Subsea Pump Thrust Bearing Offloading via Barrier Fluid Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing subsea fluid processing machines face challenges with axial thrust bearings due to exposure to process media containing wear particles or phase changes, which can lead to wear and inefficiencies, and conventional balancing pistons are not suitable in such conditions, while large axial thrust bearings result in significant frictional losses and space constraints.
Innovation Solution
The technique involves offloading the axial thrust bearing by using a barrier fluid at higher pressure than the process fluid, with impeller blades or a pump ring on the thrust disc creating a differential pressure to counteract the thrust force, eliminating the need for a conventional balancing piston and reducing bearing size and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional balancing piston is used to counteract thrust force, then the thrust bearing size can be reduced, but the tight clearances are exposed to process medium containing wear particles and solid particles, leading to wear and blocking risks
Solution Approach 1:
The patent introduces a barrier fluid as an intermediary substance that fills the clearance between the balancing piston and the process chamber. This barrier fluid acts as a protective mediator that prevents direct contact between the process medium containing wear particles and the tight clearances, thereby eliminating wear and blocking risks while maintaining the thrust balancing function.
2Reliability
If a large axial thrust bearing is used to compensate the entire thrust force without a balance piston, then reliability is improved, but frictional losses increase, space requirements increase, and system weight increases
Solution Approach 1:
The patent segments the thrust force compensation function into two parts: the balancing piston handles the majority of the thrust force by creating pressure differential across the barrier fluid, while a smaller thrust bearing compensates for the remaining unbalanced thrust. This segmentation allows the thrust bearing to be much smaller than if it had to handle the entire thrust force alone.
Solution Approach 2:
The patent uses hydraulic principles by introducing a barrier fluid that is pressurized to counteract the thrust force. The barrier fluid creates a pressure differential across the balancing piston, generating a force that balances the majority of the thrust, thereby reducing the load on the thrust bearing and minimizing frictional losses.
3Reliability
If a barrier fluid is introduced to protect the balancing piston clearance, then reliability is improved, but device complexity increases
Solution Approach 1:
The barrier fluid serves multiple functions simultaneously: it protects the clearance from wear particles, balances the thrust force through pressure differential, and acts as a lubricant. This multi-functionality reduces the need for additional protective components, thereby limiting the increase in device complexity.
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
This approach allows for smaller thrust bearings, increased effective differential pressure, and reduced frictional losses, enabling safe operation in conditions with non-clean process media, such as those with sand or phase changes, without the drawbacks of large axial thrust bearings.
Implementation Method 1
a thrust disc (256) mounted to the shaft (254) and surrounded by a barrier fluid. The lower side of the thrust disc is exposed to a higher barrier fluid pressure than the upper side of the thrust disc
Implementation Method 2
using a barrier fluid at higher pressure than the process fluid, with impeller blades or a pump ring on the thrust disc creating a differential pressure
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The axial reaction force generated by a subsea pump or compressor is partially counteracted by a pressure differential in a barrier fluid across a thrust element. The pressure differential is created using impellers or other structures on the thrust element that increases the barrier fluid pressure on one side of the thrust element when the main shaft of the pump or compressor is rotated. The pressure differential across the thrust element partially offloads the bearing surface of the thrust element.