COMPARISION BETWEEN ELECTRONIC ACCEPTANCES RECORDED BY HARVESTER AND MEASURING FRAME KESAT IN THE CONVERSION DEPOT

Jiří Dvořák¹, Pavel Karnet², Pavla Rusnáková^3
1 Department of Forest Harvesting, Faculty of Forestry and Wood Sciences, Czech University of Life Science, Prague, Czech Republic
² Czech University of Life Science Prague, University Forestry Establishment at Kostelec n.C.l., Czech Republic
³ Prague Polyedr, a.s.

ABSTRACT

The high-performance harvester Rottne H-20 is used in final felling of conifer stands in the natural forest of Polabi region. The round wood, aggregate and pulpwood are the most often produced assortments. 48.0–58.8 % of assortment volume is made-up of pine and spruce round wood. The measuring frame KESAT takes over these assortments in the log conversion depot. When we compare the electronic acceptance of software DASA 4 of the Harvester H-20 mentioned above with the measuring frame KESAT, we can see quantity differences. Summarization of these possible differences made clear for us the need for monitoring and measuring of wood samples. Qualitative wood acceptances will characterize the natural conditions of stands and the possibilities of the wood production. The quantity difference should not get over 2 % between the harvester and the measuring frame KESAT. The quantity differences lead to the financial and wood-producing devaluation of the forest production. In the case we find out some statistically significant difference between the acceptance tests, we define a correcting coefficient for the timber value and the financial risk assessment, which are among supplying and consumer firms. The financial loss of one softwood cubic meter can be up to 1850,- CZK (pine) and 2450,- CZK (spruce) in the Czech Republic.

Key words: electronic harvester acceptance, measuring frame, correction coefficient.

INTRODUCTION

There is a practical knowledge of timber acceptances in the Czech Republic (CR) today, that participants of a felling process regard their self measuring methodology as the correct one. In the CR there is no institution for the unification of the wood inspection [6]. Technically difficult three-stage acceptances of felled wood can lead to a wide difference of the timber volumes between the producer and the last customer because timber receptions are provided in a variety of ways. The first timber volume determination is carried out electronically during the timber harvesting and processing with the harvester technologies. The customers often disallow this output and they carry out self-acceptance of the produced wood that is registered in the certificate of a delivery. The last electronic acceptance is carried out by the final customer. There were 40 measuring devices serving this purposes in the CR in 2005 [3]. Therefore a producer has financial losses or the customer is blamed for a wilful timber volume reduction. Because the uniform acceptance methodology, which would be accepted by customers and producers, has not been worked-out so far, therefore we recommend determining of the timber volume difference between the primary wood processing in forest stands and the material input to an industrial processing. Due to various methods of measurement (harvester vs. measuring frame) the volume difference within acceptance is about 3% [5]. The results of new research recommend the correction coefficients 0.9966 for 2D scanning system and 1.0360 for 3D scanning system [2].

The aim of this study was to determine the correction coefficient for the timber volume, which is calculated by the measuring programme of the harvester in contrast to the operation programme of the measuring frame KESAT.

MATERIAL AND METHODS

The analysis concerned the principal felling of conifer stands in the Polabi Natural Forest Area (Table 1). The logging operations were carried out by the high-performance harvester Rottne H-20. The measuring of the wood production was based on the programme DASA 4. The harvester operating system records the timber volume, number of manufactured trees, number and volume of assortments separated according to the tree species. The output of the harvester measurement is presented by the acceptance report i.e. the measuring protocol. The round logs, aggregate round logs and pulpwood are the most often produced assortments. The spruce and pine round logs make the greatest wood volume of the produced assortments – 48.0–58.6% (according to monitored forest stands). The round logs are taken over by the measuring frame KESAT in a log conversion depot. The comparison of the electronic acceptances can show quantity differences between the software DASA 4 of the above-mentioned harvester and the measuring frame KESAT. Whether these differences spring up during total summarization, we can check it up by the sample monitoring and measurement of spruce and pine wood, which are accepted in the Borohrádek saw mill.

The wood quality depends on natural conditions of the site and on silviculture. The estimated difference between the measuring system of the harvester and the measuring frame KESAT is up to 2 %. The reduction coefficient will be calculated between the harvester electronic acceptances and the measuring frame for the difference compensation, which can arise in supply and consumer companies.

RESULTS AND DISCUSSION

Harvester ROTTNE H-20 – Measuring System DASA 4
The main function of the measuring device is the measurement of the trunk length and diameter. The trunk length is measured by a sprung tooth-wheel. The wheel moves along the trunk, which is passed through the harvester's head. The revolving wheel registers impulses, which correspond with some length unit. On the basis of the number of impulses the tree length and the assortment length are calculated. These values are necessary for the cubature enumeration in the operating system. The accuracy of measurement is one centimetre. The inaccuracy of measurement can be caused by tooth wear, bad implementation of a calibration, and the burls on the trunk in the case when wheel goes over knobs. Another reason for inaccurate measuring is bark avulsion. The stripped bark blocks the wheel and length is not measured properly (in the time of increased sap volume). At this time the wider wheels can by installed for a reduction of these inaccuracies or two wheels are installed side by side. Adjustments of the measuring wheel are possible for other specific characteristics of timber that can be for example thick rhytidome [4].

