7.7　Assembly of Roof Plates

7.7.1　All roof plates shall be symmetrically assembled based on the equal diversion lines.

7.7.2　The off-set of butt welds shall not exceed 1.2mm when roof plates are assembled.

7.7.3　The permissible deviation of diameter shall be 0.1% of the nominal diameter，and not exceed 12mm after roof plates are assembled.

7.7.4　The permissible deviation of mounting elevation for the absorber roof shall not exceed 10mm，and the off-set of the center shall not exceed 20mm.

7.7.5　The permissible deviation of the distance between stiffeners shall be 6mm.

7.7.6　Properly arranged draining measures are required for the absorber roof so that the roof plates will be capable of preventing water accumulation on the roof after the assembly.