Flow Network example: Switching a device from Low Mode to High Mode

The following example illustrates the violation checks that take place when a Controller attempts to switch a device in a Protected Location from Low mode to High mode.

Setup

"Acceptance Testing Flow Network 1 Overview" seen below is the parent network, while "Acceptance Testing Station 1" is a nested Flow Network corresponding to "Station One".

Acceptance Testing Flow Network 1 Overview

Acceptance Testing Station 1

Nesting of Child Station within Parent Station

The upstream tank "AT_FNET_N1_S1_T2" is currently emptying (see Upstream Tank belonging to Child Flow Network (tank is emptying)). Meanwhile, the downstream tank "AT_FNET_N1_T1" is currently filling (see Downstream Tank belonging to Parent Flow Network (tank is filling)).

Upstream Tank belonging to Child Flow Network (tank is emptying)

Downstream Tank belonging to Parent Flow Network (tank is filling)

The child Flow Network is associated with the Protected Location "AT_Protected_Fnet2".

Note: Refer to the following in regards to the "AT_Protected_Fnet2" protectedLocation record (see Status Points associated with the Child Flow Network figure):

• The Mode Detector – the status point used to switch the Protected Location between higher and lower operating intensities – is "ATLM_STATUS_TEST_POINT_02".

• The valve represented by the status point "AT_FNET_N1_S1_V01" is configured as one of the points that the Low Mode application monitors for a high mode violation condition.

Status Points associated with the Child Flow Network

Controller Actions

The Controller attempts to switch the status point "ATLM_STATUS_TEST_POINT_02" from the closed state to the open state (see Attempt to switch Protected Location into High Mode).

As mentioned in Setup, "ATLM_STATUS_TEST_POINT_02" is the Mode Detector for the child Flow Network "Acceptance Testing Station 1".

Attempt to switch Protected Location into High Mode

The following Command Interlock dialog appears:

Note: For analog points, the message on the Command Interlock dialog indicates the value below which the point must drop in order to exit the violation condition.

While the Controller could override the warning, he or she chooses to bring the status point "AT_FNET_N1_S1_V01" out of the state that resulted in the violation. To this end, they switch the valve represented by status point "AT_FNET_N1_S1_V01" to the OPEN state.

Fixing of Violation Condition

Then they attempt to switch the status point "ATLM_STATUS_TEST_POINT_02" from the closed state to the open state.

Second Attempt to switch Protected Location into High Mode

The following Command Interlock dialog appears:

The new violation messages are a result of violations detected further downstream after the first violation (see the above figure, Command Interlock dialog) was corrected by the Controller. The Controller repeats similar steps as above to bring the various points out of the states that resulted in the violations. When no more violation conditions exist at the depth searched as per the configured Station Search Depth, the Controller can successfully switch the status point "ATLM_STATUS_TEST_POINT_02" from the closed state to the open state (see Attempt to switch Protected Location into High Mode).

Successful Attempt to switch Protected Location into High Mode