A&J modelling aids water treatment design development
Computer aided design has without doubt improved product performance and manufacturing efficiency and A&J are no strangers to this resource, with their own 3D modelling and drawing capability and regular use of disciplines such as finite element analysis. However, some problems defy even the best that computer modelling can offer and only experience and a little empirical experimentation can find the solution.

A&J recently tackled one such problem for customer Veolia Water Technologies in developing a new thickener mechanism for water treatment plants.

The problem faced is caused by the sand used in the treatment tanks. This material settles and compacts when not being ‘stirred’ – requiring a high initial torque input when re-starting the agitation mechanism. If motor and mechanism overloads are set too low, the system constantly ‘trips out’, which is a significant problem with many of the water treatment sites being unmanned, remotely operated plants. Conversely, if the overloads are set too high motors can burn out and mechanisms become strained or damaged.

The key to being able to develop the correct level of protection for motors and equipment is knowing just how much torque is likely to be required to overcome the compacted sand and, as A&J discovered, the only way to know for sure is to experiment with the material itself.

Following a series of tests carried out in-house at A&J it was possible to establish the material shear and loading factors involved. The experiments also brought to light the fact that the sand behaved in different ways in clean water and dirty water systems; clean water treatment systems presenting greater problems for equipment on start-up.

Thanks to the data gained from the tests, A&J has been able to create a new specification for overload protection incorporating both electrical and mechanical systems, carefully designed to limit the risk of damage to plant and provide reliable, efficient operation.