Australian Forestry Contractors Association Tasmanian Logging Tilt Test

Transcription

1 Australian Forestry Contractors Association Tasmanian Logging Tilt Test Author: Jonathan Vila BEng Reviewed: Sean Carlson BEng CPEng RPEQ Date: 11/12/2018 Issue: Issue 2 File Number: E1073

2 Executive Summary The testing of log friction and various load restraint systems in Tasmania showed high values of friction for each of the log species tested, relative to other friction test performed on various log types in other regions. A log that speared during transit indicates that lower friction native logs may exist. All bar two restrained tests met the 0.8g requirements. A manual winch webbing in combination with a belly chain achieved the highest tilt angle of 55 (at 1.14G), easily surpassing the 0.8g requirements. However, it proved to be inconsistent in both its applied tension. Dyneema achieved the highest tension and with the use of air winches achieved the most consistency. The belly chain commonly used in the industry also worked very well. This was especially true in combination with webbing straps. Finally, Grip plates were seen to be very effective at holding the bottom layer of the logs. ED559-Issue 2 E /12/18 2

3 AFCA logging tilt test (TAS only) Date of test: 26-27/07/18, Orana Enterprises Pty Ltd, Legana Park, Tasmania Engistics Engineers Present: Sean Carlson Jonathan Vila Acknowledgements: Engistics wishes to thank the following organisation with this testing: Orana Enterprises Pty Ltd Forico Pty Ltd Sustainable Timber Tasmania (STT) ANC Forestry Forest Centre (Aust) Pty Ltd Australian Forestry Contractors Association Test Goals: The purpose of the testing was to: 1. Determine the static friction of four types of Tasmanian timber: E.Nitens Pulpwood, Native pulp, Native and E.Nitens. These were divided into two separate test lengths: the first at 6m and the second at 12m. 2. Assess the difference in friction between 6m and 12m log lengths. 3. Assess the change in log behaviour between restrained and unrestrained. 4. Evaluate Dyneema as a restraint system. 5. Further evaluate Belly Chains in testing. 6. Further evaluate Webbing straps as a restraint system. ED559-Issue 2 E /12/18 3

4 Test Methodology: The test method attempted to simulate the loading of logs onto a logging trailer by having two bolsters restrained to a 40ft flat rack. The test bed was then tilted from one end until the logs moved or until a satisfactory angle replicating 0.8g was reached to satisfy EN Over twenty separate tests were conducted as listed in the table below. During these tests, the type of timber, its length and the angle of the flat rack were recorded. All test lifts were recorded via video to capture the moment of movement. Figure 1: 6m s on flat rack A headboard was fixed to the forward bolster frame to both reduce the amount of log movement and reduce clean up time if logs were to move out of the bolsters. ED559-Issue 2 E /12/18 4

5 Figure 2: 6m logs test setup The test however, did have certain limitations such as: Reduced angle range due to the scale of the test and crane constraints Crane concerns over stability of test rig Headboard safety, the bay mass was reduced to ensure the headboard could adequately block the load Deformation of the flat rack anchor points due the lifting chain applying highly concentrated loads Concerns of overturning All concerns were documented in the Risk Assessment prior and during the testing. ED559-Issue 2 E /12/18 5

6 Equipment: The tests involved a variety of equipment both to measure and restrain the logs. Such equipment included: Elphinstone Engineering fabricated Log bolsters with round pegs and grip bars to replicate the transport of logs on trailers 75mm Webbing straps; Elphinstone manual load binders Belly Chain tensioned by a maxi binder manual tensioner 5m 10 ton WLL Dyneema ropes were used for the restrained tests 1x 3t tension Load cell, 1x 5t tension Load cell for measuring tension in the tie down system. Air winches with an approximate air supply pressure of 100psi. 2 x ExTe TU16 winches configured 1:1 for Webbing or Dyneema as required Various cameras and test equipment to measure angle and movement of logs 40 ft flat rack 85 ton boom crane Staunchion Dyneema/webbing strap Tension Load cell 8mm Chain on air Figure 3: Air Winch setup (with Tension Load cell) vs Manual winch setup Figure 4: Air Winch with Dyneema post log movement ED559-Issue 2 E /12/18 6

