Acetal resin combines strength with lightness

Edited by the Engineeringtalk editorial team Mar 31, 2006

A new, environmentally friendly water softening device, which solely relies on water volume for its operation rather than a power supply, is made almost entirely of DuPont Delrin acetal resin.

A new, environmentally friendly water softening device, which solely relies on water volume for its operation rather than a power supply, is made almost entirely of DuPont Delrin acetal resin.

Launched by the Belgian company Delta Water Engineering (DWE), the compact yet robust device is available for domestic or commercial use, and requires comparatively little space for installation.

It is currently sold in Belgium and Italy, and will be rolled-out across Europe in 2006.

Strong and rigid Delrin was selected for the majority of the device's parts due to the material's good moisture, heat, and solvent resistance, combined with high tensile and flexural strength plus low elongation.

Hard water is the common term for water containing high levels of dissolved minerals such as calcium or magnesium carbonates.

on heating, these minerals form layers of scale in plumbing and appliances, reducing energy efficiency by up to 60%.

It has lead to both a domestic and commercial demand for water softeners, which are designed to remove hardness.

They work either by means of chemical ion-exchange or by subjecting the hard water to a magnetic field.

DWE's new water softener is of the chemical ion-exchange type, and incorporates the major innovation that it needs no electricity to work.

"As far as we have been able to determine, all currently commercial ion-exchange devices need electric power", explains Guido Van de Moortele, DWE's owner.

"In conventional softeners, a timer determines when the ion-exchange resin needs to be regenerated".

"The timer activates one or more electric motors which open or close the valves that permit the regeneration with salt to start and finish".

"The DWE softener has no timer; the regenerating valves are operated simply by the volume of water passing through it, so our softener needs no electricity and eliminates needless regeneration operations initiated by a time-based system".

The DWE softener comes in two sizes: each measuring approximately 50cm in height, the domestic unit weighs around 4kg; the commercial one is closer to 5kg.

Its compact proportions mean that less space is required than for other, similar water-softening devices, thus facilitating installation in tight spaces.

Over 50 different components of the softener, constituting approximately 95% of its overall weight, are made of Delrin.

Indeed DuPont was involved in the DWE softener's development from the start, providing help in material selection, plus mould-flow studies and mould-fill simulation for parts of the complex valve system.

Injection-moulding guidance helped to optimise processing conditions.

Moulding is particularly challenging because the parts are in a sensitive off-white colour that require a perfect surface finish.

Dimensional tolerances are tight, to ensure good functionality and to avoid water leaks.

The complexity of many parts also means that special attention had to be paid to minimise warpage.

High tensile strength is of particular significance for DWE's water softener, which requires a minimum burst pressure of 34bar.

Further material benefits include the unreinforced polymer's weld strength, its smooth surface finish and overall colourability: all adjustable parts of the device are moulded in grey, all the others in white.

"We were impressed by the excellent mechanical properties of Delrin and its subsequent performance in field trials".

"This functional ability, coupled with its aesthetical benefits of surface finish and colourability, made it the ideal material for this water management device", commented Van de Moortele "As a result, our device weighs less than anything comparable, but without sacrificing efficiency or durability".