Thanks for replying me,below are part of the narratives for a single operation
the program should be written in ladder not function blocks
please help me with the two sections
Process Control Objective
To maintain a continuous, rated seawater flow through each Injection line.
Implementation
It is assumed that a linear flow signal is received by the input functional block, FI-901 from the turbine flow transmitter FIT-801. A reverse acting PI flow controller, FIC-801, will modulate the flow valve by an output functional block, FO-801. The electrical output of FO-801 to the valve FV-801 shall cover the full input range of 4-20 mA to I/P transducer, tagged FY-801. Other functional blocks shall be added for PI tuning, Manual/Auto selection, error calculation and gain control.
The functional block of setting the set point of FIC-801 controller receives the output signal from the Min Selector FBS-800, implemented as per template 016.
On Manual, a functional block shall be accessible to operator for manual control of flow valve, for operational and testing purposes. If the flow controller is placed into manual, to enable bumpless transfer back to auto, its output will track the flow valve. On return of control to auto mode the valve that is being tracked will ramp to its selected controlled position.
Alarms and settings where applicable are as shown on the P&ID.
Action of the valve on controller failure: FV-801 Fail Closed
Process Control Objective
To control the inlet rate seawater flow through hyper-filter during normal filtration and to isolate the hyper-filter by closing the flow valve during backwash cycle.
Implementation
During normal process, the seawater flow rate through hyper-filter is controlled by a reverse PI flow controller FIC-720 with its set point able to be driven remotely by PIC-726A. When the backwash sequence of hyper-filter is initiated, the set point value of FIC-720 will be subdued by UC-001 to closing the controlled flow valve, consequently to shut off the inlet of hyper-filter. As long the flag of backwash cycle will be active for UC-001, the flow valve will remain closed. When the flag is deleted by the batch controller UZC-720, the logic controller UC-001 will not accept another flag till it opens the flow valve, 005-FV-720, at its initial set point and mode (local or remote). The flow controller, FIC-720, shall track the flow valve position to enable the bumpless transfer on Auto. A confirmation of this transfer to UC-001 shall make this logic controller ready to receive another request of backwash cycle for the next hyper-filter.