At present, the manhole covers on the market generally include metal manhole covers, cement concrete manhole covers, composite resin manhole covers, and FRP manhole covers. Among them, the glass fiber reinforced plastic manhole cover uses glass fiber and its products (glass cloth, tape, felt, yarn, etc.) as the reinforcing material, and resin as the matrix material, which is mainly composed of unsaturated polyester resin and fillers. FRP manhole covers are a new type developed to solve the defects of steel and iron manhole covers that are easy to rust and lose, heavy weight, and easy to brittle, and to improve their economic and social benefits.
How to select a right and suitable manhole cover?
1.Manhole Cover Load Capacity
In order to ensure safety and service life, if you choose a manhole cover, you must choose a manhole cover with the same bearing level. According to European standards, there are strict regulations on the carrying capacity of manhole covers in different use positions. Analyzed from the reinforced materials of the manhole cover, the higher the content of fiber used and the longer the fiber length, the higher its bearing capacity. Glass fiber generally has a surface wetting agent that enable its interface better when used in unsaturated polyester resin.
2.Width of SeatSupporting Surface: (the contact part of well cover and well seat)
When the diameter of the well seat is less than 600mm, the width of the supporting surface shall not be less than 20mm; when the diameter of the well seat is no less than 600mm, the width of the supporting surface shall not be less than 24mm.
3.Choice of Round and Square Manhole Covers
The main reason for using a round manhole cover is because the diameter of the circle is at the same length so that no matter how the manhole cover is turned over, its diameter will be slightly wider than the wellhead below and will not fall into the well. It can better protect the safety of pedestrians and vehicles.
The diagonal of the square is obviously longer than the length of each side, so when the manhole cover is rolled up, it is easy to fall into the well along the diagonal direction of the wellhead, causing safety hazards. If the well head is round or significantly smaller than the well cover, the square well cover will not fall into the well. But this involves a problem of maximum utilization and saving of materials. If to install a manhole cover with an area far larger than the wellhead, the material utilization and practical value will naturally not be more effective than using a round manhole cover directly.
