Calibration of On-line Pulp Consistency Transmitter

Abstract

In order to maintain an accurate fine pulp blend during the mixing process, the proper functioning of flow and consistency transmitters is essential. Apart from microwave measuring systems, standard on-line consistency transmitters generate their readings based on shear stress as registered on the mixing blades. This system yields a relative reading based on accepted, theoretical values-it does not provide a real-time, absolute measurement.
This is an issue because, even under controlled laboratory conditions, consistency values will vary between samples despite shear stress sensors indicating identical consistency ratings. These meters can be affected by a host of variables, such as pulp materials, temperature, additives, particulate velocities within the pulp or of the pulp itself, turbulence, etc. Insuring the proper operation of these sensors and their maintenance are critical issues in pulp quality control.
In this paper, we detail how we have re-engineered the calibration process to produce consistent readings from our resistance sensors. Additionally, we discuss some unexpected phenomenon that was observed during the calibration and which may merit additional investigation.