GE D11 Steam Turbines are in operation all over the world. These units are generally installed in cogeneration power plants. The cogeneration (COGEN) package consists of 2 or 3 GE Frame 7 gas turbine with heat recovery steam generators (HRSG)delivering steam to a GE D11 Steam Turbine. A GE C7 Steam turbine is a smaller version of the D11 that is also used in this configuration. A D11 steam turbine is currently the most common steam turbine that ACQUIP performs internal alignments on during a major outage.
GE D11 units have specific characteristics that make them different than other steam turbines. We pay attention to these details during an outage that will determine the success of the project. ACQUIP has experience and has developed special techniques and procedures to contend with these common problems:
- Front Standard elevation
- N2 Packing box fit
- HP/IP Shell distortion
- Diaphragm Dishing
- Horizontal Joint deflection
- HP/IP Rotor Sag
Internal Alignment – Diaphragm Alignment
ACQUIP performs diaphragm alignment on a GE D11 during a major outage. Successful steam turbine internal alignment consists of 3 elements:
- As found Position
- Component Target calculation
- Alignment Moves
As found measurements are recorded on:
As Found readings are recorded in the Tops on and Tops off position. On some steam turbines ACQUIP performs an Express Alignment, this is a theoretical Tops on alignment. An express alignment can only be performed if the four corners of the horizontal joint of the steam turbine cylinder occupies the same plane. ACQUIP explains the different internal alignment methods in a presentation. The GE D11 HP/IP cylinder does not conform to an Express alignment process. Accurate internal GE D11 measurements depend on a Tops on / Tops off alignment.
ACQUIP measures all components with laser tracker set up on a MAGIE (magnetic bracket for curved and flat surfaces). Components are measured directly into CAD Software. When each component is measured we are gathering thousands of data points. This means we are not only recording 2-dimensional centerline data. In the course of taking the alignment readings we also get:
- Axial Position
- Out of roundness/distortion of diaphragms and packing
- Angle or askew of bearings and packing heads
Measurements are analyzed and the target positions are applied. Target component Calculation considers:
- Tops on -Tops off Shift
- Bore Presets
- Rotor Sag
- Rotor Position Readings
- Bearing Moves
ACQUIP provides the moves in a simple format with the left and right side up and down amounts. These moves account for vertical and horizontal moves using a diaphragm roll shift. ACQUIP also provides precut GE D11 diaphragm shims to expedite this process. HP and packing stages that are moved with screws are performed in real time with ACQUIP working with the Millwrights. After moves are made ACQUIP records a final set of readings to confirm all components are within acceptable tolerance.
ACQUIP can perform and entire Tops On / Tops off GE D11 steam turbine diaphragm alignment during an outage with 2 shifts in as little as 3 days.
ACQUIP will provide a final set of alignment data in equivalent ERAG format. After the Rotor is installed, the ERAG data recorded can be easily compared to the ACQUIP ERAG equivalent readings.
GE D11 Steam Turbine Laser Alignment
The majority of the coupling alignment can be performed during the internal alignment. ACQUIP will analyze the recorded data:
- As found Coupling Alignment
- A Coupling
- B Coupling
- Rotor Position Readings
- Bearing elevation Diagram
- Coupling Alignment Targets
This data is combined with the ACQUIP recorded data
- Bearing Position
- Cylinder End Location
- Generator Coupling
Bearing moves are calculated for the ideal bearing location. ACQUIP calculates the shim changes for bearing moves. ACQUIP will supervise and assist in proper shim changes from each bearing shim pad. After bearing moves are made the bearings are checked for blue contact 80/100 at each pad. After the bearing moves are made, ACQUIP calculates the new rotor position readings.
When the rotor is installed at the end of the outage the coupling alignment should be within acceptable tolerance or only small bearing moves (under 0.002”) will have to made. The ACQUIP coupling alignment process provides time savings on the outage because the moves are performed in parallel to internal alignment functions.
ACQUIP’s additional services for D11 Steam Turbines:
- GD&T Rotor Inspection
- GD&T Turbine Inspection
- Bearing Pedestal Elevation
- Horizontal Shell Joint / Split Line Mapping to check / confirm shell distortion
- Diaphragm Dishing measurements
- Assist in field machining setup of horizontal joint milling and internal boring bars
- Dynamic Movement Study
- Precut Diaphragm Shim Kits