Service

Laser alignment of vertical shafts

Pruftechnik-Wibrem offers professional service regarding vertical shafts laser alignment in Hydro Power Plants. Measurements are carried out with PERMAPLUMB - unique laser measurement device from Prüftechnik.

Also Pruftechnik-Wibrem offers full support regarding turbine vibration diagnostics and balancing (see Turbine Diagnostics and Balancing).

Measurement scope:

• Measurement and corrections of shaft rotating centerline plumbness
• Measurement and evaluation of coupling rigidity
• Measurement and evaluation shafts straightness

Measurement and corrections of shaft rotating centerline plumbness

Plumbness measurement of rotating centreline of vertical turbine shafts consist in determine shaft rotating centerline deviation from vertical axis result from Earth gravity.

For plumbness measurements is required shafts rotation. After attaching system brackets to a vertical shaft, shaft is rotated to four positions 90o apart. Measurement are taken at each position. Next are calculated angularity of shaft rotating centerline from plumb line in two perpendicular planes [mm/m or mils/inch] and all corrective moves at each bearing or thrust pad to be done.

This method is very fast and precise. Measurement accuracy is 0.002 mm/m (mils/inch) with measurement distance from laser to reflector 254 mm ( 10 inch ). Laser measurement allow to eliminate traditional piano wire method with all it inconveniences.

Monitoring of the corrections as they are being done and for turbines that have load cells on the thrust bearing pads, equalizing the load on the pads are also available.

Measurement and evaluation of coupling rigidity

Rigidity applies to the behavior of the upper and lower shafts across the coupling. The rigid coupling should be sufficiently stiff so that no change in collinearity between the top and bottom shafts occurs during rotation. If the plumbness of a shaft assembly is the same above the coupling as it is below the coupling, then the shaft is rigid.

Measurement and evaluation shafts straightness

Machine center of all other shaft sections.
Straightness measurement - "breaking" the shaft on coupling - can be measured and evaluated without rotation of the shaft
A complete picture of shaft straightness can be obtained from two planes 90o apart.
It is possible to have a perfectly plumb rotating centerline and yet measure runout at points along the shaft with a dial indicator.