Wood product also paper product are very very sensitive to humidity. Their physical properties are strongly dependent on moisture content.
Logs with new cut possible have a moisture content (MC) more than 80 percent, depending on what species are.
Wood Moisture Content Rate(WMCR)
What is Wood Moisture Content Rate?
In many country, the rate of water weight contained in the wood to the weight of absolute dried wood is defined as WMCR or so call wood moisture content rate. The WMCR varies with the different tree and different part of a tree, for instant the red pine's WMCR at the core is 70 percent and 200 percent at the edge. The same tree from different region also makes the WMCR different.
What WMCR is suitable for deep process?
Under certain environment for a long time, The WMCR comes to a steady value which is refered to as balance WMCR under the environment. When the WMCR is above the value, the wood will gives off the moisture and contract, but if WMCR less than the value, it will take in the moisture and inflate. High WMCR of the wood may result in loose glue connection and distortion after process. Different region and different purpose requires different on WMCR of the wood. The natural balance WMCR of the wood is between 7 percent to 18 percent which has become the check point in wood products manufacturing. Additionally, you can measure the WMCR of given stardard wood, then compare it the WMCR of the wood to be tested.
What is balance WMCR?
Under a given air condition, the final WMCR or say steady WMCR is refered to as balance WMCR(Steady water content state). The year average WMCR of some country is shown as table
How many method are there to measure the WMCR?
There are drying method, electrical method, Carbonization method, tritation method and humidity method for measuring the WMCR. Drying method and electrical method are normal adopted in production process. The drying method that calculating the weights of a wood before and after being absolute dried has high precision but takes considerable long time and complicated, it is usually adopted in laboratory. While the electric method base on some electric properties of a given wood that varying with the water content in the wood is being adopted to measure the WMCR in mass production this method has lower precision compared with the drying method, but still be able to meet the normal production process requirements.
How to measure the WMCR of a wood exactly with the unit?
As shown below, Just follow the following rules to measure on a newly cut wood or the latest texture.
1. cut the wood in direction vertical to the horizontal texture of the wood.
2. Do not measure with the skin of the tree.
3. Do not measure along the round texture side.
4. Do not measure along the straight texture.
Why are there different results measured by different manufacturers of diffenrent type of moisture meters? The electrical properties of a given wood varies with the trees, temperature and regions, and most products can not set every modified value for each tree, only one certain tree and temperature can be used as modification ground, this is the reason that different results came out.
Will Low battery affect the measurement result?
When the battery power is less than 70 to 80 percent the measurement result becomes decrease. For instant, at normal voltage the moisture meter measured reading is 14 percent, but when the battery power is less than 70 percent the measured reading might show 11 percent or even less on measuring the same wood. So once moisture meter the low battery indication displayed on the LCD, the best thing to do is replace a new battery to ensure the accuracy of measurement.
ไม่มีความคิดเห็น:
แสดงความคิดเห็น