High-Pressure Valve Packing With PTFE Anti-Extrusion Sealing
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Solution Overview
Problem
Manufacturing high-pressure valves that can retain pressures of 10,000 PSI or more is challenging due to material and geometry limitations, particularly in selecting effective packing materials around the valve stem to prevent leaks.
Innovation Solution
A high-pressure valve design featuring a packing stack with Polytetrafluoroethylene (PTFE) packing rings and anti-extrusion rings made of harder materials like carbon and Inconel, housed in a packing box with a smooth inner surface (Ra of 0.15 or less), and a packer applying pressure between 100 MPa and 200 MPa to maintain sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional packing materials and smooth surfaces are used, then sealing performance is improved, but pressure retention capability deteriorates at high pressures above 10,000 PSI
Solution Approach 1:
The packing stack combines PTFE (soft, sealing) material with carbon or Inconel (hard, structural) anti-extrusion rings to create a composite structure that maintains sealing effectiveness while withstanding high pressures up to 15,000 PSI
Solution Approach 2:
The packing box inner surface roughness is precisely controlled to Ra of 0.15 or less (extremely smooth), and packing pressure is optimized to 100-200 MPa, creating optimal conditions for PTFE packing rings to maintain sealing at high pressures
2Strength
If harder materials like carbon and Inconel are used for anti-extrusion rings, then pressure withstanding capability is improved, but material compatibility and sealing effectiveness may deteriorate
Solution Approach 1:
The packing stack combines PTFE (soft, sealing) material with carbon or Inconel (hard, structural) anti-extrusion rings to create a composite structure that maintains sealing effectiveness while withstanding high pressures up to 15,000 PSI
Solution Approach 2:
Different materials are placed in different locations within the packing stack: PTFE provides sealing contact with the stem, while harder anti-extrusion rings at the ends provide structural support and prevent extrusion, with each material optimized for its specific function
3Reliability
If a smooth packing box surface (Ra of 0.15 or less) is used, then packing seal effectiveness is improved, but manufacturing complexity increases
Solution Approach 1:
The packing box inner surface roughness is precisely controlled to Ra of 0.15 or less (extremely smooth), and packing pressure is optimized to 100-200 MPa, creating optimal conditions for PTFE packing rings to maintain sealing at high pressures
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 retains high pressures with minimal leakage, achieving sealing efficiency of less than 1.78×10^−4 millibar liters per second per millimeter of stem diameter in both static and dynamic conditions, while withstanding pressures up to 15,000 PSI.
Implementation Method 1
A packer is bolted to the bonnet and extends into the packing box. The packer is configured to apply a packing pressure (i.e. stress) on the packing, for example, between 100 megapascals (MPa) and 200 MPa.
Implementation Method 2
A valve bonnet defines a packing box having an inner surface Roughness Average (Ra) of 0.15 or less, for example, between 0.10 and 0.15.
Implementation Method 3
Multiple Polytetrafluoroethylene (PTFE) packing rings are in a packing stack
Data Source
AI summary
A valve bonnet defines a packing box having an inner surface Roughness Average (Ra) of 0.15 or less, for example, between 0.10 and 0.15. Multiple Polytetrafluoroethylene (PTFE) packing rings are in a packing stack. A packer is bolted to the bonnet and extends into the packing box. The packer is configured to apply a packing pressure on the packing, for example, between 100 megapascals (MPa) and 200 MPa. Such arrangements can allow for high pressure valves, for example valves that can retain up to 10,000 pounds per square inch (PSI) of pressure or up to 15,000 PSI.