FAQ
Are the FRP manhole covers mounted in the same way as the cast-iron ones?
The mounting procedure of the M.M. FRP manhole covers is the same as the one for the cast-iron ones, thus it is easy to carry out the work by workers who are used to the traditional systems.
The lightweight of the M.M. FRP manhole cover makes it possible to install by engaging only two workers only who use standard tools.
M.M. provides, along with the product, the necessary tools for the opening. Furthermore, the use of a forklift for lifting the covers is not necessary, which is required when dealing with the ones made of cast iron. This is also important to be considered when working in areas where access is difficult.
The manhole cover must always be of the right class according to the place where it will be installed and therefore, according to the stress to which it will undergo (as prescribed in the UNI EN124 standard); may there be any doubt, a piece of a higher class should always be applied .
The frame will have to be of the same shape as the manhole which will be laid and the stepping area could be more or less the same as the one of the manhole provided the full contact is guaranteed at the head of the manhole itself and that the maximum value of pressure, equal to 7,5 N/mm2, is respected.
It is evident from the pictures that a round cover can be installed on a squared manhole on the condition of assuring a correct and continuous contact of the squared frame with the entire perimeter of the manhole.
The height of the frame, corresponding to the standard requirements, will have to be equal or lesser than the the depth of the installation site (the highest edge of the manhole, regarding the street surface), so as to obtain, when the installation is over, the same level among the frame, the cover /grate and the paving; may it not be so a spacer should be applied.
It would be preferable if the installation site were 2 – 4 cm higher than the frame to make it possible to lay the concrete to make sure the load is correctly distributed on the supporting plane.
Whenever it is possible to close down the street, the use of cement mortar is admitted, which has a compressive strength (Rck) higher or equal to 50 N/mm2, and with a respect for the maturation time prescribed by the producer.
In case it is necessary to operate very quickly, the manhole and drainage covers must be installed on material with fast setting time with the following minimum characteristics:
| · Maximum fineness | 4 | mm | |
| · Volume amount of the mortar | > 2100 | Kg/m3 | |
| · Soundness | 1 day | + 0,5 | % |
| · Setting time | ~ 15 | min | |
| · Compressive strength | after 30 mins | > 1,5 | N/mm2 |
| after 1 h | > 8,0 | N/mm2 | |
| after 24 h | > 35,0 | N/mm2 | |
| after 28 days | >50 | N/mm2 | |
| · Compressive strength after the setting period | 50 | N/mm2 |
| · Durability and endurance of the characteristics |
Installation materials must be carefully chosen considering the use in particular temperature conditions, and must have the proper characteristics regarding mixtures and laying.
Whenever the manhole cover may get in contact or be covered by the asphalt by the end of the installation procedures, it is not damaged since the temperature of the asphalt does not modify the characteristics of the cover.
