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Copyright © 2003 Randal Bennett and Crystal Sloan
Randal D. BennettUniversity of MarylandUniversity College805 Montview DrEscondido CA [email protected]
Crystal D. SloanEagleRidge Technologies, Inc.
114 Ledgerwood LaneRockwood, TN 37854
Repeating Design Errorsor
“Where’s the History?”
Copyright © 2003 Randal Bennett and Crystal Sloan
The Original Error:Oliver Hazard Perry-Class Frigates1977
Fault-proneEngineering Control System
History in the Making:
Copyright © 2003 Randal Bennett and Crystal Sloan
Engineering Control System (ECS)
• Shielded wire-braid cable with shielding that naturally degrades over time
• Ungrounded, interconnected busses• Low-voltage digital alarm/control
systems
Copyright © 2003 Randal Bennett and Crystal Sloan
Boundary Condition – Setup
ExteriorInsulation
Wire BraidSheathing
Shielding
IndividualInsulated
Conductors
ExteriorInsulation
Wire BraidSheathing
Shielding
IndividualInsulatedConductors
Copyright © 2003 Randal Bennett and Crystal Sloan
Boundary Condition – SetupBoundary Condition – ResultBoundary Condition –
Result
Copyright © 2003 Randal Bennett and Crystal Sloan
Focus on Nominal Behavior:Collocation of Redundant Elements
Propulsion ControlConsole
Electric PlantControl Console
Bus Wiring
Harness
GroundedShield
Bus Wiring
Harness
Au
xili
ary
Co
ntr
ol
Co
nso
le
Alarm onACC
Copyright © 2003 Randal Bennett and Crystal Sloan
Focus on Nominal Behavior:Requirements vs. Usage
• Requirement: sea water (heat sink) temperature - Design: 85F, Actual: 95F
• Support system impacted: air conditioning plant
• Impact: reduced heat rejection• System impact: elevated cabinet
temperatures• Result: degraded circuit cards,
processors and power supplies
Copyright © 2003 Randal Bennett and Crystal Sloan
Focus on Nominal Behavior:Failure to Anticipate System
Deterioration Over Time
• Causes of cable deterioration– Vibration– Retention of a low-cost vessel– Insufficient allocation of
maintenance funds
Copyright © 2003 Randal Bennett and Crystal Sloan
Repeated design error:Fault-prone Machinery Control System
History Repeats:
Arleigh Burke-Class Destroyers1991
Copyright © 2003 Randal Bennett and Crystal Sloan
Machinery Control System
• Shielded wire-braid cable
• Ungrounded, interconnected busses
• Low-voltage digital alarms/controls
• Reliance on air conditioned spaces
Copyright © 2003 Randal Bennett and Crystal Sloan
Machinery Control System
• Prerequisites for failure duplicated
• Failures evident now
• Design activity – strong performance
• Why the repetition?
Copyright © 2003 Randal Bennett and Crystal Sloan
“Those who cannot remember the past are condemned to repeat it.”
Jorge Santayana (1905)
• Lack of accessible history
Studying History
Copyright © 2003 Randal Bennett and Crystal Sloan
Current Maintenance DataCollection System
• Resistant to data mining– Information buried in text blocks– Lack of refined hierarchical structure– Inconsistent naming practices
• Violates Degregorio’s critical elements– “… information architecture with internal
structures …”
• Self-perpetuating
Copyright © 2003 Randal Bennett and Crystal Sloan
Other Tools
• Casualty Reporting (CASREP) System
• Quality Deficiency Report (QDR)
• Parts Usage
• Troubled Systems Process (TSP)
• Management processes– Top Management Attention– Top Management Interest
Copyright © 2003 Randal Bennett and Crystal Sloan
Solutions
• For legacy and future data: index and make available using search engine technology– Very low cost solution
• For future data: System designchange
Copyright © 2003 Randal Bennett and Crystal Sloan
Search Engine Technology
• Establish view to data• Dynamic web page
– Search string text box– Embedded link to first record– Link to next record
• Search appliance – “Crawls” database– Maintains data security
Copyright © 2003 Randal Bennett and Crystal Sloan
System Design Change
• Data architecture discipline
• Scripted Standardized Assessment Procedures
Copyright © 2003 Randal Bennett and Crystal Sloan
Data Architecture Discipline
• Realignment of Hierarchical Structure Code (HSC)– Identical code for same equipment in
same application– Standardized across classes and ships– Expanded to cover all components
• Standardized nomenclature
Copyright © 2003 Randal Bennett and Crystal Sloan
Benefits of Discipline
• Ensures visibility of common issues
• Reduces configuration labor at ship design time
• Foundation for data warehousing
• Supports Standardized Scripted Assessment Procedures
Copyright © 2003 Randal Bennett and Crystal Sloan
Benefits of SSAP
• Ensures correct equipment reported
• Reduces maintenance-induced failures
• Provides management functions– Tool inventory– Materials requirements
Copyright © 2003 Randal Bennett and Crystal Sloan
Data Warehousing
• Stores results of SSAP
• Organized structure promotes mining
• Renders history available