From Normal to Critical: use severity as a workflow, not a coloured verdict
Severity classes organise attention. They become reliable only when the sample, trend, operating context, corroborating evidence and maintenance feedback are considered together.
Reviewed Jul 2026 · Lubricants & Fluids Wiki editorial team
This visual orients the topic; the article explains the evidence controls, method limitations and maintenance decisions in detail.
Many reports group findings into Normal, Monitor, Abnormal or Critical. The colour is not the diagnosis. It is a communication layer that should tell the maintenance team how quickly to review the evidence, what to verify, and when a qualified operating decision is required.
Understand what the class represents
A severity class usually combines fixed guidance, rate of change, peer or model comparison, analyst rules and equipment context. Two identical concentrations can receive different attention when sump volume, oil age, component metallurgy, sample interval or asset consequence differ.
Normal means no current evidence demands escalation; it does not prove the absence of every defect. Monitor means a deviation deserves closer surveillance or clarification. Abnormal indicates unsatisfactory fluid, contamination or wear evidence that normally requires confirmation and diagnosis. Critical indicates evidence serious enough for immediate qualified review under site procedures.
- Severity is relative to method and context
- A stable alarm and a rapid change are different risk patterns
- No colour authorises unsafe continued operation or automatic shutdown
Verify before diagnosing
Check the asset, compartment, fluid, sample point, operating state, units and method. Review top-up, oil change, filter replacement, overhaul, abnormal load and sampling delay. A mislabeled compartment or changed sample point can produce a convincing but false trend.
Ask whether the proposed cause predicts other evidence. High iron with increasing bulk ferrous response and cutting or fatigue morphology is more persuasive than high fine iron alone. Water should be considered with temperature, saturation, corrosion elements and ingress history. Viscosity change should be checked against grade, fuel, soot, oxidation and contamination.
Choose a proportionate response
A Monitor response may include reviewing context, shortening the next interval or adding one focused test. An Abnormal response may require a prompt confirmation sample, filter or debris inspection and a targeted operational check. A Critical response requires timely review by people authorised to evaluate equipment safety and production consequence.
Confirmation does not always mean collecting the same sample again. If the initial point is poorly located, repeating it reproduces bias. A better confirmation plan may use a corrected primary point, component-specific secondary points, filter debris, vibration or inspection evidence.
- Verify identity and comparability
- Protect the asset and people
- Confirm with independent evidence
- Correct the source
- Resample to verify effectiveness
Send findings back to the data system
Record what maintenance found: seal leakage, bearing damage, clean filter, incorrect oil, water source, no defect found or sample error. These outcomes refine limits, analyst rules and future recommendations. Without feedback, a programme cannot distinguish a good warning from a recurring false positive.
Track alert acknowledgement, confirmation time, action completion and post-action result. The objective is not to produce more red reports; it is to shorten the path from credible evidence to verified risk reduction.
Key takeaways
- 01Treat severity as an attention and response class
- 02Verify sample and context first
- 03Corroborate the failure hypothesis
- 04Match urgency to evidence and consequence
- 05Feed inspection outcomes back into the programme