Rapid and efficient preassembling method for lower rack of large water-turbine generator set

The invention belongs to the technical field of water-turbine generator set lower rack preassembling, and discloses a rapid and efficient large water-turbine generator set lower rack preassembling method which comprises the following steps that S1, firstly, four door-shaped plates are welded in the four directions of a lower rack; according to the rapid and efficient preassembling method for the lower rack of the large water-turbine generator set, four door-shaped plates are welded in the four directions of the lower rack, namely the lower rack can be taken out of a machine pit after the four door-shaped plates are 700 mm high and 40 mm thick and cement bases are completely poured for 24 h, traditional hanging basket operation is completely transferred to the horizontal ground, the construction difficulty is greatly reduced, and the construction efficiency is improved. According to the novel preassembling method, eight axial jacks and four positions are mainly used for adjusting the level, so that adjustment