Getting the jam into lots of doughnuts

Large bakeries need to automate the quick and hygienic emptying of pastry fillings from mobile mixing tanks into bakery products.

Pastries and doughnuts can be filled with a diverse range of products, from liquid chocolate sauce, to stiff vanilla cream, to jams containing fruit pieces up to 15 mm in size. In large bakeries these fillings are often prepared in mobile mixing tanks and fed to the production lines where, depending on the filling and the type of pastry, the feed speed can be up to 50 L/ min. The different fillings have different viscosities, but all have to be fed from the boiler to the pastry filling plant in a hygienic and efficient manner.

A German bakery is using the ViscoTec ViscoMT-XL barrel emptying system to move fillings for Danish pastries, puff pastries and Berlin doughnuts from 500 L preparation tanks to the filling line.

One challenge facing process-reliable feeding is to supply the different fillings to the line very quickly and at the same time ensure the output quantity of pastries.

The ViscoTec barrel emptying system fulfils this criterion and supplies the line with sufficient filling material. The automated filling, directly from the tank into the hopper of the production line, facilitates the production process and the output of finished pastries is much higher. As a result, there is no downtime in the production line and the entire supply runs reliably. In addition, the user has the advantage that filling errors and wastage are avoided.

By implementing different sensors (eg, level sensors in the tank or pressure sensors), the need to change the tank can be detected early and no production time is lost. Since the fillings are not exposed to their surroundings, there is no risk of contamination. At the end of a preparation phase in the tank, the fillings are immediately covered by the follower plate of the barrel emptying system and are ready to be filled into the pastry in a closed system.

How the system works

The progressive cavity pump forms the base of the barrel emptying system. It belongs to the group of rotary displacement pumps and is based on a volumetric pump technology. The operation is similar to an endless piston, which feeds the product from the suction side to the pressure side and thereby builds up a difference in pressure. The interaction of an eccentrically moving rotor and stator results in a feed and dosing characteristic that corresponds to that of an endlessly moving piston.

Due to the dosing geometry, a constant volume is always fed proportionally to the rotation angle per revolution. The feed direction is reversible by reversing the direction of rotation. The volume is therefore clearly defined via the degrees of angle. This technique results in a pressure-stable, linear pump characteristic, which makes a clear statement about the ratio of revolution, time and flow rate. In turn, this leads to a dosing accuracy at the pump outlet of 1% (depending on the material), which in practice often falls below this percentage.

Another benefit of this technology lies in the resulting feed chamber, whose volume remains constant over the course of the movement. This makes it possible to feed and fill solids-laden fluids and even chunky products. Even difficult, highly viscous liquids can be dosed reliably without pulsation, avoiding dosing errors or excessive stress on the material.

The barrel emptying in practice

The high suction capacity resulting from this technology is used in barrel emptying. In general, such a system consists of three essential components: frame with lifting unit, emptying pump with follower plate and control.

Barrel emptying system for a tank.

Control system for the emptying system.

Emptying pump with follower plate.

The pump — in this case, the hygienic pump 2RD50 — is arranged vertically, while the follower plate with wiper ring sits on the suction nozzle. All wetted parts are FDA compliant and food grade certified. ViscoTec pumps from the RD series (hygienic version) have good cleaning properties, are fully CIP and SIP capable, meet high hygiene standards and are EHEDG (European Hygienic Engineering and Design Group) certified.

During the process in which the various fillings are fed to the line, the pump continuously removes the pastes from the tank and feeds them via a hose line to the filling line. This creates a negative pressure in the container, which the follower plate ‘follows’. The inner wall of the container is wiped clean by the special sealing lip on the follower plate. By using this emptying principle of wiping the container, it is almost completely emptied. The remaining residual quantity is less than 1% and saves in both the cleaning effort and the pastes and fillings themselves, which would otherwise be discarded or manually emptied and fed into the line.

The emptying speed can be easily changed via the electric motor, by simply raising or lowering the motor speed. If, for example, the cycle time of the filling line needs to be increased, only the drive speed of the motor need be increased.

In addition, the system can be easily integrated into existing lines and manufacturing concepts. Even with lines where the masses and materials were previously fed manually, the system can be connected very easily: the tank emptying is operated completely autonomously, without interface to the existing filling line.

Top image credit: ©stock.adobe.com/au/Brent Hofacker