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Intakes for storage plants

Short answer

Intake types for storage plants include free-standing tower, dam-mounted, submerged, shaft, and floating intakes. A tower intake has ports at multiple levels to draw selected water quality. A dam-mounted intake is built on the upstream face, incorporating trash rack, bellmouth entrance, service gate, and air vent; its sill is set above dead storage to exclude sediment.

Discuss the different types of intakes used in storage hydel plants, with appropriate drawings illustrating the general arrangement of intake for storage plants.

An intake of a storage plant draws water from the reservoir into the tunnel or penstock. It must operate at all reservoir levels from the minimum operating level (MOL) to the full supply level (FSL), prevent entry of debris and air, and be able to shut off the flow.

Types of intakes

  1. Tower (free-standing) intake: A vertical tower in the reservoir connected to the dam crest by a bridge, with ports at several levels. Used for earth and rockfill dams.
  2. Intake in the dam body (dam-mounted): The intake structure is built on the upstream face of a concrete dam, with the penstock passing through the dam; economical and compact.
  3. Submerged (inclined or horizontal) intake: A rock-cut intake at the abutment connected with a tunnel; used in rocky valleys with a long tunnel.
  4. Shaft (gate shaft) intake: A vertical shaft in the abutment with the gate chamber and connected to the tunnel.
  5. Floating / multilevel intake: Draws the best-quality (warmer, cleaner) water from different levels.

General arrangement of a dam-mounted intake

   FSL ~~~~~~~~~~~
   MOL ~~~~~~~~~~~~~      Gate hoist house
        |  Trash rack      |  Air vent
        |  ___________     |
 Res.   | |intake mouth|-- Service gate
        | |bell mouth  |        |
        |_|____________|--------+--> Penstock
          Dam body (concrete)       to turbine

Components:

  • Trash rack: keeps out floating and large debris.
  • Bellmouth transition: smooth entrance to reduce head loss.
  • Gates: a service (control) gate and an emergency (stoplog) gate.
  • Air vent: supplies air behind the gate when it closes and prevents vacuum.
  • Sediment control: the intake sill is set above the dead storage level.

Intake tower (in the reservoir)

  bridge    ____________
 =========|  hoist     |
 Dam crest|            |
          |  upper port|--
          |  mid port  |--  gates
          |  lower port|--
          |____________|
             |
        Tunnel/penstock

The ports at different levels let the operator choose the water level of the draw-off at varying reservoir levels.

✓ Answer checked by Claude Opus 5.5 (high effort)

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