Multistage Shaft Sealing With Inlet Pressure Equalization
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Solution Overview
Problem
High differential pressures in gas processing equipment lead to increased stress on sealing elements, pressure pulsation, lubrication oil consumption, and gas emission, making it difficult to maintain effective sealing in multistage systems.
Innovation Solution
A progressive sealing system with multiple pressure spaces along the shaft, where an intermediate pressure space is in hydraulic communication with the process gas inlet, allowing leaked process gas to be recirculated back to the inlet, reducing pressure differential and contact pressure, and incorporating a pressure equalization mechanism to manage pressure pulsations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If high differential pressure is maintained in the sealing system, then the maximum allowable working pressure is increased, but stress on sealing elements increases and gas containment becomes more difficult
Solution Approach 1:
The sealing system is divided into multiple sealing members arranged in series along the shaft, creating multiple sealing stages. Each sealing member handles a portion of the total pressure differential, preventing any single seal from experiencing excessive stress while maintaining overall gas containment effectiveness at high working pressures.
Solution Approach 2:
An intermediate pressure space is introduced between the high-pressure cavity and the atmosphere, connected via a flow line from the process gas inlet. This intermediate space acts as a pressure buffer, reducing the differential pressure across individual sealing members and improving gas containment reliability without sacrificing maximum working pressure capability.
2Stress or pressure
If high differential pressure is maintained in the sealing system, then the maximum allowable working pressure is increased, but pressure pulsation within the system increases
Solution Approach 1:
The intermediate pressure space serves as a pressure pulsation dampener by decoupling the high-pressure cavity from the atmospheric side. The flow line connection allows pressure equalization while the physical separation absorbs pressure fluctuations, reducing pulsation transmission through the sealing system without compromising maximum working pressure.
Solution Approach 2:
The intermediate pressure space pre-absorbs and cushions pressure pulsations before they can propagate through the sealing system. By providing a compliant pressure buffer zone, the system dampens pressure variations in advance, protecting sealing elements from harmful pulsation effects while maintaining high working pressure capability.
3Stress or pressure
If high differential pressure is maintained in the sealing system, then the maximum allowable working pressure is increased, but consumption of lubrication oil increases
Solution Approach 1:
The segmentation of the sealing system into multiple members reduces the pressure differential across each individual seal. This lower differential pressure decreases the force driving lubrication oil through the sealing interfaces, thereby reducing oil consumption while allowing the system to operate at high maximum working pressures.
Solution Approach 2:
The intermediate pressure space acts as a pressure buffer that reduces the differential pressure across sealing members. By lowering the pressure gradient that drives lubrication oil leakage, the intermediate space significantly reduces lubrication oil consumption while the system maintains its high maximum allowable working pressure capability.
4Stress or pressure
If high differential pressure is maintained in the sealing system, then the maximum allowable working pressure is increased, but undesired emission of gas to the atmosphere increases
Solution Approach 1:
Multiple sealing members in series create multiple barriers to gas leakage. Each sealing member must overcome a portion of the total pressure differential, making it progressively more difficult for process gas to leak through the entire sealing system to the atmosphere, thereby reducing emissions while maintaining high working pressure.
Solution Approach 2:
The intermediate pressure space serves as an additional barrier and pressure buffer between the high-pressure process gas and the atmosphere. By reducing the differential pressure across individual sealing members and providing an intermediate containment zone, the system significantly reduces process gas emissions to the atmosphere while maintaining high maximum working pressure capability.
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 reduces seal wear, extends seal life, minimizes pressure pulsation, and decreases gas loss and lubrication oil consumption by maintaining lower pressure differentials and providing a cooling effect through gas expansion.
Implementation Method 1
leaked process gas to be recirculated back to the inlet, reducing pressure differential
Implementation Method 2
pressure is reduced along the shaft in stages, or progressively along a labyrinth
Implementation Method 3
providing a cooling effect through gas expansion
Data Source
Figure 1~3
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Figure 7~8
AI summary
A gas processing system includes a vessel defining a cavity for processing a gas. The vessel includes a process gas inlet for accepting process gas at an input pressure, and a process gas outlet for discharging process gas at an output pressure. The gas processing system further includes a shaft coupled to the vessel and a multistage sealing system comprising multiple seals spaced along the shaft. The shaft is configured to transfer mechanical energy to or from gas in the vessel. Each adjacent pair of seals defines a corresponding pressure space therebetween. One of the pressure spaces is an equalizing pressure space in hydraulic communication with the process gas inlet via a flow line, such that in operation, pressure in the equalizing pressure space is maintained at an equalized pressure with respect to a pressure in the process gas inlet.