Jacob H. Douma
Could you discuss these various types of gates and why they're chosen, the pros and cons
of the various types?
A:
A tainter gate is a very simple gate. It should be used in the open and shouldn't have any
water flowing over the top. When the gate is closed, no water flows underneath. When
releasing water over a spillway or into a flood tunnel, the gate is raised and water flows
underneath with very little gate vibration. Tainter gates should not be operated with large
flows over the top of the gate because that causes excessive gate vibration.
I was on a consulting board for a large dam in Puerto Rico where that had three tainter
gates on top of the crest. Unfortunately, a large storm made the water level rise quite
suddenly and water started over the top of the gates which were closed. The operator
started opening the gates, but they got jammed part open. The storm developed into a
hurricane that caused large flows over the gates from many hours. The gate vibration
caused all three gates to fail. The consulting board studied the problem and recommended
what should be done to repair the damage.
Now a roller gate. A roller gate is something used on the crest of a dam. It's round like
a drum, so that water can go over the top. Structurally, it's stronger because it's a solid
body. Large flows can go over the top without producing excessive gate vibration.
Primarily, though, the gate is lifted and large flows go underneath.
What other kind of gate did you want to talk about?
Well, the vertical lift gate.
A:
Those are used on spillway crests, also. When they're closed, they sit on the crest. When
the reservoir water level rises above the spillway crest, the gates are raised so water flows
underneath the gates and over the spillway. Water should never flow over the top of
vertical lift gates.
Tainter gates are 10 to 20 feet high, but they may be 30 to 60 feet wide. The vertical lift
gates are the other way around; they're not more than about
or 20 feet in width, but
they can be 40 to feet high.
gates are more economical for wide spillway bays
and vertical lift gates are more economical for narrow spillway bays.
So the selection of the gate is based on the basic overall design of the project.
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