Optimal biomass truck load size and work models for loading of loose biomasses Metsätehon tuloskalvosarja 3b/2016 Heikki Ovaskainen & Henri Lundberg Metsäteho Oy
Content Background and theory Part I: Optimizing driving distance and loading time Heikki Ovaskainen Part II: Biomass truck loading work model study Henri Lundberg & Heikki Ovaskainen Conclusions and future work 2
Background The most cost effective way of transport is to enable driving with full payloads. Typically loose biomass loads (stumps and logging residues) are much under the allowed weights. Load size is also dependent on the material moisture content and the material type. Work methods to load loose biomasses into the load space influence also the total load volume. The total weight of typical bioenergy truck is 64 tons and the volume of load space is about 160 m 3. Weight of empty truck is about 31 tons. Typical payload size with stumps or logging residues is under 25 t. The maximum load 34 tons is not reached often. 3
Normal loading curve for biomass loading Payload mass, t 34 t 23 t Loading curve describes cumulative payload size as a function of time. Normally /easily reached load Time for compression needed (or comp. method needed) Loading time The mass of payload can be presented as a function of loading time. It is normal to reach about 23 t payload with little compression movements but tons over that needs more compression efforts and time. 4
Fast loading curve, no compression methods 34 t Payload size, t 23 t Normally /easily reached load Time for compression needed (or comp. method needed) Loading time With this loading method, it is fast to reach 20 t payload but difficult to reach maximum load if compression movements have not been done during the whole loading time. 5
Compression loading curve 34 t Payload size, t 23 t Normally /easily reached load Time for compression needed (or comp. method needed) Loading time With compression movements during the whole loading time, it might be possible to reach full payload in a reasonable time. 6
Payload size, t Loading of loose biomass How much time is profitable to use for this? 34 t 23 t Normally /easily reached load Time for compression needed (or comp. method needed) Loading time On the other hand, is it necessary to get full payload on a short transport distance and, instead, use the saved time for driving? 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 7
Truck drivers principle for loading When discussing with truck drivers of their methods to compress load, a typical answer was: You should not use too much time for making high payload because during that time you ll drive one more load What is suitable time for loading on different transport distances i.e. what is suitable load size on different distances? 8
Moisture content vs. payload for MWh for 160 m 3 load Payload, kg 30000 25000 20000 15000 10000 5000 26400 30,8 23760 46,5 21120 65,3 87,4 18480 100 90 80 70 60 50 40 30 20 10 MWh/160 m 3 load 0 50% 40% 30% 20% 0 Moisture content, % The average loose density of logging residues is about 165 kg/m 3 in 50% moisture content. Very dry material makes it difficult to reach full tons in load. 9
Reaching the minimum unit costs There are different methods to reach the minimum biomass transport unit costs. In this study the focus was on following cases: 1. Optimize the share of loading time and transport distance With short transport distances it is not necessary to try to reach full loads, because loading takes much time and during that time extra loads could possible be transported. 2. Try to use work methods that compress the material so much in a short time that a full payload is reached The idea of work method study is that no extra compressing devices are needed in loading that would decrease the payload or increase time consumption in loading. The loading work is done with more clever crane movements. 10
Objectives of the study This study was divided into two parts and the objectives of the studies were to: Part 1: calculate optimal payload size on different transport distances Part 2: describe productive work models for truck loading with loose biomass materials 11
