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 Units19.1 PurposeCHAPTER - 19STEAM TURBINE HP-LP BYPASS SYSTEMThe HP and LP turbine bypass system is envisaged to be used <strong>for</strong> thefollowing functions:i) To enable boiler and turbine to be operated independent <strong>of</strong> each otherduring start-up and shutdown.ii) To enable in quick reloading <strong>of</strong> the unit following a turbine trip.iii) To quickly open to relieve the system from high steam pressure in theevent <strong>of</strong> generator breaker opening/ turbine tripping as well as duringlarge load throw-<strong>of</strong>f.iv) To reduce starting and loading time <strong>of</strong> steam generator.v) For house load operations.19.2 General Requirements19.2.1 A HP bypass system shall be provided between MS and CRH and shall haveaggregate capacity not less than 60% <strong>of</strong> the main steam flow at BMCRcondition considering main steam parameters at the upstream <strong>of</strong> valves &CRH steam parameters corresponding to 60% TMCR condition on thedownstream side. The HP bypass system shall have minimum 2x50%capacity valves. In addition the aggregate capacity <strong>of</strong> HP Bypass valves shallbe adequate to evacuate the required minimum steam flow from the boilerunder various start- up conditions (viz. cold/ warm/ hot start ups).19.2.2 LP bypass shall be provided between HRH and condenser and shall bedesigned to condition the incoming steam from re-heater corresponding toparameters resulting from operation <strong>of</strong> HP bypass as stated above, toparameters matching with those <strong>of</strong> LP Turbine exhaust steam. The valvecapacity shall be commensurate with that <strong>of</strong> HP bypass system plus the spraywater used in HP bypass. Number <strong>of</strong> LP Bypass valves shall be as permanufacturer’s standard practice subjected to a minimum <strong>of</strong> two (2)numbers.19.2.3 Seat tightness <strong>of</strong> the HP and LP bypass valves shall be equivalent to leakageClass V con<strong>for</strong>ming to ANSI/FCI 70-2.19.2.4 HP bypass station spray water requirement shall be provided from Boilerfeed pumps discharge & LP bypass spray water requirement shall beprovided from condensate extraction pump discharge.185
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