17.6.2. Vertical Lift Gates
These are usually rectangular in shape and made of steel which span horizontally between guide grooves in supporting piers and move vertically in their own plane. The gates are raised or lowered by an overhead hoist and water is released by undershot orifice flow for all gate openings. Sliding gates offer large sliding friction due to water pressure and, therefore, require a large hoisting capacity. The use of wheels (along each side of the gate) would reduce the
amount of sliding friction and thereby permit the use of a smaller hoist. Vertical lift gates have been used for spans and heights of the order of 20 m and 15 m, respectively. At larger heights, however, the problem of a raised operating platform becomes important.
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