Introduction to Safety in

Chemical Process Industry

- Chemical Process, Chemical Engineering,
Safety/Risk/Hazard/Loss -

Kyoshik PARK
Department of Chemical Engineering
Middle East Technical University - NCC
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Rev. Processes Involving Ideal Gas
o Summary

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 Isentropic Expansion

dP 2  dP 
Incorporate friction term:  F C1  
2
   
P dP u
2
C1   0
Po  2g c
P  C p / Cv
Ideal gas, isentropic expansion: = a,

Integrate and solve for u Mass flow rate:
 2 /   ( 1) /  
2gc M   P P 
Qm  Co APo     
RgTo  1 

 Po  P o  

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 Exposure to Release
Predict effects of exposure near the surface.
Stages
1. Source
2 3 2. Acceleration,
6
Diffusion
4 3. Gravity
4. Transition
1 5 5. Surface
6. Turbulence

Predict % affected by the exposure.

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 Gaussian Dispersion Pattern
(0,0,0)

Isopleth
z
y

A: stack height
B: effective height
Cmax at center Cmax
x
Along X u
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   ze  2 
16161    
po   4.5  

pa 2 2 2
 z   z   z 
1  e  1  e  1  e 
 0.048   0.32   1.35 

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 Objective
Prevent the initiation of the fire or
explosion and minimize the damage
produced after it.

How can it be prevented?

Inerting
Control static electricity
Ventilation
Explosion–proof equipment

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 Flammability Diagram - OSFC
A contains pure fuel
Pure N2 added till
point S, OSFC
Requires a large
amount of
nitrogen ⇒ costly

Pure N2 added till

point S, OSFC
the air forms a
flammable
mixture at the
entry point

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 Patterns of two phase flow

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 Chemical Process &
Chemical Process Industry

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 Chemical Industry: Products

Polyurethane mattress, polyester sheets

Plastic clock, nylon carpet, phenolic switch
Polyvinyl chloride insulated conductors
Sanitized water, soap, refrigerants
Fertilizers, printing inks, paper
Electrical components in TV, radio
Adapted: R.E. Sanders, Chemical Process Safety, Butterworth-Heinemann (1999)

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 Chemical Product Groups

Food, shelter, health

Electronics, computing,
communications
Biotechnology, pharmaceuticals
Automobiles, appliances, furniture
Paper, textiles, paint
Agriculture, construction

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 Chemical Industry: History I
Early to 5,000 BC
• First industrial chemical process: fire
• Burning wood for heat, cooking food
• Firing pottery, bricks

History adapted from: R.E. Sanders,

Chemical Process Safety,
Butterworth-Heinemann (1999)

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 Chemical Industry: History II
3,000 - 4,000 BC
• Chemical: soda ash (sodium carbonate)
• Arabic name for soda: al kali
• Process: burning seaweeds & seashore
vegetation including kali
• Hot water extraction to form brown lye
• Products: beads,
glass ornaments, soap

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 Chemical Industry: History III
Prior to 3,000 BC
• Alcoholic fermentation
• Ale, wine (grapes, dates, palm), cider
• Egypt, Sumerian

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 Early Living Standards
10th Century in Europe
• Life expectancy: ~ 30 years
• Food scarce, monotonous, often stale
or spoiled
• Much labor required with few rewards
• Gradually the practice of science
reduced the burdens of existence

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 Chemical Industry: History IV
17th and 18th Centuries
• Food preservatives (inorganic chemicals)
• Dyes, fabrics, soap
• Gunpowder
• First American chemical plant in Boston,
1635, made saltpeter (potassium nitrate):
gunpowder, tanning of hides

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 Chemical Industry: Na2CO3
18th Century
• Nicolas LeBlanc process (Paris, 1791) for soda
ash from salt, NaCl. First large-scale process
• HCl: first large-scale industrial pollution
• From 1861-1880 was gradually replaced by Solvay
Process (simpler & less expensive)

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 Chemical Industry: History V
Modern Era
• After 1850: coal-tar dyes, drugs,
nitroglycerin explosives
• Celluloid plastics, fiber
• Lightweight metals
• Synthetic rubber
• Fuels

