Abstract: A process for sealing the rotor of a turbine which uses wet geothermal steam under pressure in which the said rotor is provided with a plurality of adjacent labyrinth sealing rings interposed with passages which extend radially of the rotor itself. The process provides at least one step in which a flow of steam is introduced into one of the said radial passages and made to pass through the labyrinth of at least one of the said sealing rings, being throttled with a drop in pressure and reduction in temperature. The portion of steam which has been throttled is collected through another of the said radial passages and exhausted or recycled to the turbine at an intermediate stage having the same pressure as the steam. The pressure and temperature values reached by the steam after throttling are such as to maintain it in a wet state. In this way, as the steam always stays wet, the salts in the original geothermal steam remain dissolved and are not deposited, thus allowing the seals to operate correctly.