Safety

1
Safety

• The engineers role in
• risk reduction

Peter Gostomski Ken Morison Chemical Process
Engineering
2
Space shuttle disasters

• Challenger blew up on take off (1986)
• O-ring on booster rocket failed
• Leaking fuel ignited, liquid H2 tank exploded
• Columbia destroyed during reentry (2003)
• foam damaged wing tiles during take-off
• tiles failed during reentry

3
Longford gas processing plant (1998)

• Longford (Esso) supplies energy to Victoria, AU
• Energy supplies out for 2 weeks
• 3 million fines compensation
• 500 million law suit for lost revenue.
• 2 workers died

4
Firestone tyre recall (2000)

• Firestone recalls 10 x 106 tyres in 2000
• Tread separation causes rollover accidents
• 40 80 deaths attributed to bad design
• Lost sales 350 million
• Fines 41 million
• Ford cancels contract

5
Concorde crash (2000)

• Concorde crashed on take-off
• 113 people died
• Debris on runway punctured tyre, chunks of rubber
  punctured fuel tank
• Fire caused loss of power

6
World Trade Center (2001)

• Two fuel-laden jets crashed into WTC towers
• Fire caused support structure to fail
• Towers collapsed
• 2,792 people died

7
Power Outage North America (2003)

• power overload caused supply to fail
• chain reaction caused power loss in eastern US
  and Canada.
• 50 million without power
• Responsibility? Costs?
• Auckland CBD lost power on/off
• for two months in 1998

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Engineers what role in safety?

• Engineers solve problems
• The cause of all problems are solutions
• Engineers cause a lot of problems?
• NO!
• Engineers very good at preventing disasters

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Engineers vs Doctors

• Engineers try to fence off the top of the cliff
• Doctors wait at the bottom of the cliff

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Engineering versus other careers

• All professional careers can affect peoples lives
• Commerce ? large scale redundancy
• Law ? innocent people to jail
• Medicine ? misdiagnosis

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Engineering activities in safety

• Find the problem
• What will explode? What part will fail? How much
  force on impact?
• Measure the problem
• Determine probability that part fails alarm
  fails
• Toxic gas released ? how many people exposed?
• Solve the problem
• New designs
• New procedures

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Safety Goals

• Prevent
• Death/injury to workers
• Death/injury to the general public
• Damage to facilities
• Damage to surrounding property
• Damage to the environment

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Key Definitions

• Hazard physical situation that can damage
• people
• plant
• environment
• Risk likelihood of hazard occurring
• Risk hazard probability consequence

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Risk hazard probability consequence

• Flammable solvent vs nonflammable solvent
  different hazard level
• Bridge over a 5 meter gorge vs 30 m gorge
  different hazard level
• In both cases risk is lowered
• by removing or lowering hazard

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Risk hazard probability consequence

• Dangerous chemical reactor is completely
  automated.
• no risk to workers
• risk to neighbours?
• risk to equipment?
• risk to environment?
• Ladder example

Same hazard, same probability, different
consequences
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Risk hazard probability consequence

• Virtually no activity is risk free!
• Cant eliminate all hazards
• Cant make probability zero
• Cant eliminate all consequences
• As long as all three components exist,
• risk exists!

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Risk

• Engineers decrease risk by
• Identify/eliminate hazards
• Estimate/lower probability
• Estimate/lower consequence
• When is risk low enough?

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Risk

• What is acceptable risk?
• societal/political decision
• engineers identify, calculate, lower risk
• society decides acceptable level of risk
• Problem 1 Not everyone realises risk ? 0
• 2 Public perception depends on
  situation

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Risk acceptable levels

• Public perception of risk depends on a number of
  features
• Control individual control, avoidable,
  survivable
• Knowledge understanding, observable, familiar
• Magnitude number of people exposed
• Others factors

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Unknown risk
controllable risk
uncontrollable risk
Known risk
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Magnitude

