Rotor balancing method and apparatus

1. A rotor balancing method for a gas turbine, the method comprising:

providing a rotor comprising: a first bearing and a second bearing, and a plurality of correction planes comprising a first correction plane and a second correction plane;

mounting the rotor for balancing by receiving the first bearing on a first pedestal and the second bearing on a second pedestal;

performing a base run by: running the rotor at an intended balance speed and measuring vibrations at the first pedestal;

carrying out partial balancing and a first influence run of the rotor by: fitting a first balancing weight to the first correction plane in order to reduce vibrations at the first pedestal, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal; leaving the first balancing weight fitted for all following influence runs;

performing a second influence run by: fitting a first calibration weight to the second correction plane, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal, and removing the first calibration weight;

carrying out final balancing of the rotor by: fitting a final balancing weight to the first correction plane and a second balancing weight to the second correction plane dependent on the vibrations measured as part of the first influence run and the second influence run;

providing a data set containing: reference vibration measurements taken during balancing of at least one reference rotor that is the same as the rotor, or at least a first reference influence vector of the first correction plane, wherein the reference influence vector is an influence vector of the first correction plane of the at least one reference rotor:

wherein fitting the first balancing weight comprises using the data set to determine a mass and an angular position of the first balancing weight to reduce vibrations at the first pedestal;

wherein a magnitude of the first reference influence vector is greater than the magnitude of a second reference influence vector of the second correction plane, wherein the second reference influence vector is an influence vector of the second correction plane of the reference rotor, and wherein the second reference influence vector is either contained in the data set or computable from the vibration measurements of the data set; and

wherein the final balancing weight is in addition to the first balancing weight or is added to the first correction plane and the first balancing weight is removed.

2. The method according to claim 1 ,

wherein the final balancing weight is fitted to the first correction plane in addition to the first balancing weight.

3. The method according to claim 1 ,

wherein the final balancing weight is fitted to the first correction plane and the first balancing weight is removed from the first correction plane as part of the final balancing of the rotor.

4. The method according to claim 1 , the method comprising:

performing a third influence run, subsequent to the second influence run, by:

fitting a second calibration weight to a third correction plane, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and/or the second pedestal, and removing the second calibration weight; and

wherein fitting the final balancing weight and the second balancing weight as part of carrying out final balancing of the rotor also comprises fitting a third balancing weight to the third correction plane dependent on vibrations measured as part of the first influence run, the second influence run and the third influence run.

5. The method according to claim 1 ,

wherein the intended balance speed is a full operational speed at a first speed of the rotor at which a mode shape of the rotor is formed.

6. A rotor balancing method for a gas turbine, the method comprising:

providing a rotor comprising: a first bearing and a second bearing, and a plurality of correction planes comprising a first correction plane and a second correction plane;

mounting the rotor for balancing by receiving the first bearing on a first pedestal and the second bearing on a second pedestal;

performing a base run by: running the rotor at an intended balance speed and measuring vibrations at the first pedestal;

carrying out partial balancing and a first influence run of the rotor by: fitting a first balancing weight to the first correction plane in order to reduce vibrations at the first pedestal, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal; leaving the first balancing weight fitted for all following influence runs;

performing a second influence run by: fitting a first calibration weight to the second correction plane, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal, and removing the first calibration weight;

carrying out final balancing of the rotor by: fitting a final balancing weight to the first correction plane and a second balancing weight to the second correction plane dependent on the vibrations measured as part of the first influence run and the second influence run;

providing a data set containing: reference vibration measurements taken during balancing of at least one reference rotor that is the same as the rotor, or at least a first reference influence vector of the first correction plane, wherein the reference influence vector is an influence vector of the first correction plane of the at least one reference rotor;

wherein fitting the first balancing weight comprises using the data set to determine a mass and an angular position of the first balancing weight to reduce vibrations at the first pedestal;

wherein a magnitude of the first reference influence vector is greater than the magnitude of a second reference influence vector of the second correction plane, wherein the second reference influence vector is an influence vector of the second correction plane of the reference rotor, and wherein the second reference influence vector is either contained in the data set or computable from the vibration measurements of the data set; and

wherein the data set contains reference influence vectors of a first correction plane and a second correction plane of a plurality of reference rotors; and wherein the method comprises selecting the first pedestal of the rotor for partial balancing after determining that a phase of the reference influence vectors of the first correction plane of the reference rotors has a smaller statistical spread than a phase of the reference influence vectors of the second correction plane of the reference rotors.

