Bi-Directional Pressure Relief Valve Seat for Vent Line Overpressure
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Solution Overview
Problem
Relief valves experience sealing integrity loss due to undesirable lifting of the shear seal element from the seal plate, caused by overpressure conditions in the vent line, leading to potential failure and difficulty in monitoring the valve's opening pressure in situ.
Innovation Solution
The implementation of a bi-directional seal between the shear seal element and its bore, combined with a user-settable bias spring, and a check valve mechanism that allows in-situ pressure checking and adjustment of the spring force to ensure reliable sealing and proper calibration of the valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uni-directional seal is used between the shear seal element and the seal plate, then the valve can maintain sealing under normal pressure conditions, but the seal integrity is lost when overpressure occurs in the vent line causing the shear seal element to lift off the seal plate
Solution Approach 1:
The patent inverts the traditional sealing approach by using a bi-directional seal arrangement where the seal plate has sealing surfaces on both sides. The shear seal element can seal against either the front sealing surface or the rear sealing surface depending on pressure direction. This allows the valve to maintain sealing integrity whether pressure is applied from the inlet side or the vent line side, resolving the contradiction between maintaining seal under normal conditions and adapting to overpressure conditions.
Solution Approach 2:
The patent changes the sealing parameter from a fixed uni-directional contact to a flexible bi-directional contact capability. The shear seal element is designed with sealing surfaces that can engage with either the front or rear sealing surfaces of the seal plate, allowing the sealing interface to adapt its orientation based on the direction of applied pressure, thus maintaining reliability across varying pressure conditions.
2Strength
If the shear seal element is allowed to retract inwardly during overpressure conditions, then the valve body can withstand the pressure differential, but the sealing integrity is lost and the valve may become seized
Solution Approach 1:
The patent introduces the seal plate as an intermediary component between the shear seal element and the valve body. The seal plate absorbs and distributes the pressure differential forces across its structure, preventing direct transmission of these forces to the shear seal element that would cause retraction and seizure. This intermediary structure allows the valve to withstand high pressure differentials while maintaining the shear seal element in its proper sealing position.
3Productivity
If multiple valve outlets are connected to the vent line, then the venting capacity is increased, but overpressure conditions in the vent line can cause the shear seal element to lift off the seal plate
Solution Approach 1:
The bi-directional seal arrangement allows the valve to handle reverse pressure flows from multiple vent outlets. When backpressure occurs from the vent line, the shear seal element seals against the rear sealing surface of the seal plate, preventing lift-off and maintaining sealing integrity. This enables the system to maintain high venting capacity through multiple outlets while preventing the sealing failures that would normally occur under such conditions.
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 maintains valve performance by mitigating the impact of overpressure conditions and enables accurate monitoring and calibration of the valve's opening pressure, preventing sealing failures and ensuring reliable operation.
Implementation Method 1
A compressible element is present between the shear seal element and a bore in the piston within which the shear seal element is received and maintained. The compressible element is present to maintain the surface of the sealing face of the shear seal element against the sealing surface of the seal plate
Implementation Method 2
Relief valves are constructed with a uni-directional seat bias, because the inlet pressure to the valve is used to bias the annular sealing face of the shear seal element against the shear plate to assist in the sealing off of the inlet pressure from the vent pressure
Implementation Method 3
a check valve mechanism that allows in-situ pressure checking and adjustment of the spring force to ensure reliable sealing and proper calibration of the valve
Data Source
AI summary
A pressure relief valve includes a valve body including a monitored pressure inlet leading to a monitored pressure region, a piston having a shear seal bore and a surface facing the monitored pressure region, a vent passage and a the shear seal assembly comprising a seal plate having a sealing surface thereon, and the shear seal assembly includes a sealing surface facing the seal plate and having a first annular area, and a first surface having an annular surface area at least twice as large as the first area of the sealing surface, the first surface facing away from the first area, and a biasing seal in contact with the first surface.