Gates and valves
This chapter deals with the gates and valves used in spillways and in bottom outlets. The construction of gates originated in the works of irrigation, water supply and inland navigation. The excess water was discharged over the dam. Then mobile dams were built, that is to say, dams with gates, which could be moved, opened, to give way to excess water, allowing greater flexibility of operation to the hydraulic works. Controlled spillways are normally provided with gates, including the bottom outlets. The malfunction of gates, valves, lifting equipment, can result from: displacement of the structure; corrosion and aging; misalignment of parts; insufficient lubrication; improper operating procedures; lack of energy; faults in the electrical circuits. The bonneted sliding gates are usually used to regulate the flow through the outletworks of dams. They are completely encapsulated and are designed and manufactured to be embedded in concrete.