Top-Entry Ball Valve Structure for Corrosive Acid Leak Reduction
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Solution Overview
Problem
Existing acid feed valves in the HPAL process face challenges such as rapid corrosion, leakage, and mechanical weakness due to the severe conditions of high pressure and corrosive slurry, particularly when handling 98% concentrated sulfuric acid.
Innovation Solution
A two-piece valve shell design with a top-entry operating structure, featuring a single integral ball and stem structure inserted from the top downwardly into a single main valve body opening, and retained by a single bonnet structure. This design incorporates tantalum surface coatings or sleeves for corrosion resistance and uses a reduced number of gasket structures to minimize leakage paths.
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 lateral stem insertion, but the stem length is limited and additional leakage paths are created between the three pieces
Solution Approach 1:
The valve shell is divided into two main pieces (body and bonnet) instead of three, reducing the number of potential leakage paths while maintaining ease of assembly. The single bonnet structure bolted to the body eliminates the need for multiple gasket connections.
Solution Approach 2:
The stem sealing arrangement is integrated directly into the bonnet structure, merging the stem support and sealing functions into a single component. This eliminates separate sealing elements and reduces potential leakage paths between multiple pieces.
2Ease of manufacture
If multiple gasket structures are used to seal the valve, then the valve can be assembled from multiple pieces, but the number of leakage paths increases
Solution Approach 1:
The gasket is extracted from the flow path and positioned only at the bonnet-body connection, eliminating gaskets from multiple locations. This reduces the number of potential leakage paths while maintaining assembly simplicity.
Solution Approach 2:
The single gasket is pre-positioned at the bonnet-body interface before final assembly, ensuring proper sealing alignment. This preliminary positioning prevents misalignment issues that could create leakage paths.
3Ease of manufacture
If the valve stem is inserted laterally into the body, then assembly is simplified, but the stem length and seal-packing length are limited
Solution Approach 1:
Instead of inserting the stem laterally into the body and then upward, the stem is inserted downwardly from the top through the bonnet into the body. This inversion allows for longer stem lengths and greater seal-packing length while maintaining assembly simplicity.
Solution Approach 2:
The stem insertion direction is changed from lateral-horizontal to vertical-top-down, utilizing the vertical dimension for stem length extension. This dimensional change allows longer stems without complicating the assembly process.
4Strength
If a floating valve ball is used, then the valve can operate against high differential pressures, but additional components are required in the waterway
Solution Approach 1:
The ball and stem are merged into a single integral structure, eliminating the need for separate floating ball components and their associated support structures. This integration maintains differential pressure resistance while reducing the number of components in the waterway.
Solution Approach 2:
The integral ball-stem structure performs multiple functions: it provides the sealing ball, the operating stem, and the differential pressure resistance mechanism in a single component, eliminating the need for separate floating ball components.
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 and mechanical failure, enhances corrosion resistance, and allows for easier maintenance and operation under severe HPAL process conditions, while maintaining a robust and reliable performance.
Implementation Method 1
Each wetted surface of the valve shell is configured with a surface coating of tantalum or a tantalum sleeve to provide corrosion resistance
Implementation Method 2
a passive oxide layer is formed on the surface of the metal which protects the underlying metal from further oxidation or corrosion
Implementation Method 3
an exothermic reaction occurs when 98% concentrated sulfuric acid chemically reacts with the water/mineral ore slurry leading to an instantaneous temperature increase
Implementation Method 4
steam is used to maintain the autoclave at high temperature between two leaching operations
Implementation Method 5
Generated heat from both sources is conducted into the acid feed lines and the acid feed valves in the HPAL process
Data Source
AI summary
A two-piece valve shell (body and bolted-on top bonnet having external fins to dissipate heat) 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. In some implementations, a second/bottom bonnet is also attached to the body such that it covers another opening to the ball cavity.