The rated output of the turbine at its design operating conditions determines which subheading applies. Turbines rated above 40 MW fall under 840681, while those rated at or below 40 MW fall under 840682. Importers should ensure the manufacturer's technical specification clearly states the rated output, as this is the primary classification criterion for non-marine units.

Yes, parts specifically designed for steam and vapor turbines — including blades, rotors, casings, and nozzle assemblies — are classified under 840690, provided they are not more specifically covered elsewhere. The key test is whether the part is identifiable as suitable for use solely or principally with the turbines of this heading.