design strategies with respect to hazardous materials

Report
DESIGN STRATEGIES WITH
RESPECT TO HAZARDOUS
MATERIALS
THE NATURE OF RISK IN
INDUSTRIAL FACILITIES
http://www.bls.gov/iif/oshwc/cfoi/cfch0008.pdf
FATAL WORK INJURIES
http://www.bls.gov/iif/oshwc/cfoi/cfch0008.pdf
FATAL WORK INJURIES
http://www.bls.gov/iif/oshwc/cfoi/cfch0008.pdf
THE NATURE OF RISK IN
INDUSTRIAL FACILITIES
• COMPARISON VALUES DEATHS/100,000 WORKERS
–IN 1912, 21 (18,000 - 21,000
DEATHS)
–IN 1992, 4.2 (TRIPLE THE
NUMBER OF WORKERS)
SUMMARY OF MAJOR
INCIDENTS2,3
• FLIXBOROUGH, ENGLAND (1974) CYCLOHEXANE MANUFACTURING
AS A NYLON PRECURSOR 4,5
– VAPOR CLOUD EXPLOSION
– KILLED 28 PEOPLE
– CAUSE APPEARED TO BE DESIGN
FOR TEMPORARY PIPING SYSTEM
FLIXBOROUGH
SUMMARY OF MAJOR
INCIDENTS
•
SEVESO, ITALY (1976) - DIOXIN6
– TCP (2,4,5-TRICHLOROPHENOL)
REACTOR EXPLODED RELEASING
TCDD, (2,3,7,8TETRACHLORODIBENZO-p-DIOXIN
– THIS MATERIAL WAS A
COMPONENT IN AGENT ORANGE
SUMMARY OF MAJOR
INCIDENTS
•
SEVESO, ITALY (1976) - DIOXIN6
–
PLUME SPREAD OVER AN AREA THAT
CONTAINED OVER 100,000 PERSONS AND
IMPACTED OTHER MUNICIPALITIES WITH
A POPULATION OF 17000
– PRIMARY IMPACT WAS FEAR OF LONGTERM EFFECTS AND OVERCOMING
INITIAL TRAUMA
– COULD BE THE SOURCE OF SARA TITLE
III REQUIREMENTS
SUMMARY OF MAJOR
INCIDENTS
•
MEXICO CITY, MEXICO (1984) LPG (LIQUID PETROLEUM GAS)
TERMINAL
– A BLEVE (BOILING LIQUID
EXPANDING VAPOUR EXPLOSION) 7
– 650 DEATHS
– 6400 INJURIES
– PLANT DAMAGE = $31.3 MILLION
SUMMARY OF MAJOR
INCIDENTS
•
BHOPAL, INDIA (1984) - PESTICIDE
MANUFACTURING8
–
UNEXPECTED CHEMICAL REACTION WHEN
WATER ENTERED AN MIC (METHYL
ISOCYANATE) STORAGE TANK
– RELEASED ABOUT 40 TONS OF MATERIAL
OVER A 2 HOUR PERIOD
– SPREAD OVER A LOCAL POPULATION OF
ABOUT 900,000
– ESTIMATED 3800 DEAD AND 11,000 DISABLED
SUMMARY OF MAJOR
INCIDENTS
•
BHOPAL, INDIA (1984) PESTICIDE MANUFACTURING8
– TRACED TO A NUMBER OF
POSSIBLE SOURCES9
– FAILURE TO MAINTAIN SAFETY
SYSTEMS
– INADEQUATE DESIGN OF SAFETY
SYSTEMS
– MIS-OPERATION OF THE FACILITY
SUMMARY OF MAJOR
INCIDENTS
•
PASADENA, TEXAS (1989) POLYETHYLENE MANUFACTURING
–
POLYETHYLENE REACTOR EXPLOSION
– KILLED 23 PEOPLE AND INJURED 130
– TRACED TO EITHER A SEAL FAILURE ON
THE REACTOR AND/OR USE OF
INEXPERIENCED MAINTENANCE
PERSONNEL