7 Results: Test Size (m) Type Angle Friction Effective G-Force Restraint method Comments 1 6 E.Nitens Pulp (Forico) Top tier logs movement 2 6 E.Nitens Pulp (Forico) Full log movement E.Nitens (Forico) E.Nitens (Forico) E.Nitens (Forico) E.Nitens (Forico) E.Nitens (Forico) E.Nitens (Forico) - NA NA * 0.74^ 4 Full log movement Wet, Equipment failure Wet, angle adjusted, top tier movement Top tier movement, wet and angle adjusted * 0.71^ 2 Top tier movement * 1.14^ 3 No movement No movement 9 6 Native (STT) Full movement, Blocking Webbing strap failure 10 6 Native (STT) Full movement 11 6 Native (STT) * 0.85^ 4 Dyneema test 12 6 Native (STT) * 0.94^ 5 Dyneema with belly strap (chain) Native Pulp (STT) No movement Native Pulp (STT) No movement Native Pulp (STT) * 1.04^ 4 No movement Native Pulp (STT) * 1.04^ 6 No movement E.Nitens Pulp (Forico) Full movement E.Nitens Pulp (Forico) Full movement E.Nitens Pulp (Forico) * 1.09^ 7 No Movement E.Nitens Pulp (Forico) * 1.00^ 5 Top tier movement E.Nitens Pulp (Forico) * 1.03^ 4 Full movement E.Nitens Pulp (Forico) * 0.96^ 2 Full movement *Assumed from unrestrained test ^Calculated Table 1: Initial results ED559-Issue 2 E /12/18 7

8 Restraint method 1 Unrestrained 2 3 2x 75mm Webbing on ExTe Winch 2x 75mm Webbing straps on Exte Winch, Belly Chain 4 2x Dyneema on ExTe TU x Dyneema on ExTe TU16, Belly Chain 2x 75mm Webbing straps, Elphinstone Manual winch, belly chain 2x Webbing straps, Elphinstone manual winch 8 Belly Chain only Table 2: Restraint Method Day 1 of testing involved only 6m logs and day 2, only 12m logs. This allowed minimum delays for setting up the test rig. In general, all types of timber were tested both unrestrained and restrained. In the case of the restrained tests, a mix of webbing straps and Dyneema were used for restraints as well as chain belly straps to unitise the logs. It must be noted that in some cases, tilting of the test rig was limited due to safety concerns relating to crane stability. This limited both the tilt angle as well as the total logs put on the test rig itself. Test 3 was disregarded due to a malfunction of the angle measurement equipment during testing. It was fixed for the following tests. E.Nitens Pulp was tested in previous testing at 6m and was thus only briefly tested at this length. It featured more heavily on the second day with 12m log testing. E.Nitens and Native s were only tested during the first day at 6m lengths. Native Pulp was only tested on the second day at 12m lengths. The results show extremely high angles of tilt before movement and in some cases, no movement at all. ED559-Issue 2 E /12/18 8

9 Analysis of results: Friction of Tasmanian logs: The friction of the logs was evaluated using restrained and unrestrained tests. An unrestrained test evaluates the friction using a simple process of taking the Tangent of the angle to determine friction. The restrained test includes the effect of tie down force in the formula for determining friction. In both cases, a higher angle of tilt equates to a higher coefficient of friction. The static friction for unrestrained tilt tests is calculated using the formula: µ = Tan θ The static friction for restraint tilt tests is calculated using the formula: mg sin θ = μ ((mg cos θ) + F! ) where: F! = Clamping from lashing: T sine g μ = friction of logs T = tenison of lashing in kg Hence: m = mass of logs in kg μ = mg sin θ ((mg cos θ) + F! ) Below is an example of an unrestrained test: Test 1, Unrestrained E.Nitens Pulpwood with a movement of three logs: θ = 42 degrees μ = tan 42 μ = 0.9 ED559-Issue 2 E /12/18 9

