Outages Extra Costs Associated to Poor Quality Assurance:
INCREASED OUTAGE DURATION
The 501 Gas Turbine is the main alternative to a Frame 7 Gas turbine. The 501 Gas Turbine OEM is Westinghouse that was later acquired by Siemens. The design was also licensed to Mitsubishi – MHI. The 3 different OEMs for the 501-gas turbine means that it has 3 different designations. An example Westinghouse designation is W501D. Siemens kept this designation until the W501D5A when the Siemens model becomes SGT6-3000E. Mitsubishi replaces the W501 with a M501. The 501-gas turbine is a 60-HZ machine or can be a 50-HZ machine. The Mitsubishi 50-hz counterpart is designated with a 7, M701.
ACQUIP has experience working on almost all the variations of this unit:
- W501D5A – SGT6-3000E
- W501F – SGT6-5000F
Variations of the 501-gas turbine affect the dimensions, components and targets. Acquisition of internal alignment measurements is affected little due to unit model designation. ACQUIP often performs internal alignment, shaft alignment and dynamic movement studies for 501 Gas turbines. Power Generation installations employ the 501-gas turbine as part of a cogeneration package. Cogeneration (Cogen) Plants consist of 2 or 3 W501 gas turbines which will provide the heated steam for a steam turbine.
ACQUIP understands unique elements of a 501-gas turbine that have to be addressed for an acceptable as left alignment condition. An internal alignment is performed in the course of 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 501 Gas Turbine
- Document Alignment Position
- Alignment of Exhaust bearing to Inlet bearing
- Torque Tube Alignment
- Compressor Case alignment
- Exhaust Case Droop Correction
For all of these 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.
Minimum 501 Gas Turbine Internal alignment readings
- Inlet Bearing
- Compressor sections
- Turbine Stages
- Exhaust Bearing
ACQUIP measures the turbine sections with a laser tracker 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. Generally, the exhaust bearing is aligned to the inlet bearing. If moving the exhaust bearing causes a misalignment of the torque tube than a best fit line may be used as an axis. Diaphragm sections are moved if needed because the diaphragms are not adjustable on some 501 units. Component movements are performed in a controlled manner and moves are tracked during alignment. All moved components are checked to ensure they are in the correct location after a move is made. If moves to the casings are performed, dowels will have to be removed. Hydraulic jacks and chain hoist will be used to maneuver the casings. When casings are in the desired locations dowel holes are reamed and re-doweled.
The Coupling alignment for a 501 Gas Turbine is on the inlet side of the unit. Generator to turbine alignment varies depending on resources available. These can include:
- Lift Oil
- Ability to Rotate Shafts
- Overhead Crane
- Shim or Fixator Mounting
Depending on these conditions the alignment can be performed by rotating both shafts, without rotating the shafts or only rotating one shaft. Rotor Sag must be within acceptable limits before reliable alignment reading can be recorded. ACQUIP will acquire these readings with either a laser alignment system or with a laser tracker.
ACQUIP calculates and provides all move data for the machine train. 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.
REASONS TO USE ACQUIP Services
- Time savings
- Other work can go on during the alignment process
- Increased Efficiency
- We take care of the entire alignment process: we take all the readings, enter all the rotor positions, bore presets, Rotor SAG, tops on/off deviation; calculate moves, Give the moves to the Forman or floor engineer, check the alignment was done correctly
- Other measurements are recorded at the same time: Out of round, deformation, bearing elevation
- We can check blade clearance, Rotor deformation, Dimensioning
- We can project shaft alignment position during internal alignment