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 Units21.2.5 The common secondary circulating water system shall operate in parallel tothe condenser and shall receive water through a tapping on the CW inlet line tothe main condenser. Pressure <strong>of</strong> this water shall be further boosted by a set <strong>of</strong>3x50% or 2x100% capacity secondary cooling water (SCW) pumps and fedthrough the plate heat exchangers back to the CW discharge line <strong>of</strong> the maincondenser. Alternatively, separate set <strong>of</strong> pumps basis may be provided in theCW pump house to supply secondary cooling water <strong>for</strong> PHEs <strong>of</strong> each unit.21.2.6 To prevent fouling on the secondary circulating water side <strong>of</strong> the PHE,2x100% capacity self cleaning type filters shall be provided on the circulatingwater inlet header to the PHE. The filter shall be provided with an automaticback-wash arrangement to facilitate cleaning <strong>of</strong> the choked filter while thepumps are in operation. Backwashing shall be actuated and controlled eitheraccording to differential pressure and/ or by timer. Backwash shall becollected in a sump and 2x100% capacity sump pumps <strong>of</strong> adequate capacityshall be provided <strong>for</strong> disposal <strong>of</strong> collected backwash water.21.2.7 Normal/ emergency make up to the overhead tank shall be supplied throughmotorised valve(s) interlocked to open/ close automatically with level in thetank.21.2.8 A control valve shall be provided to maintain a constant pressure differentialbetween the main supply and return headers <strong>of</strong> DM water. The valve shallbypass flow to maintain a constant return header pressure to compensate <strong>for</strong>fluctuations in coolant flow to the process heat exchangers due to modulatingcontrol valves on the process coolers or if any cooler goes out <strong>of</strong> service inDM circuit.21.3 Design Requirements21.3.1 Pumps (primary side & secondary side)i) The pumps shall be <strong>of</strong> horizontal centrifugal type provided with closedtype impeller and axial split casing.ii)The pumps shall be designed as per requirements <strong>of</strong> Hydraulic Institute<strong>Standard</strong>s (HIS), USA.iii) The pumps shall have stable head- capacity characteristic with headrising continuously towards the shut <strong>of</strong>f. The shut <strong>of</strong>f head <strong>of</strong> the pumpshall be in the range 115-130% <strong>of</strong> the rated head. The powercharacteristics shall be <strong>of</strong> non-overloading type.iv)The pumps shall be suitable <strong>for</strong> continuous operation and shall operatesatisfactorily in the range 40% to 120% <strong>of</strong> the rated flow.v) The pump shall be driven by constant speed squirrel cage inductionmotor with speed not exceeding 1500 rpm (synchronous).190
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