How to avoid expansion bearing failures and maximize their life?

Problems with expansion bearings are inevitable, but the best way to fix them isn't complicated. What are the common causes of these failures, and tips for maximizing expander bearing life.

Problems with expander bearings
The high speeds involved in expanding gas require highly accurate bearings, which may be prone to failure. In addition to high speeds, expanders may be subjected to corrosive media and high temperatures. In this case, predictive maintenance instrumentation can make a significant difference in availability and total cost of ownership (TCO). With detailed inspection reports, a manufacturer can identify areas for improvement to the expander, and thereby increase productivity and process efficiency.

Optimum wheel diameter
In the design of expander bearings, an important consideration is the optimal wheel diameter. This is the diameter of the wheel at which the compressor can produce the desired air pressure. As such, the wheel diameter must be carefully chosen so as to avoid structural resonance. It is also important to understand the maximum speed that the compressor wheel can achieve. The flow rate of the compressor wheel is directly proportional to the wheel diameter.

Oil whirl
The radial and rotational amplitudes of an oil whirl in Expander Bearings are related to the degree of fluid-induced instability of the rotor. The latter occurs as a result of the interaction between the rotor and the fluid, which generates large, sub-synchronous vibration amplitudes. In contrast, the angular frequency of the whirl is the same for both the bearing and the seal. As a result, a single component may generate an oil whirl while another component is a non-whirl.

When analyzing the radial frequency of an oil whirl, it is important to distinguish between the two different configurations. The first configuration gives rise to a circular rotor orbit. The second configuration, on the other hand, generates a much more complex limit cycle oscillation with a combined circumferential and radial motion. Both of these whirls may be considered symmetry breaking.

Eccentricity slow-roll
When assessing the eccentricity of an expander bearing, peak-to-peak eccentricity is a key parameter to measure. In other words, the degree of bow the rotor takes when at rest. Peak-to-peak eccentricity can be monitored by measuring the peak-to-peak DC measurement at the proximitor. Low peak-to-peak amplitude is important to prevent seal damage and rotor rubs.

This process can be expensive and time-consuming, as it requires the modification of an entire stand. Moreover, it requires specific sets of parts that must be replaced every time the bearing needs maintenance. Fortunately, there is a solution to this problem. This new system is called Expander Bearings Eccentricity Compensation. It can help you avoid the high maintenance costs that come with bearings that are too small or too large.