Cheese company saves energy with centralised vacuum

DMK Deutsches Milchkontor is one of Germany’s largest dairy companies, employing more than 7000 staff at 28 sites. Each year it processes milk from about 9400 producers to manufacture 6.7 million tons of high-quality cheese products, which are sold to national and international retailing companies, food manufacturers and large volume consumers.

At its production facility in Georgsmarienhütte, the company produces sliced cheese and mozzarella in packaged portions.

Various types of sliced cheese are packaged in three packaging lines by thermoforming machines, with products packed as both DMK and external brands. Two additional thermoforming machines package mozzarella in 2.5 kg and 10 kg blocks for further processing by customers.

DMK conducts its energy management according to ISO 50001 standards, leading the company to seek a solution to reduce vacuum system energy consumption. All five thermoforming machines originally had two vacuum pumps each: one to form the foil into the mould and one to extract air from the packaging chamber. DMK Energy Manager Yvonne Gödeker wished to reduce the number of vacuum pumps and relocate them away from the production area. The production area is air conditioned, so heat emitted by vacuum pumps was causing increased energy costs.

Busch recommended the installation of a centralised vacuum system. Vacuum is supplied by a pipework system with three vacuum circuits:

1. Rough vacuum

Several vacuum pumps maintain a permanent rough vacuum of between 30 and 40 mbar in the vacuum reservoirs and pipework system. This vacuum is available directly at the packaging point to evacuate the packaging to rough vacuum level. The medium vacuum circuit is then activated.

2. Medium vacuum

The medium vacuum modules evacuate the packaging chamber and the packaging from rough vacuum level to the final package pressure of less than five mbar. This two-stage evacuation has the advantage of speed: the final pressure is achieved rapidly, allowing short cycle times. The two-stage process is also the most energy-efficient way of achieving a vacuum of less than five mbar. Panda vacuum pumps in a medium vacuum unit are used as vacuum boosters.

 3. Forming vacuum

This vacuum circuit is used to form the plastic foil into trays. The vacuum level required is between 100 and 200 mbar.

Busch centralised vacuum system at DMK in Georgsmarienhütte.

A controller maintains the required vacuum level in all three vacuum circuits, matching the demand created by the individual packaging lines. Vacuum pumps are switched on or off as required, maintaining the desired pressure in the vacuum reservoirs.

The three packaging lines rarely require maximum pumping speed simultaneously, so in general only some of the vacuum pumps are in operation.

In the original decentralised vacuum system, both vacuum pumps were started with the packaging machine and ran continuously at full speed. This maximum output was dimensioned to meet the demand created by the shortest cycle time and largest packaging volume of the machine. The new centralised vacuum system has drastically reduced the running time of individual vacuum pumps, which in conjunction with the two-stage package evacuation has resulted in significant energy savings. After a year of operation the centralisation of the vacuum system had saved about 100,000 kW/h, reducing DMK’s energy costs by approximately €15,000.

The centralised vacuum system is located in an intermediate floor above the production and packaging areas. The relocation of vacuum pumps installed directly to the packaging machines prevents emitted heat from reaching the packaging machines and production area. In addition, no warm air from vacuum pump exhausts is given off to air-conditioned rooms. This has reduced the cooling required by the packaging machine tools, and air-conditioning costs are also lower.

As the centralised vacuum system is now located externally, it is no longer necessary for service personnel to enter the production area. Service technicians can carry out maintenance without interrupting production, as the system has a reserve vacuum unit. Starting this reserve unit allows the first unit to be disconnected from the network and maintenance tasks to be carried out. This has reduced expenditure, as no production time is lost and maintenance is no longer required at weekends when costs are higher.