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Detecting what the others miss

The photocells usually used to detect web breaks on paper machines often give false readings or miss breaks altogether. With the arrival of SKS Vision Systems' groundbreaking camera-based system for detecting breaks and cracks, and taking paper web, wire, and felt edge measurements, this problem could become a thing of the past. A VISIEYE™ unit can replace numerous conventional systems with a single device.
SKS Vision Systems Oy

VISIEYE™ has been designed for use in any location in the papermaking process ­– on paper machines, coaters, calendars, and even outside the web area. It is the first integrated detector to be based on high frame rate image-processing technology, and offers a level of performance never before achieved in the industry.

VISIEYE technology offers highly precise and reliable contact-free detection, together with output data accurate enough for use in process and quality control.

Following capture, images are analysed and processed in an integrated processing unit. This outputs detection and measurement signals to an automation system. In the event of unexpected problems, or if a sensor is inoperable due to dirt or any another reason, a warning signal is activated.

The double-wall, stainless steel detector housing features an integrated, powerful LED lighting unit, and is specially shaped to enable compressed air purging to be used to keep the unit's window clean. In areas subject to high ambient temperatures, the detector can be cooled with a vortec tube cooler.

Advanced feature set

A VISIEYE unit is easy to install, and can even be fitted outside the paper web area, to give easy access when a machine is running and prevent dirt, condensation, or other contaminants falling on to the web.

Windows-based software provides a simple menu-driven interface, with the option to connect a laptop to set new parameters, load updated software, monitor signal levels during commissioning or maintenance, and carry out other operations. The software also provides real-time process data. Detector calibration can be carried out via the user interface or directly from the automatic control system.

Excellent field performance

VISIEYE technology has proved very reliable in even the toughest conditions, as this example from Stora Enso in 2006 shows.

Following repeated web breaks at its Kemi Mill that its previous system failed to detect, Stora Enso decided to install four VISIEYE sensors to remedy the situation. Various locations were selected in the drying sections of PM2 and PM3, where web flutter is at its lowest, but where temperatures can go as high as 125 °C.

Following a phased implementation over the summer, the system has proved highly successful, detecting all breaks without a hitch. The physical installation has also proved a success, and the camera windows have not had to be cleaned once. Cooling is handled by vortec tube coolers and compressed air, and has kept internal temperatures within the units to around 40 °C.

> Kari Rahkola
(Published in High Technology Finland )