10 Test Size (m) Type Angle Static Friction 1 6 E.Nitens Pulp E.Nitens Pulp Average Static friction E.Nitens Native s Native s Native Pulp Native Pulp E.Nitens Pulp E.Nitens Pulp Table 3: Friction values of logs (Unrestrained) The tilt testing in Tasmania showed very high coefficients of friction across the board. However previous testing of similar type logs, specifically in the Green Triangle Region identified lower friction values for Pulp logs (Globulus). Our comparisons look at Native s versus Mountain Ash and E.Nitens versus RB40 (Pine sawlogs). Engistics recognises that there are differences between these species and is happy to have clarification to improve the comparison. Restraint testing using either webbing or Dyneema showed they met the performance standards at this friction at time of test. Figure 5: Log movement in transit ED559-Issue 2 E /12/18 10

11 An issue that arose (relating to the current friction of the logs) was that during transit to the test site, one of the Native logs speared forwards. In this case, the logs were restrained using webbing straps tensioned with a basic common hand operated winch. The driver advised that no heavy braking or impact had been experienced in transit. This would indicate that deceleration occurred through moderate braking which would typically provide forces on the logs of between 0.55 to 0.6g. In this case, even if the applied load restraint had a minimal impact on the log, and the movement came from friction alone (best case scenario for the highest friction), the static friction would be in the range of Our observation is that the log that moved in transit is comparable in friction to Mountain Ash. Engistics can only theorise on this increase in friction between in transit load shift and in rig results; however, it can possibly be attributed to a few likely causes: Travel times between logging operations and test site could have allowed convection drying to impact friction; Differences in test rack configuration compared to on vehicle load configuration. Seasonal effects Increased log marks from winter operations. Time between harvesting and transport Commentary Provided by Forico indicated that during winter, additional marking on the logs occur due to operational requirements when removing branches. This would have the potential to contribute the increased friction of the logs during testing. The timing of the logs for testing in relation to the time between harvesting and transporting is reflective of most log transport tasks in Tasmania from discussions with operators during testing. Due to the high friction of logs found, the next step was to review the effectiveness of load restraint systems. This included using a combination of webbing straps, air winches, manual winches and belly chains. Dyneema was also extensively used to determine its effectiveness as a potential alternative restraint system. The effectiveness of a restraint system is measured by its applied tension and tension loss. The high friction of the logs assisted greatly to the performance of the restraint system. ED559-Issue 2 E /12/18 11

12 Summary of Dyneema tensions: Dyneema was heavily featured in the restrained tests to review its effectiveness. The results below show the measured tensions on both the high and low sides with the high side being the side of the air winch. Test Size (m) Type Figure 6: 6m s Tension (High) kg Tension (Low) kg Difference High to Low (%) 5 6 E.Nitens Native Native Pulp Air pressure approximate 100psi based on 50mm gauge from truck compressor. Table 4: Dyneema tension difference between Low and High The tension in the Dyneema was not consistent between tests but registered higher than webbing straps. Tension in the 12m logs registered the greatest disparity between High (left) end and low (right) side. Previous testing found that the ratio between the low side and high side was around 43%. Current test results are higher than this value, suggesting that the test setup was correct. However, our Dyneema tension values do not align with values found during previous testing (1000kg-1200kg high side compared to current test results of kg high side). This suggests that the test air pressure was likely less than previously understood where majority of previous tests were around 115 psi. This is potentially attributed to the gauge resolution not permitting accurate pressure measurement. An Engistics learning from this process is to ensure higher resolution gauges are available when performing similar tests. ED559-Issue 2 E /12/18 12