The trunk diameter is measured in two perpendicular directions every 10 centimetres of the trunk length, these two values are averaged. The diameter scanning is provided by the potentiometers responding to knife movements. The signals proceed to an electronic assembly and consequently to the operating system in the driver's cabin, where values are processed.

The special DASA 4 software is installed for the trunk sorting in the harvester's computer. There are loaded assortment dimensions (lengths, diameters) and prices for particular assortments, which are used for the maximal optimalization of timber yield.

The sorting technology of the harvester:

1. The trunk is felled and moved through the harvester's head. The trunk dimensions are measured for each tree species.

2. The diameter and length dimensions are collected. The assorting computer has enough data after a certain distance to be able to form the trunk model depending on the felled species. The model is formed basing on an anticipated trunk length, which the operating system has calculated.

3. The measuring installation makes a profile prognosis of the felled trunk with the use of the stem form factor. This profile prognosis is more specified during the trunk movement through the harvester's head. The optimal sorting is worked up for the maximal wood yield and the wood commercialization in dependence on the measured and supposed length.

4. The calculation of further profile prognosis is repeated after every cut of an assortment until the last section.

Manual Wood Acceptance (Measuring) on a Skidway
Wood acceptances are provided by a forester on skidways. Round log volumes are measured for a wood pile on a logging truck-and-trailer unit (length x height x width of a load). The calculated timber volume is reduced to the solid cubic meters by the reduction coefficients (spruce – 0.62; pine – 0.59). It would be more accurate to measure round logs and the aggregate round logs individually on the basis of the middle diameter and length and to calculate the volume from tables. The results are inscribed in the certificate of the delivery, which is the accompanying document for the customer let us say wood processing companies.

Forest owners and wood suppliers are increasingly aware of the accuracy of the harvester measuring system and they respect harvester output values. In the extreme cases, the total volume of the load is estimated and a forester respects electronically calculated timber volume by the customer.

Measuring Frame KESAT – URSYM PC System
The third stage of the timber acceptance is realized right on a cross-cutting line of a wood-working saw. Output results of this acceptance are usually designated as the obligatory volume of felled and delivered wood for all previous producers or customers.

The URSYM PC programme is used for the assortment optimalization of round logs and whole-stem logs on manipulation lines [1]. All data about processed trunks and produced assortments are registered and they are available for further processing and utilization. The diameter is measured when the stem goes through the measuring frame. The stem diameters are measured in two perpendicular directions every ten centimetres of the trunk length and the data are registered in the table. It may happen sometimes that buttress or remnants of the bark overshadow the frame and the regular dimensions are not measured. The frame sends error messages in this case and these data are eliminated from the further evaluation process. The determination of the regular diameter is carried out from a continuous diameter series; local influences of burls or depressions (mechanical damages) will be displaced that way. Values are stored in the diameter table and it is instrumental to the:

• determination of a mid diameter,

• trunk orientation,

• sorting depending on specifications,

• allocation of the top and mid diameters to the assortments.

The stem length is derived from the movement of the longitudinal chain conveyor, which is carrying this stem. The chain wheel of the conveyer is linked with the pulse generator. The actual length is specified basing on pulses coming from the generator at the moment of the shading and releasing of the measuring frame due to stem movement. The stem length is converted to centimetres using the transference number. A nominal log length, rounded to whole metres, is derived from the real length.

The log volume is calculated in terms of the mid diameter and the nominal length according to standard ČSN 48 0009 (Czech standard no. 48 0009).

(1)

where:
V   stem volume or assortment volume (m³)
D   mid diameter of the stem or assortment over bark (10^-2m)
2k  double thickness of the bark (10^-2m)
L   stem length or assortment length (m)

Data of the processed trunks are stored to data files respecting produced assortments and other technological entry elements (timber species, quality and others).

Results of Acceptance
Results of the electronic acceptances of the forest felling, including round logs, from the harvester Rottne H-20 are presented in Table 2, where individual forest stands are registered. The total volume of the produced round logs goes through measuring frame KESAT during acceptances in the conversion depot, and it is 1002.26 m³ in the measuring protocol of the harvester (including 431.46 m³ of spruce wood and 570.80 m³ of pine wood).

