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Valves and Gates

Penstock and Main Inlet Valves

The function of the penstock and main inlet valves is to isolate the unit and completely cut-off the water flow on the location where such valve is installed. The usual types of such valves are spherical valves and butterfly valves. They usually serve as a safety device and are capable of closing at the maximum water discharge.

Main inlet valves are positioned between the penstock and the turbine spiral case, while the penstock valves can be located anywhere inside the penstock.


  • Spherical valve
  • Solid-type butterfly valve
  • Lattice-type (or biplane) butterfly valve

Main features

  • Drop-tight leakage
  • Single- or double-seal design

Energy Dissipating Systems

Energy dissipating system (EDS) is designed to divert the water and serves as a turbine bypass system. EDS systems can be used either as a pressure relief valve (PRV) to mitigate a penstock transient phenomenon or as a long-term energy dissipation system used for flow ramping or maintaining the flow in the penstock system when the turbines are out of operation.

Litostroj Power is able to advise and design optimal PRV or EDS solutions based on the site conditions and ramping requirements. We have long tradition in design and installation of both systems, PRV as well as EDS valves. Our largest PRVs are installed on 80 MW Francis units as a penstock overpressure safety device.


Types of PRV and EDS valves

  • Howell Bunger
  • Plunger valve
  • Sleeve valve
  • Needle valve
  • Open/limited chamber
  • Water/air filled chamber


Main features

  • Bypass the turbine with any water flow from zero up to turbine maximum flow
  • Hydraulically or electrically connected with wicket gate regulation system
  • Simultaneous opening and closing with distributor closing/opening
  • Mitigate transient phenomenon in the water passage system during distributor manoeuvers
  • Can be used for discharge ramping at any ramping duration

Selected references and publications

Valves Brochure (2.85 MB)