Automatic Jet Speed Profiling System, 2000 Engineering Conference Proceedings

Claus J. Nielsen, Henning Popp, Jerry A. Baresich--A non-contact velocity sensor is now available that is capable of measuring the speed directly on the surface of the jet, without actually interfering with it. The sensor provides instant real time readings with high accuracy and repeatability and will not be affected by the hydrodynamic properties inside the headbox and on the composition of the pulp. Contrary to pressure gauges this velocity sensor measures the jet velocity in a localised point and therefore it has the unique ability to measure the cross profile of the jet speed across the machine - provided that it is mounted on a suitable traversing mechanism.

By measuring the true headbox jet speed profile it is possible to optimise side flows and to adjust the headbox front side/drive side balance manifold based on the real jet speed profile as opposed to relying on front side/drive side pressure ratio inside the headbox. The design and layout of the new system as well as selected case studies presented.