY EVENT
CONTROL RESPONSE
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.
SEE NEXT PAGE FOR MORE DETAIL.

8. EXAMPLE SHOWING FAULT TREE FOR LOSS OF COOLING WATER SUPPLY DUE TO FAILURE OF ELECTRICAL POWER SUPPLIES.

9. http://www. s-2-s. org/modules. php

10. EXAMPLE SHOWING P&ID DIAGRAM FOR COOLING WATERSUPPLY

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

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

14. INHERENT SAFETY OBJECTIVES ELIMINATE HAZARDS
Eliminate the hazardous material
Substitute a non-hazardous material
Discontinue the operation

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

16. INHERENT SAFETY REDUCE LIKELIHOOD OF INITIATION
Reduce the potential for human error through simplicity of design
Control ignition sources
Provide redundant alarms

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

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

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 atm

23. LIMITATION OF EFFECTS
KLETZ, TREVOR, PLANT DESIGN FOR SAFETY, HEMISPHERE PUB, 1991
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

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.