TECHNOLOGY IN ACTION ENERGY & ENVIRONMENT
Corus strips out cost
Steel manufacturer Corus Colors has
reported a 70% energy saving on a
hydraulic system after installing an
industrial drive at its Deeside plant.
The system is located on a 24/7
production line used for retreating
and inspecting strip material, driving
actuators and web guiding systems.
Typically, hydraulic systems waste
much of their energy as a constant
amount of fluid circulates at all
times, although work is only carried
out in short bursts. They also usually
employ positive displacement
pumps that offer far less potential to
save energy than the more common
centrifugal pumps.
Nevertheless, Corus Colors noted
significant energy savings by
retrofitting the existing system with
an ABB variable speed drive that
greatly reduced pump speed both
with the system in neutral and
during actuation of the cylinders.
When in neutral, power
consumption was initially around
9kW. Under drive control, power
consumption reduced from 9kW to
2kW. Under load, it fell from 22kW
to 12kW. With a 16% duty on-load
time for the system, the average
energy saving over time was 70%.
The lower energy consumption
under load initially surprised Corus’
engineers, as it should take the
same amount of energy to move a
hydraulic cylinder a given distance,
regardless of whether a drive or
direct-on-line operation is used.
However, tests showed that the
drive used a lower motor speed to
achieve the required pressure.
At Corus Colors, the desired
system pressure is 90 bar and the
on-load times are short. To prevent
energy waste once the hydraulic
system settles back into neutral, the
drive operates in two modes: PID
mode and single-speed mode.
When the hydraulic system is in
neutral and the pressure is at the
desired level, the drive switches to a
single speed of 450rpm, the
optimum constant speed setting.
When the actuator is operated
and the pressure drops, the
transducer feedback switches the
drive into PID operation. The drive
reacts to speed up the motor to its
pre-set value, set to 93 bar. But as
soon as the pressure reaches 90 bar,
the transducer switches the drive
back into single-speed mode,
preventing the motor from
overshooting its target speed and
reducing energy waste.
To view a Ceros magazine you need to have JavaScript enabled in your browser and have the flash player 8 or higher installed. To install the latest flash player, click the icon above, install the flash plugin and then click here to refresh this page.