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

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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Unitsxi)Minimum tube thickness at the bends in no case shall be less than theminimum tube thickness for the straight tubes calculated in the mannerdescribed above. For this purpose appropriate thinning allowance shallbe considered while calculating the thickness of the bendsxii) In case water wall orifice are provided, these should be supplied withindexing holes and index pins.xiii) Other Provisionsa) Provision for future installation of additional soot blowers shall bemade in the furnace so that after commissioning of each unit, thesame can be installed, if the operational experience warrants thesame. For this purpose the furnace construction shall preferably beprovided with wall box openings. Necessary space provision inlayout for providing approach and platform for future soot blowersshall be kept in the original design so that same can be installedwhenever the future soot blowers are required. The loads for theseplatforms shall be considered in the boiler structure design.b) Erosion resistant shields shall be provided for tubes/ headeraffected by gas impingement/ laning effects (e.g. in a betweenSH/RH, economizer and furnace walls openings for economizerbypass etc.).c) Tapping points at five levels shall be provided for furnace vacuummonitoring (in addition to routine monitoring).d) All around seal plates of stainless steel type 430 or better (6-mmthick minimum) welded to furnace hopper for sealing against airingress.e) Panel to panel welding in burner zone may be avoided to maximumpossible extent.f) Evaporator section shall be provided with sufficient number oftemperature probes for metal temperature measurement as perstandard and proven practice of the OEM. A suggested criterionfor the same is to provide one temperature probe for every threeconsecutive tubes.g) Stainless steel expansion markers/ indicators shall be provided onall four furnace walls to monitor thermal expansion and predictedthermal expansion at different levels shall be indicated.6.5.4 Steam separator(s)i) Design Code IBR.35
Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Unitsii) Design Temperatureiii) Design PressureMaximum fluid temperature plus margin as perIBR.1.05 times the maximum operating pressure oras required by IBR/ other international codes,whichever is higher.6.5.5 Boiler startup recirculation and drain water systemi) Boiler start-up recirculation & drain system shall be provided with startupdrain re-circulation pump and alternate drains shall be led toatmospheric flash tank or directly to turbine condenser. 2x50%condensate pumps shall be provided for pumping the atmospheric flashtank condensate to turbine condenser. Necessary control valves shall beprovided in the condensate line for maintaining the level in the flashtank/ drain receiving vessel.ii)The start-up recirculation & drain system shall comply with followingdesign requirements:a) Designed for fast start-up with and without the recirculation pumpsand cyclic load operation of Steam Generator.b) Designed for maximum possible recirculation & drain flow under allpossible normal, abnormal, upset and accidental conditions. Thedrain piping, valves, flash tank, drain receiving vessel andcondensate pumps shall also be sized to cater to this.c) Start up recirculation & drain piping and its supports shall bedesigned to take care of excessive vibration, which may result fromtwo phase flow conditions, if it occurs.d) The start-up drain re-circulation pumps shall be of proven design.Boiler start-up drain recirculation pumps and their motors shall meetthe following requirements:1. Number ofpump2. Type ofpump3. Motorspecification1x100% (sized for maximum flow as specifiedabove).Glandless zero leakage type with overhungimpeller.Submerged type with wet stator with watercoolers. Motor for steam generator start uprecirculation pump shall be a wet motor,specifically designed by the pump manufacturerfor the application and shall be as per thestandard adopted by the pump manufacturer.Motor windings shall be of non-hygroscopicmaterial and shall be designed to withstandcontinuous water pressure & temperaturevariation.36
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Standard Technical Features of BTG System for Supercritical 660 ...

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