An unpredicted change in a plant process is known as?

The term "disturbance" is the most appropriate choice for describing an unpredicted change in a plant process. In the context of industrial processes, a disturbance refers to an unexpected event or anomaly that affects how the system operates. This could be related to variations in input materials, environmental changes, or other factors that were not anticipated during the planning or operational phases.

Understanding the concept of disturbances is essential in process engineering, as they can lead to deviations from the desired performance or operational parameters. Identifying and managing disturbances is crucial for maintaining efficiency and safety within a plant.

In contrast, other terms like disruption, error, and malfunction carry different connotations. Disruption often implies a significant interruption or breakdown in a service or process, which may not be as nuanced as a disturbance. An error typically refers to a mistake made by an operator or system that results in incorrect outcomes, while a malfunction indicates a failure of a component or system to function as intended. Therefore, "disturbance" is the precise term that captures the essence of an unexpected change without implying a complete system failure or human error.