time categories

Time categories are standardized buckets used to classify how time is spent in a manufacturing or maintenance, repair and overhaul (MRO) environment. They provide a structured way to break total calendar time into meaningful segments, so that systems and analysts can measure utilization, performance, and causes of delay in a consistent way.

In industrial operations, time categories are commonly applied to equipment, production lines, assets, or work orders. They appear in MES, CMMS/EAM, and analytics tools as coded states or event types that describe what is happening during a given time interval.

Typical structure of time categories

While naming varies by organization and standard, time categories often follow a hierarchy, for example:

• Calendar / total time: 24/7 time, including both working and non-working periods.
• Available vs. non-available time:
  • Available time: Time when an asset or resource is scheduled or allowed to run.
  • Non-available time: Time when it is not expected to run (e.g., holidays, long-term shutdowns).
• Within available time:
  • Operating / productive time: Time spent executing value-adding production or maintenance work.
  • Planned loss: Scheduled activities that stop normal operation, such as planned maintenance, changeovers, inspections, or training.
  • Unplanned loss: Unscheduled events that reduce output, such as breakdowns, waiting for material, rework, or quality inspections triggered by issues.

Each high-level time category can be further split into more detailed subcategories, such as specific types of downtime, setup, quality-related delays, or logistics-related waiting time.

Operational use in systems and KPIs

Time categories are used to:

• Map MES or CMMS event codes (e.g., machine state, work order status) into standardized buckets.
• Calculate KPIs such as OEE, non-productive time (NPT), utilization, and turnaround time (TAT) components.
• Enable cross-site comparisons by normalizing different local codes into a shared time model.
• Support root cause and bottleneck analysis by linking delays to clear, agreed categories.

Standards such as ISO 22400 describe reference time category models for manufacturing KPI calculation. Organizations often use these as a starting point and extend them with sector-specific categories, for example detailed MRO turnaround states.

Use in MRO and turnaround management

In MRO, time categories are frequently applied at the work-package or asset level to break down turnaround time into events such as induction, inspection, teardown, repair, test, rework, waiting for parts, and customer hold. These detailed events are then aligned with more generic time categories in plant-wide KPI models so that MRO performance can be compared to other manufacturing operations.

Common confusion

• Time categories vs. event codes: Event codes are the raw labels or status values recorded by systems (for example, “Setup”, “Waiting for QC”). Time categories are the standardized buckets those events are mapped into for analysis.
• Time categories vs. shifts or calendars: Shifts and calendars define when work is planned. Time categories describe what actually happened during that time.
• Time categories vs. KPIs: KPIs are metrics (for example, OEE or TAT). Time categories are an input structure that supports calculating and interpreting those metrics.