ISO-TORQ - The Next Generation of Rotating Consistency Tracnsmitters, Capable of Being Extracted at Full Process Pressure, 1998 Process Control, Electrical and Information Conference Proceedings

The paper describes a new type of rotating consistency transmitter that can safely and easily be extracted through an insertion assembly with isolation gate valve without having to shut down the process. This paper provides a detailed discussion on the fundamental differences between shear force and frictional drag forces acting on a mechanical sensor placed into a moving pulp stream. It describes why the ISO-torq design is a fundamental departure from all previous designs of otating consistency transmitters and explains how it maximizes the influence of those forces which are directly related to consistency and minimizes flow turbulence and the influence of drag forces which negatively impact the measurement of consistency. This next generation technology is covered by five separate U.S. patents and is described in more detail. Unlike existing transmitters, the new transmitter measures torque on an absolute basis. The significance of having an absolute measurement of torque include: single point calibration, a simple, linearized calibration curve, and a self-tuning calibration system. This paper further introduces the concept of calming length, describes the flow conditions necessary to achieve a good measurement, and explains how best to obtain plug flow conditions.