Zero leakage through any sealing feature is difficult to achieve other than for dedicated pressurised marine-like applications. This means that for seal plates/F&OCP accessories fitted to conventional EN 124 ironwork, a controlled volume of water leakage should be expected under normal UK climatic temperature and pressure conditions, where sealing effectiveness is quantified by the accessory’s WiS 4-26-01 classification (Classes 0 to 3, with 3 being the most stringent).
Further, seal plate/F&OCP accessories fitted to the underside of EN 124 ironwork assemblies often result in a cavity between the ironwork cover element and the seal accessory. Unfortunately, in the event of the seal accessory subsequently allowing zero fluid leakage into the underlying chamber, this now-sealed cavity quickly fills with; rainwater, grit, mud, salt and other pavement/carriageway contaminants which then act as a perfect ‘corrosion & abrasive soup’ in which the ironwork covers permanently sit.
The outcome of this constant immersion (particularly under traffic loads) is that the ironwork cover’s seating (bearing) surfaces quickly corrode and abrade resulting in premature ‘cover-drop’ in the frame.
N.B. Ironwork cover-drop is a common phenomenon on UK roads with just the normal passage of rainwater past the seating surfaces facilitating corrosion and wear.
Helpfully, the low-leak requirements of Water UK’s The Code (former Sewers for Adoption) acknowledges the benefit of controlled rainwater leakage into sewer systems as it; maximises the longevity of ironwork and minimises the cost of sealing apparatus whilst also allowing a controlled volume of water to enter the system (but not so much for it to result in overwhelming of the pumping equipment or sewerage overflows).