EXAMPLE OF INCIDENT
•
BHOPAL RELEASE
– HOW IT OCCURRED
– HOW IT WAS ANALYZED
– RESULTING CHANGES
FUNDAMENTALS OF
PROCESSES
•
THERMODYNAMICS
–
CONSERVATION OF MASS AND ENERGY
• MASS IS NEITHER CREATED OR DESTROYED
• ENERGY IS NEITHER CREATED OR
DESTROYED
MASS IN - RAW
MATERIALS
PROCESS
MASS OUT PRODUCTS
FUNDAMENTALS OF
PROCESSES
•
THERMODYNAMICS
– PROCESSES REQUIRE CHANGING
CONDITIONSSYSTEMS MOVE
TOWARDS A NEW EQUILIBRIUM
• THE RATE DEPENDS ON THE
CHEMICAL AND MECHANICAL
PROPERTIES OF THE SYSTEM
• WATER DOES NOT FLOW UPHILL
WITHOUT A BOOST
FUNDAMENTALS OF PROCESSES
•
EXAMPLE OF ETHANOL DISTILLATION
FUNDAMENTALS OF PROCESSES
• ENERGY/MATERIAL QUALITY
CHANGES
–
ENERGY
• MAY BE ADDED OR REMOVED TO INITIATE A
SYSTEM CHANGE
• WHEN ENERGY IS ADDED, IT FLOWS
THROUGH THE SYSTEM TO BE CONSERVED,
BUT IT IS DEGRADED IN QUALITY
ENERGY QUALITY CHANGES
• EXAMPLE OF HYDROELECTRIC
POWER PLANT
ENERGY QUALITY CHANGES
•
EXAMPLE OF HYDROELECTRIC
POWER
•
WATER CHANGES ITS EQUILIBRIUM
POSITION WITH A RESULTANT
CHANGE IN POTENTIAL ENERGY AND
POWER PRODUCTION
•
WATER IN THE RIVER CANNOT BE
USED TO DRIVE THE TURBINE
BECAUSE IT IS AT A LOWER
POTENTIAL ENERGY LEVEL
MATERIAL QUALITY CHANGES
• PURE CHEMICALS THAT ARE
DISPERSED IN WATER (SOLUBLE IN
WATER) CANNOT BE RETURNED TO
THEIR ORIGINAL PURITY WITHOUT
USING ENERGY
– DISTILLATION - ENERGY TO
VAPORIZE/CONDENSE
– CRYSTALLIZATION - ENERGY TO
FREEZE/MELT
– ADSORPTION OR ADSORPTION ENERGY TO REGENERATE
REACTIONS
– RESULTS IN FORMATION OF NEW
CHEMICAL SPECIES
– ELEMENTS ARE CONSERVED, BUT
NEW MOLECULES MAY BE FORMED
– REACTIONS CAN BE SINGLE, IN
PARALLEL OR IN SERIES
– MOLAR RELATIONSHIPS EXIST
BETWEEN REACTANTS AND
PRODUCTS
REACTIONS
• EXAMPLE OF METHANE COMBUSTION:
– STOCHIOMETRIC REACTION
4 + 22 → 2 + 22 
 
 →

4 → 4
4 → 4
 
16 + 64 → 44 + 32
REACTIONS
• STOCHIOMETRIC REACTION WITH AIR FOR
THE OXIDANT
CH 4  2O 2  8 N 2  CO 2  2 H 2O  8 N 2
ELEMENTAL BALANCES
C
 C
4H
 4H
4O
16 N
 4O
 16 N
MASS
BALANCES
16  64  224  44  32  224
REACTIONS
• REAL REACTIONS MAY NOT GO TO
COMPLETION
• MAY REQUIRE AN EXCESS OF ONE
COMPONENT TO COMPLETELY REACT
THE OTHER
REACTIONS
• METHANE COMBUSTION WITH 130% EXCESS AIR
CH 4  2.6O 2  9.8 N 2  CO 2  2 H 2O  9.8 N 2  12
. O2
ELEMENTAL BALANCES
C
 C
4H
5.2O
19.6 N
 4H
 2O  2O  12
.
