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System Safety: A systematic processes

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System Safety: A systematic processes Risk Assessment An evaluation of threats in terms of severity and probability MISSION FOCUS (HAZARD VERSUS RISK) Hazard ... – PowerPoint PPT presentation

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Title: System Safety: A systematic processes


1
System Safety A systematic processes
2
Risk Assessment An evaluation of threats in
terms of severity and probability
3
MISSION FOCUS(HAZARD VERSUS RISK)
Identifying and analyzing an existing or
potential condition that can impair mission
accomplishment (No discussion of mission
significance)
HAZARD ID Analysis
A hazard for which we have estimated the
severity, probability, and scope with which it
can impact our mission and accepted it
RISK Assessment Mgmt
4
Hazard Identification and Analysis during the
Life Cycle of a system
Concept Concept Definition Development Production Deployment Termination








5
Threat assessment process
Q/Q Assess Probability
Q/Q Assess Severity
6
THE RISK ASSESSMENT MATRIX
Probability
Likely
Occasional
Seldom
Unlikely
Frequent
A
B
C
D
E
I
Extremely
Catastrophic
High
High
II
Critical
High
Medium
III
Moderate
Low
IV
Negligible
Risk Levels
7
A thorough risk assessment process might help
you better understand a hazard you have been
exposed to many times before without incident
No beavers were assaulted in production of this
slide
8
Hazard Severity
  • What impact will this threat have on people?
  • What impact on environment, equipment or
    facilities?
  • What impact on mission?

9
Severity Categories
  • A key factor in establishing a common
    understanding of a safety programs goal
  • MIL-STD 882 uses four categories
  • Cat 1 Catastrophic
  • Cat 2 Critical
  • Cat 3 Marginal
  • Cat 4 Negligible

10
Severity Qualified
CATASTROPHIC - Complete mission failure, death,
or loss of system CRITICAL - Major mission
degradation, severe injury, occupational illness,
or major system damage MODERATE - Minor
mission degradation, injury, minor occupational
illness, or minor system damage NEGLIGIBLE -
Less than minor mission degradation, injury,
occupational illness or minor system damage
11
Severity Quantified
CATASTROPHIC - Complete mission failure, death,
or loss of system and/or costs exceeding
1B CRITICAL - Major mission degradation, severe
injury, occupational illness, or major system
damage and/ or costs exceeding 1M MODERATE -
Minor mission degradation, injury, minor
occupational illness, or minor system damage
and/or costs exceeding 100,000 NEGLIGIBLE -
Less than minor mission degradation, injury,
occupational illness or minor system damage
and/or costs exceeding 10,000
12
ProbabilityExpressed in terms of time,
occurrence, proximity, etc
  • Use data to substantiate your assessment
  • Use descriptive or quantitative terms
  • Use the cumulative probability of all factors
  • Examine experientially derived or anecdotal
    information from operators
  • Acknowledge uncertainty There are no guarantees

13
THE RISK ASSESSMENT MATRIX
Probability
Likely
Occasional
Seldom
Unlikely
Frequent
A
B
C
D
E
I
Extremely
Catastrophic
High
High
II
Critical
High
Medium
III
Moderate
Low
IV
Negligible
Risk Levels
14
Qualified Probability Categories
  • FREQUENT
  • Individual piece of equipment - Occurs often in
    the life of the system
  • Individual - Occurs often in career
  • Fleet or inventory - Continuously experienced
  • All Personnel exposed - continuously experienced
  • LIKELY
  • Individual piece of equipment - Occurs several
    times in the life of the system
  • Individual - Occurs several times in a career
  • Fleet or Inventory - Occurs often
  • All Personnel exposed - Occurs often
  • OCCASIONAL
  • Individual piece of equipment - Will occur in
    the life of the system
  • Individual - Will occur in a career
  • Fleet or Inventory - Occurs several times in the
    life of the system
  • All Personnel exposed - Occurs sporadically

15
Qualified Probability (cont)
  • SELDOM
  • Individual piece of equipment - Could occur in
    the life of the system
  • Individual person - Could occur in a career
  • Fleet or Inventory - Can be expected to occur in
    the life of the system
  • All Personnel exposed - Seldom occurs
  • UNLIKELY
  • Individual piece of equipment - You assume it
    will not occur in the system lifecycle
  • Individual person - So unlikely you assume it
    will not occur in a career
  • Fleet or Inventory - Unlikely but could occur in
    the life of the system
  • All Personnel exposed - Occurs very rarely

