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Sept 2004 - The Logging and Sawmilling Journal

INNOVATIVE HARVESTING

Going underwater

Triton Logging has developed an underwater logging system, including a logging submarine called the Sawfish, that is successfully logging a lake in British Columbia, and the company has plans to produce the Sawfish on a commercial basis.

By Paul MacDonald

At the centre of Triton’s underwater logging system is what it terms the world’s first logging submarine: the Sawfish. The Sawfish is equipped with a 55-inch harvester bar (below) that methodically cuts large second-growth Douglas fir in BC’s Lois Lake.

The people behind Triton Logging have seen the future of timber harvesting—and as far as they’re concerned, it’s under water. The Vancouver Island-based company is currently involved in a prototype-to-production project that could make hundreds of thousands, if not millions, of cubic metres of submerged timber accessible. Millions of cubic metres of timber around the world—a good deal of it in Canada—lie underwater in reservoirs created by dams. And Triton is working towards a production piece of equipment that will be able to harvest this timber safely, and economically.

At the centre of all this work is the Sawfish, which is, according to the company, the world’s first logging submarine. Triton has used Remote Operated Vehicles (ROV), used for offshore oil and gas work, and oceanographic studies, as the inspiration for the Sawfish. The founder of Triton and the developer of the Sawfish, Chris Godsall, has a background in log salvage, and was simply looking for a better way to harvest submerged timber. In a rough way, the patented Sawfish could be likened to an underwater feller buncher. Taking this comparison further, the cab for this buncher sits on a barge above the water, since it is remotely operated.

The log collection system Triton has been using involves towing the logs over to a winch and choker system which maneuvers the logs. But plans are to move to a barge-mounted knuckleboom loader with grapple that will place the logs into a floating log bunk.

Currently working on Lois Lake up the coast in BC, near the forestry town of Powell River. Lois Lake was created in the 1940s, when a dam was constructed to power a nearby pulp and paper mill. Working from a barge about half-a-kilometre from shore, the Sawfish is launched into the waters of Lois Lake using a Galion model 80 mobile crane. The Sawfish is connected to the barge, and to the pilot’s control room on board the barge, with a tether that is its lifeline—it contains the wiring for the video feed and telemetry feed, and provides the power and air pressure. Powered by a 40 horsepower electric motor, the Sawfish is “flown” in the midst of literally hundreds of submerged trees, and is ready to do some cutting, 25 metres below the surface of the lake. Using the eight on-board cameras, the pilot maneuvers the Sawfish; its four-foot grapple grabs a tree and it is pulled securely up to the tree.

The 55-inch harvester bar with 3/4-pitch chain cuts slowly, but methodically, through the large, second-growth Douglas firs. Before cutting the tree, the Sawfish bolts a reusable airbag on to the log. The airbag, with 500 pounds of lift, is inflated underwater after cutting is complete, and the log shoots to the surface. The vehicle carries a payload of 36 airbags, allowing 36 trees to be cut during each dive. All of the equipment uses environmentally-acceptable canola-based hydraulic fluids. Sawing underwater presents its own challenges, says Triton operations manager Glen Fraser. “We’ve been trying to dial the sawing so we can cut efficiently underwater,” he says. “There are some big differences from running a saw underwater compared to running a saw on land. The amount of power that is sucked up just turning that chain in the water, without cutting, is comparable to the power used to cut a tree in air.

A log shoots to the surface of the lake (inset photo) after being harvested by the Sawfish. The Sawfish is currently working in Lois Lake, which has a large number of semi-submerged and submerged trees. The lake was created when a dam was built in the 1940s.

With the Sawfish, 50 per cent of the power is devoted to turning the chain in the water.” As part of the equipment tweaking process, they’ve reduced the chain speed significantly, but increased the torque. The end result is they can cut through a 24-inch tree in about 15 seconds. In the control cabin on board the barge, chief pilot Craig Elder interfaces with the Sawfish, using the cameras, the sonar system and positioning system as his below water “eyes and ears.” Elder explains that the process of attaching the airbag to a tree is fairly straightforward—navigating from tree to tree is the real challenge. There is a lot of finesse in moving around a 7,000-pound piece of equipment 60 feet below the surface of the lake. “It can be tricky work.” “Right now we rely on experts in the field to do the piloting,” says Fraser.

