Gas-Pressurized Valve Packing for Low-Emission Stem Sealing
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Solution Overview
Problem
Control valves face challenges in minimizing fugitive emissions while maintaining low friction and long service life, as existing solutions like metal bellows seals are costly and require maintenance, and increasing packing stress impairs operation and increases costs.
Innovation Solution
A gas pressurized packing system with V-shaped packing rings and a pressurized gas supply that creates a gas curtain within the valve bore, reducing leakage without excessive compressive forces, using a pressurized gas canister or external air supply to maintain a seal and reduce friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If additional compressive stress is exerted on the packing material to reduce fugitive emissions, then emission levels decrease, but friction experienced by the operating member increases
Solution Approach 1:
The patent introduces a gas pressurization system that uses pneumatic pressure to seal the packing material against the valve stem. Instead of relying solely on mechanical compression, pressurized gas (typically nitrogen) is introduced into the packing chamber, forcing the packing material to conform to the valve stem surface and seal micro-gaps, thereby reducing fugitive emissions without increasing mechanical friction on the operating member
Solution Approach 2:
The patent changes the physical state and pressure parameters of the sealing medium. By introducing pressurized gas into the packing chamber, the system dynamically adjusts the sealing pressure independent of the operating member's mechanical load. This allows the packing material to be compressed to sealing specifications while the gas pressure maintains the seal without adding to the friction experienced during valve operation
2Object-generated harmful factors
If a metal bellows seal is used to capture process leakage, then fugitive emissions are reduced, but installation cost and maintenance requirements increase
Solution Approach 1:
The patent employs conventional packing materials (such as PTFE, graphite, or aramid fibers) that are inexpensive and readily replaceable, replacing the need for expensive metal bellows seals. While the packing may require periodic replacement, the low cost of the materials and simplicity of replacement procedures make this a more economical solution than installing and maintaining metal bellows, especially in applications where the valve is easily accessible
Solution Approach 2:
The patent replaces the mechanical metal bellows seal system with a gas-pressurized packing system. Instead of using a complex mechanical bellows structure that requires precise manufacturing and assembly, the system uses simple packing material held in place by a gas pressure mechanism, significantly reducing installation cost and complexity while achieving comparable or superior sealing performance
3Object-generated harmful factors
If a metal bellows seal is installed to reduce emissions, then leakage is captured, but the travel distance of the operating member is limited
Solution Approach 1:
The gas pressurization system uses a flexible diaphragm or piston mechanism that can accommodate the full travel range of the operating member. As the valve stem moves up and down, the gas pressure system flexes and expands accordingly, maintaining sealing pressure throughout the entire travel distance without the mechanical constraints that limit bellows-style seals
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 system achieves nearly zero fugitive emissions, low friction, and extended service life without the need for high maintenance or costly components, preserving the dynamic performance of the control valve.
Implementation Method 1
the pressurized gas supply being configured to pressurize a portion of the bore arranged between the first packing member and the second packing member
Implementation Method 2
a first plurality of packing rings which have a V-shaped cross-section pointing in a downward direction
Data Source
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AI summary
A gas pressurized packing system for use in a control valve is disclosed. The gas pressurized packing system may include a first packing member, a second packing member and a pressurized gas supply. The first and second packing members may be arranged about, respectively, lower and upper portions of an operating member that extends through a bore in the control valve. The pressurized gas supply may be configured to pressurize a portion of the bore arranged between the first and second packing members. Also disclosed are a low fugitive emission control valve and a low fugitive emission control valve system.