Metso Optical Low Consistency Transmitter
Metso Optical Low Consistency Transmitter (Metso LC)
using light polarization. Compared to traditional optical consistency measurements, the biggest advantage is that this technique is independent of pulp color and brightness variations. Ash fluctuations have some impact on measurement accuracy, but even this effect is minimized with the polarization method compared to other optical single-system measurements. With screened pulps, Metso LC C is suitable for consistencies up to 1.5 %, while short-fiber pulps can be measured up to 2 %. The Metso LC CU is specially designed for ultralow consistencies, e.g. for measuring solid content from clear filtrates to levels >100 ppm.
Using two-point calibration, the transmitter start-up is quick and easy. The Metso LC is practically maintenance-free. During the automatic flushing sequence the self-diagnostics function routinely checks the transmitter’s condition and alerts the maintenance personnel in case contaminant build-up or blockages are detected. This feature ensures high uptime, whatever the process conditions. Smart electronics makes it easy to choose the correct transmitter calibration for different recipes or pulp types; four recipes can be calibrated and stored in the transmitter’s memory. Naturally, HART® communication and AMS-compatibility are among the transmitter’s standard features.
On slower paper machines where the stock contains no ash or the ash percentage is relatively stable, the Metso LC can be used for total consistency measurement in the short circulation, both headbox and white water.
Screening control is an important factor for PM runnability: maintaining the correct feed consistency with Metso LC results in uniform drainage, which in turn improves process operation.
Metso LC is ideal for disc filter feed consistency control, while Metso LC U is uniquely suited for accurate measurement of the filtrate quality. As well as reduced basis weight variation in the machine direction it enables the increasing use of filtrate to replace fresh water in the process.
Metso LC is far better than widely used turbidity transmitters for measuring fibrous sludge in paper mill effluents because of the insensitivity to color or brightness.