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Pumping yeast in wineries with a Verderflex peristaltic pump

At the end of the winemaking process, yeast is removed to avoid spoiling of flavour and to leave the wine with a clear, crisp appearance.

The process to remove yeast is usually performed by introducing diatomaceous (kieselguhr) earth into the fermented wine. The fine particles of diatomaceous earth attract the yeast cells to form clumps, which remain in a suspension referred to as yeast slurry. The yeast slurry is then pumped through a filter press with a Verderflex peristaltic pump, before the wine is finally stored or bottled.

A German company manufactures a chamber filter press system mounted on a skid with a Verderflex VF25 industrial hose pump as part of a standard filter press system.

From the yeast slurry storage vessel, the slurry is fed into the peristaltic pump through a 32mm suction line made from flexible Verderflex hose to reduce pulsation. The peristaltic Verderflex pump is fitted with DIN 11851, type SC stainless steel sanitary connections of 32mm, with reducing inserts to suit the 25mm tubing. The drive of the pump is a 1.1 kW gear reducer giving a pump speed of 48 rpm, delivering 800 l/hr of product to the filter press.

On the discharge side of the filter press pump, a 32mm flexible hose is used to feed the filter press. It is important to eliminate the pulsation on the discharge side of the peristaltic pump, so in addition to the flexible hose, an air dome is installed. The air dome has a volume of approximately 20l, allowing it to absorb pulsation, but also to act as a pressurised storage tank for the filter.

The chamber filters are evenly filled with wine/yeast slurry mixture, to a pressure of 10 bar. This pressure is maintained and not exceeded, for effective operation. To achieve this a pressure sensor is installed on top of the air dome and is set to stop the Verderflex pump running when 10 bar pressure is registered. At least one pressing shoe of the pump is always positioned to be fully compressing the hose, acting as a valve, thus maintaining the pressure in the air dome and chamber filter.

As the wine slowly flows through the filter the pressure inside the air dome reduces, until the sensor registers a pressure of 7 bar, at which point it is set to start the Verderflex pump again. The industrial hose pump continues to stop and start in this cycle, maintaining an even pressure between 7 and 10 bar until the filter is completely filled with the yeast solids. At the end of a batch, when the yeast slurry feed vessel is empty, the peristaltic Verderflex pump can run dry without damage. Or, if the filter is blocked in the middle of a batch, the hose pump can then be reversed to empty the filter and air dome of yeast slurry, leaving the filter dry, so the yeast cake can be removed.

In these wineries in Germany the duty cycle is for approximately 500 running hours per unit per year.

After each season, the hose inside the pump is replaced with a new one.