ETL 1110-2-560
30 Jun 01
(FY) 1993. To qualify as major rehabilitation projects, the work activities must extend over two full
construction seasons and the total required implementation costs must be greater than a certain minimum
threshold. The threshold amounts are adjusted annually for inflation as published in the Army
Programs Corps of Engineers Civil Works Direct Program Program Development Guidance. To
compete successfully as new starts, major rehabilitation proposals must be supported by the same level of
economic analysis as new water resource projects. Chapter 3 of Engineer Regulation (ER) 1130-2-500
establishes policy for major rehabilitation at completed Corps projects. Chapter 3 of Engineer Pamphlet
(EP) 1130-2-500 establishes guidance for the preparation and submission of Major Rehabilitation Project
Evaluation reports for annual program and budget submissions.
c. The rehabilitation of mechanical and electrical equipment is usually included as part of the
overall project. Rehabilitation may include replacement and/or reconditioning to restore or improve a
system to a like-new condition. The rehabilitation may be considered from various perspectives. It may
be necessary to restore existing equipment that has deteriorated with time or failed in service; or
equipment may become obsolete, and replacement might be desired to upgrade the equipment to modern
standards. The Major Rehabilitation Evaluation reports and supporting information will have to provide
evidence of criticality with a certain level of detail based on specific uniform engineering criteria.
Reliability assessments based on probabilistic methods provide more consistent results and reflect both
the condition of existing equipment and the basis for design.
d. Further guidance for the reliability evaluation of hydropower equipment has been published in
ETL 1110-2-550 and Mlakar 1994.
6. Reliability Concepts and Definition of Terms
a. Definition of terms.
(1) Component. A piece of equipment or portion of a system viewed as an independent entity for
evaluation, i.e., its reliability does not influence the reliability of another component.
(2) System. An orderly arrangement of components that interact among themselves and with external
components, other systems, and human operators to perform some intended function.
(3) Failure. Any trouble with a component that causes unsatisfactory performance of the system.
(4) Hazard function or failure rate. The instantaneous conditional probability of failure of an item in
the next unit of time given that it has survived up to that time. It is the mean number of failures of a
component per unit exposure time.
(5) Reliability. The probability that an item will perform its intended function under stated
conditions, for either a specified interval or over its useful life.
(6) Basic reliability. Measure of the demand for maintenance and logistic support of a system caused
by unreliability.
(7) Mission reliability. Measure of operational effectiveness of a system. A mission reliability
prediction estimates the probability that items will perform their required functions during a mission.
(8) Unsatisfactory performance. Substandard operation; partial or complete shutdown of the system;
operation of safety devices; unexpected deenergization of any process or equipment.
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