Part I Optimal payload size on different long distance transport distances 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 12
Background On long transport distances it is important that the payload is high and on short distances the driver can balance between loading time and transport distance. The optimal cost for trasportation were calculated using Metsäteho s truck transport cost calculation sheet. Calculation sheet was modified to biomass transport form from the settings of log transport. All parameters were changed to correspond typical biomass truck driving work. Some facts concerning truck drivers work: a daily driving time is 9 hours drivers work on two shifts having 3 750 working hours per year. This includes normal work time plus overtime work 250 h/driver. there are about 200 work days/year with loose materials in typical 40 % moisture content, typical total weight of truck is 55 tons loading time is higher with loose biomass materials forest energy and transport work is needed more during winter time than in summer. Transport activity can follow this demand by having holiday times and transport to terminals during summer. no other costs (such as comminution) beside transport costs are included. costs are presented as /ton. 13
16,00 Results costs of transport of loose logging residues on different transport distances /t 14,00 12,00 10,00 8,00 13,37 11,73 10,08 8,43 12,80 12,31 11,90 11,22 11,56 11,28 10,81 11,05 10,86 10,46 10,72 10,61 10,17 10,54 10,50 10,48 10,48 9,65 9,95 9,77 9,30 9,63 9,53 9,46 9,43 9,42 9,43 9,47 9,02 8,79 8,61 8,48 8,08 8,39 8,34 8,31 8,31 8,34 8,38 8,45 7,80 7,57 7,41 7,28 7,20 7,16 7,14 7,16 7,20 7,26 7,34 7,44 6,00 4,00 6,78 6,50 6,29 6,13 6,02 5,95 5,92 5,92 5,95 6,00 6,08 6,18 6,29 6,42 5,13 4,93 4,78 4,69 4,63 4,62 4,64 4,68 4,75 4,85 4,96 5,09 5,24 5,40 2,00 0,00 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Load weight, t 0,1 10 20 30 40 50 km The optimal payloads can be found from the minimum points of different transport distances (bolded values). 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 14
35 Optimal load size and transport distance in connection to loading time 140,0 Load size, tons (blue line) 30 25 20 15 10 5 0 0,1 10 20 30 40 50 Transport distance, km 120,0 100,0 80,0 60,0 40,0 20,0 0,0 Loading time, min (red line) Blue line indicates the optimal load size when loading time is consumed according to loading time curve (red line). For example, if the transport distance is 30 km, the payload should be 30 tons at least. If it takes shorter time to load a certain payload, the transport distance could be shorter and vice versa. 15
Discussion For over 50 km transport distances the load space should be full loaded with 64 ton trucks. The driving distance versus driving time optimization is very much dependent on the loading time. The loading time curve was based on the data of this study part 2 loads and did not differ much of the previous time consumptions of loading of biomasses. If the optimal load size is reached in a shorter time on a specific distance, the extra time could be used for reaching even higher payload or transporting a little longer distance. To reach 64 ton payload is very time consuming task if the material is dry, under 35% precipitation. For this reason, work methods and techniques to compress the load are needed in addition to normal work procedures. 16
Part II Productive work models for biomass truck loading with loose biomass materials 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 17
Work models Work models are systematic ways to work that lead to a good result with a reasonable effort. (Kokkarinen, J. (ed.) 2012.) The main idea of work models is to use present equipments/machines more efficiently by improving work techniques and methods. In work models, the focus is on finding and describing the fundamental issues affecting the work. Systematic work methods lead often to better total result. In addition, an important part of the work models is tacit knowledge related to work in a question. Making tacit knowledge visible increases efficiency and the work procedure clarifies. In this study, the tacit knowledge of drivers was studied by interviewing and discussing with them during the operation time. 18
