Internal Alignment

An internal alignment is performed in the course a major outage. Additional reasons to perform an internal alignment are vibration issues, evidence of rubbing, unit up-rate, catastrophic failure or component replacement. These subsequent factors will usually lead to a major outage.

There are varying levels of internal alignment on a Gas Turbine

• Document Alignment Position
• Alignment of Bearings
• Casing alignment
• Exhaust Slippage Correction
• Torque Tube Alignment
• Compressor Case alignment
• Exhaust Case Droop Correction

For gas turbine alignments the measurement process is identical. ACQUIP uses a Laser Tracker mounted on a MAGIE (magnetic bracket for curved surfaces) to acquire the readings.To record accurate internal alignment readings using any method the preparation is identical:

• The turbine is disassembled and the rotor is removed.
• The turbine is reassembled without the rotor.
• The cases are bolted back together and torqued (at least every other bolt) to specification.

Bolting the top of the unit is necessary for a gas turbine alignment, the top provides substantial support for the entire unit. This ensures that the alignment readings will be accurate. If the turbine is outside, alignment readings may have to occur at night. This is to counter the effect of thermal expansion from solar radiation throughout the day.

ACQUIP measures the turbine sections with a laser track directly into a CAD package. When we take the readings, we are gathering thousands of data points. This means we are not only getting 2-dimensional centerline data. In the course of taking the alignment readings we also get:

• Axial Position
• Out of roundness/distortion of compressors and turbine
• Flatness of the faces
• Angular relationships

All data is analyzed for misalignment to targets. Component movements are performed in a controlled manner to make the smallest move possible. All moved components are checked to ensure they are in the correct location. All alignment steps are documented. If moves to the casings are made, dowels will have to be removed. Hydraulic jacks and chain hoist will be used to maneuver the compressor sections. When compressor sections are in the desired locations dowels holes a reamed and re-doweled.

Rotor Coupling Alignment

The Coupling alignment for a gas turbine varies depending on the configuration of the unit and resources available. These can include:

• Lift Oil
• Ability to Rotate Shaft
• Overhead Crane
• Alignment Pins
• Shim or Fixature Mounting

Depending on these conditions the alignment can be performed  by rotating both shafts, without rotating the shafts or only rotating one shaft. ACQUIP will acquire these readings with either a laser alignment system or with a laser tracker. We can often complete the shaft alignment during the course of the internal alignment by shooting through the gas turbine bearings to the generator coupling.

ACQUIP calculates and provides all move data for the generator. We will provide shim changes or fixator flat moves. We can direct and supervise the shim changes and moves.

The alignment will conclude with a final set of readings to confirm alignment condition. ACQUIP also has custom shim kits available to eliminate the need to cut shim stock while making moves.