Ball Valve Metal Backup Seal for Fire-Resistant Shutoff
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Solution Overview
Problem
Ball valves with polymeric sealing rings fail to maintain a closed condition between inlet and outlet during fires due to poor high-temperature resistance, leading to fluid leakage, and existing regulations require these valves to remain closed for at least thirty minutes to allow firefighters to intervene.
Innovation Solution
A ball valve design featuring a polymeric sealing ring supported by a metal support ring with a frustoconical contact surface and an elastic influencing portion that maintains a fluid seal even if the sealing ring melts, utilizing a shape coupling mechanism to ensure contact with the shutter surface and absorb overpressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymeric sealing rings are used between the shutter and valve body, then the valve provides effective sealing under normal conditions, but the sealing rings lose consistency or melt at high temperatures causing fluid leakage
Solution Approach 1:
The invention uses a composite sealing system combining a polymeric sealing ring (for effective sealing) with a metal support ring (for high temperature resistance). The metal support ring maintains structural integrity at high temperatures while the polymeric ring provides the sealing function under normal conditions. This composite approach resolves the contradiction by leveraging the strengths of both materials.
Solution Approach 2:
The metal support ring acts as an intermediary element between the polymeric sealing ring and the valve body shoulder. It provides mechanical support and maintains the sealing ring's position and contact pressure, especially under high temperature conditions where the polymeric material would otherwise fail. The support ring mediates the thermal and mechanical stresses.
2Device complexity
If the valve uses a simple sealing ring design, then the device complexity is low, but the valve cannot maintain closed condition for thirty minutes during fire conditions
Solution Approach 1:
The dual-ring composite structure (polymeric sealing ring + metal support ring) provides the necessary fire resistance duration without excessive complexity. The metal support ring's high melting point ensures the sealing system maintains integrity for the required thirty-minute period during fire conditions, while the overall design remains relatively simple and manufacturable.
3Reliability
If the sealing ring is made of soft polymeric material for good sealing, then the seal is effective under normal pressure, but the sealing ring cannot withstand overpressure conditions
Solution Approach 1:
The soft polymeric sealing ring provides effective sealing under normal pressure conditions, while the rigid metal support ring provides the necessary strength to withstand overpressure conditions. The combination allows the sealing system to adapt to both soft sealing requirements and hard structural demands.
Solution Approach 2:
Different parts of the sealing device have different material properties optimized for their specific functions: the polymeric ring has soft, compliant properties for creating the seal, while the metal support ring has rigid, strong properties for withstanding pressure. This local differentiation of material qualities resolves the contradiction.
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 valve effectively maintains a fluid seal during high-temperature conditions, including fires, and withstands overpressure without damage, restoring the seal when conditions normalize, and operates efficiently with reduced torque requirements for actuation.
Implementation Method 1
the elastic influencing portion (46) is elastically deformed with respect to the resting condition, so as to push the sealing ring (34) towards the external surface (12a) of the shutter
Data Source
Figure 1
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AI summary
A valve (1) for intercepting a fluid in a duct comprises a valve body (2), a ball shutter (12), and a sealing device (30, 32) for forming a fluid seal with the outer surface (12a) of the shutter (12). The sealing device (30,32) comprises a polymeric sealing ring (34), located in contact with the external surface (12a), and a metal support ring (36), connected to the sealing ring (34) and comprising a coupling portion (44), comprising a frustoconical contact portion (44b), and an elastically bendable influencing portion (46), so as to form an elastic lever. In an emergency condition wherein, the sealing ring (34) is absent, for example as a result of a fire, the contact portion (44b) is in contact with the external surface (12a) of the shutter (12) due to at least the fluid pressure, forming a fluid seal even in such an emergency condition.