The sensor measures the bending stiffness of paper
'This is the first full-scale demonstration of the sensor on a commercial paper machine, while it is in operation,' said Paul Ridgeway Environment, Energy Division, Berkeley Lab Technologies (EETD), who developed the sensor is a principal investigator for the project and fellow EETD scientist Rick Russo, in partnership with the Institute of Paper Science and Technology at Georgia Tech. 2 Weeks test was conducted in February at a mill owned by Boise Cascade.
Engineers of Boise Cascade is the court will be very successful, and we hope that the 6-month trial will be conducted in the same factory, 'says Ridgeway.
Eight years in the making, the sensor was funded by the Department of Energy Office of Industrial Technologies in partnership to improve the efficiency of energy use in several industries. Under this program, the American Forest and Paper Association created Agenda 2020, which defines the way the timber industry will lead to rationalization of production processes.
Paper is an obvious candidate for improvement. To assess the quality of the paper today, 15 to 30-ton paper produced, and then a few samples were obtained from the end of the roll and analysis of their mechanical properties by observing how they bend. If the samples do not meet certain requirements, the entire roll is processed into pulp or sold as a lower class. To avoid this costly mistake, manufacturers often over engineer paper and use more pulp than necessary to ensure the final product is not low.
This method requires more raw materials and energy than necessary, so the team at Berkeley Lab has developed a sensor that tracks papers 'flexibility' on the fly in real time. In particular, the sensor measures the time it takes for an ultrasonic shock waves propagate from the laser excitation point on the moving paper, the point of detection of several millimeters away. The speed at which ultrasound waves travel from the excitation point through the paper to detect the point is related to two elastic properties, bending stiffness and shear stiffness out of plane.
Laser ultrasonic sensor conducts these measurements without touching the paper, an important advantage, given that the paper moves at 20 meters per second (45 miles per hour) and touch can cause damage to the leaf and cause costly machine downtime, or mar the lungs of classes such as paper and newsprint. The latter trial also had the highest sample rate is not reported for the commercial application of laser ultrasonics.
The next step in the implementation of the project is to work with Boise Cascade to link the sensor with sophisticated feedback controls, to maintain the rigidity of the newspaper until she stages of production. ABB Corporation, which participated in the latest trial is also likely to participate in this phase.
'Our technology enables real-time feedback,' says Ridgeway. And the successful mill trial shows that we are one step closer to realizing it. '
Mills Court is the latest in a series of successful tests in a real world. In 2003, Ridgway, Russo and engineers from the Institute of Paper Science and Technology conducted a pilot-scale tests of the laser ultrasonic sensor at the research center Mead Paper Company in Chillicothe, Ohio.
This test showed that the first complex hardware sensors can be successfully performed in accordance with the stringent conditions of industrial environment, compared with the laboratory. The sensor detection beam from the interferometer is directed commercially available rotating mirrors. The rotating mirror reflects the beam on the paper as courses on the production belt. Since both the beam and the paper moving at the same speed, the detection beam remains fixed at the same point on the paper during a brief contact.
Next, an optical encoder determines when the detection of the beam is perpendicular to the work, and at this time fires scheme pulsed laser. This is a 5-nanosecond pulse causes a microscopic thermal removal of the document, which is too small to significantly damage the paper, but strong enough to send ultrasonic shock waves through the sheet. Waves propagate until they reach the detection of light. Because the laser is synchronized only fire when the detection beam is perpendicular to the work, the distance between the ablation point and detection point is known, and the wave velocity is calculated.