Risk Analysis for Engineering Design J. M. McCarthy Fall 2003

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Risk Analysis for Engineering DesignJ. M.
McCarthy Fall 2003

• Definitions
• Hazard Analysis
• Hazard Analysis Report
• Example for Mini Baja
• Nationally Recognized Testing Laboratories (NRTL)

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Definitions
Safety The condition of being safe free from
danger, risk, or injury. Hazard An
activity or condition that is dangerous, that
poses the threat of loss (property damage) or
harm (personal injury or death). Risk The
potential for loss or harm over time for a given
hazard the combination of hazard severity and
the exposure. Severity The degree of the loss
or harm associated with a hazard. Exposure The
amount of exposure to a hazard. Risk Tolerance
The acceptable of level of risk selected for all
hazards. Mitigation An action taken or a
feature adopted to reduce the risk for a hazard.
For example, safety devices, guarding, warning
devices, procedures, and training. Hazard
Assessment A process of identifying and
analyzing sources of danger. Risk Analysis A
process of evaluating the severity of
consequences and frequency of exposure to
hazards, and evaluating of risk tolerance and
mitigation. Risk Management Activities related
to monitoring and evaluating hazards to maintain
a given level of risk.
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Hazard Analysis

• Steps in Hazard Analysis
• Identify Risk Tolerance Determine levels of
  acceptable risk. Create risk assessment matrix
  (risk level v. severity and exposure).
• Hazard Assessment Identify hazards by reviewing
  designs, codes, standards, and interviewing
  workers and users.
• Evaluate Severity and Frequency of Exposure
  Assign severity and frequency of exposure for
  each hazard.
• Assign Risk Level Categorize each hazard to a
  risk level using the risk assessment matrix.
• Design Mitigation Apply mitigation to hazards
  with unacceptable risk levels.
• Repeat Hazard Analysis Repeat until all hazards
  have an acceptable risk level.

The hazards in a machine system are primarily
fire, electrical shock, chemical exposure, and
personal injury (impact, cut, pinch, and crush).
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HA Flow Chart
Risk Assessment Matrix
Identify All Hazards
For Each Hazard
Determine Severity and Frequency of Exposure
Apply Mitigation
Next Hazard
Assign Risk Level
Unacceptable
Acceptable
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Risk Analysis
Risk Level (1) High Imperative to reduce risk
level. (2) Medium Requires a mitigation
plan. (3) Low No special risk mitigation
activities are required. Severity of
Consequences (1) Catastrophic Death or system
loss. (2) Critical - Severe injury or major
system damage. (3) Marginal - Injury requiring
medical attention or system damage. (4)
Negligible - Possible minor injury or minor
system damage. Frequency of Exposure (A)
Frequent - Expected to occur frequently. (B)
Probable - Will occur several times in the life
of an item. (C) Occasional - Likely to occur
sometime in the life of an item. (D) Remote -
Unlikely, but possible to occur in the life of an
item. (E) Improbable - So unlikely, it can be
assumed occurrence may not be experienced.
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Example Risk Assessment Matrix
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Hazard Analysis Report
Hazard Analysis Report Section 1. Definition of
Severity and Frequency of Exposure Section 2.
Risk Assessment Matrix Section 3. Itemized list
of Hazards, Initial Risk Level, Mitigation and
Final Risk Level
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Example Mini-Baja HAR
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Example BattleBot HAR
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Nationally Recognized Testing Laboratories
Nationally Recognized Testing Laboratories
(NRTLs) are third-party organizations recognized
by the Occupational Safety and Health
Administration (OSHA) that can provide product
safety testing and certification services to
manufacturers for a wide range of products.

• Some NRTL Organizations
• Underwriters Laboratories, Inc. (UL)
• TUV America Inc. (TUVAM)
• Canadian Standards Association (CSA)
• Applied Research Laboratories, Inc. (ARL)
• Communication Certification Laboratory, Inc.
  (CCL)

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Summary

• A hazard analysis report describes each hazard
  in a product and how it is mitigated to reduce
  the risk to the desired level.
• An NRTL can be helpful in defining and
  executing test to verify safe performance.