13 Belly Chain: Testing was completed with various restraint systems including combinations of Dyneema, 75mm Webbing straps and Belly Chains combined. Belly chain was tensioned with a maxi binder manually tensioned. The table below provides a comparison of tests for systems with and without belly chains applied. Test Size (m) Type 6 6 E.Nitens 7 6 E.Nitens 8 6 E.Nitens 11 6 Native 12 6 Native E.Nitens Pulp E.Nitens Pulp E.Nitens Pulp Angle G-Force Restraint Comments (degrees) x Webbing straps Top tier movement x Webbing straps, Belly No movement Chain Belly Chain only No Movement x Dyneema Dyneema test x Dyneema, Belly Chain Dyneema with belly strap (chain) x Webbing straps, manual winch, Belly Chain No Movement x Dyneema, Belly Chain Top tier movement x Dyneema Full movement Table 5: Belly Chain effect The results of test 19 are only included for completeness, as a test was not undertaken without a belly chain for comparison. In the case where Dyneema was used, a small increase in restraint capacity (by 1-2 degrees) was seen when a Belly Chain was applied. However, there was a dramatic increase in restraint capacity when a belly chain was used in combination with webbing straps (a total of 15 degrees increase in test 7 compare to test 6). This is also highlighted by the G-force achieved: In test 6 the 0.71G reached would have meant that the load would not have successfully achieved the required 0.8G. However, the addition of a Belly Chain greatly increased the G-force to 1.14G. ED559-Issue 2 E /12/18 13

14 Figure 7: 6m Sawlog testing with belly chain This discrepancy between Dyneema and webbing straps is most likely attributed to the difference in tension between the two. In all cases, Dyneema registered higher tension values than webbing straps. This would mean that a belly chain played a greater role in the restraint of the logs with webbing than it did when used in conjunction with Dyneema. Interestingly, test 8 showed that a belly chain on its own achieved the required 0.8G. This indicates a log friction of This result shows the value of a belly chain and is indicative of the gains achieved with its usage. The friction values obtained in testing also assist the performance of the load restraint in testing. This is a common feature of all tests. ED559-Issue 2 E /12/18 14

15 Webbing tension Loss: Whilst webbing straps were used for several tests, we noticed a marked decrease in tension over time as well as lower tension values overall. Test Size (m) Type High Tension (kg) Low Tension (kg) Difference High to Low (%) 6 6 E.Nitens 1 min 1 min 7 6 E.Nitens min Native Pulp Elphinstone manual winch * 12 E.Nitens Pulp Elphinstone manual winch Initial min mid test: end of test (0 degrees tilt) * Data appears inconsistent Table 6: Webbing tension difference Low to High From the table above, the tests that used webbing straps showed a significant decrease in tension values compared to Dyneema for the ExTe TU16 winch. During test 19, the tension loss over time was recorded for an Elphinstone manual winch. The tension drop over time with the Elphinstone winch was less than with the ExTe TU16. This is thought to be related to the higher initial tension provided by the Elphinstone winch transferring more effectively over the load. Whilst the initial tension was higher than the ExTe winch, the tension value dropped significantly through the test process. This highlights the concerns relating to maintaining tension over time for manual tensioning systems. A significant variation in tensions achieved by the manual Elphinstone winch was identified during testing. This is evident in the difference between the high side tensions for tests 16 and 19 that have a 120kg difference. Whilst the Elphinstone manual winch provides an initial total clamping comparable to the Dyneema system in this test, it is evident that that this tension is not easily maintained over time, including in transit. ED559-Issue 2 E /12/18 15

