Sector: Industrial Sector
Project: Business Process Change Intervention in an Engineering Prime CNC shop
A common misconception is that the majority of energy consumed in an engineering shop is by the primary production assets – the CNCs and lathes.
What is usually not taken into consideration is the auxiliary systems Compressed Air or Extraction systems that often run continuously. Over an entire working week of 168 hours, the cumulative energy cost of auxiliary systems can often be higher. If there is an issue with the auxiliary system, it is usually not noticed as they tend to be hidden away from view.
At a large engineering company, a project to ascertain the true cost of production identified an unusual spike in energy consumption during the non-working hours of the weekend. In this particular plant the production week finished at 12:00pm on a Saturday and the unusual spike commenced at 12:05pm.
On drilling down into the data it soon became apparent that the back-up compressor (an auxiliary energy source for the CNC machines) was kicking in after the main compressor powered down at midday Saturday.
This backup compressor (an old fixed speed 132kW system) did not have the control capability to power down at the same time. Therefore, when the air pressure dropped below the threshold it kicked in and stayed online until the main compressor started up again at 6:00am Monday morning.
As the compressors were located outside the factory building it was not noticed. The shut-down process was then amended to physically isolate the back-up compressor to ensure it did not run over the weekend. This reduced the cost of energy by £400 per weekend or £20,000 per annum.
The use of the old compressor as a back-up system is used across the majority of the manufacturing sector. The above example illustrates two important points – the first is the cost of leaving systems running over the weekend and, more importantly, that the cost of energy going into the auxiliary systems (compressed air, chilled water) is sometimes greater than the primary production assets.
Sharing this knowledge is key to reducing waste energy consumption during non-working hours by all companies, not just large manufacturers.