Configure the DRA Rate Management tab of the DRAInjector record for the Calculated method

The following section details how to configure the Drag Reducing agent (DRA) Rate Management tab when you have selected Calculated as the Rate Management Method.

To configure the DRA Rate Management tab of the DRAInjector record for the Calculated method

1. Open the DRAInjector record. For more information on opening a DRAInjector record, see Opening the Drag Reducing Agent Injector (DRAInjector) Record.

   The DRAInjector Row Edit dialog appears.

   

2. Select the DRA Rate Management tab.

   The DRA Rate Management tab appears.

   

3. From the Rate Management Method dropdown list, select Calculated.

4. In the Rate Setpoint Analog field, click (...) to select the analog point that is used to set the injection rate of DRA. This value is used to ensure that the desired concentration of DRA in the product is maintained.

5. In the Minimum Flow Rate field, enter the minimum allowed flow rate of product past the DRA injector. If a flow rate lower than this is detected, an alarm is generated (and the injector is shut down if configured to do so). Values 0 and greater are acceptable.

6. In the Target Concentration (ppm) field, enter the target concentration of the DRA. This value is used in the calculation to determine injection rate. This can also be changed by the Controller within the DRA Injector Control dialog.

7. In the Setpoint Tolerance field, enter how much variance in the rate of injection should be tolerated. In the event that the value from the Rate Setpoint Analog differs from the previously issued setpoint by more than the configured Setpoint Tolerance, a command will be sent to the Rate Setpoint Analog.

   Note: This value must be a positive decimal number.

8. In the Setpoint Period (seconds) field, enter a time (in seconds) that must elapse between setpoint commands. If one is attempted before this time has elapsed since the last command, an event will be generated indicating the command will not be sent until the time period has elapsed.

9. To disable the logging of all event information relating to DRA setpoints, select the Disable Setpoint Logging checkbox. If selected, information about DRA Setpoint changes will not appear in the Event Summary.

10. In the Path column, click (...) for a given row to select a flow rate. The flow rate selected is summed (or subtracted, based on the Direction) in order to see if the product flowing past the injector meets the Minimum Flow Rate that is configured.

    Note: If you need to customize the list of the RealTime database (RTDB) tables and fields that are available to select in the Path field, you can modify the DRA Injector Configuration allowlist. For information on how to modify the allowlist, see Understand the Drag Reducing Agent Injector Configuration (DRAInjector) Allowlist.

11. In the Direction column, for each flow rate configured in the Path column, select from the dropdown list the direction of the flow rate. The Direction determines whether the flow rate selected in the Path column is added or subtracted from the flow rate total. Receiving is additive; Delivery is subtractive.

    For example, one flow rate of 200 is set up as a Receiving rate. Two flow rates of 50 each are configured as Delivery. The total flow rate in this case would be 100.

12. Optional: In the Advanced Logic Processor (ALP) column, select (...) to assign an ALP record to the configured flow rate. The evaluated result of the ALP record will then be used to determine if the flow rate of the device will be included in the total flow rate calculations.

Determining if the flow rate of the device will be included in the total flow rate calculations

For each flow rate specified in step 10 of the procedure above, the system decides whether the the flow rate of the rate record will be included in the calculation of the total flow rate, which then gets compared to the Minimum Flow Rate. This decision is based on the criteria outlined in the following table.