Design for Safety

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Design for Safety

• Injury, Hazards, Conditional Circumstances
• Legal Responsibilities
• Guidelines for Safe Products/systems
• Safety Hierarchy, Safe Design Principles
• Failure Modes and Effects Analysis
• Summary

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Design for Safety..What is a safe product or
system?

• No injury to user, (products liability)
• No injury to consumer /society
• No injury to production worker (e.g. OSHA)
• No damage to personal property
• No damage to real property (environment)

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Hazards

• hazard a source of danger which has the
  potential to injure people or damage property or
  the environment

Hazards include (Lindbeck, 1995) 1. Entrapment
pinch, crush 2. Contact heat, sharp edges,
electric 3. Impact hammer, robot arm 4.
Ejection grinder sparks, saw dust 5.
Entanglement hair, clothing 6. Noise
Vibration hearing loss, HAVS
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Conditional Circumstancesthings change over time!

• 1) hazard is inherent during normal use
• 2) hazard originates from a component failure
• 3) hazard caused by user misuse
• 4) hazard exists during normal maintenance
• 5) hazard created by improper maintenance
• 6) hazard stems from lack of maintenance

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Method A Use .Guidelines for Safe
Products/systems

• Perform appropriate analyses
• Comply with published standards
• Use state-of-the-art technology
• Include reasonable safety features or devices
• Take into account how the user might misuse the
  product
• Consider hidden dangers that might surprise the
  user
• Consider variations in materials or manufacturing
  processes, or effects of wear
• Carry out appropriate testing and interpret
  results correctly
• Provide adequate warnings
• Implement superior quality control
• Document everything

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Method B Safety Hierarchy Method (Pahl Beitz)

• Eliminate the hazard pro-active approach,
  design-out the hazard (eliminate any moving
  parts, hot or sharp surfaces)
• Protect against the hazard passive approach,
  (machine guards, seat belts)
• Warn against the hazard - weak remedy, (warning
  labels, alarms)
• Provide training Provide and require operating
  training.
• Provide personal protection least effective,
  (safety glasses, gloves, shoes)

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Method C Safe Design Principles

• Safe-Life
• entire predicted useful life without malfunction.
• designers to identify all operating conditions,
  misuses and abuses
• design appropriate maintenance and repair
  schedules.
• Fail-Safe
• upon failure of a component, product/system
  shuts down safely,
• critical functions are sometimes still
  performed..
• (e.g. boiler feed-water valve failing in the
  open position)
• Redundant design
• additional product components or systems are
  designed
• to take over the principle function of the
  failed component or system.
• (e.g. multi-engine airplanes, emergency brakes)

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Failure Modes and Effects Analysis

• Determine modes of failure, causes, and effects
• Calculate Risk Priority Number
• RPN (Severity) (Occurrence) (Detectability)
• table values

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Design for Safety Summary

• Design for Safety Prevent injury or damage
• Hazards exist, and depend on conditions
• We have Legal Responsibilities
• Guidelines for Safe Products/systems
• Safety Hierarchy maximize our efforts
• Safe Design Principles
• FMEA

Safety is no accident anonymous