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Gulf Lumber: a Tradition of Excellence
Innovative pine mill in Alabama has relied on Metriguard stress grading since 1980
By Alan Froome
Date Posted: 3/17/2004
One of Gulf Lumber’s innovations in 1980 was to introduce the use of an automatic lumber stress grading machine supplied by Metriguard of Pullman, Wash. Gulf Lumber has been operating one of these machines ever since and now is using the third generation of Metriguard’s MSR system.
When Ben May first started the business in 1940, Gulf Lumber Co. was only a Southern pine lumber concentration yard set up to do dressing and finishing. The original plant consisted of a small planer mill, a lumber trimmer and some dry kilns. In those early years, all the lumber was cut by a number of small portable sawmills working within easy trucking distance of the yard in
In 1952, Ben May hired the three Stimpson brothers — Billy, Ben and Gordon — to run the day-to-day management of mill operations, lumber sales and land procurement. In the ensuing years the company’s facilities were upgraded and expanded to turn Gulf Lumber into a modern sawmill, able to make finished lumber from logs. The three brothers incorporated many innovative ideas and established a reputation for progressive thinking along with hard work.
When Ben May died in 1973, the Stimpsons acquired ownership of the company, and before long a second generation of the family was working at the mill. Billy, Ben and Gordon officially transferred ownership to the younger members of the family in 1992. Today, Fred Stimpson is president and responsible for procurement and land management, Sandy Stimpson is chief financial officer, and Ben Stimpson Jr. manages the wood treating division. Mitch Shackleford oversees manufacturing and sales.
Sawmill and Plant Layout
The Gulf Lumber mill is laid out in a logical flow. Raw southern pine logs arrive on site at one end and pass through all the processing operations in sequence to become finished lumber, which is shipped out at the opposite end of the property. The overall lumber manufacturing process is almost completely computer controlled in order to optimize lumber recovery and return on capital.
The mill produces primarily standard dimension pine lumber from 2x4 to 2x10 in lengths from 8 to 20 feet. The company buys tree length logs up to 60 feet long on the open market, and they are bucked at the mill. Log sizes range from 7 to 36 inches in diameter. In the log yard, a Cat 966 and a John Deere 854 unload and feed the logs into the sawmill bucking line.
The mill has two primary breakdown lines, one for large logs and the other for small logs. The principal mill equipment includes:
• tree length bucking line with a 72-inch diameter circular saw
• two Kockums Cambio ring debarkers, a 26-inch and a 30-inch
• an 8-foot Letson & Burpee head rig bandmill to breakdown large logs
• a 36-inch, three-block
• a Kockums 5-foot reducer twin bandmill with ASM sharp chain system and AST snapshot scanner and optimization to breakdown small logs
• a McGehee 8-inch curve gang saw with Newnes optimization and controls
• a Schurman 10-inch gang saw
• a McGehee lineal board edger
• a Coe trimmer optimizer
• Newnes 61-bin lumber sorter
• Lundin lumber stacker
• three Teaford Company dry kilns
After drying, the lumber is stored under cover. When it is ready to be finished, it is transferred across the yard to the planer mill, which consists of:
• Advanced Sawmill Machinery tilt hoist and unstacker
• Newman 990 planer line
• Metriguard 7200 High Capacity Lumber Tester (HCLT)
• Visual (operator) grading station for MSR rejected lumber
• 42-bin Hemco lumber sorter followed by bundle wrapping and strapping
Gulf Lumber also has lumber treating facilities — two 6-foot diameter cylinders, one 50 feet long and one 60 feet long. “ We changed out the old CCA (copper chromated arsenate) system to use the new environmentally approved ACQ preservative in December 2003,” said production superintendent Nathan Butts. “The system is computer controlled by a system supplied by Osmose Wood Preserving.”
The company’s treating operations are audited by the Southern Pine Inspection Bureau to ensure proper wood penetration and retention.
“We practice PM (preventative maintenance) at Gulf Lumber, using a computer program called Maximo that we have been running for several years,” said maintenance superintendent Jack Few. “We feel it is essential to do it this way on a planned basis to minimize downtime. Without a doubt, it’s the way to go.”
Metriguard MSR System
Metriguard Inc. was founded in 1973 to design and market lumber testing equipment.
Prior to the introduction of reliable Machine Stress Rating (MSR) systems, users of lumber for structural construction had to rely largely on sight, experience and luck in selecting lumber for bending and tension applications. Machine tested lumber eliminates the guesswork and adds a high level of accuracy in selecting material used for building roof trusses and other load-bearing structures. Using MSR lumber also offers the ability to build stronger and more rigid roof and floor components.
