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Before you learn what Reliability is all about and how
to go about performing Reliability Engineering,
you need to know what we are talking about. Navigate using the menu above, or
return to the index to view the definitions relative to Reliability Engineering.
A
Age Related Failures
Failures where the probability of occurrence increases with age e.g. corrosion. This
type of information can also be used to predict 'when' an item is likely to fail in terms
such as 'seconds', 'minutes', 'hours' etc and hence, mitigating action can be suggested, such as
replacement or repair of an item.
B
No definitions entered under 'B'
C
Common Cause Failures
The occurrence of more than one failure event due to the same common cause.
D
Design Based Failures
Design Based Failures generally arise when good engineering practices are not fully applied within the design process.
These failures are often attibutable to the following areas:
- A failure to adequately define the needs of the system in the Specification
- A misinterpretation of the Specification
- A failure to implement the specification fully, due to such constraints as budget, technology, politics etc.
- Inadequate components may be selected as a result of a failure to appreciate the possible normal and fault operating conditions
- Inadequate redundancy for a critical system
E
No definitions entered under 'E'
F
Failures
Items which have failed to meet one of the design requirements in terms of either function or performance.
Failure Modes
Each component or item in a system will have one or more methods or mechanisms by which it can potentially fail.
These methods or mechanisms are generally called Failure Modes. Modes of failure for any component are not necessarily
equally distributed in terms of probability of occurrence e.g. 'open circuit failure' may have a greater probability
than 'short circuit failure'. Therefore, Failure Modes generally have an associated percentage distribution
or apportionment.
Failure Rate
The number of Failures expected for an item in a specified time frame.
Failure Rate is usually expressed in terms of Failures Per Million Hours (FPMH).
Faults
A system performance deviation which does not prevent the system from performing within its functional or performance
design requirements but may result in an unscheduled maintenance action e.g. faults related to redundant
components in the system.
G
No definitions entered under 'G'
H
No definitions entered under 'H'
I
Infant Mortality
Failures that occur at an early stage of the life of the equipment, normally due to manufacturing defects.
Burn-In Testing is often used to identify any infant mortalities prior to the in-service phase of the equipment.
J
No definitions entered under 'J'
K
No definitions entered under 'K'
L
Logistic or Basic Reliability
This type of analysis considers the probability of success for every item required for a given mission or objective.
M
Maintenance Based Failures
Maintenance Based Failures are failures which occur due to inadequate or incorrect maintenance. These failures
are often attributable to the following areas:
- Poorly or incorrectly defined maintenance schedules
- A misinterpretation of the Specification
- Failure to carry out all maintenance procedures
- Incorrect implementation of maintenance procedures
Mission
The intended use profile for the system, which should include the intended time frame.
Mission Reliability
This type of analysis considers the probability of success for every item required for a given mission or objective.
N
No definitions entered under 'N'
O
Operation Based Failures
Systems are normally designed around an expected Use Profile. If the boundaries of this Use Profile are exceeded
during operation, a failure may result. These failures are often attributable to the following areas:
- A failure to adequately define/understand the Operation Use Profile
- A failure to remain within the defined Operation Use Profile
- A failure to correctly follow stipulated maintenance procedures, inspections and monitoring
P
Production Based Failures
Production Based Failures are failures which occur during assembly and are not subsequently detected by inspection
processes. These failures are often attributable to the following areas:
- Ambitious design manufacture specifications necessitating the use of new technologies, very low tolerances and
complex production processes etc.
- Ambiguous design manufacture specifications
- Aggressive deadlines resulting in a speedier and more error prone production process
Q
No definitions entered under 'Q'
R
Random Failures
A failure where the probabilty of occurence is equally distributed across any given period of time i.e.
the failure is just as likely to occur earlier in its life as it is later on. This type of failure is often
called 'Bird Strike.'
Redundency
The existence of more than one means for accomplishing a given function. Each means of accomplishing the given
function may not necessarily be identical.
Reliability
Reliability is defined as the probability that a system will have the ability to perform its intended function within
the defined performance parameters over a given period of time.
Reliability Block Diagrams
A graphical method by which the probability of success against
a defined mission or function can be determined. The process
involves the linking of all components or modules (in series
or parallel as appropriate)
which are required
for mission or function success.
End
End of definitions
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