 19.6 N
MASS BALANCES
16  83.2  274.4  44  32  274.4  19.2
REACTIONS
• PARALLEL ETHANE COMBUSTION REACTIONS WITH 200%
EXCESS AIR AND INCOMPLETE COMBUSTION
7
C 2 H 6  7O 2  28 N 2  2CO 2  3H 2O  28 N 2  O 2
2
9
C 2 H 6  7O 2  28 N 2  2CO  3H 2O  28 N 2  O 2
2
ELEMENTAL BALANCES
2C  2C
 2 C  2C
6H  6H
 6H  6H
14O  14O
 4O  3O  7O  2O  3O  9O
28 N  28 N
 28 N  28 N
MASS BALANCES
60  448  1568  88  56  108  1568  256
C2 H 6 O2
N2
CO2 CO H 2O N 2
O2
REACTIONS
•
MOST REACTIONS DO NOT GO TO
COMPLETION
•
COMBUSTION CAN HAVE PRIMARY
PRODUCTS OF CO2, H2O AND N2
•
BYPRODUCTS CAN INCLUDE CO,
UNBURNED HYDROCARBONS, NOx,
AND SO2 IN SMALLER QUANTITIES
REACTIONS
• OTHER TYPES OF OXIDATION-REDUCTION
REACTIONS
COMBINATION :
2 Mg  O 2  2 MgO
DECOMPOSITION :
2 HgO  Heat  2 Hg  O 2
DISPLACEMENT :
Zn  H 2 SO 4  ZnSO 4  H 2
REACTIONS
• OTHER TYPES OF NON-REDOX
COMBINATION TO FORM A BASE:
REACTIONS:
Na 2O  H 2O  2 NaOH
COMBINATION TO FORM AN ACID:
P2O5  3H 2O  2 H 3 PO 4
OXIDE COMBINATION TO FORM SALTS:
CaO  SiO 2  CaSiO 2
NEUTRALIZATION :
2 H 3 PO 4  3Ca( OH )2  Ca 3( PO 4 )2   6 H 2O
SEPARATION PROCESSES
• PROCESSES TO SEPARATE
COMPONENTS, BEFORE OR AFTER
REACTIONS
• PROCESSES TO CONCENTRATE
COMPONENTS
• THE DRIVING FORCES FOR MOST OF
THESE PROCESSES ARE
– CHEMICAL EQUILIBRIUM
– MECHANICAL
– RATE DEPENDENT
SEPARATION PROCESSES
• PROCESS EFFICIENCY IS RELATED TO
THE DEVIATION REQUIRED FROM
AMBIENT CONDITIONS
– THE MORE CHANGE REQUIRED, THE
LESS THE EFFICIENCY
– THE LESS CHANGE REQUIRED, THE
HIGHER THE EFFICIENCY
• ALL HAVE POTENTIAL HAZARDS
ASSOCIATED WITH THEM
TRANSPORT PROCESSES
• USED TO MOVE MATERIAL BETWEEN
PROCESS OPERATIONS
• PUMPS
• TURBINES
• CONVEYORS
• GRAVITY
• PNEUMATIC
STORAGE OPERATIONS
•
•
•
•
RAW MATERIALS
FINISHED GOODS
INTERMEDIATES
OFF-SPEC MATERIALS
CONTROL SYSTEMS
• PROCESSES FOR NORMAL
OPERATION
– CONTINUOUS OPERATIONS
– BATCH OPERATIONS
• START-UP
CONTROL SYSTEMS
• PROCESSES FOR NORMAL
OPERATION
– CONTINUOUS OPERATIONS
– BATCH OPERATIONS
• START-UP
• SHUTDOWN
– PROCESS INTERRUPTION
– ROUTINE SHUTDOWN
