Filter Bed Wall and Tile System
FP McCann are able to offer a specialist design and build service, for circular biological filter walls. The inherent flexibility of this well-proven system allows us to accommodate all ancillary requirements. FP McCann filter beds provide low whole life costs, due to the low energy and low maintenance required by the system. Offering many advantages over ASP, Baff and Saff Treatment processes the system uses zero energy, zero chemicals and has a very low carbon footprint.
Freestanding filter beds can be subject to high circumferential stresses, resulting from daily and seasonal temperature fluctuations. The pas sive pressures, which result from radial movements of the wall during cooling, are especially critical. Traditional brick, cast-in-situ concrete and stiffly joined structures have high levels of failure associated with the development of excessive circumferential stresses. The passive pressures at wall/filter medium interface increase with time in a racketing manner, during successive cycles of expansion and contraction, causing an escalation of circumferential stresses induced in the wall. The failure normally occurs suddenly, although it may take years to develop and even with thorough and regular visual inspection it is difficult to predict. As CIRIA Report58 states: “The failure by ring tension is characterised by vertical cracks which progressively increase in width, but many years may lapse before the wall collapses”.
FP McCann high strength/ high flexibility solutions
In designing for long-term serviceability , it is essential to understand the nature of the stress escalation phenomenon. FP McCann research identified the weakness inherent in stiff and stiffly connected panel structures and the potential problem of low cycle fatigues when subjected to thermal stress fluctuations. FP McCann has long recognised the dangers of insufficient flexibility and our filter beds incorporate a specially designed and patented ‘panel to panel’ connection assembly. This assembly combines the unique features of high strength (to enhance structural integrity) and high flexibility (to prevent the development of excessive circumferential stresses due to temperature variations). These features make the assembly particularly durable and lead to longer life.