The VCH model hollow jet discharge valves (howell bunger type) are generally used as control and isolation valves on the discharge area at the bottom of dams.
They offer an effective solution for flow control and energy dispersion The valve design guarantees an optimal hydraulic behaviour providing stability and an absence of vibrations and cavitation without interfering with the opening level. Its energy dissipation properties are greatly appreciated and it provides a simetrical flow.
The valve consists of a cylindrical body with a flanged end upstream and a moving jacket sliding alongside the body of the valve. This sliding movement allows for a reduction or expansion of the opening generated between the jacket and the cone shaped body.
The body of the valve is provided with some internal radial nerves which are welded to the body shaft that ends up and is welded to the narrow end on the dispersing cone. As a result of the cone shape outlet, the valve expels a high speed water jet in the shape of a hollow cone.
When the water comes in contact with the air, it is pulverized and an intense dispersion of the kinetic energy takes place. Generally, these valves discharge the water directly into the atmosphere. In this case, it is possible to provide the valve with a mobile guide vane. It is also possible that the discharge should take place into a submerged medium being the downstream water level higher than the valve installation level.