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 Chemical Industry: History VI
1930‟s
• Neoprene, polyethylene, nylon, fiberglass

After 1945
• Rapid expansion of petroleum refining
and chemical process industries
• Use, handling, & storage of chemicals
presented more potential hazards

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 Chemical Industry: History VII
After 1950
• Chemical processing more disciplined
• Larger inventories, higher T, P conditions
• More emphasis on design & process
changes
• More review of effects from modifications
• Today: U.S. & European chemical industries
among safest of all industries

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 What is a Chemical Engineer?
a) An Engineer who manufactures chemicals
b) A Chemist who works in a factory, or
c) A glorified Plumber?
d) “None of the above”
(However, chemical engineering students
bored with the relentless “pipe-flow
example” during fluid dynamics class may
begin to think of themselves as simply
“glorified plumbers”)

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 All Right, So What is a Chemical
Engineer?
Who are comfortable with chemistry.
But they do much more with this
knowledge than just make chemicals.
Who draws upon the vast and
powerful science of chemistry to solve
a wide range of problems.
Sometimes described as the
“universal engineer”

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 So What Exactly Does This
"Universal Engineer" Do?
During the past Century, chemical
engineers have made tremendous
contributions to our standard of living.
To celebrate these accomplishments,
the American Institute of Chemical
Engineers (AIChE) has compiled a list
of the “10 Greatest Achievements of
Chemical Engineering.”

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 The Atom, as Large as Life:
Ability to split the atom and isolate
isotopes
Biology, medicine, metallurgy, and power
generation
production of the atomic bomb
use isotopes to monitor
bodily functions
accurately date their
historical findings

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 The Plastic Age:
Mass produced polymers = Plastic
Age
A viable economic reality
Bakelite -1908
- Electric insulation, plugs & sockets, clock
bases, iron cooking handles, and
fashionable jewelry

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 The Human Reactor:
“Unit operations” consisting of heat
exchangers, filters, chemical reactors
and the like = Human body.
Improve clinical care
Diagnostic and therapeutic devices
Artificial organs

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 Wonder Drugs for the Masses:

Mutation and special brewing

techniques
increase antibiotics‟ yields
Low price, high volume, drugs
enables.

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 Synthetic Fibers, a Sheep's Best Friend:
Keep us warm, comfortable, and
provide a good night's rest
Help reduce the strain on natural
sources of cotton and wool tailored to
specific applications.
Nylon stockings make legs look
young and attractive
Bullet proof vests keep people
out of harm's way.

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 Liquefied Air, Yes it's Cool:
Air separation
Purified nitrogen; to recover petroleum,
freeze food, produce semiconductors, or
prevent unwanted reactions
Oxygen; to make steel, smelt copper, weld
metals together, and support the lives of
patients in hospitals.

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 The Environment
Provide economical answers to clean
up yesterday's waste and prevent
tomorrow's pollution.
Catalytic converters
Reformulated gasoline
Smoke stack scrubbers
Synthetic replacements
More efficient processing, and
new recycling technologies

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 Food, "It's What's For Dinner":

Chemical fertilizers can help provide

these nutrients to crops
Forefront of food processing where
they help create better tasting and
most nutritious foods

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Petrochemicals, "Black Gold, Texas Tea":

Form many useful products from

petroleum by developing processes
like catalytic cracking
gasoline, lubricating oils, plastics,
synthetic rubber, and synthetic fibers

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 Running on Synthetic Rubber:

Developing today's synthetic rubber

industry
During World War II, synthetic rubber
capacity suddenly became of paramount
importance.
Tires, gaskets, hoses, and conveyor belts
(not to mention running shoes)

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 Chemical Engineering Today &
Tomorrow
The highest paid of the "Big Four" (civil,
mechanical, electrical, chemical)
Upper management position
3M, Du Pont, General Electric, Union Carbide, Dow
Chemical, Exxon, BASF, Gulf Oil, Texaco, and B.F.
Goodrich
70,000 practicing chemical engineers in the
United States