• 7 people died in the Challenger Space Shuttle
• 113 died in the Concord crash
• 2792 died in 9/11
• About 1.2 people die in each fatal car crash
• 400 000 people die in car crashes worldwide each
  year

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Estimate risk (numerical)

• Fatal Accident Rate (FAR)
• FAR deaths/1000 people/105 hours
• 105 hours ? lifetime ? 35 years (8 hr day)

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FAR example

• How dangerous is being an engineering student?
  Over the last 10 yrs we have had 22 deaths
• 1 death ? terrible hacky sack injury
• 3 deaths ? American lecturer shot rude students
  
• 1 death ? sleeping student fell off chair
• 2 deaths ? engineering cafeteria food poisoning
• 15 deaths ? listening to boring lectures

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FAR example

• 22 deaths over 10 yrs
• 900 students/yr 9,000 students total
• Death rate 22 deaths/9,000 students/10 years
• Death rate 0.000244 deaths/student/yr
• FAReng 0.000244 1000 people 35 years
• FAReng 8.6

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FAR

• Simple measure of safety
• Historical analysis of industry or activity
• Prediction tool
• Estimate FAR for building a new bridge
• Compare estimate to bridge building industry
  average

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Estimate risk (numerical)

• Fatal Accident Rate (FAR)
• FAR deaths/1000 people/105 hours
• 105 hours ? lifetime ? 35 years (8 hr day)

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FAR Rock climbing

• FAR 4,000
• per 1,000 people for 35 yrs
• People that fall are replaced

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FAR Rock climbing

• 100 people in a climbing club spend 10 days/yr at
  6 hrs/day climbing, 1 person dies over 5 yrs
• 10 days/yr 6 hrs/day 5 yrs 300 hrs
• Death rate 1 deaths/(300 hrs 100 people)
• 0.000033 deaths/person-hr
• Far Death rate 1000 people 105 hrs
• 3,333

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Risk Reduction (for discussion)

• Travelling by plane is more hazardous than by
  car.
• Travelling by car is riskier than by plane.

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Traveling is more hazardous by plane than by car.

• Planes
• 13,000 meters
• 1,000 km/hr
• Low temp. pressure
• 200 400 people
• 100,000 200,000 liters of fuel

• Cars
• Ground level
• 100 km/hr
• normal temp press.
• 1 6 people
• 40 80 litres of fuel

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Traveling by car is riskier than by plane.

• Planes
• High quality parts
• High redundancy
• 2 engines, 2 pilots, etc
• Many safety devices
• Sensors, alarms
• High maintenance

• Cars
• The Warehouse
• Little redundancy
• 1 engine, 1 driver, etc.
• Some safety devices
• Sensors, alarms
• Maintenance?

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Traveling by car is riskier than by plane.

• Planes
• Preflight checklist
• Airport design
• Traffic control
• Air traffic controllers
• Training
• Flight simulators
• Pilot licence

• Cars
• Predriving checklist(?)
• Parking lot design
• Traffic control
• Traffic lights
• Training
• PlayStation/Xbox
• Watching Mum or Dad
• Car licence

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Planes versus Cars The risk?

• FARCar 30 FARPlane 40
• Risk per 109 km
• RiskCar 4.4 RiskPlane 0.2
• www.rvs.uni-bielefeld.de/publications/Incidents/DO
  CS/Research/Rvs/
• Article/probability.html
• NZ risk about 10 per 109 km

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Risk Reduction Strategies

• Procedural (people activities)
• procedures, alarms, training
• Active (automatic devices)
• switches, relief valves, auto-shutdown, sprinkler
  systems
• Passive (no moving parts)
• Stronger fuel tank, less fragile heat tiles
• Inherent (fundamental hazard)
• ground travel instead of flying, water instead of
  toluene
• Simplify process

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Summary

• Safety - prevent damage to
• People ? Equipment ? Environment
• Risk hazard probability consequence
• identify haz. ? measure prob/conseq. ? design
  solut.
• Engineers lower risk
• Society decides acceptable level
• Risk reduction
• procedural ? active ? passive ?
  inherent