Data collection methods Loading of trucks was filmed from the loader cabin point of view. Truck and trailer load spaces were divided into loading levels to control the position of every tare into the load space. Payload sizes were collected from bridge scales. Total of 12 different biomass truck drivers participated the study. 3 2 1 3 2 1 19
Material and methods Time study was conducted using following work phase division: 1. Crapple to the pile 2. Filling of crapple 3. Full crapple to the load space 4. Sorting of load space 5. Extending of trailer Work phases 1-4 exist almost for every loading cycle and the extending of trailer once per load. Time study did not include preparation or other delay times because the focus was on pure loading time and its work movements. 20
Results 21
Study loads Loads Mean, kg Min, kg Max, kg St. Dev., kg Stumps 12 24068 17500 32200 4374 Logging residues 11 22197 17580 27820 3125 23 loads of stumps, logging residues and small size trees were observed. Material in stump loads was mainly spruce and logging residue loads were typically spruce including little birch in some loads. It was able to measure moisture content of loads unloaded to terminal crush. Moisture samples directly from piles or loads were seen unreliable and they were not collected. For this reason dry ton values were not used in analysis because moisture values were obtained only for 1/3 of the loads. That s why loads were analyzed in payload tons. All the piles were stored at least for a one year so the variation in moisture contents were stabilized on some level. 22
Study loads Mean number of tares per load Minimum number of tares per load Maximum number tares per load Mean tare, kg Stumps 147 91 197 171 Logging residues 88 65 120 263 The number of tares per load was considerable higher with stumps compared to logging residues and, on the other hand, the tare weight was almost 100 kg lower on the stumps. 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 23
Work phase time division for stumps and logging residues 40,0 35,0 32,9 34,8 Proportion, % 30,0 25,0 20,0 15,0 28,1 19,9 22,0 25,3 20,0 13,6 10,0 5,0 0,0 1,5 1,4 Crapple to the load space Filling of crapple Sorting of load space Crapple to the pile Extending of trailer Stumps Logging residues The proportion of Sorting of load space work phase is considerably higher on logging residues -> very loose material needs more compression movements. The higher number of loading cycles explained also Crapple to the load space and Crapple to the piles proportions especially on stumps. 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 24
Average work phase times for stump and logging residue loads Time, min 70,0 60,0 50,0 40,0 30,0 20,0 10,0 0,0 18,8 13,4 Crapple to the load space 60,5 47,9 17,6 16,7 11,8 10,6 11,3 6,6 0,8 0,6 Filling of crapple Sorting of load space Crapple to the pile Extending of trailer Total cycle time Stumps Logging residues On average, loading of stump load took 26% more time compared to logging residue loads. The main explanation for this is the higher number of work cycles ie. lifting times to load space. 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 25
Cumulative load volume figures for stumps and logging residue loads kg Stumps 35000 30000 25000 20000 15000 10000 5000 0 0,0 20,0 40,0 60,0 80,0 100,0 min 1 1 2 2 3 4 5 6 6 11 11 12 kg Logging residues 35000 30000 25000 20000 15000 10000 5000 0 0,0 20,0 40,0 60,0 80,0 100,0 min 1 3 4 5 7 8 8 9 9 10 10 The variation in loading times was considerably higher in stump loads compared to logging residues. The homogeniety of logging residue material explains the low variation. Curves marked with red arrows represent stump material loads with small piece size. That material densified well without extra compaction movements. 26
Mean times and distributions for stump loading cycles for drivers 100,0 90,0 Work phase time, s 80,0 70,0 60,0 50,0 40,0 30,0 20,0 10,0 1 1 2 2 3 4 5 6 6 11 11 12 0,0 Lifting to load space Filling of crapple Sorting of load space Crapple to pile Extending of trailer Total time Variation in sorting of load space time was considerably high between the drivers. Extending of trailer exists only once per load. 27