16
Probabilities Quantified(In terms of failure or
exposure rates)
  • Unlikely 1 failure in 1,000,000,000 events
    instead of assuming it will not occur
  • Seldom 1 failure in 500 million exposures
    instead of it could occur
  • Occasional 1 failure in 1 million exposures
    instead of it will occur
  • Likely 1 failure in 500,000 exposures instead of
    it occurs several times
  • Frequent1 failure in 100,000 events instead of
    it occurs often

17
Qualitative AssessmentAC 25.1309-1A
  • Design Appraisal
  • Installation Appraisal
  • Failure Modes and Effects Analysis
  • Fault Tree Analysis
  • Probability Assessment

18
Quantitative AssessmentAC 25.1309-1A
  • Probability Analysis (PRA)
  • Quantitative Probability Terms (QRA)

19
FAA Fail-Safe Design ConceptAC 25.1309-1A
  • The fail-safe design concept considers the
    effects of failures and combinations of failures
    in defining a safe design
  • The following basic objectives apply
  • In any system or subsystem, the failure of any
    single element, component, or connection during
    any one flight should be assumed. Such single
    failure should not prevent continued safe flight
    and landing
  • Subsequent failures during the same flight,
    whether detected or latent, should also be
    assumed unless their joint probability with the
    first failure is demonstrated to be extremely
    improbable

20
Fail-Safe Design Concept
  • Fail-Safe designs use the following design
    principals A combination of two or more are
    usually needed to provide a fail-safe design
  • Redundant or backup systems
  • Isolation of systems, components and elements
  • Demonstrated reliability / Periodic inspection
  • Failure warning and indication
  • Flight crew procedures
  • Designed failure effect limits
  • Designed failure path
  • Increased margins or factors of safety
  • Error-tolerant design

21
Operational and Maintenance ConsiderationsAC
25.1309-1A
  • Flight crew action
  • Ground crew action
  • Certification check requirements
  • Flight with inoperative equipment

22
Quantifying or Qualifying Risk?
  • Remember Murphys Law for Management Technology
    is dominated by those who manage what they dont
    understand

23
Risk Acceptance Codes
  • RAC 1 Unacceptable
  • RAC 2 Undesirable
  • RAC 3 Acceptable with controls
  • RAC 4 - Acceptable

24
Risk Assessment Shortcomings
  • Deficiencies in RACs represent one of the major
    problems facing the system safety effort
  • Quantitative severity and probabilities scales in
    most RAC matrices are too subjective
  • The RAC is a main driver of system safety efforts
  • This code prioritizes the management emphasis
    given to a particular problem

25
THE ENHANCED RISK ASSESSMENT MATRIX
- Numeric Code is used to prioritize hazards and
determine their acceptability using a
quantitative methodology
Probability
Frequent
Occasional
Likely
Seldom
Unlikely
A
B
C
D
E
1 2 6 8 12
3 4 7 11 15
5 9 10 14 16
13 17 18 19 20
I
Catastrophic
II
Critical
III
Moderate
IV
Negligible
Risk Levels
26
THE RISK PRIORITY LIST
Highest Risk
By ranking the hazards, we address them on a
worst-first basis Safety dedicated resources
are always limited and should be directed at the
highest risk
Lowest Risk Warranting action
27
ASSESSMENT CHALLENGES
  • Over optimism
  • Over pessimism
  • Misrepresentation/Misunderstanding
  • Alarmism / Accident du Jour
  • Indiscrimination
  • Bias
  • Inaccuracy

28
Total Risk Exposure Codes
  • Expanded scale
  • Probability expressed in Exposure
  • Severity expressed in Cost
  • Combined determination expressed in quantifiable
    terms (Now you are talking a language the
    bean counters understand)

29
Verification Validation
  • Quality of data establishes process credibility
  • Avoid GIGO syndrome
  • Verify and Validate initial estimates with
    updated data
  • Failure rates
  • Exposure rates
  • Project lifecycle changes
  • Number of units in the system

30
THE PRIORITY LISTWhat does it accomplish?
Traditional Risk Management - Personnel cant
name or prioritize hazards -- can only identify
general threats ORM - Personnel can name and
prioritize RISKS that impact them and their
mission In a mature NORMal world, every
individual personally benefits by adapting the
knowledge of prioritized hazards that exist in
their life -- (Due diligence is demonstrated when
managers see that their subordinates possess this
knowledge)