The first systems were built as a joint venture between the Irvington Machine Works, which built the machine, and Metriguard, which provided the computer controls. Later Metriguard took over production of the whole package, which continues to be developed and improved.
The Metriguard model 7200 HCLT is the latest iteration of the company’s continued development of MSR technology. Metriguard has 58 of the machines in service, plus 61 of the earlier 7100 series. The latest series has been designed to run faster than ever, up to an amazing 3,000 feet per minute.
Metriguard has established an international presence. Its machines are operating in the
“Gulf Lumber was one of our first customers and is one of the greatest companies in the South,” said Metriguard president Jim Logan. “We have had a good relationship with them for a very long time.”
When discussing the benefits of machine stress grading, Jim said, “It offers the sawmiller an opportunity to improve the product and the mill’s profitability.” About 2 billion board feet of MRS lumber is produced annually, he noted – most of it tested by Metriguard machines.
Jim explained that every species of tree produces wood that it designs to take care of its own structural needs during its life cycle. When the tree is young, it needs to be flexible so that it can bend without breaking under snow and wind load. As it gets larger and taller, it needs a more rigid wood. This property is controlled by the ‘microfibril’ angle in the wood fiber itself, so the center cuts typically are not as stiff and strong as the cuts coming from further out on the tree stem. By measuring directly the wood stiffness, the Metriguard Model 7200 places lumber with this variability in the right sorting bins. The measurement also responds in the proper way to variations in moisture content and slope-of-grain.
The MSR Testing Process
The Metriguard Model 7200 HCLT processes lumber lengthwise and ‘on the flat’ — the same way it runs through the planer — so the machine can operate directly behind the planer. Three sets of clamping rollers are used in the machine to isolate the bending test from the effects of lumber overhanging the ends of the machine as it passes through. Between the clamping roller sets the lumber is deflected first downward and then upward by loading rollers while the bending force is measured. The modulus of elasticity (E) is then calculated from the bending force measurements in Windows®-based software operating in a rack-mount industrial PC.
The entire length of lumber is placed under stress during the test, Jim emphasized. A shake failure at the end of the piece, for example, will affect the measurement.
The lumber is color-coded as it exits the machine to indicate which MSR, MEL or E-Rated Lam grade would be appropriate for each piece. The HCLT can produce up to eight machine grades simultaneously from any of the machine grade systems, but most operators usually produce three or fewer grades at a time due to sorting limitations and market considerations.
Pieces that do not meet the minimum E requirements for one of the programmed machine grades will be unmarked. A visual grader will place them in one of the visual grades along with those pieces that do not meet minimum visual requirements for the machine grades.
GULF LUMBER AND MSR
Gulf Lumber was a pioneer in the use of machine lumber testing in 1980. Since then, Gulf Lumber has invested in two more machines, each one an advance on the previous model. The current Metriguard 7200 stress rating machine has been running at Gulf Lumber since 1997 and has had only minor upgrades since it was installed. The Metriguard 7200 is used to test kiln-dried pine lumber on a continuous basis after it leaves the planer. It is installed directly behind the planer and takes the full lumber flow.
Lavoyd Hudson is manager of specialty products at Gulf Lumber. “We get very good service from Metriguard,” he said, “and we process all the lumber we produce through the machine, which is running at speeds up to 2,000 feet per minute. We process around 90 million board feet a year of 2-inch lumber on a one shift basis.” (The mill also produces some 1-inch lumber to help overall mill LRF (lumber recovery factor). The new Model 7200 machine eliminated jams caused by breaking lumber in the machine, said Lavoyd.
“Here we have two strength grades,” said Lavoyd. “We grade the lumber as High with red color coding or Low, which is marked with green. Any rejected lower grade lumber goes for visual appearance grading by an operator.”
“The lumber strength grade depends a lot on the knot size of the lumber we are running,” explained Nathan. “We don’t adjust the settings often and have been running the machine on more or less the same settings for the last three or four years.”
In summary, in considering the success of Gulf Lumber as a company, a couple of things stand out. One thing for sure: the company invests in first class equipment for every operation carried out in the mill.
It is also apparent that machine stress grading the lumber is an important manufacturing concept at Gulf Lumber. Their long term experience with the process — and the fact that every piece of 2-inch planed lumber is passed through the MSR machine — indicates clearly the value they put on it and its impact on the company’s bottom line.
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