Vacuum Pump Purge Flow Control Against Gas Backflow
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Solution Overview
Problem
Existing multistage vacuum pump purge gas supply systems suffer from backflow of gases into the purge supply apparatus during operational state changes, particularly when the vacuum pump operates outside its ultimate pressure regime, leading to inefficiencies and potential contamination.
Innovation Solution
A multistage vacuum pump purge gas supply apparatus with a variable flow restrictor system that maintains sufficient pressure at the purge ports to resist backflow, featuring a gas inlet, flow controller, and adjustable orifices to provide continuous variance in gas flow rates, eliminating the need for non-return valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-return valve is used to prevent backflow of gases into the purge supply apparatus, then backflow prevention is improved, but device complexity and cost increase
Solution Approach 1:
The system applies preliminary anti-action by maintaining positive pressure in the purge supply apparatus before backflow can occur. The flow controller continuously regulates gas flow to ensure the purge ports maintain sufficient pressure to resist backflow of process gases, preventing the harmful effect before it can happen.
Solution Approach 2:
The invention replaces the mechanical non-return valve system with a pressure-based flow control system. Instead of using mechanical valves to prevent backflow, the system uses a flow controller to maintain pressure differential, substituting a simpler pressure regulation mechanism for complex mechanical backflow prevention components.
2Reliability
If the purge gas supply is optimised for ultimate pressure state, then purge effectiveness at low pressure is improved, but performance during roughing operations deteriorates due to backflow
Solution Approach 1:
The system applies dynamics by making the flow rate adjustable rather than fixed. The flow controller can continuously vary the gas flow rate to match different operational states of the vacuum pump, allowing the system to adapt dynamically between roughing operations and ultimate pressure states, resolving the contradiction between optimisation for one state versus performance across all states.
Solution Approach 2:
The invention changes the flow rate parameter based on operational conditions. By adjusting the flow rate parameter according to the pump's operational state (roughing vs. ultimate pressure), the system maintains effective purge gas supply across all operating conditions without suffering from backflow during high-pressure operations.
3Ease of manufacture
If fixed flow restrictors are used to provide proportionally fixed gas flow rates, then manufacturing simplicity is improved, but adaptability to varying process conditions deteriorates
Solution Approach 1:
The system transitions from static fixed restrictors to a dynamic flow controller that can adjust flow rates continuously. This allows the system to maintain manufacturing simplicity while gaining the ability to adapt to varying process conditions by electronically controlling the flow rate based on operational requirements.
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
Effectively reduces backflow and recirculation of gases during high-pressure operations, ensuring optimal purge gas supply and preventing contamination of the purge system without the need for additional expensive non-return valves.
Implementation Method 1
the flow controller comprising an input for receiving gas, a volume for containing gas at a given pressure, and a variable flow restrictor disposed between the volume and each of the outlets
Data Source
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AI summary
Vacuum pump purge systems can suffer from backflow of process gases into the purge supply means as the vacuum pump cycles between operational states. For instance, during roughing operations, the pressure of gas inside the vacuum pump's pumping chambers may increase above a threshold pressure resulting in ineffectual purge supply to the pump. In the broadest terms, the present invention aims to provide an improved purge gas supply that is less susceptible to the shortcomings of known systems. The invention aims to reduce backflow or recirculation of pumped gases into the purge supply apparatus by providing an arrangement where the purge ports on a multistage vacuum pump contains purge gas at sufficient pressure to resist the backflow, particularly when the vacuum pump is operating outside of its ultimate pressure regime. We have found that the embodiments described below do not necessarily need a non-return valve to resist the unwanted pump gas back-flow.