The Mantua Group

Simple Black and White Asset Management, Reliability Expertise, and Maintenance Execution Perfection.

Failure Modes

Cataloguing Failure Mechanisms

Why the Universal Catalogue of Acceleration Models is Elusive, and What to Do Instead

The reliability engineer is regularly asked the same question. Is there a catalogue of failure mechanisms and their acceleration models? The questioner is typically planning an accelerated life test, an ongoing reliability monitoring programme, or a regulatory submission, and would like to look up the relevant model and its parameters in a single authoritative source. The answer, after a century of reliability engineering practice, is that no such catalogue exists in a usable form. Existing resources, the OREDA and RAC databases, the IEEE Gold Book, the NPRD and NSWC compendia, the Rome Laboratory’s WARP project, and the Physics of Failure literature, provide partial coverage of either the models or the data, but not both, and not in combinations that allow plug-and-chug application to the practitioner’s specific situation. This paper sets out why the catalogue is elusive, what the existing resources actually offer, where the boundaries of legitimate use lie, and what the practitioner should do instead. The principles are drawn from a Speaking of Reliability conversation between Philip Sage and Fred Schenkelberg and have been translated here into a structured engineering doctrine in the TMG voice.

Backward Blueprinting

Designing Reliability Plans by Working Backward from the Decision You’ll Need to Make

The reliability plan that begins with today’s tasks and works forward toward an undefined future state is the plan that produces the parallel information economy described elsewhere in TMG’s writing: the CMMS that contains everything except the data the organisation actually needs, the ERP whose blueprints are beautiful and whose data outputs are unusable, and the project life cycle that delivers a product that the warranty subsequently absorbs the cost of. The reliability plan that begins with the future-state decisions the organisation will need to make and works backward through the data, processes, and systems that must be in place to support those decisions is the plan that produces usable outcomes. The technique that distinguishes the two is what the source conversation calls backward blueprinting. This paper sets out the principle, the failure modes it is designed to prevent, the working questions that operationalise it, and the organisational disciplines required to apply it consistently across new product development, asset management software implementation, and operational reliability programmes.

So, You Have an Environmental Test Chamber. So What?

Aligning Test Methodology with Failure Modes, Service Environments, and the Decisions the Tests are Meant to Inform

Environmental test chambers are among the most visible capital investments in a reliability laboratory. They occupy floor space, draw power, and confer a tangible sense of analytical readiness on their owners. The persistent failure mode in their use is not technical. It is cognitive. The presence of a chamber subtly biases the test programme toward the questions the chamber can answer rather than the questions the product’s service environment actually poses.

Statistical Rigour in the Regulatory Arena: Weibull Analysis Certification and the Victorian AER REPEX Challenge

How independent Weibull MLE certification, aligned with the AER’s 2024 Asset Replacement Planning guidance, contributed to the evidentiary strength of regulatory proposals across Victorian electricity distribution network submissions.

Victorian electricity network service providers are engaged in one of the most consequential regulatory processes in recent memory. The Australian Energy Regulator (AER) has reviewed the combined revenue and capital expenditure proposals of five Victorian distributors, AusNet Services, Jemena, Citipower, Powercor, and United Energy, for the five-year regulatory control period commencing 2026.

The AER’s draft determination trimmed the distributors’ collective capex claims by approximately $3.7 billion, with the contested quantum approaching $2.9 billion once the revised proposals were filed. Central to the regulatory debate is the quality and defensibility of probabilistic asset replacement expenditure (REPEX) modelling, and, in particular, the statistical validity of the Weibull-based Probability of Failure (PoF) functions that underpin each distributor’s replacement case.

The Mantua Group (TMG) provided independent Weibull Analysis certification and expert advisory services to selected network service providers engaged in this regulatory process. Our work, conducted in alignment with the AER’s 2024 Asset Replacement Planning (ARP) Practice Note and the AER REPEX Model Framework, strengthened the statistical foundation of REPEX submissions across key asset classes, including distribution transformers, substation power transformers, and overhead conductors. This white paper describes the regulatory context, the methodology we applied, and the outcomes attributable to TMG’s involvement.

Wood Decay Engineering for Transmission Pole Assessment

Applying AS 1170.5 Draft Wood Decay Modeling to Predict Functional and Catastrophic Failure Thresholds

This white paper presents an engineering methodology for predicting wood pole deterioration using decay progression models aligned with AS 1170.5 Draft, the Australian standard. The approach integrates field-measured decay rates from test stake programs with pole geometry to establish both functional failure (FF) and catastrophic failure (CF) thresholds for transmission structures.

A critical finding is that failure timing is highly dependent on original pole diameter, not simply pole age. Analysis demonstrates that functional failure for minimum-diameter poles may occur 50 years before maximum-diameter poles of the same age and treatment cohort, fundamentally changing how asset managers should prioritize inspections and replacements.

The methodology incorporates treatment effects for both Pressure Impregnated (PI) and Natural Round (NR) timber, accounting for preservative type, retention levels, and the progression of wood decay through sapwood, outer heartwood, and inner heartwood (corewood) zones.