There is nothing special to install our BMC/Polymer concrete manhole covers, sewer and drain covers, trench covers, gully gratings and grids inlets, comparing with the installation of iron cast or other types of manhole covers. However due to LESS FLEXIBILITY OF POLYMER MANHOLE COVERS, the installation has to be done more strictly than the cast iron ones for the manhole covers to work better and last longer:
The polymer manhole covers have to be installed properly, especially in busy walkway and driveway. Unfortunately we do not provide the installation services for our manhole covers sold.
The above image shows five kinds of incorrect installation of polymer manhole covers. There may not be any problems if no vehicles access to the places, should the vehicles be driven over the manhole covers installed in such ways, the manhole covers would be damaged and not last longer.
Polymer or BMC manhole covers are not as flexible as cast iron ones, without the support and protection of the surrounding concrete the edges of the cover and frame may be damage if they expose to high "point force", when the wheels "hit" or crash them. When the wheels of vehicle start to move, stop suddenly, or "jump" onto the covers as crash, the wheels apply higher point force to the cover or frame than they roll over as usual. Should such a crash force be over the load capacity of the manhole cover, or the force limitation it can stand, the damage may be caused.
In the above image, the left picture indicates the distribution of force when the wheel rolls over the manhole cover. We find 30% of the force go sidewards, this may explain why the concrete surrounding the manhole covers usually start to be broken earlier, this make the manhole covers not be protected and easily be damaged as shown in the right pictures of the above image. The duty of the concrete to be made should be well considered.
A steel framework is recommended to be made and placed along with the manhole cover to strengthen the surrounding concrete, especially for the manhole covers installed in heavy traffic areas such as filling stations. (Shown in the middle pictures of the above image)
There is no maintenance required for the polymer manhole cover itself but the surrounding concrete which should be repaired in time if damaged before the manhole cover would be broken without its protection and support.
Posted By Admin
The clear opening of the manhole cover (C1 x D1) should NOT be less than the one of manhole (C2 x D2). Should there be no duty required such as in walkway or heavy duty one to be used for medium duty function, two sides of opposite may be less (C1 < C2) while the other two have to be NOT (D1 ≥ D2) if the manhole covers of correct sizes would not be found. It's not recommended to have the manhole covers with shorter clear opening of all sides installed in any situations.
This manhole cover was installed on the driveway, the frame was damaged because it did not have the fully support from the base, one side of the frame apparently hanging over the manhole, i.e., the clear opening of the manhole cover/frame is shorter than the manhole.
Here are the examples of damaged frames due to the incorrect installation 3 and 4 described above. We all know to break into the door, it's more easier to success by kicking than pushing, that's why jumping wheel may cause edge damage especially to the frames while rolling one doesn't.