What are most common turbine failures and their causes?

05 Jul '17, 08:45

July 5, 2017, 8:45 a.m.
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The reasons of the turbine failures can be categorized into following causes:

1) Foreign material ingress into the turbine and stripping the blades.

  • a) May be originated from the piping, risk increases when steam purity effected.
  • b) Inadvertently some foreign material left in the casing.
  • c) Dislodged material from drain separators, strainers, if fitted in line.

2) Impingement of steam – breaks the blades by shock, erosion.

  • a) Water droplets entrained in high-velocity steam can be as abrasive as sand particles. They can erode pipe fittings and rapidly eat away at valve seats. And if a puddle of water is allowed to accumulate in steam pipes, it will eventually be picked up by the high-velocity steam, accelerated to near steam velocity, and crash into elbows, tees, and valves, causing erosion, vibration, and water hammer. This water hammer will gradually - and sometimes catastrophically - loosen pipe fittings and supports.
  • b) Considerable water is taken over with the steam, High boiler water level
  • c) Purity of supplied steam
  • d) Mechanical carry over of moisture – By sudden load variations, Un-steady steam and load variations, Short supply of steam and sudden fall of steam pressures, Chemical foam carryover by total dissolved solids, oils, fats and some organic compounds
  • e) Fire tube boilers normally steam-water separation by gravity and no mechanical separation provided such as cyclones or chevrons.
  • f) Drain separators in the steam inlet line are not provided or may be turned defective.

3) Blades made forging have cracks or developed cracks.

4) Touching of blade ends

  • a) Inadequate tip clearance for expansion under various conditions
  • b) Misalignment of the rotor
  • c ) Appropriate warming up and turning procedures
  • d) Proper radial and axial clearances
  • e) Too long rotor between supports allowing sag causing out of balance
  • f) Coupling alignment
  • g) Gearbox condition, eccentric loading or corner loading, bearing condition

5) Vibrations caused by

  • a) Loss of rotor balance
  • b) Misalignment
  • c) Improper steam flow
  • d) A corrosion fatigue crack
  • e) Due to corrosion may be thinned down and broken off
  • f) Shrouding wire is inadequate or not fastened appropriately
  • g) Certain vibration stress developed due to improper stressing
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05 Jul '17, 09:36

July 5, 2017, 9:36 a.m.
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