Assembly of heads and shells is conducted on special beds providing the required accuracy as per the standard documents.
The company possesses welding stations of the firm ESAB, unique welding manipulators DEUMA,qualified procedures and personnel. This enables to conduct the whole welding work package during fabrication of shells,heads and transitions.
Welding of external and internal attachments is provided by machine welding in shielding gases. Argon-arc welding with non-fusible electrode,manual arc welding and automatic submerged welding are used in fabrication of the equipment. The used welding procedures have been qualified by HAKC system.Welding procedures permitting manufacturing of vessels made from a combination of materials in shell sections - single metal +bimetal – have been developed in the company.
Automatic welding of the equipment is performed by grooving in a “narrow” gap. This type of grooving in conjunction with best performance of welding and a restriction of rate of energy input enables:
- to achieve sound welded joints with high mechanical properties,
- to reduce the heat affected zone,
- to minimize demand of welding consumables.
Infrared recessed wall heaters are applied to maintain the temperature within the interval of 150°C – 500°C during preheat and intermediate heating in the process of welding.
Examination of welded joints of large-size equipment is performed in a specially equipped ?-chamber and a betatron room. Among other methods digital image radiography Phosphomatic is employed for evaluation of the welded joints quality. Full scope of destructive and nondestructive methods of examination is provided for in the Central Laboratory by qualified experts.
Column-type equipment demands full compliance with the requirements regarding straightness (deviation not more than 30 mm for 10 m shell length), roundness (deviation not more than 1% of the shell diameter) of the shell along the whole length and spacing deviation between two adjacent trays (not more than ±3 mm). For this purpose a special computer-aided laser measuring complex is used during the whole shell assembly process accompanying by welding to the shell brackets for laser beam traps.Application of the laser measuring complexes together with in- home designed and produced special rigging makes it possible to reach high accuracy while marking and assembly.