Variable speed drives from ABB
are helping speciality paper manufacturer James Cropper save around £20,000
a year in energy costs at its mill near Kendal in Cumbria.
The energy-saving project has achieved a payback of a year and reduced the
number of pumps needed to meet the required duty from two to just one. As well
as providing variable speed to match the changing demand, the drives have enabled
improved flow through the pipelines and reduced standby pressure.
Before the new control scheme was installed, two 55kW pumps supplied medium-pressure
water to various processes throughout the mill. The rate of delivery from each
pump was controlled by a valve positioned downstream. This arrangement meant
that the pumps were constantly running at full speed, whatever the demand for
water. Furthermore, the valves placed a significant restriction on the flow
of water through the pipes, even when fully open.
James Cropper’s personnel recognised that variable speed drives could
provide a more efficient alternative and called in ABB’s Drives Alliance
partner, Slater Drive Systems, to supply and commission a new drive system.
The new variable speed drives have boosted efficiency at the Kendal mill in
three ways. First, they automatically vary the speed of the pump motors to match
the changing demand for water.
Second, they have enabled the removal of the old control valves from the pipework,
eliminating the previous flow restrictions. “We can now pump more water
and serve the maximum demand using only one pump,” says Cropper. The spare
pump, complete with its own variable speed drive, is now kept on standby to
provide emergency back-up.
Finally, with the new control system James Cropper has been able to reduce
the standby pressure in the water system when there is no demand from the mill.
“Now it’s easier to control the pump outlet on demand so we can reduce
the standby pressure,” says Cropper. “The new control system is providing
us with the same service as before but it now uses far less energy.”
James Cropper has been manufacturing on the same site for around 150 years.
The mill makes a wide range of speciality papers and technical fibres for use
in products such as insulation and fire retardant materials.