CARRIAGEWAYS MANHOLE COVERS
Spheroidal graphite cast iron
The nodular cast iron ( GS ) has been discovered during the last world war. This discovery is to transform graphite flakes present in the cast iron, in spheroids . The traditional gray lamellar cast iron is fragile because of the composition of graphite lamellae , each of which can trigger a slit beginning . ( See Figure 1 ) in ductile cast iron the graphite is concentrated in spherical nodules : the propagation lines of possible breakages are eliminated . Following tests in order to test the fracture behavior of a product in ductile iron , rifts have occurred only on some ribs without compromising the integrity of the piece ( See Figure 3 ) , as happens in the case of gray cast iron , thus avoiding to create a situation of danger to the circulation ( See Figure 2 ) . The nodular cast iron as the gray lamellar cast iron has good resistance to the natural corrosion and is easy to work but in most possesses the following advantages : | much higher mechanical characteristics . | A deformation capacity , prior to rupture , greater than that of the lamellar cast iron . | A modulus of elasticity similar to that of steel . | A high resistance to impact and break which allows to obtain lighter products than those in lamellar cast iron .
UNI – EN 124 1995 (estratto)
The Uni – en 124 (1995) defines the terminology , classification, materials , construction standards, the tests of type, marking and quality control of manhole covers and closing road wells ( drains and manhole covers ) . Also it states that the production quality control must be a minimum of iso 9002 level or equivalent and requires the presence of a quality brand devices , issued by a recognized independent body that guarantees the third party control about the characteristics declared by the manufacturer . the devices are divided into classes each of which corresponds to a place of use .
The following EN124 classification represents a first guide of selection. A second guide details for each product the performance of features, among which ergonomics, absorption, installation, safety, security.
(Group 6 according to EN124)
Access Covers and Gratings within this class are capable of withstanding 900kN (~90 tonnes) test load
Use: For use in areas where very heavy wheel loads are imposed such as aircraft pavements or docksides
(group 5 according to EN124)
Access Covers and Gratings within this class are capable of withstanding a 600kN (~60 tonnes) test load.
Use: loading areas, docks, aircraft pavements
(group 4 according to EN124)
Access Covers and Gratings within this class are capable of withstanding a 400kN (~40 tonnes) test load.
Use: carriage ways, hardshoulders and pedestrian areas where cars and lorries have access.
(group 3 according to EN124)
Access Covers and Gratings within this class are capable of withstanding a 250kN (~25 tonnes) test load.
Use: kerb areas
(group 2 according to EN124)
Access Covers and Gratings within this class are capable of withstanding a 125kN (~12.5 tonnes)test load.
Use: car parks and pedestrian areas where occasional vehicular access is likely
All covers , grates and frames should bring ( point 9 of the standard Uni en 124 ) : a) en 124 ( which marking of this standard) b ) the appropriate class ( for example, D 400 ) or the appropriate classes for the frame used for several classes ( for example, D 400 – and 600 ) c ) the name and / or identification mark of the manufacturer and place of manufacture that can be coded d ) the mark of a body certificazionee may contain: e) additional marks about the application or owner f ) the product identification ( name and / or number of catalog) .