chapter 5 primary transport (extraction)

chapter 5 primary transport (extraction) CONTENTS 5.1 Introduction 5.2 Ground based extraction systems 5.3 Manual extraction 5.4 Chute extraction 5.5 Tractor and trailers 5.6 Self loading bundle trailers 5.7 Safety precautions 5.8 Forwarders 5.9 Skidding 5.10 Agricultural tractors 5.11 Articulated skidders 5.12 Cable yarding systems 5.13 Cable yarding configurations 5.14 Highleads 5.15 Skylines 5.16 Monocables 5.17 Wire rope 5.18 Planning a cable yarding operation 5.1 Introduction Extraction or primary transport is moving the timber from stump to roadside landing by means of manual labour, skidding equipment, cable equipment and/or other means. The timber can be extracted in the form of full trees, tree lengths, long lengths or short lengths. Moving the timber past roadside to a depot/siding is not part of the extraction phase but for completeness will be discussed. 5.2 Ground based extraction systems Ground based extraction systems are the most common in South Africa and include manual systems, wheeled systems and cable systems. 5.3 Manual extraction Manual extraction involves the carrying or rolling of timber from infield to a point where it can be taken further by other means. This method of extraction is seldom used except where the timber is situated in sensitive or steep areas and no other means for extraction is available. 24

5.4 Chute extraction The extraction of timber by chute is a relatively new concept. Chutes used in South Africa consist of round or half pipes joined end-to-end to form a continuous channel guiding the timber down a slope. These pipes are normally manufactured from high density polyethylene (HDPE). Chute extraction is recommended for slopes between 20% and 60%. See Photo 5.1. 1 Photo 5.1: Installed chute system in a gum clearfell operation. 1 5.4.1 Chutes have the following advantages: Relatively low capital cost. Minimal maintenance required. Low environmental impact. Minimal damage to remaining stand if used in thinning operations. Improved productivity over manual extraction. 2 As with any harvesting operation, careful planning is required in terms of felling and identifying the chute lines. Take the following into account when planning for chute operations: The felling pattern must complement chute lines. The timber must fit into the chute. Chute operators must be able to handle the logs manually. Log diameter to be at least 5cm smaller than that of the chute. Maximum length of logs not to exceed 6m. Debranching quality to be of a high standard. For further information on the use of chutes please refer to the FESA Chute Operating Manual. 25

5.5 Tractor and trailers Tractor and trailer combinations are widely used for extraction purposes in South Africa. Trailers are either mechanically or hand loaded. 5.6 Self loading bundle trailers Self loading bundle trailers are another popular method of extracting timber. Timber is prepared in 4 5 ton stacks infield. The bundle trailer then reverses into the stack and the stack is then pulled onto the trailer via the attached chains. The bundle trailer can also be loaded by hand. Photo 5.2: Self-loading bundle trailer. 1 5.7 Safety precautions The minimum requirements for using agricultural tractors in the forestry environment are the following: Tractors should be equipped with shock-absorbent fully adjustable seats for drivers and fitted with safety belts. The operator must keep the safety belt fastened when driving the machine. All pulleys, shafts, belts and fan blades should be securely guarded. Machines must be equipped with an approved roll-over protection structure (ROPS). A 4-post structure should preferably be used. ROPS are designed to absorb energy and deform permanently in the case of a roll over. Where visible damage has been sustained, the ROPS must be assessed by the original designer or a suitably qualified registered mechanical or structural engineer experienced in this class of work. Under no circumstances is a damaged structure to be straightened. No alterations are to be made to the ROPS and nothing may be welded against it. Holes may not be drilled into the ROPS to secure anything else. Cabins should be protected against falling objects. Engines should be equipped with a stopping device which is not self turning, clearly marked and easily reachable from the operator s normal working position. The engine starter should be interlocked with the transmission or clutch so as to prevent the engine from starting if left in gear. Parking brakes must be capable of keeping the machine and its load stationary on all slopes likely to be encountered. 26

