FAQ
What norm does FIBERTOP manhole cover comply with?
M.M.’s FRP manholes are designed and produced in accordance with what the EN 124:2015 standard “Gully tops and manhole tops for vehicular and pedestrian areas” establishes.
The EN 124:2015 standard establishes which are the tests to be carried out and their methodologies, and their differences according to the type of material used.
As for the tests which are required by the standard and to which the M.M.’s FRP manhole covers have been submitted, they are the following:
- Dimensional check
A manhole piece is checked to make sure there are no evidences of defects. Then the necessary measurements are done (stepping diameter, frame height, site depth, backlash… ) all resulting values must be within the range established by the norm.
- Residual stress
A manhole piece which has not been subjected to any stress test is placed in a test device and its initial shape is assessed in correspondence with its geometric centre.
By the use of a punch with the corresponding shape and size (the norm establishes the shape and size in accordance with the shape and size of the piece to be tested) a load equal to 2/3 of the test load corresponding to the type of class is applied and then removed. This procedure is repeated five times.
By the end of the process the position of the geometrical center is assessed once again; the difference between the two results is the residual stress.
This result must be lower than the ones established in accordance to the load class and the size of the manhole as listed bellow:
| class | Acceptable permanent deformation | ||
| A15 and B125 | 1/100 (1)
of the stepping size |
||
| From C250 to F900 | 1/300 (2)
of the stepping size |
1/500 (3)
of the stepping size |
|
| If they have a blocking system | Blocked by the amount of mass per area | ||
| (1) | If DP<450 mm it becomes DP/50 with a maximum of 6.5 mm | ||
| (2) | If DP< 300 mm 1 mm maximum | ||
| (3) | If DP< 500 mm 1 mm maximum | ||
| The size of the stepping area (SSA) is the diameter of a circular manhole, or the diameter of the largest circle inscribed for manholes with other shapes. | |||
- Load strength
Soon after the test for assessing the permanent deformation is over, the test load is conducted by using the same testing device on the same manhole cover.
The load must stay on for 30 seconds and released. The manhole cover mustn’t have visible signs of rupture.
The test loads are the following:
| Class | Test load kN |
| A15 | 15 |
| B125 | 125 |
| C250 | 250 |
| D400 | 400 |
| E600 | 600 |
| F900 | 900 |
- Water and fuel absorption
Water absorption: after a manhole cover is weighed it is put into deionized water at 23 °C for 24 hours. Once it is taken out, it is weighed again and the difference must be lesser tan a 0,3%.
Fuel absorption: after a manhole cover is weighed it is put into diesel fuel at 23 °C for 168 hours. Once it is taken out, it is weighed again and the difference must be lesser tan a 0,3%.
After the assessment for the weight variation the manhole covers undergo the load and permanent deformation tests.
- Creep
Test consists in applying to a manhole cover, one to which no other test has been conducted on, a load equal to 2/3 of the test load according to the type of class, and keep it for 60 minutes.
By the end of the 60 minutes, and after a 5-minutes recovery time, the permanent deformation is assessed and the result must comply with the limits established by this specific test.
The manufacturing process can be considered of C3 class as defined by the “5th part: Gully tops and manhole tops made of composite material”, i.e. made with a sheet molding compound process (SMC) using thermosetting resins, fiber glass and other additives.
