Strapping Log Truck Loads for Improved Accountability-A Concept
|Figure 1—Branded log end.|
Ideas for Change
Several years ago, SDTDC began to look at safer, more efficient methods for log marking. As a result, this report investigates the use of sealed straps for this purpose.
Figure 2—Logs with paper tags.
Paper tags have been tried on several sales, but workers are still exposed to the same hazards when stapling the paper tags on log ends (figure 2). Also, tall decks cannot be marked without excessive effort. It is labor intensive to mark smallwood. Improved accountability will only be attained with less reliance on an individual log mark.
Many sale administrators require that 90 percent of the log ends be legibly marked. However, less than 70 percent of small logs can be tagged without sacrificing time and dedicating log handling equipment to the job.
One idea would be to replace the log marking entirely where it cannot be accomplished satisfactorily and safely. Forest products representatives support this idea and suggest securely bundling an entire truck load as an alternative. They see added benefits down the processing line, such as more efficient decks and fewer broken logs.
THE STRAPPING SYSTEM
In the summer of 1995, project personnel traveled to the Louisiana-Pacific Corporation’s (LP) sawmill in Deerlodge, MT, with technical representatives from Strapex, Inc. A log load was strapped with light polypropylene strapping, unloaded, handled and drop-tested (figure 3). Although the strapping lacked sufficient strength, results were promising, and further work was planned. A trip report is included in appendix A.
Figure 3—Load in Deerlodge, MT, with light strapping.
SDTDC began searching the market for strapping products and started testing them in the lab. A preliminary field test of this concept was performed on log loads arriving at the Sierra Forest Products sawmill in Terra Bella, CA.
The logs were somewhat larger than those originally targeted for this method. However, if the concept does not work on larger logs, it will not work on smallwood. By using commercially available cargo straps with a ratcheting takeup mechanism, project personnel were able to successfully bind two loads on the SDTDC log truck and monitor tension in the straps.
After driving many hours on surfaces ranging from freeway to rough dirt, the straps held the load together and retained ample tension to discourage any attempts to remove logs from the load. The results were encouraging.
Tests indicate that an initial tension near 5,000 pounds is desired. By October of that year, a prototype strapping system—including seals—was developed. A trip report is included in appendix B.
Nylon webbing was selected for the strapping system. The nylon webbing would relax in a short period of time, causing the tension to drop. In one test, an initial tension of 3,200 pounds dropped to 2,610 pounds in 30 minutes. A day later, it had dropped to 2,025 pounds. Log settlement had occurred throughout the transport periods, but tensile forces in the strapping remained as desired, above 1,000 pounds (figure 4).
As a comparison, steel wrappers in common use today are initially around 4,000 pounds after being tensioned with a cheater. During transport, however, log settlement reduced this tension to nearly zero, requiring occasional retightening while enroute.
Figure 4—Strapping system used in Colorado.
A 2-inch wide by 50-foot long woven nylon strap, with a breaking strength in excess of 10,000 pounds tension, was chosen. One desirable feature of the nylon strap is the high stretch rate compared with steel cable. The curves in figure 5 show the difference in stretch between a strap and a typical steel wrapper. This feature makes it possible to maintain tension as the load settles during transport.
Figure 5—Two curves showing the differences in stretch of a 50-foot steel cable and the nylon webbing selected.
The nylon webbing was sewn onto a small winch. This winch is easy to operate and safe to release; however, the winch handle was too short to bring the webbing to 5,000 pounds initial tension desired. A 3-foot custom “cheater bar” was added to the system to create a lever arm long enough to develop this initial tension. After tightening, the winch handle was closed and a seal installed to prevent further adjustment (figure 6).
Figure 6—Winch handle closed and seal in place.
The system was load-tested and certified by the supplier to exceed 10,000 pounds tensile strength. The webbing and winch cost about $35. The cost of sewing the nylon webbing to the winch was $2, and the seals were $0.50 each.
In October 1995, a field trial was planned at LP’s Oriented Strand Board (OSB) plant in Olathe, CO. LP agreed to work with SDTDC on a test of log straps (figure 7).
From LP’s standpoint, log straps could offer other benefits by keeping the logs in a uniform bundle. With the straps, more wood could be stacked per acre and yard efficiency improved. The straps should also help minimize breakage that commonly occurs when retrieving loosely stacked logs from a deck. Another hope is to obtain State Department of Transportation (DOT) approval for the straps as a replacement for the conventional cable wrappers that are required on every load. This would improve loading and offloading cycle times.