Exhaust pipes should be equipped with spark arresters. Engines equipped with turbo chargers, however, do not need spark arresters. Fire extinguishers should be available on every machine, and the operators should be trained in their use. Machines should be equipped with all-wheel drive for safe performance. Agricultural tractors used for primary or extended primary transport must be limited to terrain classification as per Table 5.1. The following must be adhered to when travelling loaded out of the compartment: Since tractor brakes have limited holding power, always use low gear whenever taking heavy loads up or down a slope. Where possible, avoid operating near ditches, embankments, and holes. Equipment needs to be kept behind the shear line of the soil and embankment. The minimum distance recommended is a 1:1 ratio to the depth of the embankment. This distance should increase with adverse soil conditions such as sandy or wet soil. Avoid high speed and reduce speed when turning and crossing slopes, rough terrain, slippery or muddy surfaces. When travelling across a steep slope which is unavoidable, you should travel slowly and always turn uphill rather than downhill. When travelling at speed across a mild slope, you should always turn downhill. Never turn sharply uphill when travelling slowly across a steep slope. It is better to edge gradually uphill. Watch carefully for obstacles and other hazards in the tractor path. Operate the tractor smoothly, avoiding jerky turns, starts and stops. Eliminate sharp corners or curves, and rough or slippery surfaces. Backing up or driving down slopes can help prevent rear overturn. If a tractor must be operated across the slope, use the widest possible wheel adjustment, very slow speed and extra caution in watching for obstacles that the wheels might hit. When the tractor gets stuck, always try to back out. Trying to drive forward is dangerous and can result in a rear overturn. If backing out is not possible, get towed out forward by hitching to the tractor frame. If the tractor must be towed out backward, hitch only to the drawbar. When towing use only a chain or steel cable and tighten slowly. Choose an appropriate gear before going up or down a slope. Keep speed down on slopes and rough terrain. Make wide turns on slopes, especially when turning uphill. Tight turns can result in slipping, loss of control and a roll over. Never take shortcuts. 5.8 Forwarders Forwarding is the extraction of timber by wheeled equipment, carrying the timber on load decks or trailers. Forwarding equipment includes tractor and trailer units as well as specialised machines. Forwarders are specialised vehicles for transporting timber (see Photo 5.3). They can be equipped with a grapple crane for loading and unloading. These machines are expensive to purchase. The length of timber that can be transported is dictated by the length of the load deck and forwarders are less suitable for timber with a DBH > 50cm. 27

3 Photo 5.3: Forwarder. 3 5.9 Skidding Skidding is the process of extracting trees by dragging or trailing them, partially suspended, behind specialized equipment. Animals are still used for skidding purposes in certain areas. Their use is however limited to the more rural and small scale operations. More detailed information regarding the use of animals for extraction can be found in Zaremba s Logging Reference manuals. Crawler tractors can be used for extraction but are probably more suitable for road building activities. 5.10 Agricultural tractors Agricultural tractors are less robust, less balanced and less protected than purpose-built forestry machines. As with all machines used in forestry, hazards include over-turning, falling objects, penetrating objects, fire, whole-body vibration and noise. Only all-wheel drive tractors should be used and a minimum of 20% of the machine weight should be maintained as load on the steered axle during operation. This may require attaching additional weight to the front of the machine. The engine and transmission may also need extra mechanical protection. Minimum engine power should be 35kw for small-dimension timber. 50kw is usually adequate for normal size timber. Agricultural tractors fitted with an A-frame or single or double drum winches can be used for extracting timber in forestry operations (see Photo 5.4). The same precautions as discussed under tractors and trailers must be adhered to when skidding timber with agricultural tractors. Skidding trails must be planned properly to minimize random driving through a compartment. Chokers and de-chokers must be trained and supplied with the correct protective equipment and clothing. These include overalls, steel capped boots, hard hats and steel studded gloves when working with skidding cables and chokers. 28

4 Photo 5.4: Tractor with winch. 4 5.11 Articulated skidders Wheeled skidders are specifically designed to winch and skid timber from stump to landing. There are three main skidder configurations, namely: cable skidders; grapple skidders; and clambunk skidders. Photo 5.5 (left): Cable skidder. 5 Photo 5.6 (middle): Grapple skidder. 6 Photo 5.7 (right): Clambunk skidder. 6 The main variables that will influence skidder productivity are: skidding distance; load size; terrain; travel speed; machine capacity; and operator decisions. For all skidding operations, planning of the felling pattern and the skid trails is very important. The drawings below are an example of three different types of skid trail layouts that can be considered with skidding operations. 5 Factors like terrain, slope and availability of haulage roads will influence the type of skidding pattern. See Annexure G for a guideline to skidder extraction production. 29

Parallel design Herringbone design Dendritic design Figure 5.1: Skidder trail layouts General notes for skidding operations and terrain limitations: With proper skid trail planning, ground disturbance and compaction will be minimised. When extracting with cable skidders, taglines should be used in smaller dimension timber to optimise load size. Grapple skidders normally work in conjunction with feller-bunchers. The feller-buncher fells the trees and bunches them into load sizes for the grapple skidder. Clambunk skidders are equipped with a grapple loader and transport full trees by supporting the buttend of the stem on a log bunk. These machines are normally used with bigger size timber being skidded over longer distances. The use of articulated skidders for extraction is a capital intensive operation and proper planning of the operations is essential. According to the Guidelines for Forest Engineering Practices in South Africa, the following terrain limitations are imposed when using ground based extraction systems. Criteria Slope % Up Down Ground roughness Ground conditions Skidding distance Agricultural Tractor Winch A-frame 0-10 0-3- Wheeled Skidders Normal tyres 0-20 0-35 High flotation 0-20 0-40 Forwarding Machines Tractor & trailer 0-10 0-20 Wheeled forwarder 0-30 0-40 Clambunk Skidder 0-25 0-40 1-2 1-3 1-2 1-2 1-3 1-3 1-2 1-3 1-2 1-2 1-4 1-3 50-300m 50-500m 50-500m 50-500m 50-1000m 50-1000m Table 5.1: Terrain limitations for ground based extraction systems. 30

