Types of spillway crest gates

Common types of crest gates

1. Vertical lift (fixed wheel / roller) gate
2. Radial (tainter) gate
3. Drum gate
4. Stoney gate (roller-train gate)
5. Flap (hinged) gate
6. Rolling (cylinder) gate

Radial (tainter) gate

A radial gate has a curved skin plate that is a section of a cylinder, supported by horizontal girders and radial arms. The arms are hinged at a trunnion pin on the piers downstream of the gate. The centre of the arc is at the trunnion, so the water thrust passes through the trunnion pin. The gate is hoisted by wire ropes or hydraulic cylinders and rotates about the trunnion.

           trunnion pin (O)
              o
             /|\   radial arms
            / | \
           /  |  \
   ~~~~~~~/~~~|~~~\  skin plate (arc)
 Water -->    |    ) <-- gate
 ___________ sill ____________
 Section through spillway pier

Working mechanism

• Closed: the skin plate rests on the sill, and seals at the sides and bottom keep the opening watertight.
• Opened: ropes attached to the lower part of the gate lift it by rotating it about the trunnion, leaving a gap at the bottom for the discharge. The gate position can be adjusted to regulate the flow.
• The water thrust is carried through the arms to the trunnion and from there into the pier; only a small hoisting force is needed because the thrust passes through the hinge (little friction).

Advantages: low hoisting force, no gate grooves in the piers, compact, good flow control. Disadvantages: the piers must be strong and long enough (in the flow direction) to carry the trunnion loads.

Vertical lift gate (for comparison)

A flat steel gate sliding or rolling in grooves in the piers, lifted vertically by a gantry hoist. It is simple, but the lifting force is large because of the friction caused by the water thrust, and grooves are needed in the piers.