Cryocooler Expander Gas Replacement to Prevent Flammable Gas Ignition
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Solution Overview
Problem
During maintenance of a cryocooler's expander, there is a risk of contact between electrical equipment and flammable gases like hydrogen, which can lead to ignition due to the ambient gas being taken into the expander.
Innovation Solution
A gas replacement method involving connecting a nonflammable gas source to the expander's connection flow path and purging residual gases with a nonflammable gas while the expander motor is stopped, using a gas replacement pipe with separate connections to the high and low pressure ports and a gas receiving port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If maintenance work is performed on the expander at the installation site, then the expander can be inspected or repaired in place, but ambient gas containing flammable gas may be taken into the expander during disassembly and reassembly
Solution Approach 1:
The patent applies preliminary action by performing gas replacement with nonflammable gas before maintenance work begins. The expander is purged of ambient gas and filled with nonflammable gas through the gas supply port before disassembly, ensuring that no flammable gas is present during maintenance operations.
Solution Approach 2:
The patent creates an inert atmosphere by introducing nonflammable gas into the expander cylinder and connection flow path. This inert environment prevents ignition of flammable gases during maintenance work, allowing safe disassembly and reassembly of electrical components without explosion risk.
2Reliability
If the expander is purged with nonflammable gas before maintenance, then contact between electrical equipment and flammable gas is avoided, but additional time and complexity are required for gas replacement procedures
Solution Approach 1:
The patent segments the gas replacement function from the main expander structure by providing a separate gas supply port and dedicated gas supply path. This allows gas replacement to be performed independently without affecting other expander operations, simplifying the overall procedure.
Solution Approach 2:
The patent introduces a nonflammable gas as an intermediary substance between the ambient environment and the expander internal components. This mediator gas replaces flammable ambient gas and protects electrical equipment during maintenance, enabling safe operation without direct exposure to hazardous gases.
3Reliability
If a gas supply port is provided in the connection flow path, then gas replacement can be performed effectively, but the expander structure becomes more complex
Solution Approach 1:
The gas supply port is designed with multi-functionality, serving both as a maintenance access point for gas replacement and as an integrated part of the normal expander operation. The port and its connection flow path can function during both maintenance and operational modes, reducing the need for separate dedicated components.
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 method ensures that the expander is filled with a nonflammable gas, preventing contact between electrical equipment and flammable gases, thereby avoiding the risk of ignition during maintenance and resuming safe operation.
Implementation Method 1
purging a residual gas in the expander cylinder with a nonflammable gas from the nonflammable gas source while the expander motor is stopped
Data Source
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AI summary
There is provided a gas replacement technique for an expander (14) of a cryocooler (10) for avoiding contact between electrical equipment in the expander (14) and a flammable gas. A gas replacement method for an expander (14) of a cryocooler (10) is provided. The expander (14) includes an expander cylinder (16), a pressure switching valve (42) that switches a pressure inside the expander cylinder (16), a connection flow path (20b) from the pressure switching valve (42) to the expander cylinder (16), and an expander motor (40) that drives the pressure switching valve (42). The method includes connecting a nonflammable gas source (60) to the connection flow path (20b) or the expander cylinder (16), and purging a residual gas in the expander cylinder (16) with a nonflammable gas from the nonflammable gas source (60) while the expander motor (40) is stopped.