Maintenance Metrology provides dimensional inspection and alignment services at hydropower facilities.  Our alignment services are beneficial throughout disassembly, refurbishment and reassembly.



Unit Center

To establish the unit’s center-line we will choose one of the embedded diameter features of the turbine for the center point.  Generally, we will establish center based on the imbedded head cover mounting flange inside diameter.  Options for choosing unit center can vary based on the type of unit.  On a Francis unit we can also use the lower seal ring and on a Kaplan we can also use the discharge ring. 


The unit center is the X and Y value of the Coordinate system.  The X-Axis is oriented upstream.  The Z-Axis of the Coordinate system establishes the elevation of the Coordinate system.  For the Z-Axis, we can choose any feature through the length of the unit. It is best to choose a feature that the drawings reference with dimensions to other feature elevations so other feature actual measurements can be confirmed.  Typically features chosen are the curb ring face, lower facing plates, or head cover flange face.
Once the features for establishing unit center and elevation are chosen and measured, we will measure level and project a level plane at the chosen center point.  Then we establish the coordinate system which has its datum through the center point of the unit and is level with the X-Axis oriented upstream.






Disassembly is a great opportunity to begin the laser tracker services for your refurbishment.  As components are removed we can measure features and provide “as found” dimensions which is very good information to know since this shows where the unit was operating.  This information provides dimensions for reassembly as well. 
If any refurbishment is being completed on any of the embedded features of the turbine or the stator core, we can move the stator core and the features being refurbished to the new unit center line. 


During reassembly, we can provide dimensional information on the final location of the refurbished features.  Generally, we would begin measuring imbedded features in the turbine.  Then as components are installed we center and set the elevations and level.  These installed components normally include the head cover, thrust bridge and upper bracket.  The final measurements of each component are taken when it is torqued down.  Re-doweling of these components can be done after metrology services are done if components are installed from bottom to top.





Generator Inspection

Stator and Rotor dimensions can be measured and analyzed to verify they are operating within acceptable tolerances.  Typically, we measure 24 equally spaced slot locations at the top middle and bottom of the stator core.  On the Rotor, we typically measure every 2nd or 3rd pole at the top middle and bottom of the poles.  Elevation measurements are also taken to determine the center elevation of the Stator and Rotor.
With these data points we can determine the Circularity, Concentricity, Verticality and the Stator and Rotor’s Center Elevation.



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