The statuses of OUT_1 and OUT_2 are determined by the statuses of BKCAL_IN_1 and BKCAL_IN_2 and the actual mode of the block.
When a BKCAL_IN input indicate that the associated downstream blocks are not in Cas mode, the Splitter function block sets the corresponding OUT value to the BKCAL_IN value. When the first downstream block is changed to Cas mode, the block upstream of the splitter block is forced to initialize such that the calculated splitter output matches the downstream block setpoint. When the second downstream block is switched to Cas mode, the difference between the calculated output and the back-calculation input is computed and the difference is added to the calculated output. Next, the difference is reduced to zero over the time defined by the BAL_TIME parameter. Select a BAL_TIME value of at least two times the RESET value in the upstream PID block to minimize process disruptions
Limit Handling
The Splitter function block is designed to combine the limit information from the two downstream blocks into limits for the upstream block. The general principle is to allow the upstream block to continue control for as long as possible.
The upstream block is high-limited (BKCAL_OUT of the Splitter block has high-limited status) when one of the following statements is true:
Both downstream blocks are high-limited (both BKCAL_INS of the Splitter block have high-limited status).
One downstream block is high-limited, the associated output slope is positive, and the other block has Bad status or is not in Cas mode.
One downstream block is low-limited, the associated output slope is negative, and the other block has Bad status or is not in Cas mode.
SP is greater than or equal to X22.
The upstream block is low-limited when one of the following statements is true:
Both downstream blocks are low-limited.
One downstream block is low-limited, the associated output slope is positive, and the other block has Bad status or is not in Cas mode.
One downstream block is high-limited, the associated output slope is negative, and the other block has Bad status or is not in Cas mode.
SP is less than or equal to X11.