– EMERGENCY SHUTDOWN
CONTROL SYSTEMS
• SAFETY SYSTEMS
– OUT-OF-RANGE CONDITIONS
– INTERLOCKS BETWEEN UNITS
INHERENTLY SAFE DESIGN10,11
•
TECHNIQUES THAT REDUCE THE
RISKS ASSOCIATED WITH
OPERATIONS
•
EQUIPMENT FAILURE SHOULD NOT
SERIOUSLY AFFECT SAFETY, OUTPUT
OR EFFICIENCY
MINIMIZATION OF THE INTENSITY
• REDUCE QUANTITIES OF MATERIALS
MAINTAINED IN INVENTORIES AND IN
THE PROCESS
– QUANTITIES IN INVENTORIES
• REDUCED CAPITAL COSTS
• REDUCED MAINTENANCE
• LESS MATERIAL TO PARTICIPATE IN A
REACTION
• HAZARDOUS REACTANT BE MANUFACTURED
ON SITE FROM LESS HAZARDOUS
PRECURSORS
REACTORS
• SMALLER REACTORS TYPICALLY
HAVE LESS MATERIAL IN PROCESS
• HAVE BETTER CONTROL OF HEAT
TRANSFER
• AND CAN BE MORE EFFICIENT12
GENERAL FACTORS TO REDUCE
REACTOR RISKS13
OBJECTIVES
METHODS
AVOID PRODUCTION OF
BYPRODUCTS - MINIMIZE
SIDE REACTIONS
PRODUCE PRODUCT OF HIGH PURITY AT HIGH
YIELD, GENERATING FEW OR NO
BY-PRODUCTS WHICH WOULD HAVE TO BE
REMOVED THROUGH
DOWNSTREAM PURIFICATION STEPS
MINIMIZE REACTION TIMES
AND RESIDENCE TIME AT
EXTREME CONDITIONS
USE REACTIONS WHICH OCCUR RAPIDLY
WHEN THE MATERIALS COME INTO CONTACT,
REDUCING THE RESIDENCE TIME REQUIRED IN
THE REACTOR AND MAKING THE PROCESS
AMENABLE TO CONTINUOUS OPERATION
MAXIMIZE MASS
TRANSFER CONDITIONS
USE SINGLE PHASE REACTION SYSTEMS OF
LOW VISCOSITY, AVOIDING THE NEED TO
TRANSPORT REACTANTS ACROSS PHASE
BOUNDARIES AND FACILITATING THE RAPID
CONTACT OF REACTANTS
GENERAL FACTORS TO REDUCE
REACTOR RISKS13
OBJECTIVES
METHODS
USE MODERATE PROCESS
CONDITIONS
OPERATE AS CLOSELY TO AMBIENT
TEMPERATURE AND PRESSURE AS POSSIBLE,
REDUCING THE POTENTIAL ENERGY FROM
ELEVATED TEMPERATURE AND PRESSURE IN
THE REACTOR SYSTEM
CHOOSE LOWER ENERGY
REACTION SYSTEMS
USE REACTIONS WHICH ARE NOT HIGHLY
EXOTHERMIC
USE REACTIONS WHICH
ARE NOT HIGHLY
SENSITIVE TO OPERATING
CONDITIONS
REACTIONS WHICH ARE VERY TOLERANT OF
VARIATIONS IN RAW MATERIAL COMPOSITION,
CHANGES IN TEMPERATURE, PRESSURE, AND
CONCENTRATION, AND THE PRESENCE OF
COMMON CONTAMINANTS SUCH AS WATER,
AIR, RUST, AND OIL.
