PM Interval Optimizer - Find the Cheapest Maintenance Frequency

How It Works

1. Enter Source-Backed Inputs

   Enter MTBF, beta, planned PM cost, failure cost, and current interval from records or engineering assumptions that can be traced to a failure mode and asset population. The screen does not calculate beta from raw records.

2. Check Cost Basis

   Use the same accounting boundary for planned PM and unplanned failure cost. Decide whether labor, parts, downtime, collateral damage, production impact, and vendor support are included before comparing outputs.

3. Review the Local Cost Curve

   The screen applies a two-parameter Weibull age-replacement formula to the entered values and displays cost and reliability prompts at sampled intervals. The local minimum is a review point, not a schedule instruction.

4. Resolve Source Gaps

   Check CMMS data quality, censored records, failure-mode separation, OEM manuals, condition-monitoring trends, criticality, safe-work requirements, and regulatory or fleet maintenance obligations.

5. Document Qualified Review

   If an interval change remains plausible, route it through reliability engineering, operations, safety, maintenance planning, and change-management controls before work orders are changed.

Built For

• Reliability engineers documenting questions before a formal Weibull or RCM review
• Maintenance planners comparing source-backed PM and failure cost assumptions
• CMMS administrators flagging intervals that need data-quality review before edits
• Plant managers checking whether a proposed change needs OEM, safety, or regulatory input
• Condition monitoring teams comparing age-based prompts with vibration, oil, thermal, or inspection trends
• Fleet maintenance teams separating local cost screens from FMCSA, TMC, OEM, and inspection requirements
• Engineering students learning the limits of age-replacement model prompts

Features & Capabilities

Entered-Parameter Weibull Screen

Uses the entered MTBF and beta to compute a local eta value and age-replacement cost prompts. It does not perform maximum-likelihood fitting, censoring analysis, or confidence intervals.

Local Cost-Minimum Prompt

Sweeps the age-replacement cost formula to identify the lowest local cost point for the entered values. The result is labeled as a review prompt rather than a PM work-order interval.

Cost Curve and Reliability Prompts

Shows sampled cost, reliability, and failure probability points across percentages of MTBF so the shape of the assumption set is visible.

Source Warnings

Calls out CMMS, failure-mode, censored-record, OEM, safety, regulatory, fleet, and qualified-review gaps before users treat outputs as decisions.

Weak Age-Trend Warning

Flags beta values near or below 1 where time-based replacement may be ineffective or harmful without RCM and condition-monitoring review.

Report Export Boundary

PDF and CSV exports carry the same source warnings and residual gaps as the screen. They are documentation prompts, not approval records.

Assumptions

• Entered MTBF and beta already apply to one failure mode, one asset population, and one operating context.
• Failure mode is single and consistent - mixed failure modes are not separated automatically.
• PM cost and corrective repair cost are constant and known - no escalation or accounting reconciliation is modeled.
• Age replacement model assumes PM fully restores the component to as-good-as-new condition (perfect renewal).
• Regulatory, safety, OEM, warranty, fleet, owner, and qualified-review requirements are resolved outside the app.

Limitations

• Does not fit Weibull parameters, process censored records, compute confidence intervals, or test goodness-of-fit.
• Does not support three-parameter Weibull, competing risks, block replacement, group maintenance, or repairable-system models.
• Does not account for condition-based maintenance triggers, inspections, alarms, or predictive-maintenance limits.
• Assumes stationary operating conditions - changes in load, speed, temperature, environment, installation quality, or maintenance practice invalidate the input assumptions.
• Does not determine work-order cadence, legal inspection interval, fleet compliance, warranty compliance, or safety-critical maintenance approval.

References

• NIST/SEMATECH Engineering Statistics Handbook Chapter 8 - reliability, survival, failure-rate, and lifetime-distribution context.
• NASA Reliability-Centered Maintenance Guide - maintenance periodicity, age-reliability, and RCM review context.
• ISO 14224:2016 source page - reliability and maintenance data collection and quality context.
• FMCSA 49 CFR 396.3 guidance - systematic inspection, repair, and maintenance context for motor carriers.
• ATA TMC Recommended Practices Manual source page - fleet maintenance practice source pointer.

Frequently Asked Questions