Objectives
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Introduction
Syllabus
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Office hrs
Textbook
Assignments and quizzes
Attendance
Chatroom and archive
Safety engineering overview
SAFE 605: Principles of Safety
Engineering
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Overview of Safety Engineering
Safety Engineering Concepts
Safety Engineering
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Safety engineering is devoted to the
application of scientific and engineering
principles and methods to the elimination and
control of hazards.
Safety engineering is an applied science
strongly related to systems engineering.
Safety engineering assures that a life-critical
system behaves as needed even when
pieces fail.
Safety Engineering Defined
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To regulate the effects of hazards, it is
necessary to employ a means of controlling
the causes responsible for the presence of
injurious agents. This is the essence of the
practice of safety engineering.

Grimaldi and Simonds
Application of the Sciences
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Safety engineering applies the sciences to
situations in an attempt
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to reduce the likelihood of the occurrence of unwanted
events
These events include:
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accidents,
injuries,
property losses,
and financial losses
Civil Engineering
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Safety engineering in the area of civil
engineering includes:
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Knowledge of structural integrity of buildings and
bridges
An understanding of the needs for controlling air
pollution and water pollution
Knowledge of the planning required to build safe
roads and highways
Industrial Engineering
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Industrial engineers are responsible for the
design of production processes.
A major safety issue for industrial engineers
involves the reduction of ergonomic hazards
in the workplace.
Hazard Control Methods
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Engineering controls
Administrative Controls
PPE
Training
NIOSH
Hazard Control Priorities
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Eliminate the hazard
Reduce the hazard level
Provide safety devices
Provide warnings
Provide safety procedures
Definitions
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A "fault“
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A "failure"
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only occurs if a human being (other than a repair person)
has to cope with the situation.
A "critical"
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when some piece of equipment does not operate as
designed.
failure endangers one or a few people.
A "catastrophic"
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failure endangers, harms or kills a significant number of
people.
Definitions
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A "probabilistically safe"
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system has no single point of failure,
and enough redundant sensors, computers and effectors
so that it is very unlikely to cause harm (usually "very
unlikely" means less than one human life lost in a billion
hours of operation).
Definitions
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An "inherently safe" system is
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a clever mechanical arrangement that cannot be made to
cause harm- obviously the best arrangement, but this is not
always possible.
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functions safely by its own means, i.e. without
auxiliary media
Safe by its nature: less hazardous chemical
Safety is built in not added
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Video watch
Definitions
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A "fault-tolerant" system can ……(1)…….. operate with faults,
though its operation may be ….(2)….. in some fashion.
(1)
(2)
Continue to
normal
fail to
degrade
Fail-Safe Designs
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A "fail-safe" system is one that cannot cause harm
when it fails.
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Fail-passive arrangements: Reduces the system to the lowest
energy level
 Will not operate again until problem is resolved
Fail-active design: Keeps system in safe operating mode until
corrective action is taken
 Battery operated smoke detector in which an alarm continues to
sound in the event of a failure.
Fail operational arrangement: Allows system to operate until
corrective action is possible.
 Excess pressure valve design in a pressure vessel allows the
valve to remain open and usable until a replacement valve can
be installed.
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Safety Factors
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Expressed as a ratio between strength and
stress.
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A safety factor for a wire rope is the ratio between
the force required to break the rope (nominal
breaking strength) and the rated load (load which
should never be exceeded while lifting
Failure Rate Reduction
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Uses components in a design arrangement
that produces expected lifetimes far beyond
their proposed periods of use.
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Methods of reducing failure rates include:
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Screening
Redundant arrangements
Timed replacements
Derating
Screening
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Quality control (QC)
Statistical process control (SPC)
Visual inspection and measurement
Redundancy
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Redundancy involves the use of backup
subsystems designed to take over the
operation of a system in the event of failure of
the primary subsystem.
Timed Replacements
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The practice of timed replacements involves
the establishment of a preventive
maintenance program in which parts which
are subject to fail, are replaced on a schedule
that ensures they are replaced prior to failure.
Derating
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Reducing stresses upon components thereby
increasing their life and reliability
Example:
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Providing fans in computers to reduce the heat
generated by the electronic components
AC system: for cooling computer rooms/PLC
Dehumidifier: reduce humidity
Primary Causes of Engineering
Disasters
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The primary causes of engineering disasters
are usually considered to be:
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human factors (including both 'ethical' failure and
accidents)
design flaws (many of which are also the result of
unethical practices)
materials failures
extreme conditions or environments
Most commonly and importantly, most
disasters are:
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a combination of these reasons.
A Study of Engineering
Failures
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The Swiss Federal Institute of Technology in Zurich analyzed
800 cases of structural failure in which 504 people were killed,
592 people injured, and millions of dollars of damage incurred.
When engineers were at fault, the researchers classified the
causes of failure as follows:
 Insufficient knowledge, 36%
 Underestimation of influence 16%
 Ignorance, carelessness, negligence, 14%
 Forgetfulness, error, 13%
 Relying upon others without sufficient control, 9%
 Objectively unknown situation, 7%
 Imprecise definition of responsibilities, 1%
 Choice of bad quality, 1%
 Other, 3%
Engineering Ethics
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Often, a deficiency in engineering ethics is
found to be one of the root causes of an
engineering failure.
An engineer, as a professional, has a
responsibility to their client or employer, to
their profession, and to the general public, to
perform their duties in as conscientious a
manner as possible.
Ethical Duty
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An ethical engineer is one who
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avoids conflicts of interest,
does not attempt to misrepresent their knowledge so as to
accept jobs outside their area of expertise,
acts in the best interests of society and the environment,
fulfills the terms of their contracts or agreements in a
thorough and professional manner,
and promotes the education of young engineers within their
field.
Math Review
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First homework assignment is to “test” your
math skills
There will not be calculus based formulas in
the course. If you can’t do them, don’t lose
sleep over them
The course will be using algebra, trig, finite
math, and physics