Figure 7—Debarking area at LP’s OSB plant.
The Colorado site provided an opportunity to strap large loads. The western-style log trucks (figure 8) hauling to this site were permitted to carry a gross vehicle weight (GVW) of 85,000 pounds. This is 5,000 pounds above the norm, but legal GVW in Colorado. The loads could also be 14 feet high. This large volume, combined with the nonsymmetrical shape of the aspen, provided an excellent test situation.
Figure 8—Western-style log truck delivering aspen to the LP plant.
The first experiment was on a load of aspen that had just arrived at the yard. Two straps were placed around the load and tensioned, using the cheater bar. This loaded the straps to around 5,000 pounds of tension when applying 150 pounds to the handle. The load was then moved to another area in the yard and offloaded. When placed on the ground, it assumed a uniform bundle shape and did not become loose. Four more loads were strapped and stacked successfully.
Project personnel wanted to try this approach from the landing to the mill. A timber sale in eastern Utah provided a good opportunity to experiment. They used small aspen that required about 100 logs to make a 30-ton load. Once the logs were loaded, and the straps placed and tensioned, it was apparent that the elasticity of the webbing allowed the load to settle without becoming slack.
After 20 miles of unpaved, rough, steep winding roads, the straps still retained a fair amount of tension where the cable wrapper—required by law—had become slack and required retensioning twice. This load was brought to the mill about 150 miles away. Upon arrival at the mill, it was stacked with the other strapped loads.
The following morning, project personnel went to another sale somewhat closer to the mill. Due to road conditions, the loggers were only able to access this landing during the darkest hours when the frost would stabilize the soil.
In order to get as many loads as possible strapped, two people worked in unison as the trucks came out five at a time. The 2-mile spur leading to the landing was too rough for an automobile to negotiate, so they waited where the spur intersected the main road and applied the straps there.
Two nylon straps were tensioned and permanently sealed around the loads of logs. Steel wrappers were also tensioned around the loads in the conventional manner to ensure compliance with DOT regulations. The initial tension in both straps was recorded (figure 9).
Figure 9—Closeup of strap and wrapper as tensioned
Figure 10—Custom torque wrench used to measure tension.
After the load was transported about 100 miles to the plant, the tension was measured again and the steel wrappers were removed (figure 10).
Figure 11—Closeup of strap and wrapper after transport—note how slack the steel wrappers are at the end of the trip.
The logs were offloaded and stacked in the log yard with the straps intact. The tensions were measured again (figure 11).
Seventeen loads were strapped. They all returned to the mill without becoming loose. The log deck, comprised of strapped bundles, was orderly and secure, providing a somewhat higher wood density in the yard (figure 12). These loads remained strapped until the wood was ready for processing. Breakage of the logs, as well as strap durability, was monitored.
Figure 12—Long view of deck comparing neatness of strapped loads with conventional decking.
Several loads were drop tested from a distance of 8 feet and observed after the drop for damage. The loads remained decked throughout the winter. In May 1996, they were picked up by the loader and transported for processing.
A technique was developed for removing the logs from the deck, unstrapping, and firmly gripping them for transport to the debarker. Technical representatives photographed the operation. Once a strapped load was removed from the deck, the stacker’s upper arms were opened. The load was then rolled along the ground by maneuvering the stacker forward and tilting the forks until the seals and winch handles were in a safe, accessible position for ground personnel to reach them (figure 13).
Figure 13—Winch handle in position to be released.
Figure 14—Seal being cut with a pocket knife.
...and stepped back to safety. The tension was released with a strike of a shovel (figure 15)...
Figure 15—Preparing to release tension by striking winch handle with the shovel blade.
...the loose straps were easily pulled free while walking away (figure 16).
Figure 16—Pulling straps while walking away.
Only once was a strap “stuck,” but it was easily released by signaling the stacker operator, who lifted the forks slightly, and released the hangup.
|BEGIN HAUL||AFTER HAUL||IN DECK|
|(in woods)||(on truck)||(in yard)|
|Figure 18 (a and b)—Examples of logs which could be removed.|
|Figure 19—Logs being pulled from deck after winter storage.|
|Figure 20—Stacker at the deck pulling out a bundle.|
|Figure 21—Arms and forks cannot encompass the load after storage. The straps must keep the load intact.|
Limited study by SDTDC reveals that it takes only 3.5 seconds per log end to brand and paint a deck of large logs on flat ground. That timeframe seems reasonable. As the diameter of logs in the deck decreases, and the slope of the ground increases, it will take longer and be impractical to mark all ends.