5.12 Cable yarding systems Cable yarders are used where infield terrain conditions prevent the use of vehicles or other extraction methods. Such conditions include steep terrain (normally > 35% slope), excessive ground roughness, environmentally sensitive areas and areas with soft underfoot conditions. 5.13 Cable yarding Configurations The configurations most appropriate for South African conditions are discussed in more detail in this section. In order to get an idea of the limitations of each configurations related to terrain, the National Terrain Classification System (TCS) for Forestry 6 is used to provide this information. The TCS is a handy tool that provides an indication of the physical characteristics and accessibility of an area. Ground Conditions (trafficability within the stand) Ground Roughness Slope* (in %) 1. Very Good 1. Smooth 1. Level (0%-11%) 2. Good 2. Slightly uneven 2. Gentle (12%-20%) 3. Moderate 3. Uneven 3. Moderate (21-30%) 4. Poor 4. Rough 4. Steep 1 (31%-35%) 5. Very Poor 5. Very rough 5. Steep 2 (36%-40%) 6. Steep 3 (41%-50%) 7. Very Steep (>50%) Table 5.2: Ground conditions. 7 Figure 5.2: Types of slopes. 7 31

Cable yarders are classified into three categories namely: highleads; skylines; and monocables. 5.14 Highleads There are basically three types of highleads: highleads with buttrigging; highleads with a highlead carriage (as used in South Africa see Figure 5.3); and shovel yarder highleads (see Photo 5.8). Figure 5.3: Highlead system as used in South Africa. 7 Highlead systems have two operating lines namely the mainline and the haulback line. During haul-in the logs are dragged on the ground. In some systems lift can be obtained by braking on the haul back line. Some lateral yarding is possible. See Figure 5.3. 1 8 Photo 5.8: Shovel yarder. 8 32

The shovel yarder hi-lead is much safer than the conventional yarders, due to the fact that the yarder is operating without guy ropes and cannot be pulled over easily. It can also operate as a swing yarder, by leaving the timber next to the machine and not in front, as a conventional yarder (see Photo 5.8). According to the Guidelines for Forest Engineering Practices in South Africa, the following terrain limitations are imposed when using cable based extraction systems. Highlead Recommended Terrain Conditions Buttrigging Highlead carriage Highlead Downhill Uphill Downhill Uphill yarding yarding yarding yarding Slope (%) 20-40 20-50 Ground conditions 1-3 1-5 Ground roughness 1-2 1-3 1-3 1-4 Yarding distance 50-200 50-200 Table 5.3: Terrain limitations for cable based extraction systems. Types of slopes conducive to high-leading are regular and concave slopes. 5.15 Skylines Skyline systems can either be standing skylines or running skylines. Standing skyline configurations are commonly used in South Africa. Standing skylines again can either be single-span or multi-span. A single-span system is used where there is adequate deflection to provide the required lift off the ground. Deflection refers to the amount of sag in the skyline, and is influenced by the shape of the terrain. The South African highlead described in paragraph 5.14, is an example of a simple running skyline. Standing skylines have the skyline cable fixed at both ends and it remains fixed throughout the operation. The carriage runs on the skyline while the haulback line, used in downhill yarding, runs through the corner and tailblock back to the carriage. The mainline runs through the carriage and the choked logs are attached to the mainline. The carriage is hauled out either by gravity (shotgun) in an uphill operation or with the haulback line in a downhill operation. See Figure 5.4. 33

Figure 5.4: Skyline system. 7 A long distance gravity skyline can be used where access to the compartment is limited. This configuration is a low productive unit, but an effective method to harvest difficult terrain with timber of high value. Photo 5.9: Long distance gravity skyline system. Photo 5.9 shows the operational area for a long distance gravity skyline over 800m, with the depot in the foreground and the harvesting area in the background. 34

Anchor tree 20mm skyline 13mm mainline Remote control 3 Cylinder Deutz lock up carriage diesel engine Intermediate Support Double deadman anchor Landing Figure 5.5: Concept design of a gravity feed skyline configuration. 35

