--- title: "Types of spillway crest gates" subject: "Hydropower Engineering" chapter: 4 key: "semester_7/hydropower_engineering:spillway-crest-gate-types" source: https://www.bctengineer.com/q/semester_7/hydropower_engineering/spillway-crest-gate-types site: BCT Engineering --- # Types of spillway crest gates Hydropower Engineering · Chapter 4: Headworks of Storage Plants - Asked in: 2082 Bhadra, 1+3 marks; 2070 Chaitra, 1+3 marks (asked 2 times) - Video: [Types of Spillway gates](https://www.youtube.com/watch?v=LTlnwFvHShY) — WIT Solapur - Professional Learning Community - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/hydropower_engineering/spillway-crest-gate-types - Whole chapter: https://www.bctengineer.com/md/semester_7/hydropower_engineering/chapter-4 ## Question List the common types of spillway crest gates and explain any one of them (or three types of gates and their working mechanism) with a neat sketch. ## Short answer Common crest gates include vertical lift, radial (tainter), drum, Stoney, flap, and cylinder gates. A radial gate has a curved skin plate hinged on trunnion pins; water thrust passes through the trunnion, requiring low hoisting force. It provides clear opening, needs no pier grooves, and allows good flow regulation. ## Answer #### 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. ```text 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. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why does the water thrust on a radial (tainter) gate pass through the trunnion pin? A. The gate is hinged at the top of the pier B. The skin plate is a cylinder section whose arc centre is at the trunnion C. Because the arms are vertical D. Because the thrust is carried by the sill Answer: B. The skin plate is an arc centred on the trunnion, so the resultant water pressure acts through the pin. (Key point: Radial gate geometry) 2. How is a radial gate opened? A. Slid sideways in grooves B. Lifted vertically in grooves in the piers C. Inflated with air D. Lifted by ropes or hydraulic cylinders so it rotates about the trunnion, leaving a bottom gap Answer: D. Hoisting rotates the gate about the trunnion, leaving an opening at the bottom for discharge. (Key point: Radial gate operation) 3. Why does a radial gate need only a small hoisting force? A. Water thrust passes through the hinge, so there is little friction B. The gate is very light C. It is lifted by gravity D. There is no water load on it Answer: A. Since the thrust passes through the trunnion, there is little friction to overcome when lifting. (Key point: Advantage of radial gates) 4. Compared with a radial gate, what is a disadvantage of a vertical lift gate? A. It needs no hoist B. It cannot be closed C. It has no seals D. Large lifting force due to friction from water thrust and grooves in the piers Answer: D. A vertical lift gate slides or rolls in pier grooves under water thrust, so friction makes the lifting force large. (Key point: Radial versus vertical lift gate) ## Related in Hydropower Engineering - [Discharge through chute spillway ogee crest](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aspillway-chute-discharge-ogee-250m) — Hydropower Engineering, chapter 4 - [Purposes of spillway; types of gates](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aspillway-purposes-and-gate-types) — Hydropower Engineering, chapter 4 - [Hydraulic jump stilling basin at spillway toe](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Astilling-basin-hydraulic-jump-80cumec-2070) — Hydropower Engineering, chapter 4 - [Overflow section stability with gates and piers](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Agravity-dam-overflow-section-stability) — Hydropower Engineering, chapter 4 ## Related in other subjects - [Types of spillway gates](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aspillway-gate-types) — Hydro Power, chapter 6, asked 2× - [Spillway gates and radial gate](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aspillway-gates-radial-gate) — Hydro Power, chapter 6 - [Spillway function, vertical and radial gates](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aspillway-function-vertical-radial-gate) — Hydro Power, chapter 6 - [DNS and its working mechanism](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Adns-working) — Distributed System, chapter 2, asked 3×