Deformable Valve Spacer Ring for Fire-Safe Stem Sealing
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Solution Overview
Problem
Existing valve configurations struggle to meet evolving fire safety standards, such as API 6FA, due to deterioration of primary stem sealing systems during high-temperature fire tests, leading to increased costs and complexity.
Innovation Solution
Incorporation of a deformable metal spacer ring into the valve assembly, which is positioned in an annular space between the stem and the bonnet and is not pre-loaded, allowing it to deform and restrict flow only after exposure to high pressures following the failure of the primary sealing system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a primary stem sealing system is used in conventional valve configurations, then the valve can operate normally under standard conditions, but the sealing system deteriorates during high-temperature fire tests leading to leakage
Solution Approach 1:
The spacer ring is pre-installed in the annular space between the stem and bonnet in a non-loaded configuration with gaps from both the stem and bonnet. This preliminary positioning allows the spacer ring to be ready for action but not yet engaged, so it can deform and seal when needed during fire conditions without interfering with normal operation
Solution Approach 2:
The spacer ring acts as a backup sealing mechanism that is positioned in advance to cushion against potential sealing failures. When the primary packing system deteriorates under high-temperature fire conditions, the spacer ring deforms under pressure differential to prevent leakage, providing a safety cushion against fire safety failures
2Reliability
If the spacer ring is pre-loaded to contact the stem or bonnet, then sealing may be improved, but the spacer ring interferes with normal valve operation and stem movement
Solution Approach 1:
The spacer ring transitions from a static non-loaded state during normal operation to a dynamic deformed state during fire conditions. The ring is designed to be flexible enough to deform under pressure differential while remaining stationary and non-interfering during normal valve operation, adapting its function based on operating conditions
3Reliability
If complex pre-loading mechanisms are added to ensure sealing, then sealing reliability improves, but device complexity and manufacturing costs increase
Solution Approach 1:
The spacer ring is designed to be self-activating through pressure differential without requiring external pre-loading mechanisms. The high-pressure side of the valve automatically pushes the spacer ring against the low-pressure side when sealing is needed, eliminating the need for complex mechanical pre-loading systems while ensuring reliable sealing activation
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 deformable spacer ring effectively restricts leakage to acceptable levels during high-pressure differential conditions, enabling the valve to meet fire safety standards without the need for pre-loading or complex manufacturing processes, thus reducing costs and complexity.
Implementation Method 1
The spacer ring is positioned in a non-loaded configuration within the annulus such that one or both of an outer diameter or an inner diameter of the spacer ring is separated from one or both of the stem or the bonnet via a respective gap
Implementation Method 2
the spacer ring have an axial thickness configured to deform responsive to a exposure to a threshold pressure after failure of the packing system
Data Source
AI summary
A valve assembly includes a valve body having a stem bore extending along a stem bore axis and a flow bore extending along a valve body axis, a bonnet coupled to the valve body via one or more fasteners, a stem extending along the stem bore axis and within the stem bore, a packing system positioned along the stem within an annulus formed between the stem and the bonnet, a spacer ring positioned axially above the packing system, and a packing gland coupled to the bonnet to axially secure at least the packing system within the annulus. The spacer ring is positioned in a non-loaded configuration within the annulus such that one or both of an outer diameter or an inner diameter of the spacer ring is separated from one or both of the stem or the bonnet via a respective gap.