Standard Technical Features of BTG System for Supercritical 660 ...
Standard Technical Features of BTG System for Supercritical 660 ...
Standard Technical Features of BTG System for Supercritical 660 ...
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<strong>Standard</strong> <strong>Technical</strong> <strong>Features</strong> <strong>of</strong> <strong>BTG</strong> <strong>System</strong> <strong>for</strong> <strong>Supercritical</strong> <strong>660</strong>/800 MW Thermal Units14.2.2 Shell shall be <strong>of</strong> rolled steel as per ASTM A-516 Gr. 70. Water box channelshall be <strong>of</strong> carbon steel as per ASTM A-516 Gr. 70 and welded to tubesheet.14.2.3 Design pressure: Tube side - CEP shut <strong>of</strong>f head at 51.5 Hz and full vacuum;Shell side - Not less than maximum extraction steam pressure with minimumdesign pressure <strong>of</strong> 3 kg/cm 2 (g) and full vacuum.14.3 Deaerator14.3.1 Deaerator shall be spray-cum-tray with integral direct contact vent condensermounted on horizontal storage tank, OR spray type with minimum two (2)spray control valves <strong>of</strong> disc type or equivalent, in order to ensure fineatomization <strong>of</strong> incoming condensate and rapid heating up by the steam.14.3.2 Design and construction <strong>of</strong> deaerator shall be as per Indian BoilerRegulations, IS 2825 or ASME pressure vessel code <strong>for</strong> unfired pressurevessels, Section-VIII or any other equivalent code.14.3.3 Anti-vortex arrangement shall be provided at discharge connections fromdeaerator.14.3.4 All pressure parts like shell, heads and nozzles shall be <strong>of</strong> carbon steel as perASTM A-516 Gr. 70. Shell shall be in welded construction with minimumplate thickness 15.8 mm. Corrosion allowance <strong>of</strong> minimum 3.2 mm shall beconsidered <strong>for</strong> the shell and dished ends.14.3.5 Hardened 400 series stainless steel impingement plates shall be provided <strong>for</strong>flashed drain inlet from HP heaters, BFP recirculation, boiler startup drainsetc.14.3.6 All water spray valves, splash plates, trays, vent condenser and otherelements in contact with undeaerated water or non-condensable gases shallbe <strong>of</strong> stainless steel 304.14.3.7 Deaerator safety valves <strong>of</strong> adequate relieving capacity made <strong>of</strong> 13%Cr. stainless steel disc and spindle shall be provided. Vent orifice shall besized <strong>for</strong> capacity equal to 0.5% <strong>of</strong> rated flow to the deaerator.14.3.8 Deaerator shall be designed <strong>for</strong> efficient steam distribution and de-aeration <strong>of</strong>condensate under all operating conditions including VWO with 1% make up,HP-LP bypass operation, HPHs out <strong>of</strong> service.14.3.9 Deaerator shall be floating pressure type. Deaerator pressure shall vary withload when it gets steam from turbine extraction. Deaerator pressure shall bepegged at 3.5 kg/cm 2 during HP-LP bypass operation, major load rejection,turbine trip and low loads when extraction steam pressure is less than 3.5kg/cm 2 . During cold start-up, the deaerator pressure shall be maintained at109
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