For over 100 years Kanawha Manufacturing Co. in Charleston, WV, has been performing fabrication and machining services for manufacturers and equipment suppliers in the power, coal and metal industries. The family-owned and operated, full service operation has two shops and 120 employees, manufacturing and rebuilding equipment, and specializing in large fabrications. From the 1940s through the 1960s, Kanawha Mfg. designed and built coal tipples for preparation plants where coal is cleaned and sized before shipment. Even earlier, its products included boilers for industrial heaters, all kinds of coal handling equipment, and even farm tractors.

Since the '60s, Kanawha Mfg. has been active in the power-generation aftermarket with products and maintenance services. Also, it supplies quality solutions for difficult welding problems, such as copper and high-alloy stainless steels. Kanawha claims it can replace or rebuild just about anything that wears out in a power plant.

Challenge
For its numerous projects involving large-sized component parts, Kanawha Mfg needed to allot many man-hours for the effort to place the parts on a truck and transport them to and from a heat-treatment furnace.

Metal parts, and particularly large-sized metal parts, typically have internal stress “locked” into them as a consequence of a previous manufacturing process, e.g., rolling, stamping, or forming. Heat treating (which has other functions as well) is one method of relieving that stress in order to ensure structural integrity of the part and any fabrications that it might be used to complete.

But, for Kanawha, the time devoted to preparing for stress relief was a significant waste of resources, including cost. In some cases, the parts manufactured were so large they did not even fit into the furnace. Thus, they could not be stress-relieved at all. For this reason, Kanawha Mfg. sought out other options for stress relief and distortion control.

A Meta-Lax force inducer and transducer are clamped to a workpiece, so the operator can measure vibratory amplitudes and determine the harmonic frequency curve. The initial curve represents the “false” harmonic frequency because the metal is stressed. After the force inducer vibrates the workpiece for 15-60 minutes at a frequency corresponding to the sub-harmonic zone of the workpiece, the harmonic frequency is shifts permanently.

Solution
About 20 years ago one of the company’s customers, the U.S. Army Corps of Engineers, specified Bonal Technologies’ Meta-Lax^® system for distortion control on some very large lock and dam parts they were building. Previously, the U.S. Corps of Engineers had had great success keeping distortion to a minimum when they used the Meta-Lax system on massive parts for heavy barges. This specification led Kanawha Mfg. to buy its own Meta-Lax system. They have been have been using the stress relief process ever since.

Bonal Technologies Inc. is a subsidiary of Bonal International Inc., and supplies sub-harmonic vibratory stress relief equipment for manufacturing metal products.

“I was around when torches were used to relieve stress,” said Carl Smith, quality assurance manager at Kanawha Mfg. “What really impressed me was that George Linnert, a renowned metallurgist, noted in one of his text books that ‘mild’ vibrational stress relief would be the way to go. I was happy to find that there was already a company promoting the right technology.

“Since we had so much success at holding down distortion on the big parts on the U.S. Army Corps of Engineers program, we started using Meta-Lax on other parts and for other uses,” Smith said. “We do very thick, heavy welds so we decided to try Meta-Lax to see if it would help with those parts. We weren’t fully aware of the value of the product for weld conditioning [as used during welding] but figured it was worth a try. Now we use it everywhere where we think we might incur distortion or warpage.”

Benefits
Kanawha found numerous benefits from utilizing the Meta-Lax system.

Productivity Increases — In productivity, Kanawha Mfg.’s savings are quite extensive. One example is of their pulverizers. Before the Meta-Lax system, the process for stress relief would take at least four days to complete when sending these parts to a heat treat furnace. With the Meta-Lax system, the pulverizers could be stress relieved in about one hour. The pulverizers weigh 8,000 pounds, are cone-shaped and made of cast steel. “Using Meta-Lax the entire repair could be completed in two days. This allows us to work on as many as 12 pulverizing units continuously,” Smith said.