Refrigerants 33 McVitie’s trials a new recipe


MCVITIE’S IS a masterbrand for United Biscuits (UK) and produces many famous sweet biscuit lines including Digestives, Hobnobs and Medley Bars at its manufacturing site in Glasgow. The Glasgow site uses refrigeration in many parts of its production processes and efficient operation is a key to its business success. Since the EU phase-out of HCFC refrigerants began in the late 1990s, the search has been on for a replacement for the R22 refrigerant that could be used in existing equipment and would provide the same cooling capacity.


The recent development and introduction of RS50 (R442A) has provided a refrigerant that has achieved this for McVitie’s. RS50 is an HFC with a Global Warming Potential (GWP) of 1888, which is below the 2500 GWP threshold in the revised F-gas legislation.


Danny Watson of Glasgow- based HRP, a wholesaler of refrigeration and air conditioning equipment, suggested to C&M Environmental, which has retrofitted many R22 systems that it was worth considering RS50.


They identified that the additional cooling capacity of RS50 was a possible solution to McVitie’s concern that R22 retrofit gases would result in a loss of capacity that would not be acceptable for its production.


This led to a trial of RS50 at McVitie’s Glasgow in the North


chill store that is used for holding ingredients at 4°C. Commenting on the outcome of the trial, Norrie Fraser, director of C&M Environmental, says: “We are delighted, the RS50 was a straightforward retrofit and the energy saving is even better than we expected.”


The performance of the system was measured when operating on the R22 and also after replacement with the RS50.


The performance with RS50 met the cooling requirements and further provided an average power saving of 16% over R22.


The successful outcome of the trial enables McVitie’s Glasgow to withdraw from using R22 before the complete ban on HCFCs at the end of 2014.


The trial


The compressor is a Bitzer 4T- 12.2 semi-hermetic unit. Retro- fitting the R22 with RS50 was a straightforward procedure. The R22 was recovered from the system and the mineral oil drained before filling with polyol ester oil Mobil EAL Arctic 68 and then recharging with RS50.


The system was then recommissioned and adjustments made to the expansion valve superheat. Over the 24 hour periods evaluated, the required duty for the chill store was achieved with 15.5% fewer compressor running hours and a resultant energy (kWhr) saving of


Refrigeration system at McVitie’s Glasgow North chill store.


Comparison of plant operating on R22 and RS50 R22


Refrigerant charge Running time per 24hrs


Compressor starts per 24hrs Amps (maximum) Discharge Temp °C


Discharge Pressure barg Condenser Outlet Temp °C kWhr over 24hr period


16.4%.


This performance is in line with the findings of both the independent blind testing and other field trials carried out in 2013.


Andrew Wilson, engineering projects manager for McVitie’s, says: “RS50 has come along at just the right time. We have been looking to retrofit away from R22 but we could not risk the potential loss of capacity


average* 11.2kg 8.4hrs 30


5.4 95 12 25


19.15


RS50


average* 8kg


7.1hrs 51


8.2 90 14 20


16.0 * average of the 24hr run periods


that was expected with other retrofit gases. We are delighted that RS50 has meant no loss of cooling capacity and also has delivered double digit energy savings.


“An extra bonus is that we have not only got a solution to the R22 issue but will be using a refrigerant that puts McVitie’s Glasgow on a gas that is below the 2500 GWP threshold that F-Gas part 2 will introduce.”


Hydra Visit ACR News online at www.acr-news.com ACR News April 2014


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