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Fundamental Concepts & Terms

Fundamental Concepts & Terms. IENG 331 Safety Engineering. Why Safety?. Read Chapter 3! Humanitarian Reasons Regulatory Reasons Economic Reasons. What is an Accident?. An event that is not expected or intended Could cause injury loss Implies “chance”. Fundamental Accident Causes.

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Fundamental Concepts & Terms

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  1. Fundamental Concepts & Terms IENG 331 Safety Engineering

  2. Why Safety? • Read Chapter 3! • Humanitarian Reasons • Regulatory Reasons • Economic Reasons

  3. What is an Accident? • An event that is not expected or intended • Could cause • injury • loss • Implies “chance”

  4. Fundamental Accident Causes • Unsafe Acts • Unsafe Conditions • Both • “Not necessarily a ‘chance’ event”

  5. Injury illness disease death damage to property, equipment, materials cost of replacement legal & medical services Loss of time, production, sales time to complete forms recordkeeping investigations cleanup hospitalization, rehab public image damage Types of Losses

  6. Losses: Direct vs Indirect Costs • Direct (Obvious) • medical expenses, WC, repair or replace damages • Indirect (Not Obvious) • 4:1 Ratio • Iceberg Theory • See Table 3-1

  7. Unsafe Acts vs Unsafe Conditions • Heinrich analyzed 75,000 accidents • 88 : 10 : 2 ratio • 88% unsafe acts • 10% unsafe conditions • 2% unpreventable causes • Engineers can attack unsafe conditions • Must understand human behavior and management principles to attack unsafe acts

  8. Accident - Injury Relationship • Heinrich’s 300 : 29 : 1 ratio • For 330 accidents • 300 result in no injury • 29 produce minor injuries • 1 produces major, lost-time injury • Opportunities to improve are great • Many accidents are “rehearsed” many times

  9. Accident - Costs Relationship • Pareto Relationship • 80% - 20% rule • 80% of the costs are related to 20% of the injuries • for example, low back lifting injuries represent 20% of all accidents, but represent 80% of the costs • if you can manage and control that 20% of accidents, you can control 80% of the costs • Figure 3-1 shows 50% of the costs are related to 2% of the injuries • “the powerful few”

  10. Terms • Safety: being relatively free from harm, danger, damage, injury • Risk: measure of both frequency and severity of hazards • Hazard: unsafe condition, the potential for an activity or condition to produce harm • Safety Engineering: application of engineering principles to the recognition and control of hazards

  11. Accident Theories • Domino Theory • Energy Theory • Single Factor Theories • Multiple Factor Theories

  12. Domino Theory (Heinrich) • Injury is caused by • Accidents which are caused by • Unsafe acts or conditions which are caused by • Undesirable traits (e.g., recklessness, nervousness, temper, lack of knowledge, unsafe practices) which are caused by • Social environment

  13. Domino Theory Cont. • Stop the sequence by removing or controlling contributing factors • Strong emphasis is placed on the middle domino: unsafe acts or conditions

  14. Energy Theory (Haddon) • Accidents & Injuries involve the transfer of energy, e.g., fires, vehicle accidents, projectiles, etc. • Transfer of energy from a “potential” to “kinetic” • Attack problems in parallel rather than serial (as is presumed in Domino Theory)

  15. Energy Theory Cont.10 Strategies to Prevent or Reduce 1. Prevent the marshalling of energy. - don’t produce the energy - don’t let kids climb above floor level - don’t produce gun powder 2. Reduce the amount of energy marshalled. - keep vehicle speeds down - reduce chemical concentrations - don’t let kids climb above 3’

  16. 3. Prevent the release of energy - elevator brakes 4. Modify the rate at which energy is released from its source or modify the spatial distribution of the released energy. - reduce the slope on roadways 5. Separate in space or time the energy being released from the structure that can be damaged or the human who can be injured. - separate pedestrians from vehicles

  17. 6. Separate the energy being released from a structure or person that can suffer loss by interposing a barrier. - safety glasses, highway median barriers 7. Modify the surfaces of structures that come into contact with people or other structure. - rounded corners, larger surface areas for tool handles 8. Strengthen the structure or person susceptible to damage. -fire or earthquake resistant structures, training, vaccinations

  18. 9. Detect damage quickly and counter its continuation or extension. - sprinklers that detect heat - tire tread wear bands 10. During the period following damage and return to normal conditions, take measures to restore a stable condition. - rehab an injured worker - repair a damaged vehicle

  19. Single Factor Theories • Assumes that when one finds a cause, there is nothing more to find out. • Weak theory, there can be so much more to learn!

  20. Multiple Factor Theories • Accidents are caused by many factors working together • The theory and the analysis is more complex, but more realistic than Single Factor Theory • Consider the Four M’s: • management, man, media, machine • And their interactions

  21. Preventative Strategies • Proactive vs. Reactive • Frequency strategies • Severity strategies • Cost strategies • Combinations • Three E’s of Safety: engineering, education, enforcement

  22. How Safe is Safe Enough? • Can absolute safety be achieved? • Remember the concept of “risk”. • What is “acceptably safe”?

  23. HW3 – Chapter Three • Review Questions (p. 24-25) • 2, 5, 8, 11, 14, 17, 20 • 15 points • Due 9/15 (beginning of class)

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