COMPARISON OF REACTOR
ALTERNATIVES
COMPARISON OF REACTOR
ALTERNATIVES
• CONTINUOUS REACTORS HAVE SMALLER
INVENTORIES THAN BATCH REACTORS
• TUBULAR REACTORS HAVE SMALLER
INVENTORIES THAN TANK REACTORS
• THIN FILM REACTORS HAVE SMALLER
INVENTORIES THAN TUBULAR REACTORS
• GAS PHASE REACTORS HAVE LESS
INVENTORY THAN LIQUID PHASE REACTOR
SUBSTITUTION
• USE OF SAFER NON-REACTIVE
CHEMICALS
• MAY DECREASE EFFICIENCY
• MAY ALSO DECREASE COSTS
SUBSTITUTION
• HEAT TRANSFER
• FOR HIGH TEMPERATURE HEAT
TRANSFER USE WATER OR MOLTEN
SALTS IN PLACE OF HYDROCARBONBASED HEAT TRANSFER FLUIDS14,15
SUBSTITUTION
• HEAT TRANSFER
• FOR LOW TEMPERATURE HEAT
TRANSFER REPLACE OZONE
SCAVENGING FLUIDS (FREONS) WITH
ALTERNATES (N2, PROPANE,
HYDROFLUOROCARBONS)16
SUBSTITUTION
• SOLVENT REPLACEMENT
– USE WATER-BASED PAINT IN PLACE OF
SOLVENT-BASED PAINTS
– USE OF WATER-BASED SOLVENTS OR
CO2 IN CHIP MANUFACTURING
PROCESSES17,18 (OFTEN WITH IMPROVED
PRODUCT PERFORMANCE)
ATTENUATION
• MODIFY CONDITIONS TO MINIMIZE
THE IMPACT OF HAZARDOUS
EVENTS19
– ADDITION OF INERT COMPONENT TO
SYSTEM CAN DILUTE THE POSSIBLE
INTENSITY OF A REACTION
– MODIFIED CATALYSTS CAN REDUCE THE
TEMPERATURES AND PRESSURES
REQUIRED FOR THE REACTION20
ATTENUATION
• STORAGE OPTIONS
– LIQUIFIED GASES STORED AT
CRYOGENIC TEMPERATURES
• STORED AT ATMOSPHERIC PRESSURE
• USES SMALLER VOLUMES THAT GAS
STORAGE
• TEMPERATURES ARE FREQUENTLY BELOW
IGNITION TEMPERATURES IN AIR
ATTENUATION
• STORAGE OPTIONS
– MINIMIZE STORAGE BY ON-SITE
PRODUCTION
• HYDROGEN GENERATED BY ELECTROLYSIS
OR PARTIAL OXIDATION OF NATURAL GAS
• CHLORINE GENERATION ON SITE
ATTENUATION
• STORAGE OPTIONS
– STORAGE IN LESS NOXIOUS FORMS
•
•
•
•
•
CHLORINE FOR POOLS
GASEOUS STORAGE
LIQUID STORAGE
SOLID FORM (Cyranuric Acid)
DILUTED SOLID FORM (Cyranuric Acid WITH
INERT FILLER)
LIMITATION OF THE EFFECTS
• OPERATE PROCESSES IN STAGES TO
AVOID PROCESS CONDITIONS THAT
CAN LEAD TO EVENTS
– MULTIPLE STAGES FOR OPERATIONS21
– CHANGING THE SEQUENCE OF REACTIONS CAN
REDUCE HAZARDS
– ELIMINATION OF UNNECESSARY STEPS TO
SIMPLIFY THE PROCESS
SIMPLIFICATION
• SIMPLIFIED CONTROL
INSTRUMENTATION
– EVERY CONTROL LOOP CAN FAIL
– ELIMINATION OF THE NEED FOR A CONTROL
LOOP THROUGH EQUIPMENT DESIGN
– ANOTHER APPROACH IS TO MAKE CERTAIN
THAT CONTROL INSTRUMENTATION SENSORS
