In considering the repair/refurbishment of the rotating components, in addition to the blades, it is necessary to consider their possible forms. The most commonly damaged components, and those most often in need of repair are the rotor, coverbands, and tie wires.

Many stages of the steam turbine utilize either coverbands or tie wires. These two groups of components have similar, but functionally different purposes within the stage. The tie wires transmit vibratory loads developed in one element to adjacent members. By accomplishing this they dampen the magnitude of vibration of the blade, and therefore lower the stress levels to which the blades are subjected. Coverbands have a primary function of limiting the steam flow around and through the tip section of the blade. But they are also used to fulfill a secondary function, as the tie wire, of helping dampen the amplitude of vibration experienced by the blade vane.

These two groups of components, while they perform necessary functions within the stage, add some measure of complexity both to its design and means of construction. They do this by changing the natural frequencies, and by adding additional centrifugal load, which must be supported by the vane and root. When these two components are used, they require a defined method of attachment to the vanes, again possibly adding some level of design and assembly complication complexity.

These components are normally batched into discrete lengths within the row, with a specific number of blades in each. In recent designs...