Transcript Chapter 7: Risk, Safety and Liability in Engineering

Chapter 7: Risk, Safety and
Liability in Engineering
How should engineers deal with issues of
risk and safety?

Engineering necessarily involves risk.
New hazards could be found in products,
processes, and chemicals that were once
thought to be safe.
Risk
Risk increases because engineers are
constantly involved in innovation.
New machines are created and new
compounds synthesized always without
full knowledge of their long-term effects
on humans or the environment.
In this chapter we will go over
The codes and engineering practice
regarding risk and safety
Difficulties in estimating risk
Normalizing deviance
Three approaches to acceptable risk: experts,
laypersons and government regulators
approach to acceptable risk
The Engineers liability for risk
Becoming a responsible engineer regarding
risk
The codes and engineering practice
regarding risk and safety
All engineering codes say that: “Engineers must
hold paramount the safety, health, and welfare of
the public.
NSPE:
II1b. Engineers shall approve only those
engineering documents that are in conformity with
applicable standards.
III2b. Engineers shall not complete, sign, or seal
plans and/or specifications that are not in
conformity with applicable engineering
standards. If the client or employer insists on
such unprofessional conduct, they shall notify the
proper authorities and withdraw from further
service on the project.
II1a. If engineers' judgment is overruled
under circumstances that endanger life or
property, they shall notify their employer or
client and such other authority as may be
appropriate.
Difficulties Estimating Risk
Detecting Failure Modes:
A failure mode is a way in which a
structure, mechanism or process can
multifunction.
Fault-Tree Analysis: a diagram of the
possible ways in which a multifunction or
accident can occur.
Event-Tree Analysis (similar with diff. Appr.)
Fault-Tree Analysis
In a Fault-tree analysis one starts with
an undesirable event, and then reasons
backward to determine what might have
led to the event. (p149)
Fault-Tree Analysis used to discover why a car
wont start
Fault Tree
Car Wont Start
Battery Charge Insufficient
Type title here
Starting System defective
Type title here
1. Faulty ground corrections
2. Terminals loose or corroded
3. Batery week
1. Rust
2. Corrosion
3. Dirt
4. Loose connections
1. lights left on motor off
2. Age
3. Bad weather
4. Defective ..........
Fuel System
Defective
ignition syste
defective
Event Tree-Analysis
In event-tree analysis one begins with
an initial event and reason forward to
the state of system to which the event
can lead. (p.150)
These have limitations p.150
Are There Normal Accidents?
Two characteristics of high-risk technologies
that make them susceptible to accidents:
Tight Coupling and
Complex Interactions of the parts of
technological systems
**These two factors make accidents likely and
difficult to predict and control
Processes are TIGHTLY COUPLED if
they are connected in such a way that one
process is known to affect another and will
usually do so within a short time.
Ex: A chemical plat is tightly coupled
because the failure in one part of the plant
can quickly affect other parts of the plant.
Ex: A university is loosely coupled, why?
Processes are COMPLEXLY INTERACTIVE if
the parts of the system can interact in
unanticipated ways. Like no one expected that
when part B failed it would affect part C.
Examples of complexly interactive and tightly
coupled technical systems:
chemical plants, nuclear power plants, space
missions, nuclear weapon systems. These can
have unexpected failures, and little time to
correct the problems. (all system affected)
The answer is:
It may not be possible to make a system
both loosely coupled and noncomplex
therefore accidents in complex, tightly
coupled systems are inevitable and
“Normal” (Perrow).
Students should read page 151-152: an example of an accident in a
system that was complexly interactive and tightly coupled and that
could have been prevented by good engineering.
Normalizing Deviance
Engineers increase the risk to the public by
allowing increasing numbers of deviances from
proper standards of safety and acceptable risk.

This is called normalization of deviance.
Accepting anomalies instead of attempting to
correct a design or operating conditions that
led to the anomalies make accidents inevitable!
(page 153 example from the challenger disaster)
 Technology
imposes RISK on the public
 RISKs are often difficult to detect and
eliminate
Three approaches to acceptable risk
The Experts Approach
The Layperson’s Approach
The Government Regulator’s Approach
Experts Approach to
Acceptable Risk
Identifying risk:
Utilitarianism and acceptable risk
Risk as maximizing benefit
Identifying risk
concept of risk involves adverse effect or harm.
Harm is a limitation of a persons freedom or well
being. (physical well being, psychological well
being, economical well being)
Risk can be defined as: “a compound measure
of the probability and magnitude of adverse
effect” (William W. Lowrance)
We can add : “probability of death or injury”
Utilitarianism and Acceptable risk
The experts approach to risk is usually
utilitarian. That the answer to any moral
question is to be found by determining the
course of action that maximizes well being.
Cost/benefit technique is often called
risk/benefit analysis. Cost is measured in
terms of risk of deaths, injuries, or other
harms associated with a given course of
action. (Ex: page145 and 155: is the risk to the
workers from the fumes acceptable? ).
Risk as maximizing benefit
An acceptable risk is one of where , given
the options available, the risk of harm is at
least equaled by the probability of producing
benefit.
Limitations: (that will yield the cost/benefit approach inconclusive)
It might not be possible to anticipate all of the costs and benefits
associated with each option
It is not always possible to translate all of the risks and benefits into
monetary terms. What is the monetary value of human life?
The method makes no allowances for the distributions of costs and
benefits.
The method gives no place for informed consent to the risk imposed by
technology.
The Laypersons Approach to
Acceptable Risk
Expert and Layperson
Public is sometimes mistaken in estimating the
probability of death and injury from various
activities of technology. Experts and lay
person understand risk differently.
Informed consent and justice: lay person
approach follows more closely the ethics of
respect of persons than utilitarianism.
Free and informed consent and compensation
Three necessities to give free and informed
consent to the risks imposed by technology:
A person must not be coerced
A person must have the relative information
A person must be rational and competent
enough to evaluate the information.
Lay criterion of acceptable risk:
An acceptable risk is one in which risk
is freely assumed by free and informed
consent, or properly compensated, and
which is justly distributed.
The Government Regulator’s
Approach to Risk
An acceptable risk is one in which
protecting the public from harm has
been weighted more heavily than
benefiting the public.
Three approaches to
acceptable risk
Risk Expert: wants to balance risk and benefit
in a way that optimizes overall public wellbeing.
Layperson: wants to protect himself or herself
from risk.
The government regulator: wants as much
assurance as possible that the public is not
being exposed to unexpected harm.
Becoming a Responsible
Engineer Regarding Risk
Includes to be aware
•
that risk is often difficult to estimate
•
that there are different approaches to
the determination of acceptable risk
•
of the legal liabilities regarding risk.
(A more general) Principle of
Acceptable Risk
People should be protected from the
harmful effects of technology, especially
when the harms are not consented to or
when they are unjustly distributed, accept
that this protection must sometimes be
balanced against (1) the need to preserve
great and irreplaceable benefits and (2) the
limitations on our ability to obtain informed
consent. Page 168 some issues (6) that arise in applying the principle.