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 Safety & Process Safety

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 The superior man, when resting in
safety, does not forgot that danger
may come…. When all is orderly,
he does not forget that disorder
may come.
Confucius (551 BC – 479 BC)

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 Basic Terms I
Safety: prevention of loss incidents by
identification, control, or elimination of hazards
Hazard: A physical situation with a potential for
human injury, damage to property, damage to the
environment, or some combination of these
Risk: The likelihood of a specified undesired
event occurring within a specified period or in
specified circumstances.
Nomenclature for Hazard and Risk Assessment in the Process
Industries - David Jones, UK Institution of Chemical Engineers,
1992

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 Basic Terms II

Risk deals with well defined

events( ) about which norms
have been negotiated amongst
different stakeholders.
Technology must be designed
such that these norms are met.

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 True and Perceived Risks 0

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 True and Perceived Risks 0

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 True and Perceived Risks I
Probability of deaths by disaster
(tornado, plane crash) overestimated by
the public
More ordinary risks (auto accident,
smoking, stroke, heart attack) are
underestimated
☞ Public ranks disease and accidents ~
equally, but disease causes ~ 15 times
more deaths.

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 True and Perceived Risks II
400,000 smoking-related deaths/year
40,000 deaths/year on U.S. highways
An airline crash with 300 deaths
draws far more attention over a
longer time.

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 True and Perceived Risks III
Example: Three years old kid killed in
water knee-deep by an alligator:
reported nationally
Only 7 recorded fatalities by alligator
Primary hazards were minimum
supervision and shallow water.
In 1995, 300 children under 4 years old
drowned at home: reported locally

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 Voluntary or Involuntary
Choice affects perceived risk.
Accept risk by coercion vs. by choice
Accept the risk of smoking
Voluntarily drive a motorcycle
Protest a plant with a much smaller risk

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 Moral or Immoral
Deaths by moral means are more
acceptable than by immoral means
Far more driving deaths than
murders per year but murder is much
less acceptable.

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Detectable vs Undetectable Risks I
People fear the undetected or the risks
that may take years to appear.
Collapse of a dam in India (1979) killed
thousands and perhaps more than killed
in the Bhopal tragedy (1984)
People are concerned far more about
chemical engineering than civil
engineering disasters.

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Detectable vs Undetectable Risks II

• Water is a familiar chemical, so

hazards are less noticed or are
accepted. Not in My Back Yard

• Pesticides and radioactivity poorly

understood, so they are feared.
• NIMBY, BANANA
Build Absolutely Nothing
• PIMFY Anywhere Near Anybody

Please in My Front Yard

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 Safety Program
System
To record what needs to be done to have an outstanding
safety program
Attitude
Positive attitude
Fundamentals
Understand and use the fundamentals of chemical process
safety in the design, construction and operation of their
plants
Experience
Read and understand case histories of past accident
Time
Time to study, time to do work, time to share experience
You
Take the responsibility to contribute to the safety program
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 Impact of Accidents
○ All for the want of a nail…..

For want of a nail, the shoe was lost,

For want of a shoe, the horse was lost,
For want of a horse, the rider was lost,
For want of a rider, a message was lost,
For want of a message, the battle was lost,
For want of a battle, the kingdom was lost,
And all for the want of a nail…..

George Herbert, in outlandish proverbs(1640)

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 Oppau, Germany
• 9/21/21
• Oppau, Germany

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 Oppau
• Location: Oppau, Germany
• Company: BASF
• Date: September 21, 1921
• Killed: 430
• Injured: unknown
• Financial: N/A
• Type of Plant: Fertilizer
• Trigger: Blasting Powder being used to break
up a 50:50 mixture of ammonium sulfate and
ammonium nitrate

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 Monsanto Texas City
•

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 Monsanto Texas City
•

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 Texas City
• Location: Texas City, Texas, USA
• Company: Monsanto
• Date: April 16, 1947
• Killed: 552
• Injured: about 3000
• Financial: N/A
• Type of Plant: petrochemical
• Trigger: fire on ship at dock – ammonium
nitrate

