STS Case Studies

The Tennent’s Brewery in Glasgow has three primary refrigeration systems. One refrigeration plant using ammonia reported poor efficiency factors. After a site visit, Star Technical Solutions (STS) identified that the running compressors were showing an unusually high discharge pressure, despite there being more condensers running than should have been the case given the number of operational compressors. In addition, the compressors suction pressure was very low while a high surface area for evaporation was available. STS decided to use a remote data gathering device in order to capture key operational parameters and review them over a prolonged period. This would allow it to undertake appropriate remedial actions and measure the benefits for the brewery. They first recommended that Tennent’s undertake general maintenance on the condensers and purge the system, to ensure these elements were not detrimentally affecting system operation. Monitoring started before the condenser maintenance. Given the poor condition of the condensers before maintenance was undertaken, it was a surprise to find that it made no difference to performance once it had been undertaken. After analysis of the data gathered over a period of one week, it appeared that the plant control system was causing the discharge pressure to be much higher then was necessary. After a detailed review of the control philosophy, it was found that the original design set points had been changed causing the high discharge pressures and consequent very poor system efficiency. With the discharge pressure set points modified back to the original design basis the compressor instantaneous power consumption immediately reduced by an average of 45kW. Additionally, the maintenance carried out along with the control system adjustments delivered a further average instantaneous saving of 60kW from optimised operation of the condensers. For the brewery, the improvements represent electricity saving of more than £50,000 per year. By reviewing data, implementing solutions and continuous monitoring, STS has provided evidence of the saving and a follow up on remedial action. The data logging is being continued to ensure ongoing optimised system operation.