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	Universal Reliability Definitions (URDs)

Universal Reliability Definitions (URDs) in Simulation Diagrams

In simulation diagrams, the universal reliability definitions (URDs) assigned to blocks define reliability and maintenance characteristics. Each URD is a resource that may be used throughout the project and can include two other types of resources:

Models are resources that represent behavior over time. In URDs, they are used to define failure behavior.
Tasks describe the conditions that determine when maintenance actions will be performed on a block. Tasks specify the logistical time and costs associated with those actions as well as their anticipated effectiveness (i.e., how much the component will be restored). Tasks may be configured to use three other types of resources:
- Tasks use models to describe how long the task takes.
- Crews describe the conditions that determine when personnel will be available to perform specific tasks. These resources also specify the logistical time and costs associated with engaging the crew.
- Spare part pools describe the conditions that determine whether a spare part will be available when needed. These resources also specify the logistical time and costs associated with obtaining the spare part.

A URD can have one corrective task and/or one or more scheduled tasks. Scheduled tasks are displayed in their priority order, which is the order in which they will be performed; you can use the up and down arrows in the cells in this column to move the task up and down the priority list.