90,0 Mean times of logging residue loading cycles for drivers Work phase time, s 80,0 70,0 60,0 50,0 40,0 30,0 20,0 10,0 1 3 4 5 7 8 8 9 9 10 10 0,0 Lifting to load space Filling of crapple Sorting of load space Crapple to pile Extending of trailer Total time Also with logging residues the sorting time in load space varied considerably between the drivers. 28
Average stump load tare weight and load sizes 300 35000 100,0 250 30000 90,0 80,0 kg/tare 200 150 100 25000 20000 15000 10000 kg/payload Loading time, min 70,0 60,0 50,0 40,0 30,0 50 5000 20,0 10,0 R² = 0,5293 0 1 1 2 2 3 4 5 6 6 11 11 12 Driver 0 0,0 50 100 150 200 250 300 Tare size, kg Figure on the left: Minimum tare weight was 111 kg and maximum 258 kg. Driver 4 had the highest tare weight and he also reached considerably high payload. On the other hand, driver 3 used rather small tare weight and reached high payload. Figure on the right: Tare weight seems to explain loading time. 29
Average logging residue load tare weights and load sizes 350 30000 80,0 kg/tare 300 250 200 150 100 50 25000 20000 15000 10000 5000 kg/payload Loading time, min 70,0 60,0 50,0 40,0 30,0 20,0 10,0 R² = 0,2623 0 1 3 4 5 7 8 8 9 9 10 10 Driver 0 0,0 125 175 225 275 325 375 Tare size, kg Figure on the left: Minimum tare weight was 162 kg and maximum 333 kg. Operators 3, 4 and 10, who reached the highest payloads, did not use maximum tare weights. Figure on the right: Tare weight explained loading time a little. 30
Work phase times and load weights for stump loads Crapple to the load space Filling of crapple Sorting of load space Crapple to the pile Payload size 100,0 35000 90,0 80,0 14,8 13,3 30000 Loading time, min 70,0 60,0 50,0 40,0 30,0 20,0 10,0 0,0 11,1 16,8 9,9 14,7 37,9 37,6 6,3 11,3 17,7 30,6 34,2 9,8 25,3 7,5 18,0 11,8 11,4 12,2 16,4 14,5 8,8 10,6 2,0 6,4 12,2 12,0 10,8 0,8 6,9 6,9 10,6 9,3 3,9 28,4 5,8 29,0 13,7 17,2 13,4 13,5 17,3 21,8 22,4 19,4 19,0 11,0 1 2 3 4 5 6 7 8 9 10 11 12 Operator 25000 20000 15000 10000 5000 0 Load size, kg Loading times varied between the operators and loads. No clear dependency. 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 31
% 60,0 50,0 40,0 30,0 20,0 10,0 0,0 Work phase times division for stump loads Crapple to the load space With the first two loads material was small size and therefore needed only a little sorting and compression work. Also load material of driver No. 12 was very compacted. Filling of crapple Sorting of load space Crapple to the pile Extending of trailer 1 44,6 22,6 2,6 28,8 1,5 1 44,8 17,9 5,1 30,6 1,6 2 28,4 22,5 25,8 20,6 2,8 2 31,8 21,9 24,8 17,7 3,8 3 37,7 15,1 23,5 22,3 1,4 4 39,7 20,9 13,9 23,2 2,2 5 28,1 19,7 29,2 18,4 1,1 6 23,7 17,9 41,3 16,1 1,0 6 25,3 16,3 42,5 15,1 0,8 11 26,7 16,6 42,1 13,7 1,0 11 25,1 14,3 45,1 14,6 1,0 12 38,4 33,5 8,3 19,4 0,4 32
Work phase times and load weights for logging residue loads Crapple to the load space Filling of crapple Sorting of load space Crapple to the pile Payload size, kg 70,0 30000 60,0 10,7 25000 Loading time, min 50,0 40,0 30,0 20,0 10,0 7,7 22,9 9,9 9,2 3,2 21,8 14,3 10,7 13,9 18,6 19,0 6,6 20,4 9,2 14,3 6,5 4,5 12,7 14,7 3,5 12,6 10,4 9,4 6,2 10,9 10,4 8,6 5,0 4,7 7,1 6,9 30,2 22,5 18,2 16,9 10,0 9,5 6,4 8,4 12,5 11,5 12,8 14,6 20000 15000 10000 5000 Load size, kg 0,0 1 2 3 4 5 6 7 8 9 10 11 Operator 0 Loading times varied between the drivers and loads also with logging residues. 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 33
% 60,0 50,0 40,0 30,0 20,0 10,0 0,0 Work phase time division for logging residues Crapple to the load space Filling of crapple Sorting of load space Crapple to the pile Extending of trailer 1 25,9 40,5 18,5 14,3 0,9 3 27,7 21,3 34,0 15,9 1,0 4 43,5 24,6 7,4 21,0 3,5 5 28,1 18,0 40,2 12,9 0,8 7 26,2 24,8 30,6 15,5 3,0 8 26,3 23,8 37,0 11,3 1,6 8 27,5 20,0 40,3 11,2 1,0 9 22,9 11,7 55,3 9,1 1,0 9 24,2 17,6 47,3 9,9 1,0 10 26,4 20,6 37,5 14,7 0,8 10 30,2 19,6 35,0 14,2 1,0 The material of driver No. 4 was very wet. 34
Average work phase times for loaded tons Work phase Stumps, s/t Logging residues, s/t Grapple to the pile 28.2 16.5 Filling of grapple on the pile 29.4 26.4 Loaded grapple to the load space 46.9 33.4 Sorting and compacting of load space 43.9 41.6 Extending of trailer 3.8 3.8 Total time, min/t 2.7 2.2 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 35
