Plastic is key to water filtration system

Edited by the Engineeringtalk editorial team Aug 26, 2002

Quadrant Engineering Plastic Products is a key material supplier for Ultrazur 450, a new water filtration system, the largest of its type, introduced to the market by Ondeo Degremont, Paris.

Quadrant Engineering Plastic Products is a key material supplier for Ultrazur 450, a new water filtration system, the largest of its type, introduced to the market by Ondeo Degremont, Paris.

Quadrant EPPs' Nylatron M AQS material was selected for the base and cap of the filtration modules because of its high mechanical strength, light weight and corrosion resistant properties.

Also important was that Nylatron M AQS is FDA compliant and is certified for products that come into contact with drinking water.

The Ultrazur 450 filtration unit, which can process over 10,000m3 of water per day, is manufactured by Aquasource, Toulouse, France, a subsidiary of Ondeo Degremont.

It consists of multiple modular columns, each containing 5000 hollow acetate fibre membranes and each measuring 1350mm high and 450mm diameter.

Untreated water enters the columns through a connection in its structural base, it is then pumped up through the columns and the ultra-filtered water exits through the cap.

The filtering process is a continuous operation and includes retro-rinsing phases.

The nylon components are made using a special casting process, which allows these complicated parts to be made to near-final dimensions.

The mechanical strength of cast nylon allows it to support higher bearing loads than is possible with many other thermoplastics and cast-in ribs provide for added structural strength.

Moreover, the resiliency of cast nylon allows it to return to its original shape without permanent deformation when deflected by any non-uniform, short-term pressures experienced by the Ultrazur unit during normal operation.

Casting the components lowers material cost and machining time.

Similar to injection moulding, casting allows several parts to be integrated into one moulding, thereby reducing manufacturing, assembly and maintenance costs.

Additionally, low forming pressures are used in casting nylon parts, thus tooling costs are low compared to injection moulding.

Minimal finish machining is required and only in those areas where critical dimensions must be held, such as the cap's inner surface to achieve a watertight fit with the ends of the membrane columns.

A further benefit is that casting allows larger cross section parts to be produced which, when compared to injection moulding, minimises flow-induced stress and results in improved dimensional stability during use, with parts less likely to distort.

Nylon has not often been used for drinking water applications: steel and aluminium are usually the materials of choice.

But, as Franck Zirilli, project manager at Quadrant EPP, points out: "If steel or aluminium had been used, the components would have needed a protective coating against corrosion, which would have to be certified for contact with drinking water.

And, it would have involved an additional manufacturing step and the coating would have been subject to abrasion or other damage.

Moreover, because of the weight of metal, installing the cap would have created a handling problem".

Confirming the success of the development, Philippe Gaudet, Director-General of Aquasource, says: "Ultrazur 450 plants are now in use in Rouen and Lorient, France, and we have developed two water treatment plants for customers in the United States and they will be operational this year".

Earlier this year Quadrant Engineering Plastic Products was presented with the European Engineering Award 2002, in recognition of its material development and processing knowledge contribution to the new Ultrazur 450 water filtration system.