8.2　Flue

8.2.1　The center base lines and elevation base marks of the flue shall be surveyed and put on the platforms of all levels to be equipped with flues，and the installation accuracy of the whole flue and all of its sections shall be controlled.

8.2.2　Prior to installation，the following requirements shall be complied with:the finned tube of flue shall be complete with the qualified certificate for ball-passing test by the manufacturer，the header shall be free of sundries，the tube orifice shall be unobstructed and the fins shall be free of any weld crack.

8.2.3　The flues shall be paired and butt welded in accordance with the following requirements:

1　Every piece of water cooling tube shall be checked to be free of sundries and blocking.

2　The oil，paint，dirt，rust and burr shall be completely removed from the area not less than 10mm away from the groove and the surfaces of both sides.

3　The pipe axle of all water cooling pipes shall be aligned.The unfitness of internal wall should be less than 10% of the wall thickness and the clearance shall comply with the welding procedure requirements.

4　The joint shall be argon arc welded.Prior to welding，the corresponding WPQ shall be carried out and the operation instruction for welding shall be prepared based on the WPQ report.The welding shall be carried out in strict accordance with the instruction.

5　The butt joints with small clearance should be welded in the way of symmetry welding at first.

6　The quality，inspection method and inspection quantity of weld shall meet the requirement of the design technical document，or related requirement for boiler installation in the current national standards in case of no requirement in the design technical document.

8.2.4　The flues shall be installed according to the following requirements:

1　The lower part of flue to be connected with the removable hood should be installed at first，and then the other parts be continuously installed from downward to upward in sections.

2　The longitudinal and horizontal center lines shall be adjusted，and the measurement by plumb wire should be carried out，with the allowable deviation of 5.0mm.

3　The elevation shall be adjusted，and the measurement by optical instrument should be carried out，with the allowable deviation of±5.0mm.

4　The verticality shall be adjusted，and the measurement by suspension wire should be carried out，with the allowable deviation of 1.0/1000.

5　The concentricity of flange joints shall be adjusted，and the measurement by ruler should be carried out，with the allowable deviation of 2.0mm.

6　The parallelism of flange joints shall be adjusted，and the measurement by ruler or feeler gauge should be carried out，with the allowable deviation of 1.5/1000（3.0mm for the overall length）.

8.2.5　The support and hanger structure of flue shall meet the requirement of the design technical document.The support and hanger should be erected prior to the lifting of flue，and shall be adjusted and positioned at the design position after completion of flue installation.They shall be installed and tightly contacted with the flue.The sliding support and hanger shall be able to smoothly slide in the direction specified in the design，while the spring support and hanger shall be subject to precompression as required in the design.