Composite, Cast Iron and Ductile Iron Manhole Cover Comparison
The choice depends on load, span/opening, environment, corrosion exposure, safety, maintenance, and the project specification; there is no universal winner for every application.
| Criterion | Composite | Cast iron | Ductile iron |
|---|---|---|---|
| Scrap value | Low resale value can reduce theft incentive and is assessed alongside traceability and site-security requirements. | Scrap value is reviewed with site security and loss risk. | Scrap value is considered with security and supply conditions. |
| Corrosion | Material class and the surrounding environment are reviewed together. | Coating, drainage, and maintenance cycles affect corrosion planning. | Coating and environmental chemistry are reviewed for the expected service duration. |
| Weight and handling | Handling load is evaluated with cover size and the lifting method. | Higher weight affects lifting and maintenance equipment needs. | Weight is checked with opening equipment and access arrangements. |
| Electrical behaviour | Insulation needs are verified against product data and the environment. | Conductivity, grounding, and contact points are addressed in the project. | Conductivity and grounding details are verified with the safety design. |
| Load class and project verification | Load class, support, and seating details are documented together. | Load class and standard compliance are verified by the project design. | Load class, frame, and seating conditions are verified together. |
| Maintenance | Inspection, cleaning, and connection planning follow site conditions. | Coating, hinge, and seating-surface inspections are scheduled. | Coating, connection, and seating-surface maintenance are scheduled. |
| Noise and seating detail | Elastomer, frame, and seating tolerances affect noise. | Seating surface and fixing details affect impact and sound. | Frame, seal, and seating details affect operating noise. |
| Application environment | Traffic, water, chemical, and access conditions are reviewed together. | Traffic load, drainage, and environmental exposure guide selection. | Traffic, environment, and maintenance access are verified in the specification. |