Operator prompts and dynamic references

Many batch processes need to allow for interaction with an operator at certain places in the recipe. An operator prompt is a type of message to the operator that requires a response before the phase will continue. After receiving and evaluating the response, the phase will continue based on the configured logic.

Phase messages for the operator are displayed on the Batch Operator Interface in several places. All active messages appear on the Unacknowledged Prompts screen until the operator acknowledges them. Messages can be viewed from the Active Phase Summary screen, the Phase Control screen, the Procedure as PFC screen, and the Procedure as Table screen; they can also be displayed in DeltaV Operate. When a phase is executed manually, messages will not appear on the Procedure as PFC or Procedure as Table screens since these views are not active for manual phases. DeltaV Operate graphics can also be configured to display batch operator prompts. This enables the operator to acknowledge prompts while still maintaining a view of the process equipment.

The following steps are used to create the prompt, receive the response, and evaluate the input to determine the course of action:

1. Create the phase message in the DeltaV Explorer as part of the phase class definition.

   For example, the message "Send this batch to product or waste?" could be created as the first phase message with a message ID of 1, and the second message "How many gallons would you like to release?" could be created with a message ID of 2.

2. In the run logic of the phase, create an operator prompt (using the REQUEST phase parameter) and specify the ID of the phase message that should be displayed to the operator.

   The phase request codes for operator prompts identify the type of response you are expecting (32nn for integer, 33nn for floating point, 34nn for Boolean, or 35nn for string-where nn in each case is the message ID). The operator responses will be written to the appropriate parameters PROMPT_INT, PROMPT_FLOAT, PROMPT_BOOL, and PROMPT_STRING and can be used in transition conditions to determine how to proceed in the logic. These parameters hold the value temporarily; for example, a new PROMPT_BOOL response will overwrite the existing one. Therefore, if you are going to send multiple prompts to the operator, you may want to save certain responses in temporary variables to use them later in the logic.

3. Configure the phase logic to continue based on the operator response.

Using a dynamic reference lets you change the value of a phase algorithm parameter during execution of the phase. The information may come from an operator entry, a recipe parameter passed from the Batch Executive, or a run-time value of a control variable. For instance, you could configure the phase to open a valve, which is referenced using a dynamic reference parameter. Then you can specify the valve you want to use at run-time by prompting the operator or by reading a value passed as part of the recipe.