How should different types of manhole covers be selected in actual use?

When selecting the type of manhole cover in actual use, multiple factors need to be considered. The following are the specific selection criteria:

I. Requirements for Bearing Capacity

1. If it is in an area such as a main urban road or a highway where there is a large traffic volume and heavy vehicles pass frequently, a manhole cover with strong bearing capacity needs to be selected.

   - Ductile iron manhole covers are usually a good choice. Their tensile strength ób≥420MPa, and yield strength ós≥300MPa. They can withstand large loads, including being rolled by vehicles, etc., and are suitable for occasions with such high bearing requirements.

   - Some plastic manhole covers or composite material manhole covers may not be able to meet such high bearing requirements and are not suitable for use in these areas.

II. Operating Environment

1. Corrosive environment

   - In an environment with corrosive substances such as moisture, acids, and alkalis, such as near a sewage treatment plant or by the sea.

   - Ductile iron manhole covers are more suitable due to their good corrosion resistance (in the water spray corrosion test, the corrosion amount in ninety days is only 1/40 of that of the steel pipe and 1/10 of that of the gray iron pipe).

   - At the same time, some corrosion-resistant composite material manhole covers can also be considered. For example, manhole covers made of composite materials such as fiberglass-reinforced plastics also have good corrosion resistance and can maintain good performance and service life in such a harsh environment. The ordinary gray iron manhole cover may be damaged relatively quickly due to corrosion and is not suitable for use in such an environment.

2. Temperature environment

   - In an area with large temperature variations, such as in some cold northern regions or near areas with high-temperature operations.

   - Ductile iron manhole covers can maintain stable performance within a relatively wide temperature range and have good applicability.

   - Plastic manhole covers may be prone to deformation at high temperatures and become brittle at low temperatures and are not very suitable for use in an environment with extreme temperature changes.

III. Aesthetics and Coordination

1. In some places with high requirements for aesthetics and environmental coordination, such as high-end residential areas, pedestrian streets, and landscape areas:

   - Manhole covers with good appearance design can be selected, such as composite material manhole covers or stainless steel manhole covers with decorative patterns or that match the color and material of the surrounding ground.

   - These manhole covers can not only meet functional requirements but also blend in with the surrounding environment to enhance the overall aesthetics. The ordinary cast iron manhole covers with a relatively rough traditional appearance may not be suitable.

IV. Cost Factors

1. For some large-scale construction projects with high requirements for cost control:

   - If the performance requirements such as bearing capacity are not particularly high, plastic manhole covers or concrete manhole covers may be a more economical choice. Their cost is relatively low and is suitable for large-scale applications.

   - But if the performance requirements are relatively high, although the cost of ductile iron manhole covers is higher than that of ordinary gray iron manhole covers, etc., due to its excellent performance and long service life, it may be more cost-effective in the long run. For example, in some important municipal engineering, after comprehensively considering factors such as maintenance cost, the ductile iron manhole cover may be a more suitable choice.

V. Functional Requirements

1. In some occasions that require special functions:

   - For example, at the wellheads of pipeline facilities such as communication and power, manhole covers with certain sealing performance and anti-theft functions may be required. Ductile iron manhole covers can meet the anti-theft requirements through special designs (such as installing anti-theft chains, anti-theft locks, etc.), and at the same time, their sealing performance can also better protect underground pipeline facilities.

   - In areas of flammable and explosive gas pipelines such as gas, the manhole cover needs to have a good sealing and protection effect to prevent gas leakage. At this time, a manhole cover with a corresponding sealing structure and strength (such as a specially treated ductile iron manhole cover, etc.) is a suitable choice.

In conclusion, when selecting the type of manhole cover, multiple factors such as bearing capacity, operating environment, aesthetic coordination, cost, and functional requirements need to be comprehensively considered to select the most suitable manhole cover for the actual use situation.