Pumping up cost efficiencies for mixing

Life cycle cost are words used in various levels of sincerity in the water industry. Yet, they are now beginning to carve a way through the corridors of purchasing, says Peter Harvey.

Engineering and process are now viewing trends of efficiency and cost, these trends having been documented for periods up to five years past. Some of the findings are more than just thought provoking, in some cases, shocking is more apt.

There are single pumps as an example, costing 1,000% and more of their purchase cost, to run per year. These costs are almost always in either sludge with rag and grit, or, inline pump stations with a high ingress of rag, grit and the

catalyst, fat.

Five years ago, P&M Pumps of Sawtry, Cambridgeshire, introduced a “revolutionary” tank mixing system to the UK ( the American system Vaughan Rotamix/STM.

This system uses the Vaughan Chopper Pump as a draw and return from tanks, the return flow being distributed through correctly placed, high velocity nozzle system. The chopper pump reduces the solids to ensure free flow through nozzles with flow orifice as small as 38mm.

More than150 systems have now been fitted to date, tanks from 20cu m to 4,000cu m.

It is the spin off from the early systems that has created growing interest and excitement from the first companies to install.

The results were, better sludge, less pump failures in post mixing application, less press or centrifuge maintenance. In some cases more than a 25% increase of sludge DS through the system.

This persuaded them to look further into recommendations of potential savings if the Vaughan Chopper Pump was to be installed in other problem areas.

One application is now emerging as the major problem solver.

That application is Digester Heat Exchange re Circulation, especially where spiral heat exchangers are installed. The days of clearing either pump, or heat exchanger of a build-up of rag, have been not just reduced, they have been eliminated.

Within days of start up, process engineers are seeing a stable temperature within the digester and we believe a list of benefits throughout the process following digestion.

P&M Pumps’ engineers state the efficiency of a sludge digestion treatment plant hinges upon these two points, stable temperature, homogenous sludge.

This is achieved 100% when the Vaughan system is installed, mixing or re circulation.

Peter Harvey is partner at P&M Pumps. T: 01487 830123.

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