The displacement of the shaft centerline depends on the bearing type. In lining bearings, the shaft typically shifts to one side due to rotation and hydrodynamic forces. This lateral movement ensures stable oil film support, reducing metal-to-metal contact and wear. In contrast, pad bearings allow more vertical movement, while lining bearings favor horizontal displacement based on operating conditions.

All Georgia Department of Labor employees involved in the administration or implementation of the PIECP Rules of General Applicability shall avoid circumstances in which the personal interest of the employee conflicts or appears to conflict with the interest of the Department of Labor or the State of Georgia, and circumstances which prevent or appear to prevent the employee from exercising official judgment, discretion, powers or duties in an unbiased manner. Georgia Department of Labor employees shall not discriminate unfairly by dispensing special favors or privileges to anyone, whether for remuneration or not, and never accept, for themselves or their family, favors or benefits under circumstances which might be construed by reasonable persons as influencing the performance of their governmental duties. Georgia Department of Labor employees shall make no private promises of any kind binding upon the duties of their office.

This is a shaft center line plot for compressor DE side, , which explains the shaft movement outside of the clearance range.

Pursuant to O.C.G.A. 42-5-120et seq. of the "Working Against Recidivism Act," enacted to authorize the State of Georgia's implementation of the federal Prison Industry Enhancement Certification Program (PIECP), the Georgia Department of Labor shall provide information to the Georgia Department of Corrections to assist the Department of Corrections in determining that inmates are paid wages at a rate that is not less than wages paid for work of a similar nature in the locality in which the work is performed, and that inmate labor will not result in the displacement of employed workers; nor be applied in skills, crafts, or trades in which there is a surplus of available gainful labor in the locality; nor impair existing contracts for services.

In the running speed range :- For tilt pad beanings the shaft centre should be just below the brg centre. For circular bearings the shaft centre should about 20% of the clearance from the bottom and slightly sideways for good stability. IF it was near the bearing centre oil whirl would develop. Don's book goes into the reasoning. Cheers John ?

SCL signatures and trajectory vary with bearing type also, Sleeve bearings typically show smoother but less stable trajectories, while the Tilting pad bearings provide greater stability under varying loads.

Shaft Centerline Plot in Vibration Analysis: A shaft centerline plot is a key diagnostic tool used in vibration analysis to monitor the position and movement of a rotating shaft within hydrodynamic bearings. It visualizes how the shaft center moves relative to the bearing clearance during startup, shutdown, or steady-state operation. The plot shows the path traced by the center of the rotating shaft as it orbits inside the bearing. The shaft’s position is tracked using proximity probes placed around the bearing (typically in the X and Y directions). The plot helps detect issues like misalignment, rubs. As the machine accelerates, decelerates, or operates at steady speed, the shaft's centerline shifts, and this shift is recorded. The data is plotted to show the shaft’s movement within the bearing clearance. 3. Interpretation of Shaft Centerline Plots: Normal Operation: The shaft centerline remains near the center of the bearing clearance but shifts slightly in response to load changes. Excessive Load or Misalignment: The shaft displaces toward the load zone, with the centerline moving closer to the bearing wall. Oil Whirl/Whip (Instability): The centerline shows erratic or looping patterns, indicating subsynchronous vibration or instability. Rubbing (Contact with Bearing): The centerline shows sudden, abrupt movements to the edge of the clearance, suggesting shaft rub against the bearing. Thermal Bow (Rotor Bowing): The plot may show the shaft orbiting in an elliptical pattern as the shaft bows due to uneven heating. Keys: Starting Position: Shaft position at rest (cold condition). Maximum Displacement: Shaft deflection under maximum load or speed. Orbit Shape: Indicates the nature of vibration (circular, elliptical, or erratic). Position Relative to Bearing Clearance: A shaft consistently near the bearing wall indicates excessive wear or misalignment. As an Example: During machine startup, the shaft centerline gradually rises from the bottom of the bearing clearance as the oil film forms and hydrodynamic pressure lifts the shaft. At steady-state speed, the shaft should stabilize near the center. If the centerline drifts towards the bearing edge during operation, it may indicate a lubrication issue, overload, or developing instability.