Turbine to Generator Alignment

  • Gib-keys are first removed from fwd. and aft sides of the Generator Compartment. All the Generator leg bolts are should be unbolted.
  • For performing the Turbine to Generator alignment , the Generator rotor is slightly pushed back for making a room for measuring the face readings, which is recorded by means of a slide parallel.
  • Slide parallel where transition fits into coupling faces, the width is measured by the inside micrometer. This is known as axial reading; it is recorded, at each quarter turn, from four positions top, bottom, left and right. Final axial readings are the average of four readings at a point.

Note: After alignment correction, new housings for gib-keys are emerged and gib-keys undergo engineering for exact fitting into that housings; by addition of shims, or thickness reduction.

  • The turning is performed on turbine, whereas, generator rotor remains stationary.
  • The dial gauge indicates the radial reading; noted from four points top, bottom, left and right.

Turbine to Generator Alignment (Case Study)

What corrective actions we need to align the couplings by considering the target values?

Accessory Base to Turbine Alignment

  • Christmas tree is a supporting structure that replaces the accessory shaft for sake of alignment. Its one end connects with the accessory gear box, and other one is used as dial indicator mountings, which interfaces with the Turbine Speed Gear.
  • Two Dial Indicators are attached, one for radial reading and other one is for face reading.
  • Before recording the readings; all accessory base legs bolts are loosened, gib keys and radial pin are removed.
  • The radial pin is located at turbine side, and grounded into the accessory base.
  • Gib keys are machined or shim addition is performed, after repositioning the accessory base, for fitting into the new housing.
  • The radial pins is re-introduced for locking the accessory base at new position.

Accessory Base to Turbine Alignment (Case Study)

What corrective actions we need to align both shafts by considering the target values?