Cryogenic Pump Shaft Sealing with External Piston Rod
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Solution Overview
Problem
Existing sealing systems for rotating shafts in cryogenic applications are costly and complex, requiring specialized components and complex measurement apparatuses to manage pressure differences and fluid circulation effectively.
Innovation Solution
A sealing system with a barrier fluid pressure device featuring a partially external piston rod, allowing for a shorter, lighter cylinder design, simplified barrier fluid management, and visual or sensor-based fluid level detection, using standard hydraulic cylinders and a spring arrangement outside the cylinder to set pressure differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piston rod is completely arranged within the cylinder, then the sealing system ensures complete barrier fluid management, but the cylinder becomes heavier and more complex
Solution Approach 1:
The piston rod is extracted from the cylinder at the top end, with only a portion of it remaining inside the cylinder while the other portion extends externally. This extraction reduces the cylinder's weight and complexity while the sealing arrangement at the top end cover ensures barrier fluid management reliability is maintained.
Solution Approach 2:
The piston rod is segmented into two portions: one inside the cylinder and one outside. This segmentation allows the system to benefit from both complete barrier fluid management (through the internal portion) and reduced weight/complexity (through the external portion).
2Reliability
If the spring and support piston are arranged inside the cylinder, then the pressure difference control is complete, but the device complexity increases
Solution Approach 1:
The spring and support piston are extracted from the cylinder's interior and repositioned outside the cylinder at the top end. This extraction simplifies the device complexity by reducing internal components, while the pressure difference control reliability is maintained through the external spring's connection to the piston rod.
Solution Approach 2:
The spring arrangement is moved from the internal three-dimensional space to an external position, utilizing the space outside the cylinder. This dimensional relocation reduces internal complexity while maintaining the functional integrity of pressure difference control.
3Reliability
If the piston rod is completely within the cylinder, then the sealing system provides complete fluid sealing, but the manufacturing cost and production complexity increase
Solution Approach 1:
The piston rod is extracted partially from the cylinder, which simplifies manufacturing by reducing the required cylinder length and internal component assembly complexity. The fluid sealing reliability is maintained through the sealing arrangement positioned at the top end cover where the piston rod exits.
4Measurement precision
If complex measurement apparatuses are used for fluid level detection, then the measurement precision is high, but the device complexity and cost increase
Solution Approach 1:
The system uses the existing piston rod position and simple visual or sensor-based detection methods to determine fluid levels, rather than requiring complex measurement apparatuses. This self-service approach maintains adequate measurement precision while significantly reducing device complexity and cost.
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 solution reduces the system's weight and complexity, minimizing pump vibration impact, enabling easy handling and cost-effective production while ensuring effective fluid sealing and leak detection, with improved thermal management and insulation.
Implementation Method 1
The additional force is applied by a spring which is arranged in the region of the cylinder filled with barrier fluid. The additional force in this respect acts on the pressure piston via a piston rod.
Implementation Method 2
The barrier fluid pressure device has a cylinder in which a displaceable pressure piston is arranged which divides the cylinder into a region filled with sealing fluid in gaseous state and a region filled with and flowed through by barrier fluid.
Implementation Method 3
The sealing system has a mechanical seal arrangement which is passed through by a barrier fluid at a barrier fluid pressure
Data Source
AI summary
The invention relates to a sealing system, in particular for sealing pump shafts of vertically arranged pumps for conveying liquefied natural gas (LNG) or other cryogenic fluids below −80° C. The sealing system has a mechanical seal arrangement. A barrier fluid flows through the mechanical seal arrangement at a barrier fluid pressure. The mechanical seal arrangement prevents a sealing fluid from exiting a sealing chamber. The barrier fluid pressure is higher than a sealing fluid pressure in the sealing chamber.