7 Flue Gas/Air Ducts，Fuel/Bulk Material Pipes and Auxiliary Equipment
7.1 General Provisions
7.1.1 This chapter is applicable to the construction and acceptance of boiler auxiliary equipments such as cold air ducts，hot air ducts，pulverized coal preparation pipes，primary air pipes，flue gas pipe，coal feed pipe，fuel（bulk material）pipes，other pipes（hereinafter referred to as flue gas ducts，air ducts and fuel/bulk material pipes），dust precipitator and so on in power plants.
7.1.2 Inspection and acceptance shall be carried out to the flue gas and air ducts，the fuel（bulk material）pipes and the auxiliary equipment prior to erection.And the following requirements shall apply:
1 The raw materials and the semi-finished products shall meet the design requirements.
2 When the equipment and materials are delivered to the site，visual examination shall be carried out.There shall be no damage，crack and rust.The overall dimensions and material inspection shall meet the design requirements.
3 The overall dimensions of the pipe processing and fabrication parts shall meet the design drawing requirements.The allowable deviation shall meet the requirements of Appendix L.
4 There shall be no pore，sand inclusion，crack or other defects in the casting parts.The surface shall be flat and smooth.
5 Inspection shall be carried out to confirm that welds in the pipes and equipment are qualified.
7.1.3 The mechanical processing method shall be used for the bolt holes of equipment and flanges.
7.1.4 The cushions shall be installed correctly on the flange connection.The bolting forces shall be evenly distributed.There shall be 2 exposed threads-3 exposed threads.The welds shall meet the requirements of DL/T 869 Code of Welding for Thermal Power Plant.
7.1.5 The internal and external sundries as well as the temporary fixing parts shall be removed in time after the erection of the pipes and equipment.
7.1.6 The nondestructive testing shall be carried out to the welds（categoryⅠandⅡ）according to the regulated proportion.
7.1.7 Pressure decay test should be carried out to inspect the tightness of flue gas/air ducts and the fuel/bulk material piping system.Pressure decay test shall be implemented according to the requirements of Article 7.4 in this Part.