Bob and the Home Again crew visited Louisiana-Pacific's siding plant in Two Harbors, Minnesota to learn more about how the SmartSystem engineered wood products used in Yonkers were manufactured. L-P located its siding plant in Two Harbors because of the abundance of aspen timber and the availability of a good labor force. Central to L-P's philosophy is its commitment to utlize primarily small diameter, faster growing trees to make its siding product. The products' strength comes from the innovation of its engineering, not from the size and kind of trees used to produce it. In this way L-P is helping to reduce the country's dependence on old-growth forest.
Logs are pre-soaked in log conditioning ponds prior to their introduction to the manufacturing process. Pond water is warmed to between 60 and 100 degrees by a heat exchanger, with heat being supplied by the plant thermal oil heater. Over the course of eight hours logs are moved through the log conditioning ponds to the discharge end by the force of incoming logs displacing them towards the outfeed end.
Logs are removed from the conditioning pond outfeed end by a jackladder. The jackladder removes logs and deposits them in a trough conveyor which introduces the logs into the debarker. The bark that is removed is collected by a series of waste conveyors and delivered to the bark hog where it is hogged to size and transfered to a storage bin. The thermal oil heater is supplied with the hogged wood fuel from the storage bin by a system of conveyors and augers. Excess hogged fuel is utilized by local schools and industry as a fuel.
After debarking, logs are fed to a deck of cut-off saws which cut or "slash" them into the size required for processing by the flaker. Broken ends and fine material are carried to the bark hog for processing as thermal-oil heater fuel. The flaker cuts logs into thin pieces which are approximately three inches long, one inch wide, and .025 inches thick.
The fresh cut green or wet flakes, which contain about 50% water by weight, are conveyed to a wet bin where they are accumulated and stored prior to introduction into the drying process. The wet bin is equipped with a "live bottom" which moves the material towards the bin outfeed, at a set rate on a "first in, first out" basis.
In the drying process flakes are mechanically and pneumatically conveyed through a direct fired triple pass dryer. Heat for the dryer is primarily provided by a wood-fired suspension burner. The moisture content of the flakes is reduced to approximately 5% during drying. Flakes leaving the dryer pass into a primary cyclone which collects the dried flakes. Exhaust gases and fine material move to the E-tube which collects particulate. An induced draft fan loacted after the E-tube provides the primary airflow through the drying system. E-tube discharges air then passes through the RTO for VOC removal and is then vented to the atmosphere.
Flakes collected in the primary cyclone drop into a drum-style rotary screen. The rotary screen is approximately eight feet in diameter and fifteen feet long. Here, undersized materials are removed from the production flakes and processed by a hammermill for use as fuel for the dryer burner. The "production" sized flakes are conveyed to dry bins for storage until introduction to the blending and forming process.
From the dry storage flakes are fed to the blender, a rotating, drum-style mixing device. The flakes actually tumble through the blender. Here special resins and wax are incorporated which bond the product together. Each of two blenders are approximately ten feet in diameter and thirty feet long. After the resins have been applied in the blender, the product goes through the SmartGuard process in which environmentally friendly borate-based wood preservatives are added making it resistant to rot, insects, and fungal decay. Next the wafers are conveyed to distribution hoppers located above each forming head which are located above the forming line.
The forming line is a system of eight foot wide conveyors and forming heads which transport and form mats of flakes, approximately four inches in depth, which are carried on caul screens into the press. Flakes are distributed onto the caul screens as they pass below the forming head, creating a bottom, core, and top surface layers of the mat. The mats are separated by a double-bladed circular saw which cuts a path along the front of each caul screen as it travels along the forming line. The saw is called the flying-cut-off-saw (FCOS). Wafers removed during the operation of the FCOS are collected by cyclone and are returned to the core layer distribution hopper. A paper primed overlay is placed on each mat after the FCOS has separated the mat, just prior to the mats being introduced into the press loader.
As each mat is separated into press-sized lengths, it is fed into an elevating rack-type device. This device, called the loader, will hold eight formed mats, one over the other, which the press is designed to accommodate. When the eight formed mats are all on this "rack", the loader will simultaneously feed them into the press. Here, the press will hydraulically close, and with heat (carried by thermal oil through the steel plates of the press) compress the formed mat into a finished sheet of board. Here in the pressing process the cedar pattern is actually pressed into the product. When the press has completed the formation of the board, another elevating rack-type device, the unloader, will simultaneously remove all pressed board into a system of saws which cut and trim each of the finished boards.
Pressed boards coming from the press unloader are fed into a system of saws which trim the edges of the pressed board, as well as center-cut the pressed board to achieve the 48" width normally produced. The boards are then fed perpendicular to this first "pass" of saws into the second series of saws which again will trim the edges and center-cut the longer side of the pressed board to achieve the normal 8" lengths. Both sets of trim saws can be adjusted for special made-to-size dimensions of pressed board. Material removed by the trim saws is used for burner fuel for the dryer. Boards are accumulated into a uniform sized stack or "unit" for finishing and subsequent shipping.
In the finishing line special proprietary edge sealers are applied to the edges to prevent moisture intrusion, swelling, and warping.
With the SmartSystem product line, consumers get a treated engineered wood product that offers the "curb appeal" of cedar, is easy to install, and very durable for half the cost of traditional cedar siding. Additionally the product comes with a five year repair/replacement waranty and a 25 year limited waranty.
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