Grids for drainage channels are made of various materials and thanks to this they can be adapted to different needs and requirements. They can also be used in different sectors and environments, such as gardens, if referring to the most common ones or industrial sectors, mentioning the most complex one, where heavy vehicles and corrosive substances are common. In this article we will discuss the most commonly used materials and how to choose the best one (spoiler alert: PAGF rules!).
How to evaluate drain grids: load classes and standards
Grids are the most exposed parts of the channel and, therefore, they must be able to withstand external loads and stresses. The loads are classified by the UNI EN 1433 standard, which also defines the characteristics and parameters that the grids must have according to the load they must withstand. The below table divides the grids resistance into 6 load classes, from the lowest one (A15) suitable for green areas such as pavements and gardens, to the highest one (F900) suitable for areas used by heavy vehicles such as airports or industrial areas.
In order to be certified, grids undergo two main tests: the first one consists in applying 2/3 of the test load to the grid near its central point. This procedure is repeated 5 times and any deformation is measured at the end of each stage; all eventual deformations must remain within a range determined by the standard. The second test is carried out immediately afterwards: the entire test load is applied for 30 seconds at the end of which no failure is to be verified.
1. Drainage channel grids load classes.
The most commonly used materials for drain grids
Among most commonly used materials are polypropylene, PAFV, galvanized steel and cast iron. Polypropylene and PAGF are two polymers: polypropylene is the material also used for the channel body molding, being highly resistant to mechanical stress and vertical loads. PAGF is glass fibre reinforced polyamide. The glass fibres compensate for the weakening feature of polyamide. The combination of these two elements results in a rigid material that is resistant to high static loads and that positively reacts to high temperatures exposure. Galvanized steel is not subject to corrosion processes because the galvanization acts as a protective layer for the steel. In addition, when comes into contact with the air, zinc creates a further layer of oxidation that thickens the zinc layer itself.
Cast iron is a material that allows the production of grids with high load classes. Indeed, these grids can withstand loads of up to 90000 kgs corresponding to load class F900.
PAGF grids: all benefits
Economic advantages of plastics
Cast iron and steel are materials made from a combination of iron and carbon, which makes them extremely vulnerable in terms of costs, as their price is determined by various factors: availability of mineral iron, supply and demand for the material. We are witnessing a strong increase in raw material costs in the last period, especially for materials such as cast iron and steel, the price of which has doubled, if not tripled, due to the latest worldwide events that have changed the production pattern of these materials. With the production decline, the global demand increase and the latest geopolitical crises, we have experienced an unprecedented sharp price rise.
Plastics, in contrast to ferrous metallurgy materials, have experienced a significant, albeit smaller, cost increase trend. Comparing the price trend from the beginning of the pandemic to nowadays, it was registered that steel has increased by up to 57% and plastics by up to 34%.
Benefits of PAGV
As mentioned above, PAGV is a plastic material, that is polyamide reinforced with glass fibres. Thanks to this combination, grids with exceptional mechanical properties are produced: they are resistant to high loads, abrasion and chemicals. PAGF fully guarantees all these characteristics due to its high stiffness and mechanical strength, which make it suitable for exposure to static loads and high temperatures. The glass fibres strengthen and stiffen the polyamide, which would be too soft and unable to withstand high loads.
Another advantage of a PAGF grid is that it is much lighter than a cast iron one within the same load class. When comparing two SABdrain C250 grids, 100 mm wide and 500 mm long, the PAGF grid weighs only 1.2 kgs, while the cast iron grating weighs 4.3 kgs. The PAGF grid is almost three times lighter and therefore easier to handle and transport.
2. PAGF grid.
Range of drain grids that SAB offers
SAB offers a full range of grids that covers all 6 load classes and this allows them to be used for different applications. By using polypropylene grids, for example, their implementation is possible in industries where aggressive chemical solvents are used and where it is not possible to use other materials as they are not immune to corrosion and would therefore risk deterioration in a short time.