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 Flixborough

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 Flixborough
• Location: Flixborough, UK
• Company: Nypro
• Date: June 1, 1974
• Killed: 28
• Injured: 104
• Financial: $635,900,000
• Type of Plant: cyclohexane oxidation
(Nylon)
• Trigger: Vapor Cloud Explosion

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 Beek, NL
• Beek
• 1975

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 Beek
• Location: Beek, NL
• Company: Dutch State Mines (DSM)
• Date: November 7, 1975
• Killed: 14
• Injured: N/A
• Financial: $114,700,000
• Type of Plant: petrochemical
• Trigger: propylene

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 Westwago
• Westwago, La
• 12/23/77

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 Westwego
• Location: Westwego, La, USA
• Company: Continental Grain
• Date: December 23, 1977
• Killed: 35
• Injured: 9
• Financial: N/A
• Type of Plant: Grainery
• Trigger: Corn dust explosion in grain elevator

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 Bhopal

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 Bhopal

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 Bhopal

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 Bhopal

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 Bhopal
• Location: Bhopal, India
• Company: Union Carbide
• Date: December 3, 1984
• Killed: 4000 – 20,000
• Injured: 100,000 + asymptomatic
• Financial: ($470,000,000 settlement)
• Type of Plant: pesticide
• Trigger: Release of MIC

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 Phillips

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 Phillips

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 Phillips
• Location: Pasadena, Texas, USA
• Company: Phillips 66
• Date: October 23, 1989
• Killed: 23
• Injured: 130-300
• Financial: $623,500,000 – 1,770,000,000*
• Type of Plant: polyethylene
• Trigger: isobutane

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Accidental Flow

Proactive Management Reactive Management

Prevention Control Protection Mitigation

Accidental
Hazard Cause Deviation Impact
Event
Material/energy Initiating event Excursion Loss of contain- Loss of contain-
Contained and of process upset; Beyond design/ ment of process ment of process
controlled during Start of accident Operating limits material/energy material/energy
normal operation event sequence
•Toxicity •Mechanical failure •No flow •Fire •Illnesses/injuries/
•Flammability •Procedural error •High temperature •Explosion Death
•Reactivity •External force •Low level •Hazardous material •Property damage
•Elevated •Fouling etc. •Impurities release etc. •Business
pressure etc. •Wrong material •Other energy interruption
•Step omitted etc. releases •Environmental
damage etc.
 Flixborough
The Chemistry
O OH

cyclohexane cyclohexanone cyclohexanol

O

N
H

caprolactam
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 The Reactor Train

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 Problems with New
Process
Serious technical and financial
problems
Hazardous process to produce
cyclohexanone
Office building close to plant
Control room was within plant

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 Events of June 1,1974
Cyclohexane circulated
Pipe assembly ruptured
Uncontrolled vapor cloud
explosion

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 The Possible Causes
No qualified engineer on the site
Connections between 4 and 6
were expedient
“Hurry up” attitude of
management ← Only Profit!

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 BHOPAL DISASTER
MIC Released at Bhopal, India
December 3, 1984
Over 2000 Fatalities

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 The Chemistry O
O CNHCH3
OH

+ CH3-N=C=O

-Napthol MIC Carbaryl

Critical Properties of MIC

Boiling point 39.1°C
Molecular weight 57
PEL(p.54) 0.02ppm
IDLH(P.56) 3 ppm
Odor threshold 2 ppm
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Exothermic Reactions with Water
and Itself
MIC + H2O 1,3,5 Trimethyl Biuret + CO2

O
H3C CH3
N N
3 MIC
O N O
H3C
TRIMER
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 Runaway Scenarios
Loss of cooling or refrigeration
Loss of Agitation
Unexpected addition of heat
Human error

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 Condition before Accident
Refrigeration turned off.
Flare down for maintenance.
Scrubber in standby mode.

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 Accident
Vessel vented at 180 psig
Released for 2 hours
MIC heavier than the air
2000 fatalities

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 The traditional method of identifying
hazards was to build the plant and see what
happens - „every dog is allowed one bite‟.
Until it bit someone, we could say that we
did not know it would do so. This method
is no longer acceptable now that we keep
dogs as big as Flixborough.

