Vacuum Pump Seal Life Extension via Leakage Path Redirection
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Solution Overview
Problem
Vacuum pumps experience corrosion and reduced seal life when pumping corrosive gases due to back leakage, which is not effectively mitigated by current nitrogen purge systems, leading to increased maintenance costs and downtime.
Innovation Solution
The introduction of additional leakage paths away from the seal arrangement in the vacuum pump design redirects back leakage gas flow, reducing contact with the seal and prolonging its life without requiring significant increases in nitrogen purge flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the axial clearance between the rotor and head plate is reduced to minimize gas leakage, then the leakage from high pressure region to low pressure region is reduced, but manufacturing tolerances are harder to achieve and thermal expansion becomes more problematic
Solution Approach 1:
The invention divides the single axial clearance path into multiple separate clearance paths by introducing additional clearance features (such as clearance grooves or multiple clearance zones) between the rotor and head plate. This segmentation allows gas to leak through distributed paths rather than concentrating through a single narrow clearance, thereby reducing the required tightness of each individual clearance while achieving overall leakage reduction.
2Reliability
If a nitrogen purge system is introduced to dilute corrosive gas at the seal lip, then some protection is provided, but the dilution effect is minimal and significantly large volumes of purge gas would be required to reduce corrosive gas levels
Solution Approach 1:
The invention introduces clearance paths that allow back-leakage gas to be diverted away from the seal lip before the corrosive gas reaches the seal arrangement. By providing alternative leakage paths upstream or at the same level as the seal, the harmful gas is redirected through clearance grooves or multiple clearance zones, preventing its contact with the seal lip in the first place, rather than attempting to dilute it after contact has occurred.
3Object-generated harmful factors
If the seal arrangement is designed to tightly seal the shaft bore, then gas passage is prevented, but the seal lip is more exposed to corrosive gas and experiences increased wear
Solution Approach 1:
The invention introduces intermediate clearance features (clearance grooves, multiple clearance zones) as intermediary paths between the high pressure region and the seal lip. These intermediate structures serve as mediators that redirect the gas flow away from the seal lip, allowing the seal to maintain its tight sealing function while the intermediate clearances absorb the back-leakage gas, preventing direct exposure of the seal lip to corrosive substances.
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 solution significantly reduces the partial pressure of corrosive gases at the seal, extending its life and minimizing operational costs, with the added benefit of being retrofittable to existing pumps.
Implementation Method 1
a seal arrangement provided between the shaft and the transverse wall for resisting the passage of gas through the shaft bore
Implementation Method 2
the rotor or rotors rotate to trap gas at the inlet at relatively low pressure, compressing it during rotation and exhausting it at relatively high pressure at the outlet
Implementation Method 3
The introduction of a seal purge which passes between the lip and the shaft provides some dilution of the process gas
Implementation Method 4
an additional leakage path for back leakage is formed spaced away from the seal arrangement along which gas can flow without contact with the seal arrangement
Data Source
AI summary
Vacuum pump for pumping gas from a process chamber, the pump comprising: a rotor supported for rotation in a pumping chamber by a drive shaft, the shaft extending through a shaft bore in a wall of the pumping chamber extending transversely to the drive shaft, and a seal arrangement provided between the shaft and the transverse wall for resisting the passage of gas through the shaft bore, wherein on rotation of the rotor gas is pumped from a low pressure region at an inlet of the pumping chamber to a high pressure region at an outlet of the pumping chamber, and wherein the rotor and the transverse wall are spaced apart by an axial clearance along which back leakage of gas can flow from the high pressure region to the low pressure region, and an additional leakage path for back leakage is formed spaced away from the seal arrangement along which gas can flow without contact with the seal arrangement so that the amount of gas which contacts the seal arrangement during use of the pump is reduced.