A method for installing a heat recovery steam generator (1) with a plurality of pre-assembled modules (10) includes arranging a pre-assembled module (10) at an installation site. The pre-assembled module (10) includes a functional unit of the heat recovery steam generator (1) housed in a casing structure (12). The casing structure (12) includes a top casing (12a), a bottom casing (12b) and a side casing (12c). An open side (15) is defined opposite to the side casing (12c). The module (10) is arranged horizontally at the installation site with the open side (15) facing downward and the side casing (12c) facing upward. The method includes attaching a structural steel (13) to the side casing (12c) in a horizontal position without lifting the module (10). The module (10) with the attached structural steel (13) is lifted to a vertical position and secured to a foundation (60). Also described is a method for pre-assembling the module (10) and a method for transporting the pre-assembled module (10) to the installation site.

Apparatus for a steam generator that employs tube support plates within a shroud that is in turn disposed within a shell. The tube support plates are made of a material having a coefficient of thermal expansion lower than that of the shroud. The tube support plates are aligned during fabrication, with minimal clearances between components. Using a tube support displacement system, a controlled misalignment is then imposed on one or more tube support plates, as the steam generator heats up. The tube support plate displacement system has only one part, a push rod, which is internal to the steam generator shroud, thereby minimizing the potential of loose parts. The tube support plate displacement system can be used to provide controlled misalignments on one or more tube support plates, in the same or varying amounts and directions, and with one or more apparatus for each individual tube support plate.

Apparatus for a steam generator that employs tube support plates within a shroud that is in turn disposed within a shell. The tube support plates are made of a material having a coefficient of thermal expansion lower than that of the shroud. The tube support plates are aligned during fabrication, with minimal clearances between components. Using a tube support displacement system, a controlled misalignment is then imposed on one or more tube support plates, as the steam generator heats up. The tube support plate displacement system has only one part, a push rod, which is internal to the steam generator shroud, thereby minimizing the potential of loose parts. The tube support plate displacement system can be used to provide controlled misalignments on one or more tube support plates, in the same or varying amounts and directions, and with one or more apparatus for each individual tube support plate.