Standard Technical Features of BTG System for Supercritical 660 ...

Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Unitsii)Best efficiencypointCombined flow of 2x50%TDBFPs shall be based onTMCR requirementand corresponding head.iii) Emergency pointTwo turbine driven feedpumps to be capable ofgenerating the dischargepressure corresponding tosteam generator highestsafety valve set pressure at100% BMCR flow.Requirement ofemergency pointshall be met byMDBFP at 50Hz grid frequency.iv) Other Capabilities Combined flow of 2x50% TDBFP shall meet thefollowing:a) BMCR flow and head corresponding to ratedsteam pressure.b) V.W.O. output, 1% makeup, worst condenserpressure (MDBFP should meet thecorresponding requirement at 47.5Hz).v) Rated dischargeflow throughinterstage bleed offfor reheaterattemperationAs per 8% of maximum reheat steam flow forthe unit as a minimum.Note: Discharge flow of main pump not to include any seal flow, warm-upflow and balance drum leakage flow.15.3 Design Requirements15.3.1 Pumpsi) NPSH Margin: The ratio between NPSH (A) and NPSH (R) at 3%head drop for booster pump and main pump shall be not less than 2.5 atdesign point corresponding to lowest level of deaerator and maximumpressure drop across the suction strainer.ii)iii)iv)Trip Speed of TD-BFP: 10% above the design speed of the feed pump.Performance Curve: The characteristic curves of booster pump andmain pump should be continuously rising type with decrease in flowand shut off head shall be in the range of 115% to 130% of TDH atdesign point.Minimum Recirculation: The minimum flow of the booster pump andmain pump shall not be less than 25% of design flow. ON-OFF ormodulating type minimum recirculation valve with valve bodydesigned for about 40% of design flow shall be provided.114