Equipment state model

An equipment state model is a defined set of machine or equipment conditions and the allowed transitions between them, used to consistently describe how equipment is being used over time. It is typically implemented in MES, SCADA, or OEE systems to classify machine time into standardized states such as running, idle, setup, planned stop, unplanned stop, or maintenance.

Key characteristics

An equipment state model commonly includes:

• Standard state definitions such as productive, standby, changeover, faulted, blocked, starved, or offline.
• Transition rules that define which state changes are valid (for example, from running to faulted, or from planned stop to running).
• Event sources such as PLC signals, operator input, or MES events that trigger a state change.
• Time-based classification so each time segment for a piece of equipment is assigned to a single, clear state.
• Mapping to performance metrics, particularly OEE components like availability, performance, and quality.

In regulated or high-reliability environments, the equipment state model is often documented and governed so that reports, investigations, and audits can interpret equipment utilization and downtime consistently across lines, plants, or sites.

Operational use in manufacturing

In day-to-day operations, the equipment state model appears in:

• Dashboards and HMIs that show current machine status (for example, running, changeover, maintenance).
• Downtime capture workflows where operators confirm or refine the reason associated with an unplanned stop state.
• Automatic data collection from controllers or sensors that update the state based on signal patterns or conditions.
• Performance and reliability analysis, where time in each state is aggregated for OEE, NPT, or capacity studies.
• Maintenance planning, where time in maintenance-related states is tracked and analyzed.

The equipment state model is often aligned with standards such as ISA-95 or ISO 22400, which describe typical state categories and KPI definitions. Implementations may customize the model to specific processes, but retain a common core to support plant-wide or enterprise-wide comparisons.

Scope and boundaries

An equipment state model:

• Includes the logical states of physical production assets such as machines, lines, cells, and test equipment.
• Includes time-based events and status changes relevant to production, quality, and maintenance reporting.
• Excludes detailed process parameters (for example, temperature, speed, pressure) that describe how the equipment is running, not what state it is in.
• Excludes work order or product status models, which describe the state of a job or batch rather than the equipment itself.

Common confusion

• Equipment state model vs. OEE calculation: The state model provides the categorized time data (for example, run vs. downtime). OEE formulas then use that data to compute availability and related metrics, but are not the state model itself.
• Equipment state model vs. workflow or routing: A routing or workflow describes the sequence of operations a product goes through. The equipment state model describes the condition of the machine, independent of which product or operation is running.