Service Life Extension

Product and service life extension involves continued usage of a product and service after the system has reached its original "design life (glossary)". Product and service life extension involves assessing the "life cycle cost (glossary)" (LCC) of continuing the use of the product or service versus the cost of a replacement system. "Service life extension (glossary)" (SLE) emphasizes reliability upgrades and component replacement, or rebuilding of the system, to delay the system’s entry into wear-out status due to prohibitively expensive sustainment or reliability and performance requirements that can no longer be met. The goal is typically to return the system to as near new condition as possible, consistent with the economic constraints of the program.

SLE is regarded as an environmentally friendly way to relieve rampant waste by prolonging the use-life of retiring products and preventing them from being discarded too early with their unexplored value. However, challenged by fast-changing technology and physical deterioration, a major concern in planning a product SLE is how fit a product might be to serve an extra life.

Topic Overview

Key factors and questions that must be considered by the systems engineer during service life extension include:

Current life cycle costs of the system,
Design life and expected remaining useful life of the system,
Software maintenance
Configuration Management
Warranty policy,
Availability of parts, subsystems, and manufacturing sources
Availability of system documentation to support life extension

System design life is a major consideration for service life extension. System design life parameters are established early on during the system design phase and include key assumptions involving safety limits and material life. Safety limits and the properties of material aging are critical to defining system life extension. Jackson (2007, pg 91-108) emphasizes that architecting for system resiliency increases system life. [42] Jackson points out that a system can be architected to withstand internal and external disruptions. Systems that age through use, such as aircraft, bridges, and nuclear power plants, require periodic inspection to ascertain the degree of aging and fatigue. he results of inspections determine the need for actions to extend the product life (Elliot, Chen, Swanekamp 1998, section 6.5).[21]

Software maintenance is a critical aspect of service life extension. The legacy system may include multiple computer resources that have been in operation for a period of many years, with functions that are essential and must not be disrupted during the upgrade or integration process. Typically, legacy systems include a computer resource or application software program which continues to be used because the cost of replacing or redesigning is prohibitive. The Software Engineering Institute (SEI) has addressed the need for service life extension of software products and services and provide useful guidance in the on-line library for Software Product Lines (SEI 2010, 1). [61]

Systems engineers have found that service life can be extended through the proper selection of materials, for example those that have special coatings. Transportation system elements such as highway bridges and rail systems are being designed for extended service life by using special epoxy-coated steel. [16]

"Diminishing manufacturing sources and diminishing suppliers (glossary)" need to be addressed early in the service life extension process. Livingston (2010) in Diminishing manufacturing sources and material shortages (DMSMS) management practices provides a method for addressing product life extension when the sources of supply are an issue. He addresses the product life cycle model and describes a variety of methods that can be applied during system design to minimize the impact of future component obsolescence issues.[46]

During product and service life extension, it is often necessary to revisit & challenge the assumptions behind any previous lifecycle cost analysis (and constituent analyses) to evaluate their continued validity / applicability early in the service life extension process.

Application to Product Systems

Product life extension requires an analysis of the life cycle cost associated with continued use of the existing product versus the cost of a replacement product. The INCOSE Systems Engineering Handbook v.3.2, Chapter 3.3 Life-Cycle stages points out the support stage includes service life extension.[5] Chapter 7 Life cycle cost (LCC) model provides a framework to determine if a product’s life should be extended. Blanchard & Fabrycky’s 5th edition of Systems Engineering and Analysis, chapter 17, provides a Life Cycle Cost methodology and emphasis the analysis of different alternatives before making a decision on product life extension. [15]

For military systems, service life extension is considered a subset of modification or modernization. Military systems use well developed detailed guidance for service life extensions (Service Life Extension Programs – SLEP). Office of the under Secretary of Defense AT&L provides an on-line reference (Defense Acquisition University, http://www.dau.mil )for policies, procedures, planning guidance and whitepapers for military product serviced life extension. Continuous military system modernization is a process by which state-of-the-art technologies are inserted continuously into weapon systems to increase reliability, lower sustainment costs, and increase the war fighting capability of a system to meet evolving customer requirements throughout an indefinite service life. [18] [62]

Aircraft service life can be extended by reducing dynamic loads which lead to structural fatigue. [42] The Boeing B-52 military aircraft and the Boeing 737 commercial aircraft are prime examples of system life extension. The B-52 aircraft was first fielded in 1955 and continues to be operated in 2011. The Boeing 737 passenger aircraft has been fielded since 1967 and continues operation today.

For nuclear reactors, system safety is the most important precondition for the service life extension. The system safety must be maintained while extending the service life. [8] Built-in test, automated fault reporting and prognostics, analysis of failure modes, and the detection of early signs of wear and aging may be applied to predict the time when maintenance actions will be required to extend the service life of the product.

Application to Service Systems

For systems that provide services to a larger consumer base, service life extension involves continued delivery of the service to end consumers without any disruption. Service life extension involves capital investment and financial planning. Service life extension involves phased deployment of changes. Examples of this are transportation systems, water treatment facilities, energy generation and delivery systems, and the health care industry. As new technologies are introduced, service delivery can be improved while reducing life cycle costs. Service systems have to continuously assess delivery costs based upon the use of newer technologies. Water handling systems provide a good example of a service system that undergoes life extension. Water handling systems have been in existence since early civilization. Since water handling systems are in use as long as a site is occupied (e.g. the Roman aqueducts), and upgrades are required as population expands, such systems are a good example of "systems that live forever." For example, there are still US water systems that use a few wooden pipes, since there has been no reason to replace them. Water system life extension must deal with the issue of water quality and capacity for future users. [47] Water quality requirements can be further understood from the American Water Works Association (AWWA).[12]

Application to Enterprises

Service life extension of a large enterprise such as NASA’s national space transportation system involves service life extension on the elements of the enterprise such as the space vehicle (Shuttle), ground processing systems for launch operations and mission control, and space-based communication systems that support space vehicle tracking and status monitoring. Service life extension of an enterprise requires a holistic look across the entire enterprise. A balanced approach is required to address the cost of operating older system components versus the cost required to implement service life improvements. Large enterprise system such as oil and natural gas reservoirs which span large geographical areas can use advance technology to increase service life. The economic extraction of natural resources from previously established reservoirs can extend the system life of oil and natural gas reservoirs. Life extension methods include pumping special liquids or gases into the reservoir to push the remaining oil or natural gas to the surface for extraction. [7]

Practical Considerations

The cost associated with life extension is one of the main inputs into the decision to extend service life of a product or a service. Often is the case that the funding required for service life extension of large complex systems span several fiscal planning cycles and is therefore subject to changes in attitude by the elected officials the appropriate the funding.

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