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Losses associated with worn turbine packing rings can become significant and the costs related to a reduction in performance are large enough to warrant having complete turbine ring distortion measurements taken to main control of the final seal clearances. Which in turn, helps to minimize these losses and improve steam turbine efficiency.

The inner shells, diaphragms, and packing holders, which hold the stationary packing rings, are often subjected to large temperature differentials during turbine start-up. This condition can cause the normally round packing ring holders to become out-of-round, leading to reduced clearances which often result in a packing rub.  This is especially prelevant in combined cycle D-11 and A-10 turbines.

A Distortion Assessment includes:

Diaphragm & Packing Measurements

  • Hook fit diameters
    • Admission & discharge side
    • Upper & lower halves
  • Vertical diameter
    • Upper & lower halves
  • Bore diameters
    • Bolted together if needed
  • Diaphragm drop check to determine if dished


  • Diameters at all packing locations
    • A minimum of three readings per location
  • Total number of rotor lands
  • Depth of rotor lands
  • Measure wheel diameter for spill strips

Turbine Packing Ring and Spill Strip Information

  • Verify and record ‘As Found’ OEM part numbers on packing rings and spill strips
  • Visually inspect parts and record observations
  • Verify proper materials for manufacture
  • Reverse engineer parts which were not identified or previously modified

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