Safety System & Scene

Overview Safety Terms Hazards Hazard Lists Worst Case Conditions Hazard Characteristics Analysis Sumary

Safety Terms Hazard: Condition with potential to injure Danger: Exposure to hazard Damage: Severity of injury Risk: Probability of occurrence times damage (RHI)

Hazard Types: –Primary Hazard: Immediate damaging causing –Initiating Hazard: Starts event sequence leading to damage ( rope abrasion leading to reduced tensile strength and ultimate failure) –Contributing Hazard: Subordinate hazard adding to the ultimate failure of a system ( inadequate Belay System rigging, fails in Main failure)

Hazard Lists Hazard lists are the first step in recognizing hazards and preventing damage Development: (best lists use combination) –Past experience –Theoretical possibility ( What can you imagine) –Predictive testing ( rope testing… load, abrasion, UV etc)

Safety & Murphy’s Law* Worst case scenario –Max loads –Most serious outcomes –Combined events ( UV, Abrasion, Overloads) –Ignores probability of occurance *“If something can go wrong it will” –“It will go wrong at the worst possible time”

Categories of Hazards Inherent Hazard: Properties or characteristics of system make it hazardous (High angle rope systems, working hi- voltage) Failures (material or human): Rope fails under load ( material defect), knot lets go ( tied incorrectly) Environmental stresses: Lightning strike, Wind shear, UV degredation, “Acts of God”

Accidents Failure to prevent damage –Almost all accidents can be traced to human error (although not necessarily the primary hazard event). –May not be on the part of the immediate victims ( may be dissociated in time and space from accident event, for example: poor rope maintenance/inspection)

Human Error 2 types ( also like hazards may be primary or contributory) –Predictable: “could have been expected” usually driven by: Fatigue Sensory limitations ( poor visibility etc) Physical limitations ( coordination etc) –Random: “unpredictable” unexpected or unusual sequence of events, no history of similar occurrences, driven by a rare or unique event

Minimizing Human Error 2 Man Concept –Credited to the Military to minimize potential for human error in nuclear system procedures –Probably goes back to the first attempts at controlling risky processes. Training ( most human error occurs under stress and haste, training minimizes error under stress

Accidents and Human Error Accidents rarely occur due to willful actions Most are situations in which human capabilities are inadequate or overwhelmed by the “Need for rapid response to a critical situation” –Inadequacies can be permanent or transient Permanent: Physical limitations, lack of training Transient: Fatigue, communications breakdown

Hazards and Accidents Accidents occur when” Hazards potential to cause damage reaches a probability of 1 This leads to 2 obvious approaches to safety: –Minimize hazards –Reduce probability

Accident Analysis Vs. Hazard Analysis Accident Analysis is Post Mortum Hazard Analysis is predictive in nature Hazard Analyses are conducted on systems A system is all the components which combine to perform a function…. Rope, anchors, prussics, people!

Safety Factors & Margins Safety Factors are a ratio of strength to expected stress Safety Margins are the difference between max stress and min strength

Hazard Analyses Qualitative- non-mathmatical –A review of potential hazards, excluding probabilities Quantitative- must be preceded by qualitative review –Probability of occurrence of a specific failure mode, based on history or speculation.

Hazard Analysis Requires review of: –Mission requirements –Performance capabilities –Operational sequence –Environmental impacts –Codes, regulations, specifications, standards

Probability Probability is the expectancy of frequency with which an event will occur in a specific number of trials Determined by –Actuarial methods ( using historical data) –Experimental methods (test and count failures) –Predictive models ( usually based on similarity to known systems ) Heads/Tails 100K trials 50K heads.. Next flip 50/50.. Individual event is could be any outcome

Failure Modes, Effects, & Capability Analyses- FMECA Review of component failure modes –Fails How? Effects of such failure will have on the rest of the system Establish which part failures would have critical (catastrophic) impacts on the system Calculate the probability of such failures

RHI- Relative Hazard Index RHI- probability of event occurrence times expected damage if event occurs A quick way to prioritize safety issues

Risk Risk is a method of comparing relative hazard exposures RHI is a risk measure Hazard analyses which include both qualitative hazards and quantitative probability of hazard damage can also be used to rank or compare risks

Summary Safety is “No Accident” Prevent accidents by: –Mitigating hazards –Mitigating probability of occurrences Evaluate hazards thru analyses Compare Risks between options