ARE SEPARATE FROM ALARM
INSTRUMENTATION SENSORS
EXAMPLE OF USE OF SPECIAL
MATERIALS OF CONSTRUCTION
• OXYGEN COMPRESSORS
EXAMPLE OF USE OF SPECIAL
MATERIALS OF CONSTRUCTION
• IF THE COMPRESSOR ROTOR GOES
OUT OF BALANCE, IT WILL RUB
AGAINST THE STATOR AND CAUSE A
FIRE
• FIRE EMITS INTENSE THERMAL RADIATION
• COMPRESSOR IS EQUIPPED WITH VIBRATION
SENSORS
• COMPRESSOR WAS INSTALLED IN A SEALED
HOUSING
• PARTS THAT WOULD RUB FIRST WERE
FABRICATED FROM SILVER, A METAL THAT WILL
MELT BEFORE IT IGNITES
HAZOPS PROCESS FLOWCHART
HAZARDOUS ANALYSIS
STUDIES
• PROCESSES
DEVELOPED
TO IDENTIFY
PROBLEMS
INHERENT IN
PROCESS
DESIGNS.
Initiate
Study
Assemble
Team
Collect
Data
Define
Process Nodes
Analyze
Parameters
Determine
Intent
Human
Factors
Engineering
Factors
Examine
Deviations
Define
Risk
Estimate
Severity
Predict
Frequency
Complete
Report
Create
Revision List
Prepare
Op. Manual Summary
SEQUENCE OF EVENTS FOR A HAZOPS
ANALYSIS
• INTENTS
• DEFINE PROCESS HAZARDS
– HUMAN FACTORS ANALYSIS
– SAFETY & HEALTH IMPACTS OF LOSS OF
CONTROL
• DETERMINE HISTORY OF INCIDENTS IN
RELATED FACILITIES
• CONFIRM ADEQUACY OF OPERATING,
ENGINEERING AND ADMINISTRATIVE
CONTROLS
• EVALUATE IMPACT OF FACILITY SITING
ANALYSES ARE NOW
REQUIRED FOR PROCESSES
• SARA TITLE III - COMMUNITY
RIGHT TO KNOW AS PER EPA
DEVELOPED 40CFR67, RISK
MANAGEMENT PROGRAM
• OSHA REGULATION CFR 1910.119
HAZOP - (HAZARD AND
OPERABILITY STUDY)
• EXAMINES CONDITIONS AT
DIFFERENT LOCATIONS IN THE
FACILITY
• RESULTS IN A REPORT WITH
• LIST OF CHANGES FOR PROCESS
• DEFINITION OF PROCESS HAZARDS
• CLARIFICATION OF OPERATING
PROCEDURES
SEQUENCE OF EVENTS FOR A
HAZOPS ANALYSIS
•
ASSEMBLE ANALYSIS TEAM - WHO
HAVE NECESSARY PROCESS
EXPERIENCE AND KNOWLEDGE
–
–
–
–
–
DESIGN ENGINEERS
OPERATORS
MATERIALS SPECIALISTS
EH&S SPECIALISTS
MAINTENANCE PERSONNEL
SEQUENCE OF EVENTS FOR A
HAZOPS ANALYSIS
• COLLECT DATA
– DESIGN DRAWINGS
– EQUIPMENT DRAWINGS, CALCULATIONS AND
SPECIFICATIONS
– MAINTENANCE INFORMATION
– MSDS
• DEFINE PROCESS NODES
– BREAK PROCESS INTO AREAS FOR ANALYSIS
– LOCATE THESE ON A SET OF DRAWINGS
SEQUENCE OF EVENTS FOR A
HAZOPS ANALYSIS
• ANALYZE PARAMETERS FOR EACH
NODE
– PURPOSE OR INTENT
• PROCESS FUNCTIONS
• PROCESS VARIABLES
• HUMAN INTERACTION - HOW IS THE OPERATOR INTEGRATED INTO
THE OPERATION OF THE PROCESS AT EACH NODE.
