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AVEVA Pipeline Operations for Liquids

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Define Return-to-Normal Deadband

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  • Last UpdatedJul 04, 2024
  • 3 minute read

The Return-to-Normal Deadband Percentage (or RTN Deadband %) column can be used to specify when the system should return to normal after a deviation alarm. There are two types of limit alarms, the Volume Over Limit alarm and the Volume Short Limit alarm.

Volume Over Limit

After a Volume Over Limit alarm has been raised due to the volume deviation going above the specified value X, the system does not raise a Return-to-Normal (RTN) alarm until the volume deviation reaches or goes below X ´ RTN Deadband %.

Volume Short Limit

After a Volume Short Limit alarm has been raised due to the volume deviation going below the specified value X, the system does not raise a Return-to-Normal alarm until the volume deviation reaches or goes above X ´ RTN Deadband %.

Note: If the RTN Deadband % value is set to 0, the system will not apply any deadband to the limits.

There are three behavioral cases depending on the Alarm Type configured for each term:

Case A: When the Alarm Type is set to Volume

After a Volume Over Limit alarm has been raised due to the volume deviation going above the specified value X, the system does not raise a Return-to-Normal alarm until the volume deviation drops below X ´ RTN Deadband %.

Example 1—If the Over Limit alarm is configured at 200 m³ and the RTN Deadband % is configured at 15%, then:

  • A Volume Over Limit alarm is raised when the volume delta > 200 m³.

  • A RTN alarm is raised when the volume delta £ 30 (calculated as 200 ´ 15%).

Example 2—If the Over Limit alarm is configured at 200 m³ and the RTN Deadband % is configured at 100%, then:

  • A Volume Over Limit alarm is raised when the volume delta > 200 m³.

  • A RTN alarm is raised when the volume delta £ 200 (calculated as 200 ´ 100%).

After a Volume Short Limit alarm has been raised due to the volume deviation going below the specified value X, the system does not raise a Return-to-Normal alarm until the volume deviation goes above X ´ RTN Deadband %.

Example 1—If the Short Limit alarm is configured at -200 m³ and the RTN Deadband % is configured at 15%, then:

  • A Volume Short Limit alarm is raised when the volume delta < -200 m³.

  • A RTN alarm is raised when the volume delta ³ -30 (calculated as -200 ´ 15%).

Example 2—If the Short Limit alarm is configured at 200 m³ and the RTN Deadband % is configured at 100%, then:

  • A Volume Short Limit alarm is raised when the volume delta < -200 m³.

  • A RTN alarm is raised when the volume delta ³ -200 (calculated as -200 ´ 100%).

Case B: When the Alarm Type is set to Flow Percent

The logic explained in Case A applies to the Flow Percent limit.

Example 1—If the Over Limit alarm is configured at 10% and the RTN Deadband % is configured at 15%, then:

  • A Volume Over Limit alarm is raised when the Flow Percent calculated using the volume delta > 10%.

  • A RTN alarm is raised when the Flow Percent £ 1.5% (calculated as 10% ´ 15%).

Example 2—If the Short Limit alarm is configured at -10% and the RTN Deadband % is configured at 15%, then:

  • A Volume Short Limit alarm is raised when the Flow Percent calculated using the volume delta < -10%.

  • A RTN alarm is raised when the Flow Percent ³ -1.5% (calculated as -10% ´ 15%).

Case C: When the Alarm Type is set to Switching

The logic explained in Case A and Case B applies depending on whether the system is using Volume limits or Flow Percent limits.