Mandrel Bearing Assembly Load Distribution
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Solution Overview
Problem
Thrust bearing failure in downhole drilling motors due to high dynamic loads and drill string vibrations, which leads to rapid failure and the need for over-designing bearings to withstand hostile downhole environments.
Innovation Solution
A bearing and mandrel assembly with a tubular design featuring a circumferential ring and carbide layers for enhanced strength and durability, along with a sealed or mud-lubricated bearing system to manage loads and prevent lubricant injection failure, allowing for continued operation even if the sealing system fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bearings are over-designed to withstand high dynamic loads and vibrations, then reliability improves, but device complexity and cost increase
Solution Approach 1:
The bearing assembly is divided into modular components including thrust bearings, radial bearings, seals, and lubrication systems that can be independently selected and replaced. This segmentation allows the system to handle high dynamic loads through properly designed individual components rather than requiring all components to be over-designed, thus improving reliability while controlling complexity.
Solution Approach 2:
The patent employs different bearing types (thrust bearings for axial loads, radial bearings for radial loads) and material selections based on specific load conditions. By changing parameters such as bearing geometry, material properties, and lubrication characteristics to match actual operating conditions, the system achieves reliable performance without unnecessary over-design of all components.
2Reliability
If sealed bearing systems are used to prevent lubricant loss, then reliability improves, but susceptibility to sealing system failure increases
Solution Approach 1:
The patent introduces seals as intermediary components between the bearing assembly and the external environment. These seals prevent lubricant leakage and contamination while allowing the bearing assembly to rotate. The seals act as a mediator that protects the lubrication system without requiring complete sealing, thus maintaining reliability while reducing vulnerability to total sealing failure.
Solution Approach 2:
The bearing assembly incorporates lubrication systems that can be self-lubricating through material selection (e.g., porous bearing materials that retain lubricant) or through design features that distribute lubricant automatically during operation. This self-service capability reduces dependence on complex sealed systems while maintaining reliable lubrication under high dynamic loads.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design reduces mandrel failure by distributing loads more effectively and providing continuous lubrication, enhancing the longevity and reliability of the bearing assembly under high-stress drilling conditions.
Implementation Method 1
a layer of carbide on at least a portion of the lower portion of the bearing housing and a layer of carbide on at least a portion of the lower end of the mandrel, wherein the layers are adapted to contact one another during rotation of the mandrel within the bearing housing
Implementation Method 2
Thrust bearing failure in downhole motors is a problem because of high dynamic loads produced by the action of the bits and by drill string vibrations
Data Source
AI summary
A downhole drilling motor beating assembly includes a tubular mandrel adapted to connect to a rotational power output of downhole motor. The bearing assembly includes a mandrel having: an upper end proximal to the downhole motor, a lower end with a pin connection distal from the motor, and a longitudinal passage through the mandrel from the upper end to the lower end. The assembly further includes at least one circumferential ring projecting radially outward from an other surface of the tubular mandrel. The ring has and upper shoulder and a lower shoulder and a radial surface. A circumferential upper thrust bushing contacts the upper shoulder of the ring and a circumferential lower thrust bushing contacts the lower shoulder of the ring. An upper thrust beating contacts the upper thrust bushing and a lower thrust bearing contacts the lower thrust bushing. A tubular bearing housing includes a longitudinal passage from an upper end of the housing to a lower end of the housing. The passage includes a lower portion with an internal diameter adapted to receive the lower end of the mandrel and an upper portion with a larger internal diameter adapted to receive the lower beating and bushing and the outer radial surface of the circumferential ring projecting from the mandrel and the upper bushing and beating.