-Kletz and Lawley

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 To Prevent Accidents We
Need Knowledge In
Design (inherently safe)
Thermodynamics
Kinetics
Control
Management and ethics

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 Routes to Carbaryl, Bhopal

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 Routes to Carbaryl, Alternative

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 Measurement of Safety

How to measure safety of a process?

Is a safety procedure effective?
Incident and loss statistics models
Perspective of risk, real and
perceived, is needed for assessment
of results of these models

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 Measure Danger of a Job

1. Number of fatalities in a job or group

2. Fatality Rate (FR): # fatalities / year
# population
Independent of exposure time
FR group
3. Relative Risk Index (RRI):
FR all
Compare risk to average job

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 Measure Danger of a Job
RRI (fatalities), 1995
Finance, insurance, real estate: 0.4
Chemical industry: 0.6
Average job: 1.0
Petroleum refining: 1.8
Truck driving: 5.3
Metal workers: 13.1

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 Measure Danger of a Job
Fatal accident rate (FAR)
8
# fatalities/10 hr
8
10 (# fatalities)
FAR 
hours worked

Dependent on exposure time, unlike FR

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 Fatal Accident Rate

 The FAR period of time,108 hours, is

based on 1,000 employees working for
a lifetime.
 Work lifetime is assumed to be 50 years
 One work year is 2,000 hr[250•8]
 1,000(2,000 hr/yr)(50 yr) = 108 hours

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 FAR Statistics for Industry
Chemical industry improved from a FAR of
4.0 in 1986 to 1.2 in 1990 (Crowl, Tab. 1-3,
p. 8)
Causes of fatalities divided about equally
between physical accidents and chemical
exposures.
FAR of 1.2 for all manufacture vs 3.7 for
agriculture (synthetic vs natural fibers)

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 Accident Statistics for Various
Selected Industries

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 FAR for Chemical Worker
For 1000 workers during lifetime (50
years) in chemical industry‡
2 work deaths (1 physical and 1 chemical)
20 non-work accident deaths
370 non-work disease deaths
Some common activities more
dangerous than chemical plant work
(Crowl, Tab. 1-4, p. 9)
‡ T.A. Kletz, Chem. Eng. (Apr. 1, 1985)

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 Fatality Statistics for Common
Nonindustrial Activities

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 OSHA Incident Rate (IR)
Based on work-related injuries,
illness, and fatalities or lost
workdays for 100 worker years
50 weeks/yr x 40 hr/wk = 2,000 hr/yr
100 yr x 2,000 hr/yr = 200,000 hr

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 OSHA Incident Rate (IR)

Deaths, injuries, and illnesses:

# incidents 1 5
OSHA IR  2 10 hr
hours worked hr

Lost # lost workdays 5
workdays: IR  2 10
 hours worked
Dependent on exposure time, like FAR
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 The Nature of the Accident
Process
Type of Probability of Potential for Potential for
Accident occurrence fatality economic loss

Fire High Low Inter-

mediate
Inter- Inter-
Explosion High
mediate mediate
Toxic Low
Low High
release

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 Safety in the Chemical Industry
Risks, perceptions often misunderstood
Chemical industry is held to a higher than
average safety standard.
This responsibility must be accepted to
work for an accident free workplace.
Continuous improvement is necessary for
credibility and the public trust.

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 Losses in Chemical Industry
Largest causes of loss: mechanical
failure and operator error (Crowl, Fig.
1-7, p.16)
Losses are sometimes divided into
mechanical failure (#1) and operator
error (#2).

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 Causes of loses in the largest
hydrocarbon-chemical plant accident

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 Hardware associated with
largest losses

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 Loss Trends in Industry
Number and magnitude of losses from the
1960‟s have increased.
Consistent with trend of larger & more
complex plants and processes. Also
higher pressures and temperatures.
Drop is shown in Crowl, Fig. 1-9, p. 18, for
1992-1996 period, but trend is not clear.

