Cryogenic Pressure Relief Valve Thermal Deflection Sealing
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Solution Overview
Problem
Pressure relief valves used in cryogenic applications experience premature leaks due to temperature differences between the process fluid and ambient conditions, leading to ineffective sealing and potential galling, which exacerbates leakage issues.
Innovation Solution
A disc-nozzle combination design that utilizes thermal gradients to cause axial deflection of the disc and nozzle, minimizing leaks by sealingly contacting each other, with features like grooves and notches to manage thermal mass and direct thermal deflection, and materials with high coefficients of thermal expansion to enhance sealing during cryogenic service.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional disc design is used in cryogenic service, then the valve can operate at low temperatures, but temperature differences cause thermal deflection leading to premature leaks and galling
Solution Approach 1:
The patent applies local quality by creating a non-uniform disc design with varying thickness. The disc is thinner at the periphery and thicker at the center, creating localized thermal mass distribution that directs thermal deflection away from the sealing surface. This localized structural variation allows the disc to maintain reliable sealing at cryogenic temperatures while accommodating thermal gradients.
Solution Approach 2:
The patent utilizes thermal expansion principles by designing the disc with specific thermal mass distribution. The varying thickness creates controlled thermal deflection patterns that prevent galling and leakage. The disc's thermal characteristics are engineered to deflect in a manner that maintains sealing contact under cryogenic temperature differentials.
2Stability of the object's composition
If the disc is made thinner to reduce thermal mass, then thermal deflection is reduced, but sealing contact area is decreased
Solution Approach 1:
The patent resolves this contradiction by making the disc locally thin at the periphery (reducing thermal mass and thermal deflection) while maintaining adequate thickness at the center (ensuring sealing contact area). This localized variation in thickness allows the disc to achieve both thermal stability and sufficient sealing surface area.
3Reliability
If materials with high coefficients of thermal expansion are used, then sealing is enhanced during thermal deflection, but galling risk increases
Solution Approach 1:
The patent addresses this contradiction through localized thickness variation that controls where thermal deflection occurs. By concentrating thermal mass reduction at the periphery while maintaining center thickness, the design allows controlled thermal expansion that enhances sealing without creating the excessive friction and contact pressure that cause galling.
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 effectively minimizes and prevents leaks in cryogenic service by maximizing set tightness and utilizing thermal characteristics to ensure the disc and nozzle deflect axially, reducing fluid flow through the valve, as demonstrated by test data showing significant improvements in leak reduction.
Implementation Method 1
A disc-nozzle combination design that utilizes thermal gradients to cause axial deflection of the disc and nozzle
Implementation Method 2
materials with high coefficients of thermal expansion to enhance sealing during cryogenic service
Data Source
AI summary
A pressure relief valve for cryogenic service includes: a fluid inlet and a fluid outlet; a nozzle disposed within the fluid inlet, said nozzle having a nozzle groove radially formed on an exterior cylindrical surface of the nozzle and an outwardly disposed ledge having a lower ledge surface comprising a portion of an exterior surface of the nozzle groove and an upper ledge surface comprising a seat; a substantially cylindrical closure disc with a lower portion including a groove formed on an exterior radial surface of the cylindrical body, an outwardly disposed lip having an upper surface comprising a portion of an interior surface of the groove, said lip of the closure disc having a lower closure surface. The lip of the closure disc being adapted to deflect downward and inward in response to a cryogenic thermal gradient applied across the lip.