Moisture Measurement – a Must in the Wood Processing Industry

Posted in: , on 2. Jul. 2015 - 14:36

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Moisture Measurement – a Must in the Wood Processing Industry

The field of application for wood is extremely varied. Using wood as a renewable energy source is one of the fastest growing application area for wood. In this kind of timber industry wood is processed in quiet different ways. The energy extraction through renewable resources is CO2 neutral, as during its life time wood absorbs as much CO2 as wood combustion sets free. If wood is used for energy extraction, fossil fuels like crude oil, coal and natural gas would be saved. Due to these powerful advantages of wood as a renewable energy source the timber industry will increase more than ever before.

Until we are able to use wood as a renewable energy source as a final consumer, the wood has to be processed in different ways. A few examples for usable material- or transport forms are wood-chips, wood-pellets, wood-shavings or sawdust. To reach a highly effective combustion in the wood-burning ovens a moisture measurement is absolutely essential. On one hand a moisture measurement is able to measure the exact residual moisture in the material. The quality of all produced wooden bulk-materials increases highly by using a moisture measurement. And on the other hand there is also the possibility to raise the efficiency of a plant through optimizing cost-intensive drying- and irrigation processes.

A very important aspect by installing a moisture measurement sensor is a well conceived mounting position in the production plant. Every production plant has its own individual character, so an intensive consulting is advisable. In some cases individual mechanical solutions are indispensible. Based on the long-term experience in moisture measurement solutions and the close cooperation with customers of the wood industry ACO (Automation Components) can offer you a high quality product as well as a outstanding consulting. A particularly high market share for the pellet-industry is the figurehead for the excellent quality and the extraordinary product support by ACO from the Black Forest.

ACO – moisture measurement systems

The ACO moisture measurement systems were developed especially for measuring directly in the production processes (online measurement). To reach a wide range of many different applications ACO offers two sensor systems (DMMS and AMMS). The digital moisture measurement system “DMMS” from ACO is based on the capacitive measuring principle. The heart of the system is the golden sensor in a robust housing. The sensor is able to measure through the material up to a depth of 120mm to 150mm depending on the wooden material. Due to the high measuring depth any pollution on the sensor surface does not disrobe strongly and a high amount of the material flow will be measured. Through the capacitive measuring principle the moisture on the material surface and the moisture content in the material are measured. The highly sensitive measuring surface of the sensor is protected through a strong ceramic plate. The DMMS system is averaging the moisture values (adjustable by user) to guarantee a stable output signal.


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Fig 1.:

ACO - DMMS System Components



The digital moisture measurement system (DMMS) is offered as an all-in-one system. On each evaluation unit (DIGYSIS) 16 sensors can be connected. The communication in the system works via Profibus DP standard communication. Additionally the system is able to provide the signal in the traditional 0V…10V or 4mA…20mA analog output signal. Through the ACO calibration software the system can be calibrated easily and quickly. It is possible to set up 16 different materials per sensor. Each of these 16 materials can be adjusted with 10 calibration points or a polynomial function.

Beside the digital moisture measurement system ACO offers their recently developed “AMMS” system. The “AMMS sensor” is a compact sensor that has the possibility to calibrate via software too or even adjust the values via turn-switch directly on the sensor (well-known two point calibration). There is the possibility to set up 10 calibration points. The averaging of the moisture values is also adjustable. The AMMS Sensor will be integrated directly in the production plant without an evaluation unit. The communication between the sensor and the plant is realized by a standard 0V…10V or a 4mA…20mA output signal.


aco_fig_2_amms system

Fig. 2:

ACO – AMMS System



The right mounting situation is already half of the battle

To operate a production plant efficient and with a high quality output the mounting situation of a moisture measurement is one of the main points in the planning period. Especially by producing wood chips, pellets or sawdust it is important to guarantee a constant material flow and always the same material height and density above the sensor. ACO is specialized to solve difficult measuring situation and offers individual solutions therefore. All mechanical applications and individual solutions are working with the AMMS and with the DMMS System.


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Fig. 3:

“SFM 1 compaction unit” with optional “SFM 3 housing”





One of many developments from ACO is the “SFM 1 - compaction unit“. An electronically-pneumatically controlled cylinder is compacting the wooden material. The result is a high reproducibility of the measured values. The “SFM 1” unit suit perfectly for measuring wood shavings and sawdust. It was developed for installation situations on transition points, especially for mounting in a free material fall. Additionally ACO offers the appropriate housing “SFM 3 – housing” with a service and maintenance flap that avoids a construction by your own. Through the acrylic glass and the particular maintenance flap it is very easy to control the function or reach the “SFM1 unit” if necessary.


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Fig. 4:

SFM 1” and “SFM 3” (blue apparatus) after water conditioning




The long time proven „SFM1 compaction unit“ was adapted for measuring wood chips. An electronically pneumatic cylinder is leading the material with a constant material height and density above the sensor. With the compaction unit “SFM1-Hack” sawdust can be determined at its residual moisture too.


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Fig. 5:

„SFM 1 Hack“




If an installation in a free material fall is not possible, ACO offers a further solution. The “SFM 4 screw conveyor” removes the material via screw conveyor directly out of the production process and led it back into process after the moisture measurement. The special constructed screw pitch guarantees an efficient and reproducible measuring situation in front of the sensor (constant material height and density).


aco_fig_6_sfm4

Fig. 6:

„SFM 4 Screw conveyor“




In many producing plants some moisture measuring possibilities already exists. The ACO sensor can be integrated in an existing screw conveyor as well. Further options for installing a moisture measurement is in silos or above conveyor belts.


aco_fig_7_dmms in bestehender schnecke

Fig. 7:

DMMS sensor built in an already existing screw conveyor




An extensive consulting is advisable, because there are many ways to do it wrong. Every structure of each producing plant is not like the other.

The Future is Gold!

Optimization of the product quality:

One of the many advantages from an ACO Online-Moisture Measurement is the enormous improvement of the product quality.

Cost savings through ACO sensors:

A well implemented Online-Moisture Measurement can not only improve the quality of your end product, you are also able to reduce the production costs highly as well.

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