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 Unitsii)iii)iv)Pressure drop in reheat steam circuit (cold reheat, hot reheat line &reheater) should not exceed 10 % <strong>of</strong> HP turbine exhaust pressure.Pipes shall be sized <strong>for</strong> the worst operating conditions (i.e. maximumflow, temperature and pressure values). In case <strong>of</strong> BFP suction piping,transient analysis shall be carried out <strong>for</strong> optimum sizing <strong>of</strong> the systemin order to establish the pipe inside diameter <strong>for</strong> minimum pressuredrop in system to match with the pump NPSH requirement under worstoperating conditions.The design pressure <strong>for</strong> BFP discharge piping up to and includingdownstream valve at feed regulating station (FRS) shall be selectedsuch that the minimum calculated thickness <strong>for</strong> various pipes at designtemperature is sufficient <strong>for</strong> the following conditions, consideringallowable stresses as per ASME B31.1:a) Discharge pressure corresponding to turbine driven BFP tripspeed at shut <strong>of</strong>f head condition, if TDBFP characteristics isgoverning <strong>for</strong> calculation <strong>of</strong> boiler feed discharge piping designpressure.b) Discharge pressure corresponding to motor driven BFP trip speed(frequency 51.5Hz) at shut <strong>of</strong>f head condition if MDBFPcharacteristics is governing <strong>for</strong> calculation <strong>of</strong> boiler feeddischarge piping design pressure.v) With feed regulating station (FRS) located at upstream <strong>of</strong> HP heatersand no isolating valve provided at inlet <strong>of</strong> economiser, the designpressure <strong>of</strong> boiler feed discharge piping at downstream <strong>of</strong> FRS shall beworked out corresponding to design pressure <strong>of</strong> the boiler. This shallbe <strong>for</strong> HP heaters provided with spring loaded relief valve(s) or havingprovision <strong>of</strong> media operated three way valves at inlet/ outlet <strong>of</strong> HPheater(s) as per approval <strong>of</strong> IBR so as to prevent BFP shut <strong>of</strong>f pressurefrom being communicated to downstream piping system and HPheaters.vi)The design pressure and temperature, down-stream <strong>of</strong> any pressurereducing valve upto and including the first block valve shall be thesame as that at up-stream <strong>of</strong> pressure reducing valve. If a pressurerelief valve is provided in the down stream <strong>of</strong> PRV, the downstreampiping shall be designed to a lower pressure as per set pressure <strong>of</strong> therelief valve.The piping at down stream <strong>of</strong> de-superheater shall be designed <strong>for</strong>spray failure condition. The length <strong>of</strong> piping system considered <strong>for</strong>spray failure condition shall not be less than the length required <strong>for</strong>proper spray mixing as recommended by de-superheater supplier.172
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