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ED –Belvédère: mechanical maintenance

EDF’s Unité de Production Méditerranée [Mediterranean generation unit] engaged us to carry out mechanical maintenance works in the Belvédère plant (Alpes Maritimes), which is owned by EDF.

The plant’s horizontal Pelton turbine set is driven by water held in by the La Fous dam which captures the waters of the Gordolasque. We were asked to resolve recurrent problems with the plating of the mobile ring of the rotary valve. The functionality of the closing mechanism had not been entirely reliable since 2012, particularly in relation to requirements for lockout of turbine components. Its function as a safety mechanism for the generator set in the event of an incident increased the critical importance of the improvements to be undertaken.

We worked with EDF to establish a procedure for monitoring and delivery of the improvement works.

On-site disassembly

  • Removal of access components and making safe of the platform for access to the gate.
  • Removal of instrumentation and the removable pipe in order to access the mobile ring.
  • Removal of internal guide and automatic locking system.
  • Drilling and tapping of the mobile ring to allow full disassembly and removal.
  • Delivery of the mobile ring to our workshops in Martigny.

Expert analysis and works in the workshops

  • Manufacture of several new components and adjustment of existing parts.
  • Manufacture of a flange for testing of functionality.
  • Assembly of the mobile ring with replacement of seals and testing of functionality.
  • Delivery of the mobile ring to the site.

On-site assembly

  • Assembly of the entire mobile seal.
  • Repositioning of the downstream removable pipe and instrumentation with replacement of the pressure sensors in the plating chamber.
  • Repositioning of access components.
  • Qualification testing of the mobile ring and the operation of the rotary valve.

The expertise we have gained in the operation of hydroelectric plant and the skills of our staff enabled us to resolve all the problems encountered in this project, and our client was highly satisfied.

The Belvédère power plant

This small power plant is part of the Groupement d’Usines de la Vallée de la Vésubie which groups a number of plants of the same type, generating 220 Gwh per year.

  • 1 horizontal twin-jet Pelton turbine set
  • Commissioned 1966
  • Height of fall 556m
  • Flow 4.3 m3/s
  • Power 16 MW


HYDRO Exploitation SA
Rue de l’Industrie 10
CP 750 - CH-1951 Sion
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Rue de l’Industrie 10 CP 750 - CH-1951 Sion +41 (0)27 328 44 11
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