In the tests, 30 out of 100 log ends on the evenly arranged end of a 7-foot high deck could not be reached by hammer or stapler without redecking. Half of these could not be reached with a bare hand. On higher decks, over half could not be reached.
This experiment indicates that the strapping concept has potential. Some refinement in the areas of tensioning devices, webbing material, tamper-proofing, and identifying seals is needed. Most of the truckers were optimistic about this concept, as was the mill superintendent. Log strapping appears to be the most promising method to provide a high percentage of log accountability.
The straps selected for this trial have been approved by DOT for use in tying down highway loads. However, investigations have not been made to determine the appropriateness of replacing steel wrappers with this system. Should that prove acceptable, then virtually no time and motion would be lost in marking the logs. The straps could be put into place and sealed as rapidly as the wrappers are installed.
With DOT approval, the straps could facilitate loading and unloading without taking extra time. Drivers would only need to tension them once, and would not have to get out of their trucks to unload. The straps are also safer than having a deckhand brand and paint each individual log and are more economical. The ratchets are reusable and the webbing is recyclable.
The strap system could be supplied with these additional features:
Since the entire bundle was removed from the deck, the stacker carried a larger load; however, this may overtax smaller stackers. To adequately handle these load-sized bundles, a larger stacker than the ones available for this test would be advantageous. Strapping loads will permit the density of wood in a deck to be increased, thereby improving the efficiency of the log yard.
One reason for branding is to mark the log with a sale-specific mark. The load receipt can serve this function until the straps are removed. Should it become necessary to remove the straps, it would then be easier and safer to mark the logs in a yard with cleared, flat ground, and where power could be made available. Removing logs from the bundle is not a major issue. It would be slow, cumbersome, require a loader, and create obvious slack in the straps should several logs be removed.
Some administrative features have not been addressed. Among these are methods of controlling strap and seal distribution, numbering schemes, handling/recycling the strap and winch upon removal, and regulations regarding the timing of strap removal.
It is recommended that serious thought be given to developing this idea. Marking each end of small logs is laborious, and frequently waived from timber sale requirements. Further study should be given to solving the problems mills might have with smaller log-handling equipment, determining how to deal with mixed species loads, and delineating situations where the overall cost of strapping would be acceptable.
Results of Trip to Deerlodge, MT, to Test Strapping
By Lamoure Besse, P.E.
Bob Brown, Louisiana-Pacific Yard Foreman
Tony Coulter, Louisiana-Pacific Yard Superintendent
Dan Castillo, Forest Service, Regional Office, Northern Region
Tom Garrett, Strapex, Inc. Representative
LaMoure Besse, SDTDC Project Engineer
Joe Fleming, SDTDC Engineering Technician
On Monday evening, August 15, 1994, we arrived in Deerlodge, MT, after driving from Spokane, WA. Tom Garrett had taken a similar drive. We learned that evening that Tom had lost his baggage—as we had. However, his was a little more sensitive because it involved his tensioning device, sealing device, and $5,000 worth of customized strapping he had specially run for this event.
We coordinated with the airlines and chased bags the next morning until 1:00 p.m. At that time, we gave up on the strapping being found. The tools showed up, but the strapping—which was attached in a separate container—had torn loose and was not present. Since the tools and strapping were only marked with one baggage claim, which arrived with the tools, there was no further way to pursue the location of the custom strapping. Mr. Garrett had brought along some relatively light 700-pound tensile strength strapping, which we decided to try on a very limited basis to learn what we might be looking at in tensile loads.
I had explained that the purpose of our visit was to work with this strapping to learn the potential for requiring its use to improve our ability to account for logs. We were interested in seeing whether this might be viable when a load is strapped in the woods with a permanent seal and left that way until processed.
As I saw it, the logs would need to be branded and painted if the strap were cut in the log yard and the logs were not processed in some short period of time, say, 4 hours. Tony expressed concern that this would not work because most loads are mixed species or size and need to be sorted, which occurs at the debarking chain.
Dan later explained that it would probably only be necessary to require that any log leaving the mill be branded and painted because the Forest Service (FS) has an arrangement with mills accepting National Forest (NF) logs that they cannot leave and go to the export yards. (For correct details, ask Dan).
Other than this, I could not detect other reasons why the concept would not work. Tony was concerned about plastic getting into the byproducts, but Tom alleviated those concerns when he said that he would buy back the straps.
