Cheese company cuts energy costs with centralised vacuum supply

DMK Deutsches Milchkontor is one of the largest dairy companies in Germany, processing milk from about 9400 producers to manufacture 6.7 million tonnes of dairy products per year for national and international retailing companies, food manufacturers and large-volume consumers. The company has a wide product portfolio, ranging from basic milk products and cheese, to milk-based food manufacturing ingredients, to baby food, ice-cream and health food.

One of the company’s 28 sites is a production facility in Georgsmarienhütte, which manufactures mainly sliced cheese and mozzarella in packaged portions. These products are distributed throughout Germany and exported to other European countries. Other products include milk and whey concentrates, which are mostly used in-house for further processing. The site operates a three-shift system, five days a week, and employs a total of 350 staff.

At the facility, various types of sliced cheese for end consumers 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, which was ultimately commissioned in October 2014. 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 Busch centralised vacuum system at DMK in Georgsmarienhütte.

This saving was achieved by a combination of factors, but a major factor was the vacuum control system: only the vacuum pumps needed to meet current demand are in operation.

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 5 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 5 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.

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.

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 on weekends when costs are higher.

Gödeker says she is completely satisfied with the Busch vacuum supply energy reduction project, which has exceeded the projected energy savings.