SEQUENCE OF EVENTS FOR
A HAZOPS ANALYSIS
• DEFINE RISK - SEVERITY AND
PROBABILITY
– DETERMINE CAUSE
–
EQUIPMENT FAILURE
– OPERATOR ERROR
– ENVIRONMENTAL CHANGES
– EXTERNAL IMPACTS
SEQUENCE OF EVENTS FOR A
HAZOPS ANALYSIS
•
ESTIMATE SEVERITY
RANKING
IMPACT
CATASTROPHIC
FATALITY(S), MAJOR EQUIPMENT LOSSES (>$5M), DOWNTIME > 1
MONTH, LONG-TERM PUBLIC HEALTH & SAFETY ISSUE
HIGH
LOST TIME INJURY, EQUIPMENT LOSSES > $100K, DOWNTIME>1
W EEK, OFF-SITE RESPONSE REQUIRED
MODERATE
REPORTABLE INJURY, EQUIPMENT LOSSES > $10k, DOW NTIME>1
DAY, EMISSION REPORT
LOW
EQUIPMENT LOSSES > $1000, DOWNTIME < 1 DAY
NONE
NO EQUIPMENT OR MATERIAL LOSSES & NO DOWNTIME
SEQUENCE OF EVENTS FOR A
HAZOPS ANALYSIS
• PREDICT FREQUENCY OF EVENT
RANKING
FREQUENCY
HIGH PROBABILITY
1/6 MONTH
HIGH
1/YEAR
MODERATE
1/2YEAR
LOW
1/5YEAR
NONE
1/PROCESS LIFETIME
HAZARDS ANALYSIS (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
GENERIC FAULT TREE FOR HAZAN - DOUBLE JEOPARY
HAZARDS
ANALYSIS
(HAZAN)
STUDY
PRIMARY
EVENT
CONTROLLER
RESPONSE
SECONDARY EVENT
EVENT
OCCURS
CONTROL
SUCCEEDS
EVENT
DOES NOT OCCUR
• CAN BE
ORGANIZED
WITH FAULT
TREE (FTA)
EVENT
OCCURS
EVENT
OCCURS
CONTROL
FAILS
EVENT
DOES NOT OCCUR
CONTROLLER
RESPONSE
CONTROL
SUCCEEDS
CONTROL
FAILS
CONTROL
SUCCEEDS
CONTROL
FAILS
CONTROL
SUCCEEDS
CONTROL
FAILS
CONTROL
SUCCEEDS
CONTROL
FAILS
HAZARDS ANALYSIS (HAZAN)
STUDY
• FAULT TREE SYMBOLS
• FAULT TREES USE PROGRAMMING SYMBOLS FOR
EACH TYPE OF JUNCTION
BASIC EVENT FAILURE THAT IS
THE START POINT
FOR THE ANALYSIS
CONTR.
EVENT
BASIC
EVENT
INTER.
EVENT
INTERMEDIATE
EVENT -EVENT
THAT RESULTS
FROM PREVIOUS
EVENTS IN THE
TREE.
AND GATE OUTLET
CONDITION
RESULTS ALL OF
THE INLET
CONDITIONS
EXIST.
OR
CONTRIBUTING
EVENT - CAN OCCUR
IN PARALLEL TO THE
BASIC EVENT AND
CONTRIBUTE TO THE
OVERALL IMPACT.
OR GATE -OUTLET
CONDITION
RESULTS IF ONE OF
THE INLET
CONDITIONS EXIST.
TYPICAL FAULT TREE
SYMBOLOGY -ALSO
REFERRED TO AS
ALTERNATE DIGITAL
LOGIC, ADL
FAULT TREE EXAMPLE - NO PAPER FOR
BREAKFAST
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

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