Improvement of Wood Volume Measurement Method

Keywords: wood volume; measurement methods; sampling inspection method In the production, sale and use of wood, measuring only the size can not meet the needs of measurement, we must find out how much the amount of timber, that is to calculate the volume. In the paper industry, only one item of wood accounts for 75% to 80% of the cost per ton of sulphate wood pulp. Therefore, accurate measurement of wood volume plays an important role in reducing the cost of wood pulp.
International methods for calculating timber volume such as logs include:
(1) Digital inspection method: statistics the number of round wood products.
(2) Re-examination method: Weigh out the weight of the wood.
(3) Shape inspection method: According to the measurement factors such as diameter, length, width and thickness, etc.
(4) Bundle (åž›) inspection method: Measure the volume of the wood bale or rake to calculate the volume of the bale or rake.
At present, China mainly adopts the shape inspection method to obtain material volume and a small amount of application of heavy inspection method. Only when the wood is irregular in shape, small in size, or fragmented wood (such as small-sized material, board skin, etc.), the use of the bundle method is required. Some countries in foreign countries have applied heavy inspection methods to carry out timber inspections, and they allocate and sell wood in units of weight (tons). The following commonly used shape inspection method, re-examination method and the sample inspection method recommended in this paper for analysis and comparison.
1 The seismology method measures the length and diameter of timber using a ruler, calculates the volume of material using a material scale, and allocates and sells wood in terms of volume (m3). Its calculation formula is a theoretical empirical formula, which is based on higher mathematics. Analytical method derived. The volume of individual wood is calculated as follows:
L--material length, m
V - volume, m3
D--small head diameter, cm
In practical application, it is often necessary to conduct full inspection on the diameter and length of a batch of wood, and according to the inspection result, consult the national standard wood material accumulation table and accumulate the volume of a batch of wood.
Where: Vi - single root volume for different material lengths, m3/Si - number of logs of different material length, root V - total volume of the tested lot, m3
On the surface, this method is a full-scale test and the accuracy should be the highest. However, 100% inspections may also have misidentifications and missed inspections. Moreover, due to the large workload and full labor intensity required for full scale inspections, it requires a lot of labor and time, and it also affects the loading and unloading speed of wood. The method is generally difficult to achieve. For a large number of large-scale paper mills, they often do not have enough funds, time, and inspection personnel. They can only spot-check part of the supply lines of some suppliers, greatly reducing their accuracy. It transferred the responsibility of the timber supplier for the quality and quantity of delivery to the inspectors and created opportunities for unscrupulous traders.
2 The heavy inspection method means that the vehicle's wood is weighed with a weighing instrument, and then converted to the product volume using the determined formula. In recent years, in China's northeast and Inner Mongolian forest areas, the original bar, logs, and harvested residues transported from the cutting area to the lumber yard have been widely examined by heavy inspection methods, and the weight conversion has been used as the volume of material. The error rate is 1%~ 3%. The conversion formula is as follows:
In the formula: V--check the amount of wood volume, m3
G--Total weight of wood vehicles, kg
G1--vehicle weight, kg
Wood bulk density of each tree species r1, r2, r3 -, kg/m3
A, B, C - Proportion of the number of species in the car, %
The weighing instruments used in the system include Dizhongheng and the train scale (high precision, reliable technology, and strong applicability). They have been widely used in industrial and agricultural production and can be used with confidence. The only problem is the determination of the bulk density of the wood. The bulk density of wood is the weight per unit volume of wood in its natural state. The wood bulk density is related to the tree species, site conditions, water content, and the location of the material. The same tree species grows on sunny slopes or shady slopes, ditch ponds or ridges. The wood bulk density is different; the tree cutting season is different, the length of wood storage time affects the amount of wood moisture, and the wood bulk density is also different, the water content Many are heavy on weight. The same log, in general, the root weight, followed by the middle, tip light. The determination of wood bulk density plays an important role in the accuracy of wood weighing. The method of determining the bulk density of wood at the site is generally to the production of cutting areas, taking full account of the various factors affecting the bulk density of the timber, selecting a representative sample of trees to be measured, and determining according to statistical methods. The wood bulk density is measured at least once for each tree species in the four seasons. The more the number of tree species measured each time, the higher the accuracy. With the increasing tension in the country’s forestry resources, the paper industry’s selectivity towards wood is getting smaller and smaller. The incoming materials range from the north to the south, even to Russia and Australia, and more and more wood species make the measurement of wood bulk density almost impossible. This method is also not easily applied.
3 Sampling inspection method The scientific sampling inspection method - that is, the research and application of sampling inspection based on mathematical statistics theory, has been more than 60 years of history, and is widely used in the acceptance process of industrial and agricultural products. We believe that it is entirely possible to apply spot inspection methods to the inspection of wood. The application methods are summarized as follows:
3.1 Prerequisites The wood species of the same wagon are the same. The cutting time and cutting location are similar. After a certain period of storage and transportation, the moisture content is basically the same.
3.2 Principle The total weight (W) of the vehicle's timber is pre-weighed using a track scale. A certain proportion of wood is randomly selected during the unloading process and weighed and accurately inspected to obtain the weight (W1) and volume (T1) of the sample. Finally, calculate the timber volume (T) of the vehicle. Calculated as follows:
In the formula, K is the bark, including the vehicle floor garbage deduction coefficient.
3.3 Features Based on the weight detection, the modern instrument has been fully used with high accuracy and reliability.
Only 20% of the wood is sampled for inspection, and the workload is greatly reduced. It is possible to focus on the higher-level excellent inspection technicians, to conduct centralized inspections, to reduce false inspections and missed inspections, to eliminate human errors to the utmost, and to facilitate technical improvements and management.
3.4 Implementation Steps (1) The vehicle has passed the pound: After the on-duty staff of the track scales weighs the weighed car, record the car number and the weight of the empty car, fax the result to the inspection center.
(2) After the wagon is fixed at the designated position, the unloading starts. The inspection staff checks the decay, bark, and other residues at the bottom of the wagon. The records are kept in the book, including the wagon number, the weight of the empty vehicle, and the unloading of the wood to fill the transfer car. Notice inspection center.
(3) The inspection center determines the number of vehicles to be inspected according to the random number table, and the designated person will concentrate the full-loaded trolley used for sampling to the inspection shed for accurate inspection. Record the total amount of sampled wood, the weight of empty cars, the net weight, the total wood volume of the sampled wood, and the volume and proportion of each diameter.
(4) Enter all the above records into the computer, automatically calculate and print out the results.
(5) Without sampling directly from the wagons and vehicles transported by vehicles without transportation, a sampling table can be used to determine the number of sampling points, randomly selected during the unloading process, and concentrated on a small vehicle. Refer to the above-mentioned method for measuring the scale.
3.5 One single platform railroad scale for equipment and equipment (600,000 yuan); 10 tons of Zhongheng (52,000 yuan); one simple shed for inspection; 2 to 3 fax machines (0.8 million yuan); Related software configuration (10,000 yuan).

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