6 Prefabrication
6.1 General
6.1.1 The chord length of each arc sample plate used for test shall not be less than 1.5m.The length of each linear sample plate shall not be less than 1m.The chord length of each arc sample plate intended for measuring angular deformations of the welds shall not be less than 1m.
6.1.2 All steel plates and members shall be sand blasted before prefabrication，and the derusting grade shall comply with GB/T 8293.4.
6.1.3 Prefabrication methods shall not result in damages to the base metal or deterioration of its properties.
6.1.4 Steel plate cutting and weld groove preparation shall be conducted as specified below：
1 Mechanical processing or auto/semi-auto flame cutting is preferred for carbon steel plates.Mechanical processing or plasma cutting is preferred for alloy steel plates.The surface shall be finished smooth after the cutting.
2 Shearing processing，cold gagging or cold bending shall not be applied to plain carbon steel when the ambient temperature is lower than-16℃.
3 Plate edges should not be processed by shearing when the plate thickness is greater than 10mm.
6.1.5 All grooves of steel plates shall be flat and free of any defects such as slag inclusions，delaminations and cracks.The hardened layer on the surface which is produced by the cutting of grooves by flame or plasma shall be removed.
6.1.6 Butt joints shall be applied for the welding of the absorber body.
6.1.7 The welded joints groove form and size shall be selected as specified in GB/T 985 and GB/T 986 in case no requirements are provided in design drawing.The joint forms of longitudinal seam gas shielded welding and circumferential seam submerged arc welding should be as specified below：
1 For butt joints of longitudinal seam gas shielded welding，single-sided grooves may be used if the thickness of steel plates does not exceed 24mm，and double-sided grooves should be used if the thickness of steel plates exceeds 24mm.In addition，the groove gap（G）shall be 4mm-6mm，the root face（F）shall not exceed 2mm，and the width（W）shall be 16mm-18mm（See figure 6.1.7-1）.
2 For butt joints of circumferential seam submerged arc welding，single-sided grooves may be used if the thickness of steel plates does not exceed 12mm，and double-sided grooves should be used if the thickness of steel plates exceeds 12mm.In addition，the groove angle（α）shall be 45°±2.5°，the root face（F）shall not exceed 1mm，and the gap（G）shall be 0-1mm（Figure 6.1.7-2）.
Figure 6.1.7-1 Butt joint model of longitudinal seam gas shielded welding
Figure 6.1.7-2 Butt joint model of circumferential seam submerged arc welding
6.1.8 The radian of reinforcement rings for absorber shell openings shall be the same as that of the shell.The maximum gap at any point shall not exceed 1.5mm.The fabrication of reinforcement rings shall conform to the requirements of JB/T 4736.
6.1.9 The flame cutting for bolt hole processing is prohibited.
6.1.10 All prefabricated plates or members shall mark serial codes with waterproof which should not be shown on the side requiring anticorrosion lining.
6.1.11 Effective measures shall be taken to prevent deformations，damages and rusting for all prefabricated members when being stored，transported and stockpiled on the site.All high-alloy steel plates and their parts shall be separated from other steel materials when being stored，and proper measures shall be taken to maintain surface smoothness.
6.1.12 The following documents shall be furnished together with the prefabricated members：
1 Prefabricated member list，including，as a minimum，the name，serial number，materials，specifications and quantity.
2 Material quality certificates.
3 Inspection records for prefabricated members.
4 Cutting plan.
5 Modified design documents.