Service life
Encyclopedia
A product's service life is its expected lifetime, or the acceptable period of use in service. It is the time that any manufactured item can be expected to be 'serviceable' or supported by its manufacturer
.
Expected service life consists of business policy
, using tools and calculations from maintainability
and reliability analysis
. Service life is a unique commitment made by the item's manufacturer and is usually specified as a median. Actual service life is the maximal recorded life of a product.
Service life is different from a predicted life, or MTTF/MTBF (Mean Time to Failure/Mean Time Between Failures)/MFOP(Maintenance-free operating period). Predicted life is useful such that a manufacturer may estimate, by hypothetical modeling and calculation, a general rule for which it will honor warranty
claims, or planning for mission fulfillment. The difference between service life and predicted life is most clear when considering mission time and reliability in comparison to MTBF and service life.
For example: A missile
system can have a mission time of less than one minute, a service life of 20 years, active MTBF of 20 minutes, dormant MTBF of 50 years and a reliability of .999999.
A consumer
item will have different expectations about service and longevity
based upon factors such as use, cost, and quality.
will commit to very conservative service life, usually 2 to 5 years for most commercial and consumer products (for example computer
peripheral
s and components
). However, for large and expensive durable good
s, 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.
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.
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
.
Expected service life consists of business policy
Product life cycle management
Product life-cycle management is the succession of strategies used by business management as a product goes through its life-cycle. The conditions in which a product is sold changes over time and must be managed as it moves through its succession of stages.Product life-cycle Like human beings,...
, using tools and calculations from maintainability
Maintainability
In engineering, maintainability is the ease with which a product can be maintained in order to:* isolate defects or their cause* correct defects or their cause* meet new requirements* make future maintenance easier, or* cope with a changed environment...
and reliability analysis
Reliability engineering
Reliability engineering is an engineering field, that deals with the study, evaluation, and life-cycle management of reliability: the ability of a system or component to perform its required functions under stated conditions for a specified period of time. It is often measured as a probability of...
. Service life is a unique commitment made by the item's manufacturer and is usually specified as a median. Actual service life is the maximal recorded life of a product.
Service life is different from a predicted life, or MTTF/MTBF (Mean Time to Failure/Mean Time Between Failures)/MFOP(Maintenance-free operating period). Predicted life is useful such that a manufacturer may estimate, by hypothetical modeling and calculation, a general rule for which it will honor warranty
Warranty
In business and legal transactions, a warranty is an assurance by one party to the other party that specific facts or conditions are true or will happen; the other party is permitted to rely on that assurance and seek some type of remedy if it is not true or followed.In real estate transactions, a...
claims, or planning for mission fulfillment. The difference between service life and predicted life is most clear when considering mission time and reliability in comparison to MTBF and service life.
For example: A missile
Missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
system can have a mission time of less than one minute, a service life of 20 years, active MTBF of 20 minutes, dormant MTBF of 50 years and a reliability of .999999.
A consumer
Consumer
Consumer is a broad label for any individuals or households that use goods generated within the economy. The concept of a consumer occurs in different contexts, so that the usage and significance of the term may vary.-Economics and marketing:...
item will have different expectations about service and longevity
Car longevity
Car longevity is of interest to many car owners and concerns several things: maximum service life in either miles or time , relationship of components to this lifespan, identification of factors that might afford control in extending the lifespan. Barring an accidental end to the lifespan, a car...
based upon factors such as use, cost, and quality.
Product strategy
ManufacturersProduct lifecycle management
In industry, product lifecycle management is the process of managing the entire lifecycle of a product from its conception, through design and manufacture, to service and disposal...
will commit to very conservative service life, usually 2 to 5 years for most commercial and consumer products (for example computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
peripheral
Peripheral
A peripheral is a device attached to a host computer, but not part of it, and is more or less dependent on the host. It expands the host's capabilities, but does not form part of the core computer architecture....
s and components
Electronic component
An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...
). However, for large and expensive durable good
Durable good
In economics, a durable good or a hard good is a good that does not quickly wear out, or more specifically, one that yields utility over time rather than being completely consumed in one use. Items like bricks or jewellery could be considered perfectly durable goods, because they should...
s, 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
Bathtub curve
The bathtub curve is widely used in reliability engineering. It describes a particular form of the hazard function which comprises three parts:*The first part is a decreasing failure rate, known as early failures....
, a plot of the varying failure rate
Failure rate
Failure rate is the frequency with which an engineered system or component fails, expressed for example in failures per hour. It is often denoted by the Greek letter λ and is important in reliability engineering....
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
Exponential distribution
In probability theory and statistics, the exponential distribution is a family of continuous probability distributions. It describes the time between events in a Poisson process, i.e...
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
Retread
A retread, or "recap," is a previously worn tire which has gone through a remanufacturing process designed to extend its useful service life.Retreading starts with a safety inspection of the tire. The old tread is then buffed away, and a new rubber tread is applied to the bare "casing" using...
and the casing.
Service life examples
For maintainable items, those wear-out items that are determined by logistical analysis to be provisioned for sparingSpare part
Spare Parts may also refer to:* Spare Parts , by Status Quo* Spare Parts is a Doctor Who audio drama.* Spare Parts , by Servotron* "Spare Parts" , by Bruce Springsteen* "Spare Parts"...
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
Car longevity
Car longevity is of interest to many car owners and concerns several things: maximum service life in either miles or time , relationship of components to this lifespan, identification of factors that might afford control in extending the lifespan. Barring an accidental end to the lifespan, a car...
to the extent of a single set of tires.
An individual tire's life follows the bathtub curve
Bathtub curve
The bathtub curve is widely used in reliability engineering. It describes a particular form of the hazard function which comprises three parts:*The first part is a decreasing failure rate, known as early failures....
, 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
Pothole
A pothole is a type of disruption in the surface of a roadway where a portion of the road material has broken away, leaving a hole.- Formation :...
), 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
Retread
A retread, or "recap," is a previously worn tire which has gone through a remanufacturing process designed to extend its useful service life.Retreading starts with a safety inspection of the tire. The old tread is then buffed away, and a new rubber tread is applied to the bare "casing" using...
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
Consumer
Consumer is a broad label for any individuals or households that use goods generated within the economy. The concept of a consumer occurs in different contexts, so that the usage and significance of the term may vary.-Economics and marketing:...
products as, in general, efforts at actuarial analysis are not taken to the same extent as found with that needed to support insurance
Insurance
In law and economics, insurance is a form of risk management primarily used to hedge against the risk of a contingent, uncertain loss. Insurance is defined as the equitable transfer of the risk of a loss, from one entity to another, in exchange for payment. An insurer is a company selling the...
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.