• Reliability and Maintainability are key ingredients to preserving production efficiency.. Properly managed, they lead to lower total life cycle costs, helping organizations maintain
Trang 1Chapter 20
Trang 2• Reliability and Maintainability are key
ingredients to preserving production
efficiency Properly managed, they lead to lower total life cycle costs, helping
organizations maintain a competitive edge.
Trang 3• Reliability is the probability that
machinery/equipment/system can perform continuously, without failure, for a
specified time interval when operating
under stated conditions Increased
reliability implies less failure and
consequently less downtime and loss of
production.
Trang 4• Maintainability is a characteristic of
design, installation, and operation, usually
expressed as the probability that a
machine can be retained in, or restored to, specified operable condition within a
specified interval of time when
maintenance is performed in accordance
with prescribe procedures.
Trang 5• Reliability engineering provides the
theoretical and practical tools used to
determine the capability of parts,
components, equipment, subsystems and
systems to perform their required
functions without failure for specified
periods in specified environments
Trang 6• Life Cycle Curve
Trang 7• Causes of Unreliability
– Improper design
– Improper materials
– Manufacturing errors
– Assembly and inspection errors
– Improper testing
– Improper packaging and shipping
– Improper start-up
– User abuse
– misapplication
Trang 8• Infant Mortality Failure Causes
– Inadequate test specifications
– Inadequate quality control
– Inadequate manufacturing processes or tooling
– Inadequate materials
– Improper handling or packaging
– Marginal components
– Overstressed components
– Improper setup or installation
– Improper use procedures
– Power surges
– Inadequate marketing
– Inadequate training
– Incomplete final testing
Trang 9• Random Failure Causes
– Insufficient design margins
– Misapplication: overstress
– Use in wrong environment
– Predictable failure levels
– Intermittent failures
– Inherent manufacturing failures
Trang 10• Wearout Failure Causes
– Scratching
– Material wear
– Aging
– Incipient stresses
– Limited-life components
– Inadequate or improper preventive maintenance
– Assembly interference fits
– Loose hardware
– Misalignments
Trang 11• Reasons for Reliability Programs
– Successful companies are able to control the
reliability of their products
– Increasing complexity of products requires
higher component reliability
– Consumers are becoming more reliability
conscious
Trang 12• Basic functions of a reliability program
– Establish reliability in design
– Assure reliability by proper manufacturing
– Assure reliability through quality assurance
– Verify reliability by well designed test programs
– Maintain reliability by proper packaging and shipping
methods
– Assure reliability by proper field service and training
– Improve reliability through feedback to design,
engineer, purchase, manufacture, package, ship, sell, and service.
Trang 13• A well thought out reliability program will
include the areas of design, testing,
manufacture, raw material and component purchases, production, packaging,
shipping, marketing, field service, and
maintenance
Trang 14• A sound reliability program will consider:
– The entire system
– The humans in the system
– Maintenance of the system
– Simplicity of design
– Redundant and fail-safe designs
– Manufacturing methods and purchasing requirements
– Maintenance of complete product or system
performance records
– Communication
Trang 15• Reliability testing:
– Failure terminated tests
– Time terminated tests
Trang 16• Measures of Reliability: time dependent
– Failure Rate
– Mean Life
– Availability
λ estimated = number of failures observed
sum of test times or cycles
θ estimated = 1
λ
number of failures observed
Trang 17• Calculating System Reliability
– Reliability in Series
– Rs = R1 x R2 X R3
Trang 18• Calculating System Reliability
– Reliability in Parallel
– Rp = 1 – (1 – R1)(1 – R2)
Trang 19• Calculating System Reliability
– Reliability of Redundant or Back-up
components
– Rb = R1 + Rb(1 – R1)
Element 1 Element backup