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 Program to Prevent Incidents
Safety involves many levels: design,
management, control systems, interlocks,
detectors, alarms, shutdown systems,
protective systems, emergency response
procedures, Table 5-10, p. 214.
For safer and more economical processes,
it is much better to eliminate rather than to
control hazards.

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 Inherent Safety
Inherent safety involves prevention
or reduction of hazards
Applies throughout the plant at any
time but best at the design stages
Minimize amounts, substitute for
safer, moderate to reduce hazards,
simplify to limit error, Crowl, Tab. 1-9,
p. 22

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 Trend of Chemical and Energy
Industries
More dangerous operating conditions
– high pressure, low temperature
• More toxic and environment-
dependent products
• Increased work and information
overload for human operators
• The public and the international
society are more sensitive and
regulation-minded about the safety
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 Future Features of
Chemical Plant Accidents
More severe personal injuries
More potential for major accidents
– Fire, explosions and toxic material releases
• Greater economic loss
• International environmental damage
• Human casualties in the wider
surrounding area

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 Goals for Safety and Environment in the
21st Century
Handle disasters with local communities
Prevent pollution
Operate safe plants
Distribute products in a way that reduces
hazards to people and the environment
Protect the health of people at plant sites
Promote the safe use of chemicals from
manufacture to recycling and disposal

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 Present Safety Problems
Complex & diverse energy facilities
Lower priority to safety-related
investment
Inspection only for facilities
Present safety management
reached its limit.

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 The Nature of the Accident I

Refinery
Others
Compressrs
H/E
Heaters
Pumps
Tankage
Vessels
Piping

0 10 20 30 40

Large Property Damage Losses in the Hydrocarbon-Chemical Industries:

A Thirty-Year Review, Marsh, 19th Ed. 2001
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 The Nature of the Accident II
Petrochemical Plants

Others
Columns
Furnaces
Compressors
Piping
Tankage
Vessels
Reactors

0 10 20 30 40 50
Large Property Damage Losses in the Hydrocarbon-Chemical Industries:
A Thirty-Year Review, Marsh, 19th Ed. 2001
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 The Nature of the Accident III
Gas Processing Plants

Others

HP Separator

Tankage

Cryogenic

Piping

0 10 20 30 40 50

Large Property Damage Losses in the Hydrocarbon-Chemical Industries:

A Thirty-Year Review, Marsh, 19th Ed. 2001
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 The Nature of the Accident IV
Terminals

Others

Piping

Ship/Barge

Tankage

0 10 20 30 40 50

Large Property Damage Losses in the Hydrocarbon-Chemical Industries:

A Thirty-Year Review, Marsh, 19th Ed. 2001
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 Examples of Loss by Accident
Direct Loss (Cost)
Recovery of facility and equipment
Off-spec.
Compensation for the contractors
Legislation fees for suit
Increase in insurance
Indirect Loss (Cost)
Production & Selling Interruption
Cost for Accident Investigation
Loss of customers & buyers
Disrepute
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 Safety Pyramid, Crowl, Fig, 1-3, p. 11
※ International Safety Rating System, DNV, 5th Ed.(1993)
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 An INHERENTLY SAFER DESIGN
is one that avoids hazards instead
of controlling them, particularly by
removing or reducing the amount
of hazardous material or the
number of hazardous operations.

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Layer of Protection Analysis (LOPA)
Community emergency response
Plant emergency response
Fire protection, steam/water curtain
정량적 위험평가 구성 III
Passive physical protection - walls, dikes, bunds, zoning
Pressure relief device

Automatic action, ESD

Critical alarm/Operator supervision
Manual intervention
Basic controls/ Process alarms
Operator supervision
Inherent safer
process design

Independent Layer of Protection “Onion”

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 SAVINGS
1. Less protective
equipment needed, say
5-10% of capital.
2. Less maintenance of
plant & systems.
3. SMALLER SIZE.
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Avoid a Narrow Focus

Human
Environment

Bad Science! Machine

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• Many accidents occur as the result of
interactions between matrix elements

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