Main Turbine Sealing Steam - 1 Flashcards
What does the MT Sealing Steam provide steam to?
a. Reactor Feed Pumps - Turbine shaft , Control and Stop Valves
b. HP and LP Turbine shafts
c. Bypass Valves
d. Main Turbine Stop Valves
e. Main Turbine Control Valves
f. Combined Intermediate Valves
Where does the Steam Seal Evaporator get its heating steam?
Main steam from near the bypass line or from extraction steam
Is there another source of steam to the MT sealing steam system other than comes from the Steam Seal Evaporator?
Yes, Aux steam can be applied directly to seals
What occurs on a SSE drain tank high level condition?
- LIC-2004 will open LV-2004 and drain the tank to the main condenser. LV-2004 will close once level is returned to normal
- LV-200495(Steam Seal Evaporator Drain Tank Alternate Level Control Valve) will throttle open to control drain tank level
What occurs on a SSE shell side high level condition?
HV-2013 the shell side make-up isolation valve will automatically close
Describe the starting sequence of the steam packing exhaust fan.
START - When momentarily depressed, the fan discharge valve will open. Once the valve is partially open the fan will start.
What interlocks are associated with the steam packing exhaust fans?
The fan will not start until its discharge valve is partially open.
What cools the Steam Packing Exhauster Condenser and where does any condensed steam drain too?
Steam Packing Exhaust Condenser is cooled by condensate and drains to the condensate drain tank via a loop seal
What is the normal supply pressure for the sealing steam supply header?
4 psig
Where does MT Sealing steam exhaust too?
a. Main Condenser
b. Feedwater Heaters 3A, 3B, 3C
c. Cross Around Piping
d. Steam Packing Exhauster Condenser
What is the danger of operating with a vacuum in the condenser without sealing steam in operation?
Thermal stress from pulling cold air accross the hot turbine rotor shaft. Never shutdown the Main Turbine Sealing Steam System while there is vacuum in the Main Condenser
What is the series of events that occur in the MT Sealing Steam system when a turbine trip occurs?
the AIR RELAY DUMP VALVES,(Main Turbine EHC System) lose EHC emergency trip oil pressure -> DUMP VALVES REPOSITION -> BLEEDER TRIP VALVES VENT-> BLEEDER TRIP VALVES CLOSE when normal flow stops or if reverse flow occurs
What conditions must be met for the MT Sealing Steam bleeder valves to open?
they will receive an open signal from instrument air when the turbine is reset and extraction steam pressure is 5 psig above the modulated value of evaporator main steam supply pressure.
When does extraction steam take over supplying the steam seal evaporator condensor?
When the extraction steam pressure is approximately 5 psig above the main steam supply pressure
What happens to the bleeder trip valves in the MT sealing steam system on a turbine trip and why?
They shut to stop steam flow from the 4 FWH to the tube side of the seal evaporator condenser.
When turbine trip occurs the pressure in the FWHs will lower. If they were still connected to the evaporator condenser than the tube side of the condenser would flash to steam and draw steam from the turbine contributing to a possible overspeed condition.
