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 Unitse) Maximum allowabletube metal skintemperaturef) Maximum depth <strong>of</strong> tubebanks/ sections in theii) Minimum tube thickness at the bendsin no case shall be less than theminimum tube thickness <strong>for</strong> thestraight tubes calculated aboveincluding erosion allowance. For thispurpose appropriate thinningallowance shall be considered whilecalculating the thickness <strong>of</strong> the bends.Oxidation limit <strong>for</strong> the tube metal.2.5 m or maximum soot blowing radiuswhichever is lower.direction <strong>of</strong> gas flowg) Thermal shock aspect The economiser shall be suitablydesigned to take a thermal shock <strong>of</strong>sudden change <strong>of</strong> feed water temperaturefrom rated value to approximately 140 0 Cduring HP/LP bypass operation.ii) Construction <strong>of</strong> economizer shall have following features:a) Economiser shall be bare tube and inline type, arranged <strong>for</strong> counterflow <strong>of</strong> feed water and flue gases in case <strong>of</strong> two pass boiler andparallel cross flow <strong>of</strong> feed water and flue gases in case <strong>of</strong> tower typeboiler.b) Economiser shall be fabricated from seamless tubes complete withspacers and supports etc. to facilitate erection at site.c) Minimum 3.0 mm thick stainless steel erosion shields shall beprovided <strong>for</strong> leading tubes <strong>of</strong> each tube bank <strong>of</strong> economizer. Inaddition minimum 5.0 mm thick sturdy cassettes baffles shall beprovided <strong>for</strong> all front side and rear side bends <strong>of</strong> the economizerbanks. The cassette baffles shall cover complete bends andadditional 300 mm straight tube length.d) Economiser shall be supported by steam/ water cooled hangertubes/headers <strong>for</strong>ming part <strong>of</strong> steam circuit with hanger tubesdesigned <strong>for</strong> a minimum <strong>of</strong> 2 times the calculated load so as not tocause any dislocation/damage to the tube banks/ sections.e) Economiser shall be provided with minimum 50 mm clear sidespacing (gas lane), with proper barriers installed, to avoid gaslaning.f) Economiser shall be without any valve in the pipeline from theeconomizer outlet to evaporator section <strong>of</strong> steam generator.43
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