Note on the (N, T) Replacement Rule

Charles S. Tapiero, Peter H. Ritchken

Research output: Contribution to journalArticlepeer-review


A model is presented for analyzing (N, T) replacement policies. This rule consists of a T Age Replacement Policy, combined with replacement after N failures, whichever comes first. Using renewal arguments, an optimal (N, T) policy is established. The model applies to situations where repair and/or replacement costs depend on the number of failures. An example illustrates the procedure with a Poisson process. Under special circumstances, the (N, T) maintenance model reduces to simpler forms. This model can be extended to handle (N, T) replacements of k-out-of-N reliability systems, for example.

Original languageEnglish (US)
Pages (from-to)374-376
Number of pages3
JournalIEEE Transactions on Reliability
Issue number4
StatePublished - Oct 1985


  • (N
  • Renewal theory. Reader Aids-Purpose Present a model Special math needed for explanations: Probability Special math needed to use results: Probability optimization Results useful to: Reliability and maintenance analysts
  • Replacement policy
  • T) policy

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality
  • Electrical and Electronic Engineering


Dive into the research topics of 'Note on the (N, T) Replacement Rule'. Together they form a unique fingerprint.

Cite this