LSG Sky Chefs FRA ZD GmbH prepares about 100,000 meals daily for Lufthansa and its partner airlines at Frankfurt Airport. These services create 26 tonnes of refuse every day, which are collected from the aircraft and delivered to the company's modern sorting and cleaning plant to be separated for cleaning, recycling or disposal. The extraction of residual waste after separation is carried out by a centralized vacuum system. The original vacuum system was equipped with three liquid ring vacuum pumps, which will be replaced one by one with Busch Tyr rotary lobe blowers. The new blowers are considerably more energy efficient, and require significantly less maintenance. When the conversion is complete the resulting savings will be an estimated EUR 70,000 per year.
The new centre for Lufthansa Services was commissioned in 2008, and uses modern logistics to process catering refuse from aircraft. Most processes are fully automated, from the reception of the used food trays at the return bay to residual waste disposal and the cleaning and preparation of crockery and cutlery. Only the waste separation process is carried out manually. All workstations which separate residual waste are equipped with chutes connected by a 300 m pipeline to the waste containers. Material is transported through the pipeline to the containers by a suction conveying system. The vacuum required was previously supplied by three liquid ring vacuum pumps, with one acting as a standby in the event of vacuum pump failure or pipe blockage. The production technology coordinator was not completely satisfied with this arrangement, as all the vacuum pumps needed a water supply to compensate for evaporation losses in the recirculation system and to replace contaminated water as required. The original system used a 2 m3 water tank with fresh water connections and a controller unit.
An additional problem was presented by food acid contamination of the water in the recirculation system, which caused some damage to the vacuum pumps and increased the frequency of repairs. After the proposed repair of one of the three liquid ring vacuum pumps was found to be too expensive, Peter Salbreiter, the Head of Facility Management at LSG Sky Chefs Frankfurt ZD GmbH, decided to search for another supplier in the Frankfurt area. The objectives were to decrease repair costs, reduce the travel time required for service personnel, and identify a competent partner company. An enquiry made to the vacuum specialists at Dr.-Ing. K. Busch GmbH resulted in a recommendation to replace the liquid ring vacuum pump with a Busch Tyr rotary lobe blower, which requires no operating fluids and is thus practically maintenance-free. The recommended blower is also more economical: it requires only 26 kW, substantially less than the 80 kW needed by a liquid ring vacuum pump of similar output. Further savings are achieved by demand-driven control – the blower only runs when the process requires vacuum. The waste chutes are closed by a hydraulic slide valve until the quantity of material in the chute exceeds a certain level. The blower then starts, generating the vacuum level required for extraction. When this level is reached the hydraulic slide valve opens, transporting the contents of the chute through the pipeline to the waste container. The slide valve then closes and the blower is stopped. For technical reasons the original liquid ring vacuum pumps took longer to start and stop, resulting in higher average power consumption.
The facility managers were initially sceptical of the new technology and the promised advantages, so Busch supplied a Tyr rotary lobe blower for a free test. The airline caterer then conducted a trial in which the blower was installed outside the building in the open air, and connected to the extraction process by provisionally laid pipes. After four months of testing, all expectations were met:
- The energy savings were immense
- No blower wear or food acid damage occurred
- No maintenance was required
After the test phase the company purchased the Busch Tyr rotary lobe blower, and installed it in the intermediate floor directly above the waste container. The new blower is more compact than the original liquid ring vacuum pump, as a water tank is no longer required. A separate silencer reduces the noise generated in operation.
The new unit has proved to be the ideal vacuum generation solution for Peter Salbreiter, who now intends to convert the entire system to dry-running vacuum technology with Busch Tyr rotary lobe blowers. When completed, this conversion will save an estimated EUR 70,000 every year. He is also impressed by the competent advice, rapid reaction times and professional service provided by Busch.
About LSG Sky Chefs FRA ZD GmbH
LSG Sky Chefs is the wholly-owned catering subsidiary of Deutsche Lufthansa, and the global market leader in airline catering services. The 133 companies of the LSG Sky Chefs group have 208 centres in 54 countries, and supply 300 airlines throughout the world. LSG Sky Chefs operate two centres at Frankfurt Airport: the first provides catering for an average of 420 flights per day for Lufthansa and its partner airlines, with about 2,000 staff preparing between 90,000 and 120,000 meals daily depending on the season. The second centre serves other airlines at the Frankfurt location.