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Reliability Growth

Reliability Engineering
mechanicalelectrical

Definition

The improvement in reliability achieved through systematic identification and elimination of failure causes over time. Reliability growth is measured by tracking MTBF, failure rate, or other reliability metrics as corrective actions are implemented. The Duane model and AMSAA/Crow model are commonly used to quantify reliability growth rates and project future reliability improvements.

Context

Reliability growth programs are used during equipment development, fleet introduction, and ongoing operations. Tracking reliability growth demonstrates the effectiveness of FRACAS programs and justifies continued investment in reliability improvement. In Reliatic, reliability growth is visible through MTBF trending on the reliability dashboard.

Formula

Duane model: MTBF_cumulative = (1/lambda_0) * t^alpha, where alpha is the growth rate

Examples

  1. A compressor fleet shows reliability growth from MTBF 3,000 hours to 8,000 hours over 3 years, with a Duane growth rate of 0.35, confirming that the corrective action program is effective.
  2. Reliability growth tracking reveals that MTBF plateaued at 6,000 hours — no further improvement from current corrective actions — indicating that a design change is needed to achieve the target MTBF of 10,000 hours.

Applicable Standards

  • IEC 61164:2004
  • MIL-HDBK-189A

Related Terms

Mean Time Between Failures(MTBF)

The average time between consecutive failures of a repairable system or component, calculated as the total operating time divided by the number of failures during that period. MTBF is the primary reliability metric for repairable systems and represents the expected time of continuous operation between failure events. Higher MTBF indicates better reliability.

Failure Reporting, Analysis, and Corrective Action System(FRACAS)

A closed-loop process for systematically reporting failures, analyzing their root causes, implementing corrective actions, and verifying that those actions effectively prevent recurrence. FRACAS captures failure data, triggers investigation based on severity, tracks corrective action implementation, and feeds lessons learned back into the design, maintenance, and operating procedures.

Corrective Action

An action taken to eliminate the root cause of a detected nonconformity, failure, or undesirable situation to prevent its recurrence. Corrective actions address why something went wrong, not just the immediate symptoms. They are distinguished from immediate actions (containment) and preventive actions (proactive measures for potential future problems).

Failure Rate(Lambda)

The average number of failures per unit of time for a population of items, typically expressed as failures per hour, per year, or per million hours. Failure rate (lambda) is the reciprocal of MTBF for constant-failure-rate systems. It is a statistical average measure, distinct from the instantaneous hazard rate, and is most accurate when the failure rate is approximately constant (beta near 1).

Where this appears in Reliatic

This concept is used in the Reliability Analytics module.