16 At the end of the testing day, a tension load cell was mounted on the webbing strap of a logging trailer. The purpose was to see the change in tension in dynamic conditions. The initial tensioning of the straps showed a value of 640Kg on winch side. Within 15 minutes, that value had dropped to 580kg on winch side. From there, the truck and trailer was driven for 20 minutes for 15km. At the first stop, the load showed a value of 397kg, i.e a loss in tension of over 200kg. The load was re tensioned and the driven a further 15 km. On the second and final stop, the tension remained constant at 550kg. The testing showed that using webbing straps for restraint was least efficient due to large gaps between low and high side tension, as well as significant loss in tension over time in both testing and in transit. However, it is important to note that loss in tension is potentially due to the test setup where a load cell was introduced into the restraint system by means of a secondary system and choking. It is feasible that slippage occurred during the testing or log compression, provided tension losses in the results. The table below also compares the difference in tension between Dyneema and webbing. Tests 5 and 6 show that during Sawlog testing, Dyneema (test 5) registered higher tensions than webbing (test 6). Whilst in test 19, the webbing tension decreased when testing began whilst Dyneema remained constant in test 20. Test Size (m) Type Tension (left) kg Tension (right) kg Restraint system Comments E.Nitens E.Nitens E.Nitens Pulp E.Nitens Pulp Initial: 640 Start: 410 End: 330 Initial: 320 Start: 410 End: x Dyneema rope/ ExTe16 winch 2x 75mm webbing straps with ExTe 16 Winch 2x 75mm Webbing straps, Elphinstone manual winch 2x Dyneema rope, ExTe 16 winch, Belly Chain Table 7: Dyneema vs Webbing tension Top tier movement, wet and angle adjusted Top tier movement No Movement Top tier movement ED559-Issue 2 E /12/18 16

17 12m vs 6m lengths: The table below shows a comparison between E.Nitens Pulp 6m and E.Nitens Pulp 12m, and E.Nitens 6m and Native Pulp 12m logs. Whilst there is an organic difference between Native pulp and E.Nitens, the comparison was made due to the quantity of logs used and their similarity in diameter. This comparison only compares unrestrained results. Due to time and availability restrictions, no testing was conducted on 12m s. In the case of Nitens Pulp, there was a significant difference between the 6 and 12m lengths, with higher friction found the 6m logs. This was reversed in the second comparison, with the 12m Native logs having a higher friction value (although not a significant increase). Due to these results, it is recommended that the lowest friction value regardless of log length be considered due to inconsistencies of friction across lengths. Size (m) Type Average Friction Friction Data Points 6 E.Nitens Pulp E.Nitens Pulp E.Nitens Native Pulp 0.88 Table 8: Log length comparison Lashing angles on central logs: The angles on the lashings applied to the central logs in the pile were very low to nil. This meant very little tie down force was applied to these logs and was the main reason why many of the tests saw spearing of the top layer. This itself highlights one of the main issues with the current restraint system: its effectiveness is strongly dependent on the shape of the log pile in the bolsters. A crowning effect would allow increased downwards force to be applied to the central logs and provide an overall better restraint system. However, achieving this crowning is difficult and often inconsistent. ED559-Issue 2 E /12/18 17

18 Figure 8: Angle on central logs Potential solutions include: Blocking or containment methods of restraint. Another solution could be the establishment of a clear diagrammatic standard on what good crowning looks like for each log type. Finally by having cameras included in certain areas of forwarders or loaders would allow operators to better visualise the load on the truck. Grip plate effect: A grip plate was used in all tests. The results show that the grip plate ensured that the critical friction was between log on log, instead of log on steel, which has a lower friction. The image below of the deformed plate shows that the plate dug into the logs ensuring improved friction. Due to their effectiveness in testing, it is recommended that grip plates be used on horizontal beds to improve load restraint. Figure 9: Grip or Crocodile plate ED559-Issue 2 E /12/18 18

