Valmet Optical Consistency Measurement - Valmet OC
The Valmet Optical Consistency Measurement (Valmet OC) is part of the Valmet portfolio of consistency transmitters that uses state of the art technology with a new design, offering reliable measurement at all times. The Valmet OC is suitable for many fiber consistency installations. The operating range is between 0 - 12% consistency, as majority of the applications are in the lower part of that range.
Inline consistency measurement has never been easier
In mechanical pulping (e.g. TMP, GW and CTMP) typical applications are grinders, cyclone cleaners, latency removal, screening and low consistency refining. In chemical pulping, the new transmitter can be used for screening, washing, refining, and drying machine applications.
State of the art technology
Inline consistency measurement has never been easier – the Valmet OC employs the latest electronics technology with multiple optical fiber channels, using a single light source and optimal probe design for reliable measurement. There are no electronic components or other sensitive parts on the probe, making it resistant to high temperatures, pressure and vibrations.
The Valmet OC‘s profiled coupling secures that the probe position will be correct without any special tools or measurement. Installation is simple and safe. Inserting and retracting the measurement probe is safe and easy, even at a high process pressure. Calibration is quick and easy, the Valmet OC can be calibrated with just one laboratory sample. However, in demanding applications multipoint calibration is available as well with Valmet OCR and Valmet OC2R. No regular maintenance is needed – the entire transmitter-related cost stays low.
Valmet OC2R offers the possibility to measure ash in recycled pulp manufacturing applications as well as general stock preparation applications in paper, tissue and board. It shares the total consistency measurement method utilized in the original Valmet Optical Consistency Transmitter, with the added capability of measuring ash content available as a second measured value. The addition of the ash measurement to total consistency opens new possibilities for greater control of stock preparation processes with all kinds of furnishes from virgin or recycled fiber to mechanical and chemical pulp.
In mechanical pulping (e.g. TMP, GW and CTMP) typical applications are grinders, cyclone cleaners, latency removal, screening and low consistency refining. In CTMP pulping, the new transmitter can be used for screening, washing, refining, and drying machine applications.
Eucalyptus pulp applications
Eucalyptus pulp has different optical properties compared to other pulps; which has led to the design of the special optical sensor and measurement method of the Valmet OCE. Results with the new transmitter in several commercial installations have been successful in applications where competing inline optical transmitters have failed. A typical application is the control of refiner feed consistency, where improved refiner freeness results and reduced specific energy consumption have been reported.
Unscreened and Screened OCC and RCF applications
OCC and RCF processes are a challenge for any measuring device, where sand, metal and other contaminants as well as non-organic fillers are present. The Valmet OCR features a robust probe to survive the harsh physical environment and multi-point calibration for ash tolerant measurement. So ash variations that normally prevent the use of inline optical consistency measurements is not problem anymore. Installations in OCC processes before coarse screening have proved the probe’s robustness and the total consistency measurement accuracy is excellent throughout the stock preparation area even with wide ash variations.
Chemical pulping applications
The Valmet OCS now features a sapphire window to withstand chemicals used in chemical pulping and enables inline consistency measurement.
Specifications of the different Valmet OC models
(click in the image to enlarge)