Method for assembling a steam generator

Method for assembling a steam generator including at least a boiler steel structure, a boiler steel structure top grid having an outer and an inner top grid section, and a gas pass delimited by a boiler wall around which buckstays and header wall boxes are arranged and in which internal components are arranged, the boiler steel structure defining an inner area forming a quad, the method comprising the following steps:

• a) erecting the boiler steel structure and simultaneously preassembling assembly modules for boiler front walls and rear walls on the boiler base exterior to the boiler steel structure quad, whereby each assembly module is comprised of a self-supporting auxiliary steel structure on which are placed buckstays and header cross-ties with headers mounted thereon;
• b) hoisting the assembly modules, placing the assembly modules onto the boiler steel structure to form a steam generator assembly wherein each subsequent assembly module is placed above an upper prior assembly module of the steam generator assembly and affixed to the steam generator assembly;
• c) hoisting the outer top grid section of the boiler steel structure top grid, placing the outer top grid section of the boiler steel structure top grid on the boiler steel structure, and affixing the outer top grid section of the boiler steel structure top grid to the boiler steel structure;
• d) simultaneously with or immediately after step c), preassembling the inner top grid section of the boiler steel structure top grid on the boiler base inside the boiler steel structure quad;
• e) placing a lifting strand system having downward extending tension cables on the outer top grid section;
• f) preassembling register by register areas of the boiler wall, inserting the areas of the boiler wall into the boiler steel structure from above through the outer top grid section, and affixing the areas of the boiler wall to the outer top grid section;
• g) preassembling the internal components in a lower region of the boiler steel structure with the inner top grid section during the building of the boiler wall, subsequently hoisting the inner top grid section and the internal components with the lifting strand systems up to an installation location in an upper region of the gas pass, and connecting the inner top grid section with the outer top grid section;
• h) hoisting segments of the external support pipes onto the assembly modules if the segments of the external support pipes had not been placed on the assembly modules during step a);
• i) welding the segments of the external support pipes to each other and to any external support pipes suspended on the outer top grid section;
• j) connecting the buckstays lying free on the assembly modules to the boiler wall, connecting the header cross-ties lying free to the boiler wall and the external support pipes, and connecting the headers with the boiler wall and with the internal components;
• and
• k) subsequently dismantling the assembly modules and the lifting strand system.