Design for Safety

1. 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

2. 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)

3. 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

4. Conditional Circumstances…things 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

5. 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

6. Method B: Safety Hierarchy Method (Pahl & Beitz) • Eliminate the hazardpro-active approach, “design-out” the hazard (eliminate any moving parts, hot or sharp surfaces) • Protect against the hazardpassive 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)

7. 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)

8. Failure Modes and Effects Analysis Determine modes of failure, causes, and effects Calculate Risk Priority Number RPN = (Severity) (Occurrence) (Detectability) table values

9. 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