31
System Safety PrecedenceA systematic approach to
Hazard ID Risk Assess and Control
  • Design to minimize hazards
  • Robust Redundant systems, assemblies,
    components, etc
  • Install physical barriers
  • Isolate known threatening conditions or
    environments
  • Use Warning devices
  • Alerts to prevent or reduce unwanted event
  • Develop Procedures and Training
  • Most commonly used abused hazard control

32
Risk Analysis
33
Assessing Risk Controls
34
2 Major Risk Control Approaches
  • Employ Macro Risk Control Option(s)
  • Reject Avoid Delay Transfer Spread
    Compensate Reduce
  • Implement System Safety Precedence Control
    Option(s)
  • Engineer Guard Improve Design Limit
    Exposure Personnel Selection Train Warn
    Motivate Reduce Effect - Rehabilitate

35
Swiss Cheese Model of Defenses
Hazards
The ideal
The reality
Potential losses (people and assets)
James Reason Managing the Risks of
Organizational Accidents
36
Swiss Cheese Model of Defenses
Some holes due to active failures
Defenses in depth
Other holes due to latent conditions
James Reason Managing the Risks of
Organizational Accidents
37
Macro Options
  • REJECT
  • Risk outweighs benefit
  • AVOID
  • Go around the risk, do it in a different way
  • DELAY
  • Maybe the problem will be resolved by time
  • If delay is an acceptable option consider if
    operation is needed at all
  • TRANSFER
  • Better qualified system, i.e.,Pros From Dover

38
Macro Options (cont)
  • SPREAD
  • Modular or separate Hazardous Operations
  • COMPENSATE
  • Design parallel and redundant systems
  • REDUCE
  • Design for minimum risk
  • Incorporate Safety Devices
  • Provide Warning Devices
  • Develop SOPs Train

39
The Risk Control Macro Option List
  • Reject
  • Avoid
  • Delay
  • Transfer
  • Spread
  • Compensate
  • Reduce
  • QUESTION Why isnt eliminate on this list?

40
Determine Risk Control Effects
  • How will this effect probability?
  • How will this effect severity?
  • How will this impact other sub-systems?
  • Some controls support other sub-systems
  • Some controls may hinder other sub-systems
  • What are the costs vs. benefits?
  • Direct Costs
  • Indirect Costs

41
Direct vs. Indirect Costs
  • As a rule of thumb, it is generally acceptable
    to calculate indirect costs of a mishap to be 7
    times greater than those costs which can directly
    be accounted for in the incident or accident

42
Risk Control ROTs
  • Use the System Safety Precedence order
  • Choose the most mission supportive combinations
  • Use Integrated Product Teams
  • Look for synergistic enhancements
  • Man Machine Medium Mission - Management

43
Use the 5 M model as you look for systemic issues
  • Man
  • Doesnt know
  • Doesnt care
  • Cant physically accomplish
  • Machine
  • Poor design
  • Faulty maintenance
  • SOPs

44
5 M systemic issues (cont)
  • Medium
  • Weak design considerations
  • Lack of provisions for natural phenomena
  • Management
  • Inadequate procedures
  • Inadequate policy
  • Inadequate standards controls
  • Mission
  • Poorly thought out
  • Poorly executed
  • Weak understanding
  • Incompatibilities

45
Providing Management Risk Control Options
  • Program Manager looking for optimum combinations
  • Mission supportive
  • Some Risk Controls are incompatible
  • Evaluate full cost versus full benefit
  • Be prepared for numbers game
  • Some Controls reinforce one another
  • Win-Win option
  • Redundancy Robustness
  • Is it needed?
  • Can you afford it? i.e., , s, real estate

46
Aid to Decision Making
  • Be prepared to assist decisions at the right time
  • Dont rush Make them as late as possible
    without negative impact on timeline
  • Insure decisions are made at the right level
  • It should be establish who makes the tough calls
  • Use RAC or TREC to quantify who, what, when
  • Provide Mission supportive options
  • Use the Macro Option list as a starting point
  • Be prepared to offer sound advice

47
Dont be one who says, data or information was
not available and our department could not prove
it was unsafe to allow the operation.
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