The situation: Client Alstom was operating two 45 kW CompAir speed regulated air compressors at its Train Care Centre at Wembley. A study of the compressors’ operation and lubricating oil condition, led us to suggest that the machines appeared to be significantly oversized for the required application. Excessive moisture retention within the oil circuit of one machine, which never got to the required operating temperature, saw a compression element (air end) seize and as a result the machine was deemed irreparable – too old and too expensive to repair.
The solution: rather than simply replacing the failed machine with a new unit of the same size as requested, we recommended that a data log / energy audit should first be conducted on the remaining machine. On reviewing the findings we found a significant reduction in compressor size was possible and despite initial concerns raised by the site, two new 5.5kW variable speed drive compressors capable of precisely matching consumed power to actual air demand were purchased and installed, thereby providing the site with duty / standby, duty rotation and duty assist. Both machines have since proven their worth and run trouble-free since installation.
The outcome: Given the larger machines limited usage, it could be argued that minimal power cost savings have been achieved. However, with the change reliability has improved with maintenance costs reduced. Estimated reduction in CO2 output is 4.19 tonnes per annum, based on an oversized 45kW machine with a fixed offload running period of five minutes per on load operation.