Appendix E-2.c.i Energy Plan 2004-2013 Follow-up Studies and ...

1.1 Main Steam
Re-powering Study for the Northport and Port Jefferson Power Stations
Appendix II Northport System Descriptions
1 System Descriptions for Hybrid Option
Refer to PID-03-1A and 03-1B in Appendix III.
1.1.1 Main Flow Path
The Main Steam system conveys superheated steam from the HP superheater outlet of each HRSG to the
steam turbine via the turbine main steam trip and control valves. The HRSGs supply main steam within
the pressure and temperature limits required by the turbine design.
Inside each HRSG boundary, the HP superheater contains an attemperator which uses HP feedwater to
provide temperature control and maintain the HP superheater outlet temperature.
Isolation of each HRSG from the main steam system header, in the Northport Hybrid Option HRSG
configuration, is provided by a stop-check block valve located near the header. The turbine main steam
trip and control valve provides positive isolation of the steam turbine from the main steam system.
The Main Steam System also supplies steam to the steam turbine gland seals during startup. A pressure
reducing valve and spray desuperheater is provided in the line to this service to lower the steam pressure
and temperature to match the ST manufacturers’ requirements.
Low point drain pots are located in the system in accordance with ASME TPD, “Recommended Practices
for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation”.
Depending on the location, low point drains are directed to either the condenser or the atmospheric
blowoff tank associated with each HRSG.
1.1.2 Bypass Flow Path
The main steam bypass flow path provides the means to convey main steam from each HRSG to the cold
reheat system via a main steam bypass conditioning valve station. During normal load operation, the
main steam by-pass valves are shut. The bypass station permits main steam generated in each CT/HRSG
set to be removed during normal CT startup, normal shutdown, steam turbine trip, or when the steam
turbine is removed from service.
The conditioning valve controls main steam pressure by bleeding off main steam, reducing its pressure
and temperature to match the operating parameters of the cold reheat steam system. The conditioning
valve controls the temperature of the outlet by spraying HP feedwater at a controlled rate to match the
cold reheat steam temperature.
1.2 Cold Reheat
Refer to PID-03-02A in Appendix III.
The Cold Reheat Steam System directs the high pressure steam turbine exhaust to each HRSG reheat inlet
header. In the case of the Northport 4 Option, the cold reheat steam line from the steam turbine joins into
a common header, which then splits into branches, one to each HRSG reheater inlet.
For this option, a non-return valve is provided in the cold reheat line to prevent backflow into the high
pressure turbine. This valve protects the turbine when the main steam system is bypassed to the cold
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