NOVELTY - The installation has an alternator-speed multiplier system (4) fixed with a shaft of a turbine (7). The turbine, the alternator-speed multiplier system and a distributor form an one-piece assembly (E), with a support piece (E1) mounted in a removable manner on a main support and pivotingly on the support between a first position permitting withdrawal of the assembly outside the support and a second position permitting maintenance of the assembly placed in a working position of the turbine in the support and preventing withdrawal of the assembly outside the support.    USE - Hydroelectric installation for production of hydroelectric energy (claimed) i.e. hydroelectricity, from river water.    ADVANTAGE - The turbine, the alternator-speed multiplier system and the distributor form the one-piece assembly, with the support piece mounted in a removable manner on the main support and pivotingly on the support between the two positions, thus ensuring easy and rapid maintenance or standard replacement of the turbine of the installation without using any stoplogs and without any hazardous risks, drowning dangerous risks, electrocution dangerous risks and suffocation dangerous risks to a maintenance person, while reducing stopping time of the installation at maximum during maintenance. The design of the installation ensures good sealed connection between an outlet conduit or open end and the turbine without the intervention of plungers. The design of the installation ensures maintenance of the installation without completely isolating the installation and without completely setting the installation in a dry state in a simple and inexpensive manner. The design of the installation ensures easy transportation of the assembly or the turbine on a trailer without requiring any special approvals.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for maintaining a hydroelectric installation.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional perspective view of a removable assembly.    One-piece assembly (E)    Support piece (E1)    Alternator-speed multiplier system (4)    Distributor (6)    Turbine (7)