Patent Application
20120257998
This disclosure generally relates to techniques for circulating lubricating oil in sealed thrust bearing assemblies.
Rotating machinery often includes thrust bearing assemblies to handle thrust loadings generated during operation. A conventional thrust bearing assembly may include stationary thrust bearing pads that engage a rotating thrust runner (“runner”). The thrust bearing pads and runner may be enclosed in a sealed casing that is filled with high dielectric oil. When the equipment is started, the rotating runner normally “drags” oil into and between the bearing pads and the runner. Importantly, delays in forming an oil film between the contact surfaces of these parts may be harmful. For instance, in situations when the assembly is static, an axial loading may displace the oil between the thrust bearing and the runner. Moreover, because the contact surfaces of the thrust bearing and runner may be extremely flat, these parts tend to “stick” together, an effect sometimes referred to as “wringing.” The lack of oil at the contact faces of parts that have stuck together at the crucial moment of equipment start-up can damage these contact surfaces as they rub together. If this process is repeated enough times through repeated starts and stops, a catastrophic failure may eventually occur.
The present disclosure addresses these and other problems of the prior art.
In aspects, the present disclosure provides an apparatus for handling axial thrust in rotating equipment. The apparatus may include a thrust bearing and a runner having a contact surface engaging the thrust bearing. The runner may include a central bore and one or more internal passages that convey a lubricating fluid to the contact surface. This lubricating fluid may be pressurized using an impeller-type pump incorporated into a lock ring assembly that secures the runner to a drive shaft. Also, the contact surface of the runner may include one or more cavities or pockets that act as reservoirs for the lubricating fluid. These oil pockets are immediately available at equipment start-up to lubricate and protect contact surfaces.
Examples of some features of the disclosure have been summarized rather broadly in order that the detailed description thereof that follows may be better understood and in order that the contributions they represent to the art may be appreciated.
For a detailed understanding of the present disclosure, reference should be made to the following detailed description of the embodiments, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein:
This disclosure relates to devices and methods for rapidly and efficiently lubricating the contact surfaces of sealed thrust bearings at equipment start-up and during operation. This enhanced lubrication may allow thrust bearing assemblies to use lubricating oils (hereafter, “oil” or “oils”) formulated for adverse operating conditions (e.g., high-temperature environments). Such oils may have properties (e.g., high viscosity, density, weight, shear resistance, etc.) that resist flowing into a gap between contact surfaces. Thus, embodiments of the present disclosure make oil readily available at motor start by using oil pockets formed in a contacting runner surface and an impeller-type pumping device to force oil between contact surfaces. These features enable immediate coating of contact surfaces and development of a hydrodynamic wedge between these contact surfaces. Illustrative non-limiting embodiments are discussed in greater detail below.
Referring now to
In certain embodiments, the runner 20 may include passages through which oil can be forced into a gap 24 between the contact surfaces of the pads 18 and the runner 20. The lock plate assembly 50 may include an impeller-type pump arrangement that supplies pressurized oil to the passages of the runner 20. Also, the contact surface of the runner 20 may include pockets that act as oil reservoirs. Further details regarding these and other embodiments are discussed below.
Referring now to
The runner 20 may include passages that direct oil flow into the gap 24. For instance, the passages may be holes 34 at the geometric center of the figure eights. The holes 34 may be drilled completely through the runner 20, i.e., between the contact face 28 and the back face 30. In some arrangements, the holes 34 may incorporate a geometry that increases the pressure of fluid flowing from the back face 30 to the contact face 28. For example, the holes 34 may include an inlet section 34a that has a larger diameter or cross-sectional flow area than an outlet section 34b. The reduction in diameter/flow causes a pressure multiplication in the fluid exiting the outlet section 34b.
Referring to
In one arrangement, the lock plate assembly 50 may secure the runner 20 on the shaft 14 (
Referring now to
Once the pump assembly 10 is activated, the oil in the pockets 32 (
It should be appreciated that thrust bearings according to the present disclosure immediately coat and protect contact surfaces at the moment the pump 10 is started. Thus, the risk that the runner 20 and bearing pads 18 will be damaged by unlubricated contact surfaces at start-up is minimized, if not eliminated. As discussed previously, this enhanced fluid circulation may be useful in instances where a pump may be used in environments that require relatively heavy or highly viscous oils. For instance, subsurface oil and gas production applications encounter ever increasing well temperatures. Such situations require heavier oils in order to maintain an adequate oil film thickness. These types of lubricating oil have properties (e.g., high density, viscosity, etc.) that may initially resist flowing into the gaps between contact surfaces. Favorably, the positive or active pumping of oil, together with the oil pockets, can rapidly coat the contact surfaces even when the relatively heavier oils are used.
It should further be appreciated that while the oil circulation techniques of the present disclosure have been discussed in the context of an electrical submersible pumps, the present teachings may be applied to thrust bearing assemblies used in any rotation machinery.
While the foregoing disclosure is directed to the one mode embodiments of the disclosure, various modifications will be apparent to those skilled in the art. It is intended that all variations be embraced by the foregoing disclosure.
