So many popular products are made from wood, and the transformation involves a considerable number of processes.
One particular element that is common in most wood manufacturing is drying. Drying wood in a wood dry kiln is a crucial stage of production that often occurs in challenging environments.
An essential monitoring aspect of drying is using humidity sensors to determine when timber is ready for use, but their efficacy faces significant challenges.
This guide will explore the processes used in wood production, why humidity sensors are essential in wood dry kilns and their challenges.
Why use a Wood Dry Kiln in Wood Manufacturing?
The Journey of Wood from Tree to Final Product
Trees start their life growing in a forest where they absorb water and nutrients through their roots into their trunks to grow.
When a tree is cut down, the trunk will be sawn into planks. This new wood is known as green wood.
Green wood is unsuitable for many uses as it will have expanded, like a sponge, with the water absorbed during the growth cycle. Green wood has a 100% moisture content relative to dried or seasoned timber.
The problem with green wood planks is that they will shrink over time as the wood dries out. For many uses, such as in construction, this would be disastrous.
To overcome the moisture issue, wood must be dried by air drying or a kiln before being ready for use.
International Timber refers to kiln-dried wood, timber that is placed in a kiln and dried using warm air. The drying process is much quicker than air drying resulting in a more rigid product which is frequently used in the construction industry.
How does a wood dry kiln work?
The purpose of a wood dry kiln is to remove the maximum amount of moisture from timber planks to create dry wood that will not shrink once used.
Green wood planks will be placed in piles inside a dry wood kiln where hot air will circulate over many hours.
As you would expect, the heated moisture will be released from the wood as vapour. Naturally, this will increase the humidity in the kiln.
Measuring the humidity in the kiln is the optimum way to calculate when the wood is dry and ready for use. Humidity sensors are essential for this measurement.
Challenges Faced by Humidity Sensors in Wood Dry Kilns
Humidity sensors are usually placed on the walls of a wood dry kiln to determine when the wood is ready. As the moisture content in the wood decreases, the humidity in the environment will increase.
The drying process provides several challenges for sensors in addition to the humidity itself. Acids and oils evaporating from the wood can affect a sensor’s performance.
Accumulation of these residues on sensors can reduce their accuracy and cause some drift.
How Humidity Sensors can be Protected
At Omni Sensors and Transmitters, we supply E+E Elektronik humidity sensors. They have been specifically designed to operate accurately in wood dry kilns.
Our EE 310 and EE23 humidity sensors feature:
- IP65 Stainless steel or Polycarbonate transmitter enclosure to keep moisture out
- Stainless steel probe body and filter cap designed for high temperature environments..
- E+E’s unique sensor coating which protects sensing elements against corrosive and electrically conductive pollution ensuring a long working life.
- Detachable probes for fast exchange and easy cleaning
EE 310
EE 23
