Bearings vibration analysis

Various monitoring methods are used in practice. The method most commonly used in large systems is vibration analysis. With this method, any defects can be assigned to particular bearings or gearwheels and targeted measures can be initiated at an early stage. 

It is important to note that the linearised displacement and velocity coefficients, commonly used in lateral vibration analysis, only facilitate the estimation of change of oil film force components from an equilbrium condition. In contrast with this, the oil film force components given by equations [5] and [6] are the total values. The estimation of the oil film force components at any location of the journal within the bearing... 

Check the belts, bearings, and sheaves, visually or by vibration analysis Replace worn or damaged equipment... 

Taylor, J. I. 2003. The Vibration Analysis Handbook, 2nd ed. Tampa, FL Vibration Consultants, Inc. While the other two books with Taylor as author or co-author focus on vibration in specific locations (gears and bearings), this work is more general in nature. It discusses machinery vibration in general, time and frequency analysis techniques, how to evaluate the condition of machinery, plus chapters on gears, bearings, and press roll and nip problems. 

Vibration analysis is the best detector of problems with components not directly in contact with the gas path, such as bearings, accessoiy drives, and so forth. 

Pump vibration measurements and analysis of the ampHtude—frequency spectmm have led to the deterrnination of possible equipment ailments. Examples of frequency relationships to particular pump vibration problems are available (62). Eor example, a one-time (lx) frequency corresponding to a mnning speed usually indicates the presence of rotor unbalance, a 2 x peak may mean a bent shaft, and a - O.dx may be a symptom of an oil whip at the sleeve bearing. 

Compressor analysis is done by monitoring the inlet and exit pressures and temperatures, the ambient pressure, vibration at eaeh bearing and the pressure and temperature of the lubrieation system. Table 19-5 shows the effeet various parameters have on some of the major problems eneountered in a eompressor. Monitoring these parameters allows the deteetion of ... 

Figure 43.25 illustrates a simple vector analysis where the vertical and horizontal radial readings acquired from the outboard bearing cap indicate a relative vertical vibration velocity of 0.5 inches per second peak (IPS-PK) and a horizontal vibration velocity of 0.3 IPS-PK. Using simple geometry, the amplitude of vibration velocity (0.583 IPS-PK) in the actual direction of deflection can be calculated. 

Machine components The EIS should provide information on all components (e.g., bearings, gears, gearboxes, electric motors, pumps, etc.) that make up the machine-train. Since these components generate vibration energy and unique frequency components, this information is essential for proper analysis. At a minimum, the information sheet must include detailed bearing information, passing frequencies, and nameplate data. 

This method provides the means to quickly monitor the mechanical condition of critical machine components, not just the overall machine condition. This technique provides the ability to monitor the condition of gear sets, bearings and other machine components without manual analysis of vibration signatures. 

Note The principal objective of shop verification by response to unbalance is to verify the existence of a critical speed (vibration peak) within tolerance of the calculated value, or if the analysis predicted a highly damped critical speed, the absence of a vibration peak within tolerance of calculated value. Shop verification by this method is feasible only for pumps that have sleeve bearings and are furnished with proximity probe pairs at each journal bearing. 

After the initial programming of the state-of-the-art data collector units, a display window on the module provides a description of each piece of equipment on the surveillance route in sequence. The vibration inspector, prompted by the instrument readout, walks up to the operating equipment described on the display and thrusts a probe on the indicated bearing or other data point. When the analyst presses a button, the module captures the vibration level and any required analysis data. The data collector automatically identifies troubled sets based upon preset alarm values and collects spectrum data. Once the data col-... 

---