Winery Pumps
Winery Pump Types and Uses
Pumps used in wineries can basically be divided into two groups, namely centrifugal pumps and positive displacement pumps. In general, the pumps that are used for juice transfers can also be used for wine, while those used for must and pomace have special requirements.
Centrifugal Pumps
At the heart of a centrifugal pump is a spinning impeller housed in a volute casing (Figure 23.1). The rotation of the impeller imparts velocity to fluid as it is cast out from the impeller vanes against the walls of the volute, eventually finding its way to the casing outlet. Fluid exiting the casing creates suction at the central inlet of the impeller, drawing fluid into the casing from the inlet. Although there are exceptions, centrifugal pumps require priming to operate successfully. Centrifugal pumps are good at moving lowviscosity fluid at high volumes and low pressures. These pumps generally maintain a smooth flow rate over time, free of oscillations.
Pump Cavitation
Simply defined, pump cavitation is the formation of bubbles or cavities in liquid, developed in areas of relatively low pressure around an impeller. The imploding or collapsing of these bubbles trigger intense shock waves inside the pump, causing significant damage to the impeller and/or the pump housing.
Positive Displacement Pumps
Positive displacement pumps operate using a completely different mechanism of action from centrifugal pumps. In all positive displacement pumps, a fixed amount of fluid is pulled into the pump with each stroke through creation of a vacuum and then pushed out on the outlet or discharge side. Because they are creating a vacuum at their inlet, positive displacement pumps are self-priming and will draw the liquid to the pump. This principle applies to all types of positive displacement pumps whether the pump is a diaphragm, elliptical lobe, flexible impeller, rotary lobe, rotary piston, peristaltic, or piston. Due to this mechanism of action, they have a throughput which is directly proportional to their rotational speed (every stroke moves exactly the same amount of fluid).
Diaphragm Pumps
Diaphragm pumps have many applications in a winery (Figure 23.2). They are operated by compressed air and have many desirable features. Diaphragm pumps work by contracting a rubber diaphragm to pull fluid into a chamber through an inlet valve, then expanding the diaphragm to push fluid out of the chamber through an outlet valve. This isolates most of the moving parts of the pump from the juice or wine.
Flexible Impeller Pumps
Flexible impeller pumps are considered for general use in the wine industry (Figure 23.3). The flexible impeller working principle consists of a rotating rubber impeller with vanes that maintain contact with the pump inner walls. These vanes bend and then straighten as the impeller turns to conform to shape of the pump internal walls. The vacuum caused by the movement of these vanes push the fluid round from the inlet to the discharge pipe.
Elliptical Lobe Pumps
Elliptical lobe pumps are rare in the U.S. but commonly used in Italy. They are meant only for moving pomace and must. As the name suggests, they consist of a single elliptical rotor inside of a flattened, near-elliptical cavity with a squoval cross-section. Grapes, must, or pomace are fed into the side by a helical screw and rotor-pushed through the pump.
Peristaltic Pumps
Peristaltic pumps are popular in precision pumping applications that require an exact amount be pumped per shaft rotation (Figure 23.4). The pump works by turning a lobed shaft that progressively squeezes a soft tube filled with fluid, thus pushing the fluid out of the pump on the high-pressure side of the housing. A peristaltic pump is ideal for moving must and does well with wine. These pumps meet all the wine-pumping requirements; they are simple, reversible, easy to clean, and very gentle on the fluid being handled.
Progressive Cavity Pumps
Progressive cavity pumps are also known as Moineau pumps (Figure 23.5). The pumps work by turning a helical rotor within a helix-shaped elastomeric stator. These complex shapes create fixed volumes that move along the axis of the rotor to move fluid from one end of the pump to the other. Progressive cavity pumps are self-priming positive-displacement pumps that minimize the shearing and agitation of the pumped fluid.
Rotary Lobe Pumps
Rotary lobe pumps are a type of positive displacement pump featuring large, non-contacting chambers that handle must, lees, juice, and wine (Figure 23.6). Rotary lobe pumps are extremely common in the U.S. wine industry. The internal structure of the pump generally consists of two intermeshed, counter-rotating, gearlike rotors in an ovoid chamber. Typically, the lobes are equilateral trefoils, but bi-lobed, winged bi-lobe, and helical lobe designs are available.
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