Plastic Tank Weld Joint Integrity Verification
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Solution Overview
Problem
Large vertical cylindrical plastic water tanks face challenges in shipping and assembly due to bulkiness, and ensuring the integrity of weld joints formed at non-controlled environments, particularly when workers infrequently perform welding.
Innovation Solution
The solution involves creating a fusion weld element within the flanged joint of a base and top combination to form concentric welds, which are then heated and cooled to create a fused mass connecting the inner and outer welds, allowing for easy assembly and verification of the weld's integrity using pressure or vacuum testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a one piece plastic tank is made by blow molding or rotational molding, then the tank has good integrity, but the cost of shipping from factory to point of use can be high due to bulkiness
Solution Approach 1:
The tank is divided into separate modular components (base, walls, top) that can be manufactured independently and shipped separately. These segments are then assembled at the point of use through welding, reducing shipping costs while maintaining tank integrity through quality-controlled weld joints.
2Weight of stationary object
If tanks are made by mating two bucket-like parts and welding them, then shipping cost is reduced due to nesting, but the weld joint integrity may be compromised when formed at non-controlled environments
Solution Approach 1:
Weld preparation features are pre-formed on the tank components during manufacturing, including aligned weld surfaces, embedded weld elements, and pre-drilled test ports. This preliminary preparation ensures that when components are assembled at non-controlled environments, the weld joints can be formed reliably without requiring specialized welding equipment or controlled atmospheres.
Solution Approach 2:
A vacuum or pressure testing system is used as an intermediary verification method to ensure weld integrity. After assembling the tank components, a vacuum is applied through test ports to detect leaks in the weld joints, providing reliable verification without requiring complex inspection equipment or controlled environments.
3Adaptability or versatility
If weld joints are formed at non-controlled environments by workers who infrequently do welding work, then assembly flexibility is improved, but the quality and reliability of the weld may be compromised
Solution Approach 1:
The weld elements are designed to be self-aligning and self-fusing. When the tank components are mated together, the weld elements automatically position themselves and fuse the components without requiring skilled welders or complex equipment. The design includes features that guide the weld elements into proper alignment, ensuring consistent weld quality regardless of operator expertise.
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
This method enables leak-proof assembly and convenient cleaning of large tanks, facilitating faster and more reliable verification of weld integrity compared to conventional methods, while allowing for efficient shipping and assembly of nested tank components.
Implementation Method 1
the weld element is heated to cause melting
Implementation Method 2
heated to cause melting and then cooled
Implementation Method 3
then cooled
Implementation Method 4
verification of the weld's integrity using pressure or vacuum testing
Implementation Method 5
verification of the weld's integrity using pressure or vacuum testing
Data Source
AI summary
A plastic tank is comprised of two parts, a base and a top, that are permanently joined to each other by welding at a circumferential joint formed by two mating flanges of the parts. Fusion weld elements are captured on the faying surfaces of the flanges of the assembled parts, and the elements are melted by internal heating of metal portions of the elements. Two spaced apart circumferential welds which define an annular space are formed. The pressure within the annular space is changed in a test procedure to verify the integrity of the welds.