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In this article, I would like to convey the importance of the correct handling of filter press pumps, the proper functioning of which depends on how they are handled during the filtration phase.
However, this analysis also applies in all cases where there is a transfer of pressurised fluids.
This topic has already been introduced in this article.
We have in fact seen how during the filtration phase it is important to adapt the pump to the demands of the filter press, clearly in terms of both pressure and flow rate.
Autemi srl’s piston or piston/membrane pumps equipped with the energy-saving E.S.S. system is able to do this.
This is made possible by the special technological solution applied to the hydraulic power unit that controls the supply pump.
However, this conceptual solution can also be transferred to mechanically driven piston or diaphragm piston pumps – i.e., the Libra series.
It is in fact possible to equip a simple mechanically driven piston pump with an inverter that modulates the motor speed depending on the pressure value read by, for example, a pressure transducer with a 4-20 mA signal.
In this way, the flow rate can be modulated once the desired pressure is reached, by appropriately programming the inverter.
Adopting this solution is also very important to increase the useful life of the pump. In fact, in addition to the benefits we have just seen in terms of energy savings and flow rate modulation, by doing so, I can avoid abrupt pressure starts when the pump restarts.
Let us suppose that during the end-of-filtration phase, the logic of the filter press forces the pump to stop when a certain pressure is reached and restarts it at another pressure value (which will in any case be high and close to the end of filtration): with this restart mode we avoid abrupt pump strokes as otherwise the restart would be quite abrupt because at high pressure values.
These prolonged starts and stops with high pressure values can cause damage to the pump if repeated constantly, often if the operator has set the start and stop pressure values very close together.
This behaviour is physiological for any mechanically driven piston pump that is not controlled by an inverter.
The advice is therefore to equip the pump with an inverter and to tie the variation of the motor speed to the variation of the filtration pressure.
An alternative may be the use of a soft starter: in this way, restarting takes place in a precisely gradual manner, avoiding the abrupt jolts when starting the pump, which can damage the moving parts, although it does not solve the problem of energy containment due to a decrease in flow rate.
From my own experience, I have seen several filter press pumps whose operation was mismanaged during restarts.
These machines lasted only a few months, while once the management was fixed, both in terms of operating logic and inverter insertion, they continued to run for several years with only scheduled maintenance.