We detoured a loaded log truck which arrived at the mill and wrapped the 50,000-pound load of logs with seven wraps of this light strapping at each end. We then sealed each of the straps without tension and had the truck proceed to the log yard for unloading.
The entire load was picked up by a log-handling machine in a manner similar to the way every load would be unloaded. The load was moved with this loader to a designated area and set on the ground as the loader backed from under the load. The light strapping held the load intact. Then the loader moved in again, drove the forks under the log load, and picked it up. Finally, as the operator rotated his forks and began to slide the logs off the front of the forks, a strap snapped, causing the load to slide off in a random fashion.
Everyone was impressed with the light strapping’s performance. Some of the thoughts and performance criteria that were discussed are as follows:
Metal bands and inexpensive cable have been, and are used, in this type of application at present. However, a major drawback appears to be safety. Some of the problems are with bands snapping back, logs rolling into millwrights, and breaking and removing the straps, and so on. Using this strapping will require that the load be placed in specially built bunks near the debarking chain.
Porterville Trip Report
By Lamoure Besse, P.E.
During the week of November 13, 1995, we visited a sawmill to perform preliminary experiments with log strapping. After rectifying some problems with our test vehicle, we arrived at Sierra Forest Products yard in Terra Bella and loaded a 29-log load, giving us a gross vehicle weight of 77,750 pounds.
One conventional “wrapper” was secured midway around the load, then two nylon straps with double-ratchet winch drums were placed around the load, with the front strap located approximately 2 feet behind the tractor bunk, and the rear strap approximately 3 feet ahead of the trailer bunk. The rear strap was tensioned to 2,600 pounds with two wraps on the drum. The front strap was tensioned to 3,000 pounds while still on the first wrap. In order to be street legal, a cable wrapper was secured around each end of the load as well.
We then drove 8 miles to town on a paved 55- mile per hour road and parked. By then, the rear strap had only 800 pounds of tension on it, and the front had 1,000 pounds. We checked the straps again the following morning, and there was no noticeable difference. After driving around for a few hours on paved winding roads, we returned to the mill and checked the straps again. There was no appreciable change in the strap tension from where it had been when we parked the night before.
After removing the cable wrappers, a loader removed the entire load with the straps still in place. It then dropped the load from about 4 feet, picked it back up, and dropped it again. At this point, there was more tension in the straps that we could relieve with the extension handle we were using to measure the tension. That would mean that it was in excess of 3,000 pounds, but probably no more than 5,000 pounds. One strap had visible damage and was photographed.
We took on a second load of 27 logs, yielding a GVW of 74,000 pounds. Three cable wrappers were set, one at each end and one in the middle. They were tensioned in the customary manner, and then the straps were placed at each end of the load. This time the front strap was about 5 feet ahead of the trailer bunk. The straps were both tensioned to 2,600 pounds and both on the second wrap around the drum.
The truck was then driven for a short distance, for about 5 minutes, and tension was checked. The tension in the front strap had dropped to 1,700 pounds and the rear strap to 1,250 pounds. We then drove around for several more hours on the rear strap to 1,250 pounds. We then drove around for several hours on the highway and on an oil field service (dirt) road.
The end result was that both straps had only about 800 pounds of tension. This was considered to be at the low end of acceptable performance. We parked for the evening, and put one of the straps used on a previous test (pre-tensioned) around the middle of the load. This was tensioned to 3,000 pounds and by morning it carried 2,250 pounds. Throughout this period, the cable wrappers were never retensioned, and upon returning to the mill they were completely slack with the binders dangling freely beneath the load.
This experiment demonstrated potential for using straps as a means of log accountability, load security, and improved yard handling and decking. Although there are still some areas that will require some development (i.e., more tension in the straps initially, prestretching the webbing before use, a means of releasing straps safely prior to processing, and tamperproofing the ratchet). We did learn that the webbing will probably have sufficient strength and elasticity to perform favorably on loads of numerous logs, perhaps 50 to 100 logs per load, which is the intended application.
We also learned that the two ratchet systems we thought might be necessary to achieve ample tension in the webbing are probably unnecessary. Instead, it appears that a longer lever, or “cheater,” should suffice, particularly if the webbing is prestretched. Plans are to experiment with this system using small timber from an actual sale in areas where small diameter logs are commonly harvested. Refinements shall be made as problem areas are identified.
Forest Management Program Leader
San Dimas Technology & Development Center
444 East Bonita Avenue, San Dimas CA 91773-3198
Phone 909-599-1267; TDD: 909-599-2357; FAX: 909-592-2309
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