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

Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Unitsextraction from CRH line, the maximum expected HPT exhaust pressureshall also be taken into account.14.5 Flash Tanks14.5.1 The flash tanks shall be provided receive the drains and safety valveconnections from various equipments and systems. These, as a minimum,shall include Unit flash tank, turbine drain flash tanks (left & right), HP drainflash tank and LP drain flash tank.14.5.2 The drains shall be connected to the flash tanks via headers which shall begraded according to the pressure, the farthest from the tank being the drainconnection with highest pressure. The arrangement for connection of variousdrains to the flash tanks shall be as under:i) The drains from MS piping and HP bypass piping including warm upline shall be connected to unit flash tank.ii)iii)The turbine integral and power cycle drains shall be connected toturbine flash tanks with left side drains connected to left side flash tankand right side drains to the right side flash tank.The drains from CRH, HRH, LP bypass piping including warm-up line,extractions to HP heaters, CRH and auxiliary steam to BFP turbine anddeaerator (high pressure side) and drain, vent and safety valveconnections on HP heaters shall be led to the HP flash tank. The drainsof extractions to LP heaters, IP extractions to BFP turbine, BFP turbineintegral system, CRH to BFP turbine and deaerator (low pressure side),auxiliary steam header, drain, vent and safety valve connections of LPheaters and drain coolers, deaerator overflow and CEP discharge ventshall be led to the LP flash tank.The alternative scheme/ arrangement for connection of drains to differentflash tanks as per standard proven practice of OEM shall be acceptable.14.5.3 Flash tanks shall be designed as per the requirement of ASME boiler andpressure vessels (B&PV) codes, and ANSI standard. The design pressure andtemperature for the pressure vessels (except bellows) to be designed shall be3.5 kg/cm2 and 215 0 C respectively. Flash tanks shall also be designed forfull vacuum condition.14.5.4 Corrosion allowance of 3 mm shall be added to the design thickness of theshell and head of the vessels. The minimum thickness of the vesselsincluding corrosion allowance shall not be less than 8 mm.14.5.5 The Shell, head, wear plate/ baffles shall be made of ASTM 285 Gr. C orequivalent material. The material of nozzle neck shall be ASTM A 106 Gr. Bor equivalent.111