What are the main time categories used in ISO 22400?

ISO 22400 defines a common time model for manufacturing equipment and lines so that KPIs such as OEE and availability are calculated consistently. At a high level, it splits the calendar into a small set of top-level time categories, which are then refined into subcategories. Naming in implementations can vary, but the core structure is:

1. Non-scheduled time

Periods when the equipment is not planned to be available for production. Typical examples:

• Planned plant closure (weekends, holidays, shutdowns)
• Outside the defined shift pattern

Non-scheduled time is usually excluded from OEE calculations but is part of the full calendar time budget.

2. Operation time (productive time)

Periods when the equipment is scheduled and actually being used for value-adding production or directly supporting it. ISO 22400 further refines this into categories such as:

• Processing / execution time: The machine is actively processing a workpiece or batch.
• Manual production-related time: Operator actions directly needed for production (loading/unloading, in-cycle inspections, etc.).
• Production-related setup and adjustment: Activities required to prepare equipment for the next product, batch, or order when considered part of effective operation for KPI purposes.

Implementations differ on whether some setup and changeover elements are counted in operation time or classified separately, but ISO 22400 gives reference categories and definitions to keep this transparent.

3. Standby time (planned interruptions within scheduled time)

Periods within scheduled time when equipment is not producing but is not in failure. Typical reasons include:

• Lack of input material, tooling, or components
• No order currently dispatched to the equipment
• Downstream blockage or buffer full
• Planned micro-breaks or organized pauses that are not modeled as non-scheduled time

ISO 22400 distinguishes standby from failures so that availability losses driven by planning or flow issues are not conflated with technical downtime.

4. Planned downtime within scheduled time

Time during which the asset is scheduled in the overall plan but intentionally taken out of production. Examples:

• Planned preventive maintenance
• Planned cleaning or sanitation cycles
• Planned changeovers and setups, when modeled as a separate category
• Planned engineering trials or qualification runs

Whether this is included or excluded in OEE calculations depends on your agreed KPI definition, but ISO 22400 provides explicit categories so that decisions are visible and traceable.

5. Unplanned downtime (failure time)

Unscheduled loss of capability during scheduled time. This covers:

• Equipment failures and breakdowns
• Quality-driven stops (e.g., out-of-spec product requiring stoppage)
• Unplanned safety or compliance-related stops
• Unplanned maintenance interventions

ISO 22400 encourages subcategorization (mechanical, electrical, automation, external utilities, quality block, etc.) to support root cause analysis and consistent KPI reporting.

6. Supporting and ancillary time

Some ISO 22400 categories capture time that is not strictly direct processing but is necessary to keep operations running, for example:

• Calibration or verification activities carried out during scheduled time
• Operator training on the machine during scheduled time
• Engineering tests, software updates, or minor adjustments

Plants differ in whether these are rolled into planned downtime, operation time, or tracked as a distinct ancillary bucket. ISO 22400’s value is in giving a standard vocabulary so such decisions are explicit.

How this plays out in real plants and brownfield MES

In practice, most regulated and brownfield environments do not implement ISO 22400 literally as printed. Existing MES, SCADA, historian, and CMMS systems often have legacy time and state codes that only partially align.

Common realities:

• Mapping, not replacement: You typically map existing machine states to ISO 22400 categories rather than redesigning the whole state model. Full replacement can be risky due to validation effort, integration impacts, and operator retraining.
• Configuration- and data-dependent: The accuracy of each category depends on how well automation signals, operator inputs, and schedule data are integrated. Ambiguous or manual state changes can blur the lines between standby, planned downtime, and failures.
• Traceability and change control: Any reclassification of time categories affects trend data and KPIs. In regulated environments this usually requires documented change control, impact assessment, and in some cases revalidation of KPI reports and dashboards.
• Different KPI conventions: Some sites include certain planned downtimes in OEE; others exclude them and track a separate KPI (e.g., loading or TEEP). ISO 22400 helps standardize definitions, but your corporate KPI standard and regulatory expectations will drive the final choices.

For new projects, it is often safer to align new equipment and interfaces to ISO 22400 from the start, then progressively harmonize legacy areas, rather than attempting a big-bang replacement of all time-state logic across the plant.