A Product’s Service Life is its normal lifetime, or the satisfactory time of utilization in administration. The time any fabricated thing can be required to be “serviceable” or bolstered by its maker.
Expected administration life comprises of business arrangement, utilizing devices and estimations from practicality and unwavering quality investigation. Administration life is a one of a kind responsibility made by the thing’s maker and is normally determined as a middle. Real administration life is the maximal recorded existence of an item.
Administration life is not quite the same as an anticipated life, or MTTF/MTBF (Mean Time to Failure/Mean Time Between Failures)/MFOP (upkeep free working period). Anticipated life is valuable such that a producer may evaluate, by theoretical demonstrating and count, a general guideline for which it will respect guarantee claims, or making arrangements for mission satisfaction. The contrast between administration life and anticipated life is most clear while considering mission time and unwavering quality in contrast with MTBF and administration life.
For instance: A rocket framework can have a mission time of short of what one moment, an administration life of 20 years, dynamic MTBF of 20 minutes, lethargic MTBF of 50 years and an unwavering quality of .999999.
A consumer item will have different expectations about service and longevity based upon factors such as use, cost, and quality.
Manufacturers will commit to very conservative service life, usually 2 to 5 years for most commercial and consumer products (for example computer peripherals and components).
However, for large and expensive durable goods, the items are not consumable, and service lives and maintenance activity will factor large in the service life. Again, an airliner might have a mission time of 11 hours, a predicted active MTBF of 10,000 hours with maintenance (or 15,000 hours without maintenance), a reliability of .99999 and a service life of 40 years.
The most common model for item lifetime is the bathtub curve, a plot of the varying failure rate as a function of time. During early life, the bathtub shows increased failures, usually witnessed during product development. The middle portion of the bathtub, or ‘useful life’, is a slightly inclined, nearly constant failure rate period where the consumer enjoys the benefit conferred by the product. As the time increases further, the curve reaches a period of increasing failures, modeling the product’s wearout phase.
For an individual product, the component parts may each have independent service lives, resulting in several bathtub curves. For instance, a tire will have a service life partitioning related to the tread and the casing.
For maintainable items, those wear-out items that are determined by logistical analysis to be provisioned for sparing and replacement will assure a longer service life than manufactured items without such planning. A simple example is automotive tires – failure to plan for this wear out item would limit automotive service life to the extent of a single set of tires.
An individual tire’s life follows the bathtub curve, to boot. After installation, there is a not-small probability of failure which may be related to material or workmanship or even to the process for mounting the tire which may introduce some small damage. After the initial period, the tire will perform, given no defect introducing event such as encountering a road hazard (a nail or a pothole), for a long duration relative to its expected service life which is a function of several variables (design, material, process). After a period, the failure probability will rise; for some tires, this will occur after the tread is worn out. Then, a secondary market for tires puts a retread on the tire thereby extending the service life. It is not uncommon for an 80,000-mile tire to perform well beyond that limit.
It may be difficult to obtain reliable longevity data about many consumer products as, in general, efforts at actuarial analysis are not taken to the same extent as found with that needed to support insurance decisions. However, some attempts to provide this type of information have been made. An example is the collection of estimates for household components provided by the Old House Web which gathers data from the Appliance Statistical Review and various institutes involved with the homebuilding trade.
BOL and EOL
For certain products, such as those that cannot be serviced during their operational life for technical reasons, a manufacturer may calculate a product’s expected performance at both the beginning of operational life (BOL) and end of operational life (EOL). Batteries and other components that degrade over time may affect the operation of a product. The performance of mission critical components is therefore calculated for EOL, with the components exceeding their specification at BOL. For example, with spaceflight hardware, which must survive in the harsh environment of space, the capacity to generate electricity from solar panels or radioisotope thermoelectric generator is likely to reduce throughout a mission, but must still meet a specific requirement at EOL in order to complete the mission. A spacecraft may also have a BOL mass that is greater than its EOL mass as propellant is depleted during its operational life.