Author Archives: Seymour Morris
Common Definitions Related to Reliability, Maintainability and Availability
Time Concepts
Time is of fundamental importance in the quantification of the basic terms which were defined in other definitions found in this blog, for it is this factor which permits the attributes to be measured rather than described in merely qualitative terms. The usual measures of time – the year, the month, the day, and the hour form the basis for the computation of reliability. Where appropriate, the time concepts may be replaced by distance, cycles, operations or other quantities.
Intrinsic Availability
The intrinsic availability of a system or equipment is the probability that it is operating satisfactorily at any point in time when used under stated conditions, where the time considered is operating time and active repair time.
Thus, intrinsic availability excludes from consideration all free time, storage time, administrative time, and logistic time. As the name indicates, intrinsic availability refers primarily to the built-in capability of the system or equipment to operate satisfactorily under stated conditions.
Servicability
Serviceability is the ease or difficulty with which an equipment can be repaired
Intuitively, it would seem that some term should be used to represent the degree of ease or difficulty with which an equipment can be repaired. The term “serviceability” has been selected for this concept. Serviceability has a strong influence on repairability, but the two are essentially different concepts. Serviceability is an equipment design characteristic,
while repairability is a probability involving certain categories of time.
Maintainability
Maintainability is defined as the measure of the ability of an item to be retained in, or restored to specified condition when maintenance is performed by personnel having specified skill levels, using prescribed procedures and resources, at each prescribed level of maintenance and repair.
Repairability
Repairability is defined as the probability that a failed system will be restored to operable condition in a specified active repair time.
System Design Adequacy
System design adequacy is the probability that a system will successfully accomplish its mission, given that the system is operating within design specifications.
Operational Readiness and Availability
The capability of a system to perform its intended function when called upon to do so is often referred to by either of two terms: “operational readiness” and “availability.”
Mission Reliability
Mission reliability is defined as the ability of an item to perform its required functions for the duration of a specified “mission profile.”