Number and location of tares in load space in comparison to load weight with stumps Bottom part Middle part Upper part Payload size, kg 250 35000 200 30000 Number of tares 150 100 50 0 96 88 85 77 89 76 77 68 99 62 54 39 32 42 34 48 35 51 42 27 25 36 34 18 33 45 51 62 31 35 33 45 49 29 33 36 1 1 2 2 3 4 5 6 6 11 11 12 Operator 25000 20000 15000 10000 5000 0 Payload size, kg The number of tares was the highest in the upper part of the load space. This means that the tare size was the smallest there and the drivers filled the upper part of the load with small tares. 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 36
Number and location of tares in load space in comparison to load weight with logging residues Bottom part Middle part Upper part Payload size, kg 140 30000 120 25000 Number of tares 100 80 60 40 20 0 72 59 58 56 68 41 39 41 39 46 43 27 31 27 28 20 18 13 13 12 11 13 17 20 26 19 18 19 16 18 23 12 12 1 3 4 5 7 8 8 9 9 10 10 20000 15000 10000 5000 0 Payload size, kg Operator In logging residue loads, the number of tares was the highest also on the upper part of the load space. Driver 9 used large tares in the lowest part of the load space and for this reason the total payload size was under the average. On the other hand, driver 10 loaded many tares (small tare size) to the lowest part of the load space and reached rather high payload. This means that compacting movements are important also at the bottom level although the upper mass of the load compresses the bottom level. 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 37
Work model descriptions 38
Common features of effective work models for stump and logging residue loading Independent of the loaded material some common features exist for effective loading work: Short loadingdistancefrom pileto load space The closer the truck was located the pile, the faster the driver could lift the tare to the load space. The use of extension of the trailer Some drivers did not move the extendable rear part of the trailer closer the crane for loading but, instead, they loaded the rear end of the trailer by reaching it with very long crane. With this work method extra time was spent. In stump lifting, the size of stump piece is dependent on the lifting method and operator. Instead, logging residues are not comminuted or split during the cutting or short distance transportation operations and, therefore, the piece size is rather homogenous. For these reasons, material size influence also the work method, especially on stumps. 39
1. Work model for loading of small sized stump material Stump material in small size enables very compact and close to the maximum being payloads. This kind of material did not need many compressing movements in the load space, which speeded up loading. The principle of filling the load space was so called puzzle filling where suitable sized empty places in the load space were filled with suitable sized stump tares. Compacting in the load space was done by pressing with open or closed grapple. 11.4.2016 Metsätehon tuloskalvosarja 3b/2016 40
2. Work model for loading of typical sized stump material Stumps are typically split into 3 or 4 pieces in stump lifting phase and roots are part of the stump piece. To enable high payload, it is important to focus on suitable tare weight, numerous compaction movements, correct placing of a tare in the load space and anticipation of load space filling. The main principles to reach high payloads are: Fill a layer of stump material to the load space starting from the back side of the load space and after the base layer use smaller tares to fill the holes of the layer. Load carefully bottom layer of the load space -> this makes possible high total load. Generally, use small tares (140 to 170 kg), even single stump pieces. Use puzzle technique to place the pieces. Make compaction movements almost with every tare (see Compaction loading curve influence) Take benefit of tare weight in the grapple. The spikes of the grapple are effective when compacting the load by pushing with open grapple. Use small tares. Compact with a tare. 41
