From Reliability Engineering Handbook, Volume 2


Reliability apportionment encompasses the problem of assigning the correct numerical reliability to each sublevel of an item in such a manner that the overall item reliability is equal to its reliability goal. It can also be thought of as the assignment of allocation to each sublevel of the allowable levels of unreliability. Reliability goal could also be set for every part, such as screw, wiring, connector, etc.; however, this is usually not practical. In designing for reliability, goals must be assigned to every major component for which the designer is responsible. Once these sublevel reliabilities are established, the designer can select the materials, configurations, and types so that the overall reliability requirement can be achieved.

Reliability goals are usually established by either the customer or proposed by the manufacturer for customer approval. The assignment of reliability goals by the customer is usually based on studies of strategic necessities, logistic requirements, mission accomplishment, operational readiness, maintainability, safety, budgetary limitations, and other factors of intrinsic importance. Apportionment is required when the manufacturer is obliged to decide how reliable various subsystems must be in order to design an end product that will meet the specified reliability requirement. It should be noted that, as reliability approaches perfection, each advance becomes very much more expensive. Morever, the manufacturer should be able to advise the customer as to what a given reliability requirement will cost in terms of time, performance, and money.


Key reasons for reliability allocations are the following:

Products & Services
Reliability Software
Reliability software enables organizations to improve product safety and reliability by measuring performance against industry-wide standards.
Project Management Software
Project management software is a term covering many types of software, including scheduling, cost control and budget management, resource allocation, collaboration software, communication, quality management and documentation or administration systems
Direct Mail and Fulfillment Services
Direct mail and fulfillment services are specialized contract services that broadcast mailed marketing materials to target audiences who are usually identified by databases, provided by a direct mail company or the client.
Furniture consists of seating, benches, tables, cabinets and chairs for indoor or outdoor applications.
Broadcasting, Studio, and Theatrical Services
Broadcasting, studio and theatrical services specialize in the planning and production of television shows, radio programs, movies, films, plays, concerts, and other audio or video recordings.

Topics of Interest

16.1 INTRODUCTTON Reliability growth [1 5] is either a projection of the reliability of a system or an equipment to some future development time from information available now from predictions or...

5.3 Reliability Allocation In a large complex system, it is necessary to translate reliability requirements into detailed specifications for the numerous units that make up the system. The overall...

CHAPTER LIST Chapter 11: Design and Assurance Techniques Chapter 12: Design Review and Test Chapter 13: Field Data Collection and Feedback Chapter 14: Factors Influencing Down Time Chapter 15:...

CHAPTER LIST Chapter 7: Basic Reliability Prediction Theory Chapter 8: Methods of Modelling Chapter 9: Quantifying the Reliability Models Chapter 10: Risk Assessment (QRA) 7.1 WHY PREDICT RAMS?...

To this point, we have concentrated mostly on behavioral modeling of a digital system. Behavioral models are more concerned with describing the abstract functionality of a module, regardless of its...