Hydroelectric Turbine Materials
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Questions and Answers

What is the primary consideration for selecting material for runners and buckets?

  • Weight and ease of fabrication
  • Fatigue hazards and erosion due to slit content (correct)
  • Cost-effectiveness and aesthetic appeal
  • High strength and resistance to corrosion

    • What type of alloy steel is used for small units?

  • High carbon alloy steel
  • High quality alloy steel (correct)
  • Low carbon alloy steel
  • Stainless steel alloy

    • What is the composition of stainless steel used for very high head and large size plants?

  • 13% Cr and 2% Ni
  • 13% Cr and 4% Ni (correct)
  • 18% Cr and 8% Ni
  • 15% Cr and 5% Ni

    • Why is the runner, nozzle, and associated components installed above the maximum water level of the tailrace?

    <p>To prevent the turbine from being affected by floods</p> Signup and view all the answers

    What is the primary material used for manufacturing the bucket?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of the dividing wall in the bucket?

    <p>To divide the impinging jet into two equal streams</p> Signup and view all the answers

    What is the primary purpose of the deflector in the nozzle-spear system?

    <p>To deflect the path of the jet emerging from the nozzle</p> Signup and view all the answers

    Why is the nozzle-spear system made of stainless steel (13% Cr, 4% Ni alloy)?

    <p>For its corrosion-resistant properties</p> Signup and view all the answers

    What is the advantage of the monocast system in the runner fabrication?

    <p>It is particularly advantageous in high capacity power units</p> Signup and view all the answers

    What is the purpose of finishing the nozzle-spear system to a very smooth surface?

    <p>To reduce the frictional losses</p> Signup and view all the answers

    What is the consequence of rapid closure in the high velocity nozzle?

    <p>Water hammer problems in the penstock</p> Signup and view all the answers

    What is the shape of the buckets in the runner assembly?

    <p>Ellipsoidal</p> Signup and view all the answers

    What material are the guide blades usually made of?

    <p>Cast steel</p> Signup and view all the answers

    What material are the runner blades typically made of?

    <p>Stainless steel</p> Signup and view all the answers

    Which of the following materials is not commonly used for runner blades?

    <p>Copper</p> Signup and view all the answers

    What material is used for the crown or hub of the runner?

    <p>Cast steel</p> Signup and view all the answers

    What type of construction is used to join the blades, crown, and shroud ring of the runner?

    <p>Welded</p> Signup and view all the answers

    Why is the surface of the vanes made very smooth?

    <p>To minimize shock</p> Signup and view all the answers

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