7. A rotor balancing method for a gas turbine, the method comprising:

providing a rotor comprising: a first bearing and a second bearing, and a plurality of correction planes comprising a first correction plane and a second correction plane;

mounting the rotor for balancing by receiving the first bearing on a first pedestal and the second bearing on a second pedestal;

performing a base run by: running the rotor at an intended balance speed and measuring vibrations at the first pedestal;

carrying out partial balancing and a first influence run of the rotor by: fitting a first balancing weight to the first correction plane in order to reduce vibrations at the first pedestal, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal; leaving the first balancing weight fitted for all following influence runs;

performing a second influence run by: fitting a first calibration weight to the second correction plane, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal, and removing the first calibration weight;

carrying out final balancing of the rotor by: fitting a final balancing weight to the first correction plane and a second balancing weight to the second correction plane dependent on the vibrations measured as part of the first influence run and the second influence run;

providing a data set containing: reference vibration measurements taken during balancing of at least one reference rotor that is the same as the rotor, or at least a first reference influence vector of the first correction plane, wherein the reference influence vector is an influence vector of the first correction plane of the at least one reference rotor;

wherein fitting the first balancing weight comprises using the data set to determine a mass and an angular position of the first balancing weight to reduce vibrations at the first pedestal;

wherein a magnitude of the first reference influence vector is greater than the magnitude of a second reference influence vector of the second correction plane, wherein the second reference influence vector is an influence vector of the second correction plane of the reference rotor, and wherein the second reference influence vector is either contained in the data set or computable from the vibration measurements of the data set;

wherein the data set contains reference influence vectors of a second correction plane of a plurality of reference rotors; and

wherein the method comprises selecting the first pedestal of the rotor for partial balancing after determining that a phase of the reference influence vectors of the second correction plane of the reference rotors with respect to the first pedestal has a greater statistical spread than a phase of the reference influence vectors of the second correction plane with respect to the second pedestal of the reference rotors.

8. A rotor balancing method for a gas turbine, the method comprising:

providing a rotor comprising: a first bearing and a second bearing, and a plurality of correction planes comprising a first correction plane and a second correction plane;

mounting the rotor for balancing by receiving the first bearing on a first pedestal and the second bearing on a second pedestal;

performing a base run by: running the rotor at an intended balance speed and measuring vibrations at the first pedestal;

carrying out partial balancing and a first influence run of the rotor by: fitting a first balancing weight to the first correction plane in order to reduce vibrations at the first pedestal, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal; leaving the first balancing weight fitted for all following influence runs;

performing a second influence run by: fitting a first calibration weight to the second correction plane, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal, and removing the first calibration weight;

carrying out final balancing of the rotor by: fitting a final balancing weight to the first correction plane and a second balancing weight to the second correction plane dependent on the vibrations measured as part of the first influence run and the second influence run;

providing a data set containing: reference vibration measurements taken during balancing of at least one reference rotor that is the same as the rotor, or at least a first reference influence vector of the first correction plane, wherein the reference influence vector is an influence vector of the first correction plane of the at least one reference rotor; wherein the data set contains a plurality of reference influence vectors of the second correction plane, wherein the reference influence vectors are influence vectors of a plurality of reference rotors; and

wherein the method comprises selecting the first pedestal of the rotor for partial balancing by:

determining that a phase of the reference influence vectors of the first pedestal of the reference rotors has a statistical spread which is approximately equal to the statistical spread of a phase of the reference influence vectors of the second pedestal of the reference rotors, and

determining that greater vibrations are detected at the first pedestal than at the second pedestal as part of the vibration measurements of the base run of the rotor.

9. The method according to claim 8 ,

wherein fitting a first balancing weight comprises calculating an average influence vector from the reference influence vectors of the first correction plane for determining a mass and an angular location of the first balancing weight.

10. A non-transitory computer-readable medium for rotor balancing of a rotor comprising a first bearing and a second bearing, and a plurality of correction planes comprising a first correction plane and a second correction plane, wherein the rotor is mounted for balancing by receiving the first bearing on a first pedestal and the second bearing on a second pedestal, the computer-readable medium comprising:

instructions for:

performing a base run by: running the rotor at an intended balance speed and measuring vibrations at the first pedestal;

carrying out partial balancing and a first influence run of the rotor by: fitting a first balancing weight to the first correction plane in order to reduce vibrations at the first pedestal, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal; leaving the first balancing weight fitted for all following influence runs;

performing a second influence run by: fitting a first calibration weight to the second correction plane, running the rotor at the intended balance speed and measuring the vibrations at the first pedestal and the second pedestal, and removing the first calibration weight;

carrying out final balancing of the rotor by: fitting a final balancing weight to the first correction plane and a second balancing weight to the second correction plane dependent on the vibrations measured as part of the first influence run and the second influence run;

wherein the final balancing weight is in addition to the first balancing weight or is added to the first correction plane and the first balancing weight is removed

storing, in a data set, reference vibration measurements taken during balancing of at least one reference rotor that is the same as the rotor, or at least a first reference influence vector of the first correction plane, wherein the reference influence vector is an influence vector of the first correction plane of the at least one reference rotor;

wherein the fitting the first balancing weight comprises using the data set to determine a mass and an angular position of the first balancing weight to reduce vibrations at the first pedestal;

wherein a magnitude of the first reference influence vector is greater than the magnitude of a second reference influence vector of the second correction plane, wherein the second reference influence vector is an influence vector of the second correction plane of the reference rotor, and wherein the second reference influence vector is either contained in the data set or computable from the vibration measurements of the data set; and

wherein the final balancing weight is in addition to the first balancing weight or is added to the first correction plane and the first balancing weight is removed.

11. A balancing machine comprising:

a first pedestal and a second pedestal;

the computer-readable medium according to claim 10 .