Chapter 6
Gates and valves
6.1 General
Although this chapter deals mainly with gates and valves used in dam
engineering some parts of its text have a wider or special application, e.g.
gates used in river engineering at weirs and at tidal barrages and surge
protection works.
The main operational requirements for gates and valves are the
control of floods, watertightness, minimum hoist capacity, convenience of
installation and maintenance and above all failure free performance and
avoidance of safety hazards to the operating staff and the public. Despite
robust design and precautions, faults can occur and the works must be
capable of tolerating these faults without unacceptable consequences.
Gates may be classified as follows:- position in the dam – crest gates and high-head (submerged) gates
and valves; - function – service, bulkhead (maintenance) and emergency gates;
- material – gates made of steel, aluminium alloys, reinforced concrete,
wood, rubber, nylon and other synthetic materials; - pressure transmission – to piers or abutments, to the gate sill, to the
sill and piers; - mode of operation – regulating and non-regulating gates and valves;
- type of motion – translatory, rotary, rolling, floating gates, gates
moving along or across the flow; - moving mechanisms – gates powered electrically, mechanically,
hydraulically, automatically by water pressure or by hand.
Because of the variety of criteria many gate and valve designs are in
use; only the salient features of some of the more important types can be
dealt with here.