Top-Entry Ball Valve Structure for HPAL Acid Leakage Control
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Solution Overview
Problem
Existing acid feed valves in the High Pressure Acid Leaching (HPAL) process face challenges such as rapid corrosion, leakage, and mechanical weakness due to the severe conditions of 98% concentrated sulfuric acid and high temperatures, leading to frequent inspections and refurbishments, and limitations in stem sealing arrangement and mechanical strength.
Innovation Solution
A two-piece top-entry valve design with a single integral ball and stem structure, machined from corrosion-resistant materials like Alloy 20, and coated with tantalum for enhanced durability, featuring a reduced number of potential leak paths, improved mechanical strength, and a stem sealing arrangement that allows for additional sealing features and reduced friction, along with pressurized gasket chambers for hermetic sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a three-piece valve shell design is used, then the valve can be assembled with separate components, but the number of potential leakage paths increases and stem length is limited
Solution Approach 1:
The patent merges the valve body and bonnet into a two-piece construction, eliminating the central body of the three-piece design. This reduces the number of flanged connections and potential leakage paths while maintaining assembly flexibility through top-entry installation of the stem and ball assembly.
2Ease of manufacture
If the stem is inserted laterally into the central body, then assembly is facilitated, but the stem length and sealing arrangement are constrained
Solution Approach 1:
The patent inverts the traditional stem insertion approach by using top-entry installation where the stem and ball assembly are inserted vertically from the top of the valve body. This allows for longer stem lengths and more extensive sealing arrangements without the spatial constraints of lateral insertion through flanged connections.
3Ease of manufacture
If standard materials are used, then cost is reduced, but corrosion resistance at high temperature is insufficient
Solution Approach 1:
The patent employs Alloy 20 (a nickel-copper-chromium alloy) as the base material for the valve body, ball, and stem, providing inherent corrosion resistance. Additionally, a tantalum coating is applied to critical surfaces to enhance corrosion and erosion resistance at high temperatures, creating a composite material system that combines the advantages of both materials.
4Reliability
If the valve operates against high differential pressure, then sealing performance is improved, but the risk of stem blow-out and mechanical failure increases
Solution Approach 1:
The patent incorporates a blow-out prevention feature in the stem design, typically an enlarged section or shoulder that prevents the stem from being forced out of the valve body under high differential pressure. This preventive design element protects against mechanical failure before it occurs.
Solution Approach 2:
The use of Alloy 20 and tantalum coating provides enhanced mechanical strength and structural integrity to withstand high differential pressures while maintaining corrosion resistance, preventing both sealing failures and mechanical failures simultaneously.
5Reliability
If frequent inspections and refurbishments are performed, then reliability is maintained, but operational downtime and cost increase
Solution Approach 1:
The combination of Alloy 20 and tantalum coating provides superior corrosion and erosion resistance, extending the service life of the valve components exposed to hot sulfuric acid. This reduces the frequency of inspections and refurbishments required, minimizing operational downtime.
Solution Approach 2:
The two-piece valve shell design with top-entry access allows for easier disassembly and reassembly of internal components such as the ball, stem, and seats. This simplified maintenance approach reduces the time required for refurbishment operations while maintaining reliable sealing performance.
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 two-piece valve design significantly reduces the risk of leakage, enhances mechanical strength, and allows for easier operation and maintenance, providing a more reliable and durable solution for handling high-pressure and corrosive environments in the HPAL process.
Implementation Method 1
machined from corrosion-resistant materials like Alloy 20, and coated with tantalum for enhanced durability
Implementation Method 2
featuring a reduced number of potential leak paths, improved mechanical strength, and a stem sealing arrangement that allows for additional sealing features and reduced friction, along with pressurized gasket chambers for hermetic sealing
Data Source
AI summary
A two-piece valve shell (body and bolted-on top bonnet) structure reduces possible leakage paths while also providing a top-side ball/stem installation/removal path (when the bonnet piece is not present) to facilitate initial valve assembly as well as subsequent inspection/removal of the ball/stem and other valve internals for conducting valve maintenance without requiring the valve body to be removed from its process connections. Internal wetted valve surfaces are coated with tantalum to provide a tantalum ball valve suitable for use as a sulfuric acid feed valve in severe high-temperature high-pressure industrial processes such as HPAL processes. Sealing cavities created by spaced-apart body-to-bonnet and/or stem-to-bonnet sealing structures can be inertly pressurized to hermetically isolate the sealing structures from ingress/leakage of corrosive process materials.