The round logs are transported from the forest stands to the Prague Polyedr, a.s. company – Borohrádek Sawmill. We can't differentiate round logs according to the production places (forest stands) in this case because wood is transported from the mature stands to common piles on skidways. In table 3 the electronic measurement of single loads (i.e. acceptances in the saw mill) is shown. We can compare the wood volumes between the manual measurements of the load made by supplier, which is registered in the certificate of a delivery and the electronic acceptance of the measuring frame KESAT. We can see high disparity between manual measurements and electronic acceptance of the frame KESAT because the manual cubature measurement is worked up for wood stack placed on a logging truck-and-trailer unit and it ii not too accurate, since stacked cubic meters have to be converted to solid cubic meters by using of the reduction coefficient. Differences between those two acceptance technologies lie within the interval of the absolute values from 6.99 m³ / load in favour of supplier to 4.48 m³ / load on behalf of the customer. The average deviation is 2.45 m³ / load and the difference of the whole monitored supply reaches 3.6 %; – wood cubature is higher for the timber manually measured in comparison with values from electronic acceptance made by the measuring frame KESAT.

Absolute values of the whole monitored production are presented in Fig. 1. The harvester PC registered electronically 1002.26 m³ of round logs, the supplier declared 1021.64 m³ of round logs in the consignment documents and the measuring frame KESAT measured out 986.50 m³. The disparity between electronic acceptances of the harvester and the measuring frame is 1.6 %. This value is within the acceptable limit of 2%. The maximal difference between the manual acceptance of a supplier (measurement of wood stacks) and the measuring frame KESAT reaches 3.6 %.

Financial Results
The customer must follow redemption prices (Table 4) and conditions given by suppliers. The spruce assortment has to have the top end at least 0.13 m wide, the butt end diameter is unlimited. A wood stain is acceptable only for the "D" quality, most to the ½ of the butt area. Composite curvature of the stem is not acceptable. In the case of single curvature an assortment must be able to go through the manipulation line and the electro measurement.

The minimal diameter of the top end for pine is 13 cm (inside bark). The maximal curvature is for the "C" quality 2 % and for the "D" quality 3%. The wood stain is allowed only in the "D" quality, most to 1/2 of the butt end area. The butt diameter is unlimited. Crooked trunk must be able to go through the manipulation line and the electro measurement. If an assortment does not meet criteria of the contract, redemption price will be 350 CZK/m³ (12 €/m³). The financial results of the experimental monitored production are presented in Table 5. Tables 4 and 5 show that prices of round logs slumped after the hurricane "Kyrill" in the Czech market from February to July. The Czech crown strengthened to the Euro about 0.20 Heller during the same period. The total wood delivery from the monitored stands was assessed to 71 483 €. The prices of pine round logs slumped about 100 – 450 CZK/m³ (3.6 – 18.0 €/m³) and of spruce round logs about 150–1050 CZK/m³ (5.3 – 37.1 €/m³) depending on quality class and diameter grade.

CONCLUSIONS

The results show, that the accuracy of electronic measurements made by logging mechanizations and stationary measuring devices on manipulation lines and in saw mills is high. After all there is some risk of possible inaccuracies caused during measurements by knobs, bark avulsion and slide of the measuring wheel and other factors, but the difference is still acceptable. On the contrary specifications embody inaccurate administrations of manual acceptances, which are often subjective estimations of the wood pile volume on the skidway or on the logging truck-and-trailer unit.

We can consider as unavailing to accuse customers for inaccurate measuring of received wood. As the main reason for an eventual inaccuracy of the measuring we can mark incorrect calibration of measurement systems and a human failure.
In conclusion we recommend:

• Electronic acceptances in metrical units made by customers shall be respected - harvester measurement results confirm the accuracy.

• The reduced coefficient is 0.984 for softwood (round log) produced by harvesters.

• Unification of the round log measurement for producers, suppliers and customers.

The difference between the electronic acceptances of the harvester Rottne H-20 and the electronic measuring system of the frame KESAT is 1.6%.
The difference between manual acceptances made by suppliers, which are registered in certificates of delivery, and the measuring frame KESAT is 3.6%.

REFERENCES

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2. Horáček P., Hunková V., Janák K., Ondráček K., Pejzl J., Peter B., Vojtová M., Zukal R., 2006. Srovnání metod ručního a elektronického měření dříví. Návrh pravidel elektronického měření a přejímky dříví v ČR [Comparison of Hand and Electronic Methods of Round-wood Measuring. Proposal of rules of electronic measuring and inspection of roumd-wood in Czech republic]. Brno, 12 [in Czech].

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4. Malík V., Dvořák J., 2007. Harvestorové technologie a vliv na lesní porosty [Harvester Technologies and Impact on Forest Stands]. ČZU v Praze, 84 [in Czech].

5. Sládek P., Neruda J., 2007. Analysis of Volume Differences in Measuring Timber in Forestry and Wood Industry, In: Astro 2007/FORMEC'07, Vinna and Heilegenkreuz, 1-11 [in Czech].

6. Ulrich R., Neruda J., Zeman Vl. (sen.), Zeman Vl. (jun.), Zemánek T., 2006. Harvestorové technologie a jejich optimální využití v praxi [Harvester Technology and Their Optimal Practical Utilization]. Brno, 2006, 87 [in Czech].

Accepted for print: 15.10.2008

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.