The role of a filter press in recovering valuable saleable product is an important consideration for a mine operator. The high pressures associated with operating a filter press, however, may cause the pump to underperform.
As a mission-critical system in the mineral concentration process, the filter press demands a carefully selected pump to ensure optimal performance and uptime, advises slurry handling equipment supplier Weir Minerals Africa.
The operation of a filter press involves a spectrum of pressure and flow conditions within each cycle, ranging from high-flow, low-pressure conditions when slurry is initially being pumped into the press, to low-flow and high-pressure when full.
The company emphasises that it is not enough to specify a pump for the average of this range of conditions but that the minimum and maximum values on the spectrum need to be established, in order to specify and select an appropriate pump.
According to the company, filter presses in the market can demand pressures of up to 45 bar, where the application may require high-pressure pumps such as the Warman AHPP high pressure range. In conditions where lower pressure requirements are present, the Warman WBH could be used, as it is regarded as a more efficient pump with longer wear life of spare parts.
Failure of the pump to deliver enough pressure to the filter could result in the solid-liquid separation process being inefficient. The selection of the right size of pump can therefore play an important part in ensuring optimal operation.
Weir Minerals Africa has positioned itself to advise customers on the selection of an appropriate pump for specific applications and offers a range of pumps suitable for use with filter presses.
The company also assists customers in the selection of a sealing arrangement, as this aspect of the pump may lead to leakage of product. It advises that an expeller seal is not usually recommended, as the pressure it generates to seal the pump may not be sufficient in a filter press application.
The stuffing box option can be used under certain conditions. However, the pressure of the surface water needs to be higher than the pressure inside the pump. This means that it would usually be suitable on a low-pressure pump for a low-pressure filter press.
When the filter press requires a higher pressure, then the plant will have to provide a water line with a higher pressure to feed the gland, or it will not seal properly, asserts the company.
According to the company, the preferred sealing option is a mechanical seal. While more costly, the mechanical seal can offer the customer savings by preventing product being lost and downtime being incurred. These seals should be installed by a technical specialist.
A further consideration is the level of corrosiveness of trace elements in the slurry. This can lead to rapid corrosion of mild steel pumps, and the need for stainless steel options.
The company offers a suite of services for customers seeking advice on pump selection, as well manufacturing processes, assembly spares availability and service exchanges for refurbished pumps.