Air-operated valves LCV-4025 and LCV-4026 control steam generator level for the “A” OTSG, and LCV-4007 and LCV-4009 for the “B” OTSG. The level control system for each valve receives a level input signal from a startup range OTSG level transmitter in the essential controls and instrumentation (ECI) system. This signal is compared with a level setpoint, and the resultant error signal modulates the control valve using a proportionalplus- integral controller. Manual control is available in both the main and auxiliary control room. Parallel flowpaths (one from a motor-driven pump, one from the turbine-driven pump) and redundant instrumentation and control power supplies for the level control valves ensure flow to each OTSG. Motor-operated block valves (V-14A and V-31B in the “A” OTSG supply, V-37A and V-20B in the “B” OTSG supply) provide redundant feedwater isolation of an OTSG. The turbine-driven and motor-driven pump discharge lines combine to supply the auxiliary feed ring in each OTSG. Click Here For Complete Article Text
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