John Guthrie, Energy Efficiency Manager, ABB writes: If you had a group of employees who found themselves without work for half of their day, you’d no doubt do something about it. After all, you still have to pay their full salary – yet you are only getting a half day’s work from them.
It’s a similar story with assets such as vans or machines – who would let them stand around unused for half the time, not earning money yet still running up costs?
This was the situation facing Newtown Plastics. It suspected it was wasting energy on some of its injection moulding machines by paying for electricity to run motors that were not doing any useful work for much of the time.
Newtown Plastics of Wales makes a wide variety of moulded plastic components, both its own ranges and bespoke designs. These range from display cases to caps and closures and a wide variety of components for use in the pharmaceutical, retail, construction, automotive, aerospace, electrical and other industries.
An energy appraisal by ABB identified a machine with an 18.5 kW motor as worthy of attention as it had such a long cycle time. It operates for 40 weeks a year making a perfume display case and requires a long cooling time. During this time, the hydraulic motor is not doing any work but is still running at top speed, so this was an obvious choice for an energy saving project.
The process – which has a 50 percent load and a 50 percent idle cycle - was logged for seven days to confirm cycle times and on and off load values.
The machine was retrofitted with a drive whose internal load measurements are used to decide when the pump is doing useful work or recycling back to the tank.
When the pump is recirculating fluid back to the tank, while the plastic part is being cooled, the speed of the motor is dropped to 50 percent. Off load power has been reduced from 7 kW to 3.7 kW, giving an annual saving of £1,963 a year.
The result? Newtown Plastics is now saving nearly £2,000 a year on this one machine. And that’s no half measure.
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