Cast Nylon Key to High-capacity Filtration System

• non-corrosive material

• minimal machining needed

The Ultrazur 450 water filtration system, manufactured by Aquasource, Toulouse, France, processes over 10,000 cubic meters (2.6 million gal.) of water per day. Raw water arrives through a connection in the structural base of the unit, and is pumped up through an array of columns, each containing 5,000 hollow acetate fiber membranes (pore size: 0.01 µm). Ultra-filtered water exits through the cap of each column. The filtering process is a continuous op-eration and includes retro-rinsing phases. The base and cover for the module’s main housing are made of a lightweight, corrosion-resistant, dimensionally stable nylon, Nylatron M AQS, produced by Quadrant Engineering Plastic Products.

The nylon components are made using a special casting process, which allows these complicated parts to be made to near-final dimensions. Minimal machining on the cap’s inner surface makes it perfectly watertight to the ends of the membrane columns. Similar to injection molding, casting allows several parts to be combined into one. Additionally, casting produces larger cross sections and minimizes flow-induced stress. Compared to injection molding, this results in improved dimensional stability during use, with parts less likely to distort or change shape. Cast nylon’s mechanical strength allows support of higher bearing loads than possible with many other thermoplastics. Cast-in ribs provide added structural strength. The resiliency of cast nylon allows it to return to its original shape without permanent deformation when de-flected by the non-uniform, short-term pressures experienced by the Ultrazur equipment during normal operation.

Franck Zirilli, project manager at Quadrant EPP, points out, “If steel or aluminum had been used, the components would have needed a protective coating against corrosion. Further, the coating would have to be certified for contact with drinking water. The coating would have been an extra manufacturing step and the coating would have been subject to abrasion or other damage.”