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 Unitscold condition or as per the recommendation of TG supplier to ensurethat there is no transfer of undesired pipe weight/ load on the turbinevalves/nozzles.ii)iii)All pipes hangers and supports shall be designed to carry the weight ofthe piping, fitting, thermal insulation, self weight of the hangerassembly and medium transported or test medium whichever isheavier. In addition, all rigid rod hangers and variable spring shall bedesigned to carry the operation load in hot condition.Design and Manufacture of hangers and supports shall conform toANSI B 31.1, MSS-SP-58, MSS-SP-89.18.1.11 Metallic expansion jointsi) The expansion joints shall be of metallic multi-bellows constructionand shall be used to reduce the reactions (forces and moments) at theconnected equipment terminals due to thermal expansion/contractionand/or vibration of connected equipment and piping.ii)Expansion joints shall comply with the currently applicablerequirement of EJMA, Boiler and Pressure Vessel Code Section III,ANSI B-31.1 and all statutes, regulations and safety codes.18.1.12 Chemical cleaning of piping systems and equipmentsi) The following piping system shall be cleaned chemically:a) Boiler feed discharge pipingb) Heater drains pipingc) Main condensate pipingd) Extraction steam pipingii)The following equipments which form a part of the above system shallalso be included in the cleaning operation as per OEM’s provenpractice:a) HP Heatersb) LP Heatersc) Deaeratord) Gland steam condensere) Drain cooleriii) Before introducing chemicals, all the piping systems and equipmentlisted above shall be water flushed. Water flushing will be followed byalkaline cleaning, acid cleaning and passivation or by EDTA (EthyleneDiamene Tetra Acid) and passivation.iv) Strict safety precautions shall be exercised at all times during thechemical cleaning and during storage and handling of the chemicals.Protective clothing, apparatus and equipment alongwith necessary firstaid kits as required shall be envisaged for handling the chemical andfor carrying out the cleaning operation.179
Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units18.1.13 Steam blowing of piping systemsi) The following piping systems shall be cleaned through steam blowingoperation:a) Main steam, HRH, CRH, HP bypass & LP bypass piping.b) Auxiliary steam piping including TG gland sealing lines.c) Steam lines feeding turbines of boiler feed pumps.ii)iii)Steam blowing shall be carried out for removal of particles (rust,scales, weld splatter etc.) from various piping systems to avoid damageto turbine bladings. Cleanliness of system shall be checked by meansof test plates made of steel, which will be installed in the centre line ofthe piping system.Cleaning shall be achieved by steam purging i.e. by blowing of steamthrough the piping such that the momentum of flow is greater than thatof steam flow during normal operation of unit (at TMCR). Thedisturbance factor during steam blowing (ratio of momentum of flowduring purge to that during TMCR) shall be more than 1.4.18.2 Control Valves18.2.1 General requirementsi) The control valves shall comply with the latest applicable requirementsof code for pressure piping ANSI B 31.1, the ASME Boiler & pressurevessel code, Indian Boiler Regulation (IBR), ISA as well as inaccordance with all applicable requirements of the FederalOccupational Safety and Health Standards, USA or acceptable equalstandards.ii)iii)iv)The control valve sizing shall be suitable for obtaining rated flowconditions with valve opening at approximately 80% of total valvestem travel and minimum flow conditions with valve stem travel notless than 10% of total valve stem travel. All the valves shall becapable of handling at least 120% of the required rated flow. Further,the valve stem travel range from minimum flow condition to rated flowcondition shall not be less than 50% of the total valve stem travel.The sizing shall be in accordance with the latest edition of ISA oncontrol valves. The valves port outlet velocity shall not exceed 8 m/secfor liquid services, 150 m/sec. for steam services and 50% of sonicvelocity for flashing services.Valve body rating shall meet the process pressure and temperaturerequirement as per ANSI B16.34.All control valves shall have leakage rate as per leakage Class-IV.180
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Standard Technical Features of BTG System for Supercritical 660 ...

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