Manhole Lid Base Connection Corrosion Resistance
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Solution Overview
Problem
Manhole assemblies in sanitary sewer systems face significant corrosion and deterioration due to hydrogen sulfide exposure, with existing coatings being unreliable, time-consuming, and expensive, and current plastic linings failing to provide 360° protection against interior corrosion.
Innovation Solution
A manhole assembly design featuring a corrosive-resistant liner integrated into the casting process, using materials like polypropylene, PVC, and fiberglass reinforced plastics, with a spigot connection system that eliminates gaps and provides a continuous, impervious seal, reducing microbial-induced corrosion and infiltration issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing coatings are applied to protect against corrosion, then corrosion resistance is improved, but installation time and cost increase
Solution Approach 1:
The corrosive-resistant liner is integrated directly into the manhole base structure during the casting process, merging the protective function with the structural function. This eliminates the need for separate coating application steps, thereby reducing installation time while maintaining corrosion resistance.
Solution Approach 2:
The corrosive-resistant liner is pre-formed and integrated into the manhole base during manufacturing before installation. This preliminary action ensures protection is already in place upon installation, eliminating post-installation coating applications and reducing overall installation time.
2Reliability
If existing coatings are applied to protect against corrosion, then corrosion resistance is improved, but cost increases
Solution Approach 1:
The protective liner and structural base are manufactured as a single integrated component, combining two functions into one manufacturing process. This eliminates the need for separate coating materials and application labor, thereby reducing overall cost while maintaining corrosion resistance.
3Reliability
If plastic linings are used to protect against corrosion, then corrosion resistance is improved, but 360° protection is not achieved
Solution Approach 1:
The spigot connection design creates a continuous, gapless interface between the manhole base and riser, ensuring the corrosive-resistant liner extends seamlessly to the very edges. This local attention to edge coverage eliminates unprotected zones where microbial-induced corrosion could occur, achieving comprehensive 360° protection.
4Reliability
If spigot connection system is used, then seal integrity is improved, but manufacturing complexity increases
Solution Approach 1:
The spigot protrusion and recess features are integrated directly into the molded manhole base and riser structures, merging the connection geometry with the primary structural components. This eliminates the need for separate gaskets, flanges, or fastening hardware, thereby maintaining simplicity while achieving gapless seal integrity.
Data Source
AI summary
A manhole assembly including a base, riser, and cap. The base having an upper surface forming a bench, a bottom surface, and a radially outward surface with penetrations there through; and a radial spigot in the radially outward upper edge of the base. The base having a corrosive-resistant layer covering the channels, bench, and radial spigot. Also disclosed is a riser comprised of a corrosive-resistant polymer pipe having a radially outward surface, an inner surface and a bottom surface in contact with, supported by, and sealed to the radial spigot. The cap having a radial spigot, and access hole; the radial spigot in the radially outward bottom edge of the cap resting upon and sealed to an upper edge of the riser. The radially outward surface of the cap and base are aligned with the radially outward surface of the riser.