Vacuum packaging of meat and sausage products offers a fundamental advantage: the elimination of the air in the packaging drastically reduces the oxygen content, slows down the activity of bacteria requiring oxygen and thus significantly increases shelf life. Additionally, vacuum packaging is hygienic and enables the products to be presented in an attractive manner. A wide range of vacuum packaging machinery is available on the market, which means a suitable packaging machine can be found for all packaging requirements. Regardless of their design or size, these packaging machines have one thing in common: for all machines, vacuum must be generated to meet the requirements for vacuum packaging. This can be achieved by either an integrated or a separate vacuum pump. Other alternatives include central vacuum supply systems to which several packaging machines are connected.
Integrated vacuum pump
Normally, the vacuum pump is integrated or set up separately in the immediate vicinity for any vacuum packaging machine – whether it be a vacuum chamber packaging machine, tray sealer or thermoforming packaging machine. Oil-lubricated rotary vane vacuum pumps are almost exclusively used for this purpose (Fig. 1). This type of vacuum pump, developed specifically for the packaging industry by Busch Vacuum Pumps and Systems in the 1960s, has long been the standard in vacuum packaging. Continuous further development ensures that these vacuum pumps are always state-of-the-art, with millions in operation across the globe. The newest generation of these vacuum pumps is optimized with regard to energy in such a way that it produces energy savings of 20 percent.
Fig. 1: The R 5 RD 0360 A rotary vane vacuum pump is one size of the newest generation of vacuum pumps for packaging
The vacuum pump, either integrated or set up separately at the packaging machine, is the simplest and most common way of generating the vacuum for packaging. Short pipes between the vacuum chamber, sealing station and the vacuum pump guarantee that the air is rapidly removed from the packaging. Larger-scale thermoforming packaging machines with high packaging volumes may also be fitted with a vacuum booster. Higher speeds can be achieved by combining rotary vane vacuum pumps with vacuum boosters, thus reducing pump-down time. In practice, this means shorter cycle times and thus a larger quantity of packaged products per time unit. If several thermoforming machines are operated, at least partial centralization of the vacuum supply should be considered.
With partial centralisation (Fig. 2), the rotary vane vacuum pumps are removed from the actual packaging room and integrated into a central pre-vacuum system for all packaging machines in a separate room. Dry, oil-free vacuum boosters are installed directly in the packaging machines and connected to the central pre-vacuum technology system with a system of pipes. Partial centralization means the rotary vane vacuum pumps are eliminated from the production room, thus preventing the danger of aerosol emissions. A partially centralized system always makes sense when two to a maximum of five thermoforming packaging machines operate close to one another in one area. If more packaging machines are used, the investment costs are too high due to the vacuum boosters in the individual machines; thus it is recommended to fully centralize the vacuum supply.
Fig. 2: Partial centralization of the vacuum supply
Central vacuum supply
• Economic efficiency
Full centralization of the vacuum supply (Fig. 3 and 4) is generally an economically viable option when there are six or more packaging machines. Usually, it is safe to assume that substantially fewer vacuum pumps are required for a central vacuum supply than for a set-up of individual vacuum pumps directly alongside the packaging lines. If the vacuum supply is subsequently converted from a decentralized to a centralized system, existing vacuum pumps can be integrated into the new centralized system, reducing the investment costs. The substantially lower energy costs when using vacuum boosters should not be underestimated. The cooling requirements for the air conditioning system are also reduced due to the fact that all vacuum pumps are located outside the packaging room. This, in turn, clearly improves the total energy consumption in favour of a centralized system
Fig. 3: Full centralization of the vacuum supply
The absence of all vacuum generators in the production and/or packaging room in turn eliminates the danger of food contamination through oil aerosols. Additionally, there is no need for employees to enter the hygienically sensitive packaging room for maintenance or repair work. Clean-room conditions can therefore be created in the area surrounding the packaging lines.
• Operation method
The individual packaging chambers are evacuated in two stages to be able to run maximum cycle frequencies on the packaging lines. To do so, the critical pressure gradient is utilized and thus achieves the fastest possible evacuation.
This requires a rough vacuum pump unit for the initial evacuation and a medium vacuum pump unit for the evacuation to packaging pressure. The reversing valves with the corresponding control units are attached to the packaging machines. They control the transition from a rough to a medium vacuum.
For thermoforming packaging machines, the moulding station is supplied using a separate thermoforming vacuum pump unit. This ensures that the previously heated base foils are sucked into the tray mould and take the desired shape.
On the one hand, this separation into various vacuum stations is necessary as the moulding and sealing functions run at different vacuums and, on the other, as a substantially lower pumping speed is required for the two-stage evacuation of the sealing chamber. The pipework serves as a vacuum buffer. This buffer is necessary to keep the packaging pressure at a constant level, even when all the packaging machines are running with the same number of cycles.
The central vacuum system is fully automatic: it activates individual vacuum modules if a greater vacuum is required and/or switches off individual vacuum modules if a smaller vacuum is required. If a vacuum pump fails in the rough, medium or thermoforming pump units, then the reserve pump is automatically activated. This ensures maximum operational reliability for the vacuum supply to the packaging machines.
A central vacuum supply system has a modular design, meaning that individual modules can be disengaged for maintenance. When this happens, a reserve unit automatically activates. This means that maintenance work can even be carried out during operation without affecting the production output of the packaging machines. In the central system, the individual rotary vane vacuum pumps are subjected to substantially lower loads relative to the individual units, thus extending the maintenance intervals. The central system's installation location outside the production area also benefits maintenance, as maintenance work does not result in interruptions to operational processes or hygiene breaches.
• Integration into the process control system
Central vacuum supply systems are very well-suited for integration into the operational process control system, meaning that the vacuum plant can be controlled and monitored from a PC. Any indications of imminent faults can be easily identified and rectified before the machines fail. The necessary technical parameters can be permanently called up and the pressures in the vacuum lines are displayed in graph form. This allows all process-related data to be evaluated and archived. Valuable information is supplied to the quality assurance and repair departments.
Fig. 4: Centralised vacuum system for 30 packaging lines with thermoforming packaging machines
In systems using two or more vacuum packaging machines, the operator or responsible head of operations should consider how the vacuum is generated. They should not forget that production, e.g., with sausage fillers or tumblers, also requires vacuum that can likewise be supplied from a central vacuum supply. The different vacuum levels and pumping speeds at the various vacuum applications make it necessary for a vacuum specialist to precisely analyze the actual situation and then offer tailored solutions. For decades, Dr.-Ing. K. Busch GmbH has assisted its customers throughout the world with designing and manufacturing central vacuum supplies. As the world's largest manufacturer of vacuum pumps for packaging, Busch's specialists offer expert advice and calculate precisely which vacuum solution is the most economically and technically viable for each individual case.