A batch process is one that leads to the production of finite quantities of material by subjecting specified quantities of input materials to an ordered set of processing activities over a finite period of time using one or more pieces of equipment. The term batch is used for the material produced or being produced by a single execution of a batch process.
An area is a physical, geographical, or logical grouping of equipment in a process control system. Areas typically represent plant locations or main processing functions. Areas contain process cells. A process cell is a logical grouping of unit modules, equipment modules, and control modules required for production of a batch.
At the lowest level in the physical hierarchy, control in DeltaV software is based on reusable control entities called control modules. Control modules link algorithms, conditions, alarms, displays, and other characteristics of a particular piece of equipment, such as a motor or valve. A control module class defines properties for a group of similar control modules.
When an item is created using a class definition, that item is referred to as an instance of the class. Also, the item is said to be instantiated from the class.
An equipment module in DeltaV batch is usually a module in which several devices (control modules) are involved with control of a single parameter. For example, a Totalizer may contain three control modules to control a coarse inlet valve, a fine inlet valve, and a flow meter, all of which are involved in input of an ingredient to a reactor. An equipment module class defines properties for a group of similar equipment modules.
A unit is a major piece of equipment that performs a specific task. A unit can contain more than one physical piece of equipment (for example, a tank, its inlet valves and outlet valves, level indicators, etc.), each of which is controlled by a control module or equipment module. A unit class defines the properties (unit parameters) for a group of similar units. For example, for mixing tanks, the tank class might have unit parameters to specify the material of construction, the tank volume, and whether the tank has the capability to heat, cool, or adjust the pH of the contents. Alias names are created in the unit class as placeholders for the actual references to control signals, variables, and so on. A unit module is an instance of a unit class.
A phase is a series of steps that causes one or more equipment- or process-oriented actions, for example, filling a tank or agitating the contents. The phase logic defines the states (running, holding, restarting, aborting, and stopping) of the phase and the logic associated with each state. In most batch applications, the phase logic is defined in the phase class. Phase classes define common properties for a group of phases.
Typically one or more phase classes are assigned to a unit module. The assigned phase classes are called unit phases. In unit modules, aliases are resolved, that is, they are assigned unit-specific parameter references.
Another type of module, a phase logic module, can be used to define the phase logic for a single unit. In this type of module, the logic is fully defined in the module itself rather than in the phase class. The phase logic module is then assigned to the specific unit on which it will run. In general, batch applications are best configured using unit modules rather than phase logic modules because unit modules are more flexible and efficient. Phase logic modules are not covered in this book.
A recipe is a set of information that uniquely identifies the parameters, procedures, and equipment required to manufacture a product. A recipe hierarchy is a procedural model that defines the relationship of procedures, unit procedures, and operations. The flow of an individual recipe is defined using a procedural function chart (PFC). A PFC is a diagram similar to a sequential function chart (SFC). It uses steps, transitions, and a termination to define the algorithm for a recipe (an operation, unit procedure, or procedure). You can categorize your recipes in DeltaV Explorer using recipe folders.
A procedure is the highest level of the recipe hierarchy. It is used to control a sequence of unit procedures to perform a function across one or more units. A unit procedure is used to control a sequence of operations to perform a certain function on a unit. An operation executes a sequence of phases to perform a certain function on a unit. There can be one or more phases within an operation that may execute sequentially or concurrently.