Alert Hub · Thresholds + escalation
Predictive alert thresholds (practical guide for industrial plants)
Who this is for
- Reliability and maintenance engineers
- Shift supervisors managing alerts
- Operators on PdM routes
- Plant managers reviewing alert ROI
- Sensor vendors and integrators
- Contractors on condition monitoring
- New engineering graduates learning PdM
What's in this guide
Why threshold design matters more than sensor count
Most predictive maintenance programs in Philippine plants fail at the threshold layer, not the sensor layer. The plant buys good sensors, the sensors generate accurate data, and the alerts get silenced because every alert is treated as critical or because the alerts cry wolf and the team learns to ignore them.
Threshold design is the difference. A well-tuned threshold fires once a quarter, gets acted on, and prevents a real failure. A poorly-tuned threshold fires daily, gets dismissed, and trains the team to ignore the sensor. The sensor is the easy part; the threshold tuning is the discipline.
The 3-tier alert architecture
| Tier | Meaning | Response | Owner |
|---|---|---|---|
| Notice | Reading is rising above baseline but still within normal | Log in WorkHive Logbook for trend tracking; no action this shift | Operator |
| Warning | Reading crossed first action threshold; degradation in progress | Schedule investigation within 7 days; trend daily | Maintenance supervisor |
| Action | Reading crossed second action threshold; failure imminent | Stop or de-rate asset; investigate this shift | Reliability engineer + supervisor on call |
Three tiers, not seven. Many sensor vendor dashboards ship with 5 to 7 alert levels which look sophisticated and fail in practice. Three tiers map to three distinct human responses: keep watching, plan a check, act now.
ISO 10816 vibration thresholds by asset class
ISO 10816 defines vibration severity zones for industrial machinery. The standard is the right starting point; tune from there based on your plant's history.
| Asset class | Zone A (Good) | Zone B (Acceptable) | Zone C (Unsatisfactory) | Zone D (Unacceptable) |
|---|---|---|---|---|
| Class I (small motors below 15 kW) | < 0.71 mm/s | 0.71 to 1.8 | 1.8 to 4.5 | > 4.5 |
| Class II (medium motors 15 to 75 kW) | < 1.12 | 1.12 to 2.8 | 2.8 to 7.1 | > 7.1 |
| Class III (large rigid foundation) | < 1.8 | 1.8 to 4.5 | 4.5 to 11.2 | > 11.2 |
| Class IV (large flexible foundation) | < 2.8 | 2.8 to 7.1 | 7.1 to 18.0 | > 18.0 |
Map to the 3-tier system: Notice fires at the Zone A to B transition, Warning at the B to C transition, Action at the C to D transition.
Temperature alert design
Bearing temperature is the cleanest predictive signal for rotating equipment after vibration. Indicative thresholds for an ambient 30 deg C Philippine plant:
- Notice: bearing temperature 5 to 10 deg C above the running baseline (which itself is measured during commissioning, not assumed)
- Warning: 10 to 20 deg C above baseline, or absolute above 75 deg C
- Action: more than 20 deg C above baseline, or absolute above 85 deg C, or rate of rise more than 5 deg C in 1 hour
Always tune the absolute thresholds to your asset's OEM specification; the rate-of-rise threshold is the one that catches sudden failures the OEM did not anticipate.
Escalation rules and named owners
Every alert tier must have a named owner. Unowned alerts get silenced. The pattern that works:
- Notice alerts go to the operator on duty for the asset. Logged in WorkHive Logbook automatically. If no action recorded in 24 hours, escalates to Warning.
- Warning alerts go to the maintenance supervisor in addition to the operator. If no action recorded in 72 hours, escalates to Action.
- Action alerts go to the reliability engineer and the supervisor on call simultaneously. Phone call (not just notification) within 15 minutes is the SLA.
Preventing alert fatigue with weekly review
The single most important discipline: weekly review of any alert silenced more than 3 times. If a Notice alert keeps firing without action, one of three things is true:
- The threshold is too tight (false alarms); retune to a higher value
- The asset is genuinely degraded; promote the alert to Warning
- The asset is being run outside design conditions; root-cause that, not the alert
15 minutes per week with the reliability engineer and the operator. Acknowledge and resolve the alert in WorkHive Alert Hub, then document the retuning reasoning in a logbook entry. This single discipline is the difference between a PdM program that compounds and one that dies in year 1.
The tool this guide is about
WorkHive Alert Hub manages the threshold + escalation discipline
Define 3-tier thresholds per asset, name owners per tier, configure escalation timing, get the weekly silenced-alert report. Integrates with Predictive Maintenance, Logbook, and Asset Hub. Free at the worker tier; phone-call escalation via SMS/voice gateway unlocks at Stage 3.
Open Alert HubNo hive yet? Join WorkHive first (free, takes 30 seconds).
Frequently asked questions
What are the right number of alert tiers?
Where do ISO 10816 vibration thresholds fit in?
How do I prevent alert fatigue?
What is a reasonable alert volume per asset per month?
Who should own each alert tier?
Should I use vendor-default thresholds or set my own?
Sources
- ISO 10816, Mechanical vibration: Evaluation of machine vibration by measurements on non-rotating parts, all parts.
- ISO 20816, Mechanical vibration: Measurement and evaluation of machine vibration (successor to ISO 10816).
- API 670, Machinery Protection Systems. Source for absolute vibration shutdown thresholds on rotating equipment.
- WorkHive platform positioning, "Four Gaps One Hive" with Alert Hub as the Intelligence-gap accelerator. workhiveph.com
- Related WorkHive guides: Predictive maintenance on a budget · MTBF vs MTTR