19 Conclusion Overall, the testing showed a very high static coefficient of friction across all log types. Applying a restraint system increased the capacity of the logs to withstand higher G-forces. This had the effect of making it difficult to understand the differences between length variations and restraint systems. Since the testing showed such high friction values, all restraint methods were deemed adequate: Webbing achieved the 0.8G requirements in all cases except when testing E.Nitens s. This also occurred when Dyneema for this particular test. The addition of a belly chain improved all systems to achieve the 0.8G requirements. Due to the high measured friction of the logs, each load restraint method was reviewed for its efficiency in both its applied tension and tension loss over time. It is important to note that a lack of crowning of the logs often caused the top tier logs to move. Logs were loaded and crowned consistent with how typical loads would be completed at a landing. Goal Outcomes: In line with the test goals, the following outcomes were achieved: 1. The static friction of four types of Tasmanian timber: o Static friction of all four log types was found to be very high as seen below. This is in conflict with previous testing which showed lower values for similar log types. The cause of this was attributed to potential seasonal conditions and convection drying during transport. Test Size (m) Type Angle Friction 1 6 E.Nitens Pulp E.Nitens Pulp E.Nitens s Native Native Pulp Table 9: Log type friction values ED559-Issue 2 E /12/18 19

20 2. The difference in friction between 6m vs 12m beam lengths: o The differences between 6m or 12m log lengths in the table below showed that using the lowest friction value, regardless of log length, was the most effective option due to the inconsistencies in friction with different lengths. By taking the lowest value, a system of restraint can be developed using the lowest common denominator and account for all log types. Size (m) Type Average Friction 6 E.Nitens Pulp E.Nitens Pulp 0.75 Friction Data Points E.Nitens Native Pulp Table 10: Estimated friction values between 6m and 12m log lengths 3. Change in log friction behaviour between lashed and unlashed: o Low crowning angles meant that spearing of the top middle logs accounted for most log movements. Below highlights the main areas for log movement during testing. o The testing showed no discernible changes to friction values when logs were lashed compared to when they were unlashed. 4. Evaluate Dyneema as a restraint system: o A combination of air winches and Dyneema proved to be the most effective restraint system at maintaining consistent high tensions throughout testing. o Dyneema appears to be a suitable lashing system for the restraint of logs. However, this is subject to evaluation of long-term wear and ensuring 110psi is achieved on air delivery. ED559-Issue 2 E /12/18 20

21 5. Further evaluate Belly Chains in testing: o The use of a belly chain, whilst effective in both restraint systems, proved to only be a major influence when in combination with webbing straps. This can be attributed to more consistent tension values from the Dyneema as opposed to the webbing straps and the lower performance of the webbing systems. However, Belly chain tensioned with a non-recoiling binder (I.e no overcenter load binders) is recommended for the restraint of Native and Nitens logs. Test Size (m) Type 6 6 E.Nitens 7 6 E.Nitens 11 6 Native 12 6 Native E.Nitens Pulp E.Nitens Pulp E.Nitens Pulp Angle Restraint Comments (degrees) 40 2x Webbing straps Top tier movement 55 2x Webbing straps, No movement Belly Chain 47 2x Dyneema Dyneema test 49 2x Dyneema, Belly Chain 52 2x Webbing straps, manual winch Dyneema with belly strap (chain) No Movement 50 2x Dyneema, Belly Top tier movement Chain 49 2x Dyneema Full movement Table 11: Belly Chain effect 6. Further evaluate Webbing straps as a restraint system: o The use of webbing straps with an air and manual winch showed lower tensions in the lashings than when using Dyneema. o Webbing straps suffered the most loss in tension over time in both testing and in transit. Other test outcomes: o Air winches were more effective than manual winches as they were able to maintain tension throughout each test o Winch tension from the Exte TU was noted to be almost half that of previous testing, which would have a significant effect on the results. This is thought to be due to low air pressure delivery to the winch. A high-resolution gauge should be used to ensure 110psi pressure is achieved. o Grip plates ensured friction outcomes were between log on log and not log on steel. Grip plates proved to be effective. ED559-Issue 2 E /12/18 21