Passive Magnetic Radial Bearings
Downhole rotating tools have a significant number of radial bearings for supporting the rotor; having over 100 radial bearings in one tool is not uncommon. These mechanical sleeve bearings require active lubrication, which can be the production oil, water or an isolated lubrication supply, to operate for extended periods of time. Transient conditions, such as gas lock and contaminates in the fluid, can significantly impact conventional mechanical radial sleeve bearing performance and operating life. In a downhole compressor application where the speeds are 10 times the speed of conventional downhole pump systems and no fluid is available, a non-contacting high-speed bearing system is an enabling component, since conventional bearings are not able to have an economically viable life.
To address reliability, availability and cost, Upwing has developed a unique passive magnetic radial bearing. Upwing’s Passive Magnetic Bearing™ (PMB) does not require any controllers on the topside.
How Upwing Passive Magnetic Bearings Work
Upwing PMBs utilize permanent magnets of identical polarities in both the shaft and the stator to magnetically support the shaft. Having magnets of similar polarity in proximity to one another creates a repulsion force that keeps the bearing shaft radially suspended in a magnetic field. While the shaft is suspended within the stator magnet assembly with no mechanical contact between rotating and non-rotating components, it can have a rotation about a longitudinal axis that is not reduced by surface-to-surface friction typical of fluid film bearings. Furthermore, the shaft can operate with significant fluid gaps, over 20 times the gaps of conventional mechanical bearings, without any active controllers on the top side and no wear or friction created between the rotating and non-rotating surfaces.
The magnets, imbedded in Inconel and hermetically sealed from the environment, provide radial stabilization without contact and are not affected by the fluid properties (liquid, gas, pressures, temperatures, etc.) present in most wells.
Furthermore, the passive radial bearing performance is not effected by the imbalances caused by fluid dynamics or mechanical changes to the rotating parts, such as imbalance, pitting, erosion of hydraulic sections, etc. The radial passive magnetic bearings allow the shaft to rotate about its mass center as the rotating components wear, and does not transmit vibration to the non-rotating components within its design criteria.
Upwing Smart Damping System for Low Resonate Frequencies
The Upwing Smart Damping System™ (SDS) is used to damp the low resonate frequencies of the shaft and housing that are excited by the rotation of the shaft. The SDS system only focuses on damping low frequency shaft rigid body and housing resonances, and ignores higher frequencies, such as synchronous displacement, allowing the shaft to rotate about its mass center. This minimizes the SDS power and damping required during nominal operation. A SDS magnet is radially imbedded into the bearing shaft in conjunction with a passive radial bearing shaft magnet assembly. Each pole of the damper magnet is equipped with magnetically conductive pole shoes to ensure uniformity of the magnetic fields generated by the damper magnet around the rotor axis. A damper sleeve is installed over the outer diameters of the damper magnet, and the damper pole shoes to hold them in place and prevent relative motion during rotation, and hermetically seal the magnet from the environment.
Whether for slow speeds for pumps or higher speeds for compressors, the radial passive magnetic bearings are fully compatible with the working fluids of an oil or gas well, can support a rotor in almost any environment, and do not have any wear characteristics that impact the life of the bearing, making them the ideal non-contact bearings for all downhole applications.