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
Rotor Measurements
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
