Code for Selection of Pressure Penstocks for Hydropower Stations

A penstock is a closed conduit that conveys water under pressure from an intake, forebay, or surge tank to the turbine of a hydropower station. Its main function is to deliver the required flow with minimum head loss while withstanding internal pressure, external loads, and hydraulic transients.
Penstocks may be surface-mounted, buried, or underground. Common materials include steel, reinforced concrete, ductile iron, high-density polyethylene (HDPE), and fiber-reinforced plastic (FRP). Material selection depends on head, discharge, terrain, climate, service life, and cost. Steel is preferred for high-head schemes because of its strength and ductility. Concrete and plastic pipes are often used for low- and medium-head plants.
Hydraulic design focuses on diameter and head loss. A smaller diameter reduces construction cost but increases friction loss and energy loss. Engineers therefore determine an economic diameter that balances capital cost and operating cost. Wall thickness must resist internal pressure, vacuum, external soil or water pressure, and water hammer. Water hammer—a pressure surge caused by sudden changes in flow—can damage or rupture a penstock. Surge tanks, air valves, flywheels, and controlled valve closure are used to limit it.
Structural design includes anchors, supports, expansion joints, and drainage. Surface penstocks require saddles, rocker supports, and anchor blocks at bends to resist thrust. Buried penstocks need proper bedding, backfill, and corrosion protection. Coatings, linings, and cathodic protection extend service life.
During operation, penstocks should be inspected for corrosion, leakage, vibration, support movement, and expansion joint damage. Pressure tests and monitoring systems help detect faults early. A penstock failure can cause flooding, equipment damage, and injury, so regular maintenance is essential.
In conclusion, the penstock is a vital component of a hydropower station. Careful hydraulic, structural, and material design ensures safe, efficient, and reliable power generation.