3. Work model for loading of middle size load with short loading time The point of this work model is to make a payload in a short time. This model is for short transport distance. To enable fast loading, it is important to focus on high tares, short loading cycle times, filling of big gaps in the load space and close-topile positioning of truck. The main principles to reach fast full payload are: After getting some tares to the load space, use big puzzle technique with every tare. Big tares are placed into one tare size holes. Use as high tares as possible (over 200 kg). Make a compaction movement only when you release the tare to the load space Compaction is connected closely to the tare releasing moment. At the end of loading, press the load space throughout and see if the are still some gaps for tares. Minimize loading distance by driving the truck as close the pile as possible. Releasing of tare to the load space and filling a gap with next tare. 42
4. Work model for loading of logging residues In logging residue loading, compression methods are even more important than in stump loading. To enable high payload, it is important to focus on compressing the whole load in a load space and forming of a tare on to a suitable package already at a pile by taking into account the fill rate of the load. The main principles to reach high payload are: Large tares are lifted to the bottom of the load space and when reaching the upper layers of the load space more compacted and smaller tares are used. At the pile, long branches and the whole tare at the same was crushed into a compressed shape by squeezing and rolling it. Important to compact the load after releasing the tare The most effective compacting method was to press, squeeze and turn the grapple at the same time in the load space. To finalize the load, the driver pressed the load of its whole length and if there were still some gaps they could be filled with small tares. A tare need to be compressed already at the pile. Pressing, squeezing and turning the grapple at the same. 43
Discussion Three effective work models for stump and one for logging residue loading were described. Although the moisture content of the loads was not measured and only the real payload was used as an output value to describe the load volume, the results seemed to be justified. Moisture values of loads would have improved the reliability of the results, but on the other hand, most of the entrepreneurs were paid according to transported tons. Material size proved to be important factor in stump loading work models -> for this reason, two of the models were based on material size. To speed up stump loading with small size material, a larger grapple would be one option. 44
Discussion In logging residue loading, compressing movements are even more important compared to stump material. The drivers aimed to make compressed bundles of the tares by making different kinds of movements with the grapple in the pile and in the load space. Therefore, the most effective way to improve loose logging residue loading would be a grapple that would densify and bundle a single tare during the lifting moment to the load space. 45
Conclusions This was a pioneer study from the field of work models of biomass truck loading. In the future, it would be beneficial to make controlled experiments with homogenous biomasses in terminal conditions and to study the described work models more carefully. Especially testing of logging residue compressing method would be important. 46
Literature Kokkarinen, J. (ed.) 2012. Koneellinen puunkorjuu hallitusti hyvään tulokseen. Metsäteho. 107 p. Korpilahti, A. 2015. Bigger vehicles to improve forest energy transport. Metsäteho s slide series 3/2015. 33 p. Ovaskainen, H. 2012. Työmallit koneellisessa puunkorjuussa. Metsätehon raportti 221. 46 p. Poikela, A. 2015. Compression potential doupling energywood load size. Metsäteho s slide series 2/2015. 15 p. 47
BEST thanks The work was carried out in the Sustainable Bioenergy Solutions for Tomorrow (BEST) research program coordinated by CLIC Innovation with funding from the Finnish Funding Agency for Innovation, Tekes. 48