Some advantages of a conventional skyline over a long distance: Capital layout much cheaper than for a traditional skyline. Can work over a longer range than conventional machines available in the country. With a traditional skyline a haulback line of 1600m would be needed on an 800m span. With the gravity skyline only an 800m haulback line is needed. Range of the biggest skyline currently available in the country is only 600m. According to the Guidelines for Forest Engineering Practices in South Africa, the following terrain limitations are imposed when using cable based extraction systems. Skyline Skyline Recommended Terrain Conditions Downhill yarding Full Uphill yarding Partial suspension suspension Slope (%) 0+ 0+ Ground conditions 1 5 1-5 Ground roughness 1 3 1-5 1-4 Yarding distance 100-600 100-600 Table 5.4: Terrain limitations for cable based extraction systems. 5.15.1 Single-span skylines The types of slopes conducive for single span skyline configurations are regular, undulating, terraced, and concave. Slopes that are conducive for multi-span skyline configurations include regular, undulating, terraced, convex and concave. Advantages of a single span: set-up time is quicker; cycle time is faster; and not as complex as multi-spanning. Disadvantages of a single span: the length of a rack is restricted to the distance where the required deflection occurs; and yarding is restricted to concave and regular slopes. Compartments often have areas with little or no deflection, such as convex, undulating and long regular slopes. In such conditions deflection can be provided by installing intermediate supports. The carriage must be able to operate over the intermediate support jack. The intermediate supports are chosen along the length of the rack to provide skyline lift where deflection is inadequate. Supports are therefore normally positioned at a change in topography. 36

5.15.2 Multi-span skylines Advantages of a multi-span: better deflection and clearance on unfavourable terrain; higher payload; higher lift; less yarder wear and tear; extended yarding distances; bigger yarder; higher road density; aerial harvesting; roads higher on hillside; less excavation; less environmental damage; and reduced lateral deflection of skyline in thinnings. Disadvantages of a multi-span: slower operation; planning is more complex; rigging is more difficult and time-consuming; and multi-span systems can be more expensive than a single span (eg additional rigging, longer yarding distance). 5.16 Monocables A monocable system consists of a continuous cable that runs through a series of open side blocks that are hung in support trees. The cable is powered by a capstan winch. Logs are choked to the moving line. Monocables are used in thinnings or other small scale operations and can be up to 1,000m of continuous loop. See Figure 5.6. 37

Figure 5.6: Monocable system. 7 5.17 Wire rope It is recommended that IWRC (independent wire rope core) type wire rope be used in cable yarding operations because of its strength and crush resistance. Wire ropes in a cable yarding operation experience both static and dynamic loading. Experience has shown that if tensions due to static loading are kept below one-third of the braking strength of the cable, there is adequate provision for the combined loading of static and dynamic loads. Therefore, a safety factor of three is typically applied to all wire ropes in cable yarding. Safe working load (SWL) = Breaking strength / 3. 5.18 Planning a cable yarding operation Planning for cable yarding operations is an important part of a total harvesting operation. The following should be noted when planning for cable yarder operations: A paper plan detailing the operation should be compiled. The paper plan should indicate landings, felling direction, transport direction and areas that would incur special management. Guyline anchor availability and suitability must be checked. Landings should be as level as possible to ensure equipment stability. Landings should be big enough to accommodate all subsequent operations. Landings should be away from sensitive areas. The infield cable profile needs to be checked as it will have an influence on payload. 38

Intermediate support trees must be marked clearly. Cable yarding operations are one of the most dangerous forestry operations. The yarder crew must therefore be properly trained, experienced and equipped. Only experienced crew members must be used if at all possible. Special attention must be given to the communication between the yarder operator and the choker men out in the field. Common hazards caused by incorrect rigging: Guyline failure caused by: insufficient number of guy lines; incorrect guy line angles; insufficient guy line strength; incorrect guy line tensions; small sheaves; fatigued guy lines; and guy lines are not in the lead at the point of attachment to the anchor. Anchor failure caused by: using the wrong type of anchor system for the particular situation; poor selection and notching of stumps; incorrect guy line tension; and overloading of the yarding system. When yarding on convex slopes, cables will rub heavily on the ground causing wear and tear, which could lead to wire rope failure. Wire rope running over rock will also be damaged and could cause fires. Poor selection of intermediate supports and tail trees could injure workers. Intermediate supports, towers and tail trees can be pulled over if rigged incorrectly. Failure of rigging accessories due to not matching all the accessories and cables within the system. Detailed information on rigging requirements and all safety aspects pertaining to cable yarding can be obtained from the South African Cable Yarding and Operating Handbook. 7 1 Photos by A. Immelman. 2 FESA - 1994. 3 www.harvesterbetrieb.de 4 www.logloader.com 5 Smidt and Blinn - 2004. 6 Erasmus - 1994. 7 FESA South African Cable Yarding Safety and Operating Handbook July 2001 8 P Schoombe 2006 39