The DeltaV system supports the ISA S-88.01 definitions of hierarchy and modular approach to configuration development. This standard provides a good structure for control development, while still allowing you to define modules that are specific to your process. The DeltaV system provides the control module, equipment module, and area functions defined by S-88.01.
The order of the modules in the DeltaV Explorer tree does not imply any execution order in the controller.
Control modules and equipment modules can execute separately or may be contained by other modules with some restrictions. Control modules typically provide control for a single control element such as a valve. Equipment modules typically provide supervisory control for a collection of control modules and other equipment modules that are contained inside the main equipment modules. The algorithm for the containing equipment module manages the operation of the contained modules. Another type of hierarchy exists when control modules are contained within other control modules. However, note that control modules cannot contain equipment modules. Modules can be contained within other modules four-deep. Circular references are possible, but this is typically not a good engineering practice.
Equipment modules interface to the module-level parameters of the control modules that they contain. The user defines the control module interface to the equipment module by elevating key control module parameters to the module level by using input parameters. These well-defined interfaces support good engineering practice for debugging and configuration. Access to the contained control module is simplified and the underlying algorithm is protected. This also makes it possible to substitute one contained module for another, provided the input parameters are of the same names and types.
Use equipment modules for coordinating the operation of multiple modules that need to work together to control related equipment.