Process Sensors (Europe) Limited
Process Sensors

 Applications - Wood

  Why Measure?
Dependent on the end product of, and on-line measurement location in a wood processing line, there will be an optimum moisture level, which if attained, will maximise line efficiency in terms of increased throughput, lower wastage and lower energy usage. The ideal moisture content at a specific location will vary according to the species, cut of wood, further processing required and final product. For example, sawdust at the dryer exit in a pelletising plant is targeted at 9% MC and OSB pre-former is within the range 5-10% to ensure the strength of the board and prevent the production of blown boards.
 

 

Wood Product Applications

Particleboard Particleboard   Medium density fiberboard (MDF) Medium density fiberboard Oriented StrandboardOriented Strandboard
Hog Fuel Hog Fuel Wood Pellets Wood Pellets Green wood chips
Hardboard Flakeboard Woodchips
Woodfibre Sawdust Woodflakes

Sensor
The MCT 360-WP wood products sensor measures moisture in wood flakes, chips and particles. NIR (Near Infrared) technology is ideally suited to on-line moisture measurement as it is non-contact, safe, non-destructive and unaffected by changes in density, the latter being an issue with radiofrequency and microwave technologies. The sensor incorporates a cooling panel, air-purge diffuser and well proven algorithm.
The Atex22-MCT 360 is a specially adapted MCT 360-WP designed for use in hazardous dust environments e.g. hammer mill location, and the MCT 230 is a low cost “at-line” moisture gauge which can deliver instantaneous moisture readings and provide a more representative measurement owing to the larger sample test volume than a moisture balance.

Accessories
For installation locations which are subject to temperature extremes, heating blanket and vortex cooler options exist. Product loss sensors are available for discontinuous product flows preventing measurement update when product is absent. (Note that a good bed depth of product is essential when product is running, intermittent gaps will cause erroneous readings). A sight window can be installed in hoppers or incline chutes and a probe or powder sampler in vertical chutes to view product.

Gauge Outputs, Operator Interface & Display
The MCT 360-WP is available with or without a local operator interface or display as all the processing is carried out within the sensor head and the measurement is output via 4-20mA, 0-10V, RS232, RS485 or any bus. Installation time and effort is minimised by dispensing with a local OI, but should samples be collected for cross checks an OI is useful... in this event, one could be simply plugged into the gauge at the sampling location.

 The measurement


Measurement of the moisture content of small particulates such as sawdust is more accurate, at 0.1% than measurement of larger woodchips( 0.3 – 0.5%), as the latter will not have reached a state of moisture equilibrium by the time it reaches the gauge sited at the exit of the dryer. Measurement accuracy can be improved by moving the gauge further from the dryer exit. Moisture in Hog fuel and a mixture of wood species can be measured provided the overall composition remains approximately the same over time.
Resin content in OSB and board production can be trended, but percentage coverage of individual strands/chips isn’t possible.

 

 

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