These pilots, like Elder, have a lot of experience in using ROVs in the oil and gas industries, and in scientific studies on the ocean floor. Elder’s background includes many years of instrumentation development for oceanography, with the last seven years specializing in ROVs for several research institutions. He has done work for the Canadian Scientific Submersible Facility, the Woods Hole Oceanographic Institute, and the National Geographic Society, as well as several universities. These projects focused primarily on exploring underwater volcanoes and hydrothermal vents in water of depths from 1,500-5,000 metres. Elder has worked all over the world, from the Black Sea to the High Arctic.

Triton expects to develop the equipment and controls further, to the point where they can train people in-house. “Our goal is to make it no more difficult to run the Sawfish than it is to run a feller buncher,” says Fraser. Over the past year, they have steadily made improvements to the Sawfish technology, to the point where it now runs fairly smoothly. Lately, Triton has been focusing on the above-the-water operations. “Now that the Sawfish is working at a fairly high rate, we can surface trees every three to six minutes,” explains Fraser. “The question now is what type of equipment, machinery and processes do we develop that will allow us to efficiently process those trees on the surface and move them out of the water.”

The collection system they have been using involved boom boats towing the logs over to a two-drum winch and choker system, which maneuvers the logs. The logs are then “hung” from floating boom sticks. The hanging is necessary because the waterlogged logs would otherwise sink. Plans are to move to a barge-mounted knuckleboom loader with grapple that will lift the logs out of the water so, first, the reusable air bag can be retrieved. The logs would then be moved to a floating log bunk, what Fraser calls a “floating logging truck trailer.” “It’s a continual improvement process. Originally, we had this basic surface collection system, and it wasn’t being pushed because the Sawfish was going slowly. Now, the Sawfish is working well, and we need to improve the collection system before it becomes a bottleneck.” Once they complete improvements to the surface collection system, they will re-focus their efforts on the Sawfish and continue to tweak it.

Triton first started work with the Sawfish at Lois Lake last July. And while things are now moving along fairly smoothly, Fraser says it was anything but that at the beginning. That’s understandable, he says, considering the Sawfish they are working with is a prototype, rather than a production machine. “It was tough at first because we were essentially doing a lot of research and development,” he says. But it beat the heck out of doing prototype work in some on-land shop. “Having the barge and being able to test things day in and day out really allows us to move along the development work. If there is something that needs fixing, we can pull the Sawfish out of the water and fix it, and put it back in the water. “It’s a lot of working the bugs out and fixing it as we go. But being able to work and be on the lake every day has certainly allowed us to move up that learning curve.”

Now well along that learning curve, Triton expects to move into commercial production of the Sawfish later this year. Both Fraser and Sawfish inventor Chris Godsall acknowledge that there have been a number of different approaches—some successful, some not—to harvesting timber underwater. The distinction of the Triton system, they believe, is that it has been able to separate the harvesting phase from the surfacing phase with the airbags. Other types of technology that have been used before, and some still currently being used, involve equipment, a logging arm for example, that cuts the tree and also brings the log to the surface. “With those systems, each time you have to bring the log to the surface, and then you have go back down to where you were before and find the spot where you were cutting.”

Doing this in deep, sometimes murky, water can indeed be a challenge. “The cycle times are what drives efficiency and production,” says Fraser. “The Sawfish grapples the tree, attaches the air bag, cuts the tree—and then carries on cutting in the same underwater area while that log goes to the surface. There is a completely different system going on at surface level. So we don’t have to worry about bringing the cutting head to the surface.” Some of these traditional water-based logging operations have been able to achieve good cycle times in relatively shallow water, but deep water presents difficulties.

There are practical limits to the length of an underwater cutting arm. “But for us, the only difference between logging in shallow water and deep water is the length of the tether,” says Fraser. “As long as we have a long enough tether, we can go as deep as we need to go.” The Sawfish has barely touched the surface in terms of harvesting the 80 year-old second growth—mostly Douglas fir in Lois Lake—which has gone to various markets. So far, they have only harvested a small section of the lake. But the major overall goal of the company, and its engineering division, is to get to the point where they are turning out Sawfish equipment in a production mode, to help other logging companies tap the huge potential for harvesting sunken wood. Fraser cites estimates of upwards of $50 billion worth of submerged, preserved wood in reservoirs, worldwide.

Canada accounts for about five per cent, or $2.5 billion, of that. Fraser points out that one lake in the BC Interior, Ootsa Lake, has enough submerged timber to support 30 Sawfish units. And while a small amount of timber has been harvested using arm-mounted cutting equipment, 85 per cent of the wood in Ootsa Lake is below 60 feet, ideal depths for the Sawfish. And with estimates of upwards of 10 million cubic metres of wood in the lake, there’s enough timber to keep a school of Sawfish busy for years.

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