The new facility, opened in 2016, is expected to reduce maintenance costs by 20% over the next five years, provide energy savings and keep the Total Cost of Ownership of the plant to a minimum. Lloyd Hopkinson, Managing Director of the principle contractor JJL Design & Build Ltd, said: “The end result is fantastic, definitely one of the best cold room projects we have worked on. The design, installation and final product are something everyone involved should be really proud of.”
The cold store
The new facility in Reading comprises two cold stores: a 45,000m³ freezer and a 20,000 m³ chill/freezer. The temperature in the cold store chamber is kept at a constant -24 °C storing frozen food products for onward distribution to supermarkets. Goods are turned over in an average of seven days. The plant’s 30 staff operate the cold store around the clock, 7 days a week, 24 hours a day.
The GEA technology
The plant had already been using GEA compressor packs that had been providing reliable service to the company for 16 years. As these had proved to be trusted technology they were incorporated in the new design. Additional refrigeration equipment, including three GEA Grasso M compressor packages, provided the extra capacity required.
GEA launched the newly developed M packages in 2015; it was chosen for the cold store in Reading for its efficiency, flexibility, wide capacity range, long service intervals and an extended, best in class warranty. The primary contractor for the project was Stonegrove Refrigeration Services Ltd. According to Stonegrove’s design engineer: “It was the efficiency of the GEA equipment that very much tipped the scales in favor of the GEA equipment.”
The GEA Grasso M packages feature a new screw compressor design for optimal efficiency with each unit providing a cooling capacity of 260.8 kW using the natural refrigerant ammonia. They have the ability to operate at a variable speed range of 1,000rpm – 4,500rpm and so benefit from a very low capital cost per kW and increased part-load efficiency. Their variable internal volume ratio allows the compressors to react flexibly to ambient temperature changes, for example, between summer and winter: In winter the condensing temperature of the ammonia is around 20°C compared with 32°C in winter. This ensures that the compressors can sequence to different loads, another decisive factor in the selection of the GEA equipment for the refurbishment of the facility.
In addition, GEA has designed the new M Series to have fewer components than previously. This reduced complexity improves reliability and makes routine servicing much easier. These characteristics, with the resulting significant reduction of total costs over their entire life cycle, have exceptionally positive effects on their cost effectiveness. Stonegrove expected that these efficiencies will reduce maintenance costs by approximately 20% over a five-year period compared with the old plant.
How the refrigeration system works
The refrigeration plant is a direct evaporation system with one ammonia cycle. The ammonia liquid is distributed through the central pumping station to the air-cooled evaporators installed at the cold store. While the ammonia evaporates in the air-cooled evaporators at -32 °C it turns to gas and takes the heat from the air streaming through the evaporators. The cold air then exits through the outlet of the evaporators and cools down the cold store to -24 °C. Ammonia gas coming from the evaporators is now transferred again through the central pumping station to the GEA Grasso M packages where the cold ammonia gas is compressed to a high temperature and pressure level. It is then condensed in the evaporative condenser and turns into liquid at 32 °C (in summer) or 20 °C (in winter). Through an expansion device, the liquefied ammonia is released to the lower pressure level and is then pumped through the central station back again to the evaporators where it evaporates at -32 °C.
Redefining Total Cost of Ownership (TCO)
Stonegrove Refrigeration’s commissioning engineer Garry Dawson who also oversaw the rigorous testing and monitoring of the installation states: “It’s a very energy-efficient system. Looked after properly, it will last a long time. And by choosing ammonia, you are future-proofing your business.” The GEA Grasso M packages have been chosen to minimize Total Cost of Ownership. Advanced engineering and GEA’s extensive application experience have allowed savings in energy, servicing and operating costs and helped to provide the customer with an efficient and economical facility that will give excellent service for many years to come.