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Research extends life of railroad crossties


 

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Posted: 7/22/2010

 

In 1985, a young and energetic Mississippi State University forest products professor began testing a new treatment on railroad crossties. At the time, Terry Amburgey had little notion that his experiment would change railroad infrastructure almost 25 years later.

Amburgey, along with U.S. Forest Service colleague Lonnie Williams, thought that treating railroad crossties with borates and creosote would extend their service life. Borates are chemicals used as both an insecticide and fungicide, and creosote is an oily liquid often used for wood preservation. They also hypothesized that borate treatment of nonseasoned ties would protect them from fungi and insects while they were air-drying.

While creosote treatment has been used on the nation’s railroad infrastructure for more than 100 years, most wood species, especially white oaks and hickories, were not completely protected by the oily, tar-like substance.

"Some wood species, such as black gum, are completely penetrated by creosote and can be in service for almost 50 years. Ties made of white oak and other hard-to-treat species were failing after as few as 7 years in high-hazard regions such as the Southeast," Amburgey said. "These failures were primarily from decay fungi and iron corrosion of spikes, which caused the wooden beam to weaken."

With more than 140,000 miles of railroad track and 3,000 ties per mile, changing ties every 7 years was expensive, Amburgey said.

"At the time of the initial study, treating ties that were already in service to extend their life was about $5 per tie, per year," Amburgey said. "The cost for replacing ties was much higher."

After preliminary tests on the MSU campus, double-treated ties were placed on a stretch of track in Cordele, Ga., where severe decay was a problem.

"We knew that the borates would penetrate and protect the interior against wood-destroying organisms, such as decay and termites, and protect spikes from corrosion. We also knew the traditional creosote would weatherproof the outer portion of the wood," Amburgey said. "However, we had no idea that after 23 years, the double-treated method would protect the wood to such a degree that the ties remain in perfect condition today."

Amburgey said the borates move to the areas of the tie with the most moisture, keeping decay fungi out. Additionally, the creosote coating keeps the borate from leaving the wood.

Norfolk Southern, a transportation company that operates 21,000 miles of track, adopted the dual-treatment standard in 2005 for use in high-hazard regions.

"The dual-treatment system is saving us money and extending the natural resource by providing significantly greater tie life," said Jeff McCracken, assistant vice president for maintenance of way and structures for Norfolk Southern.

"We also are experimenting with using less creosote retention in the dual-treated ties to not only extend the creosote in times of shortage, but also find savings as we determine the best combination of borates and creosote," he said.

Norfolk Southern is not the only company to adopt the technology. Some 25 years after the research idea was conceived, nearly a million ties are dual-treated and installed annually by Class 1 railroads, a classification given to the largest revenue-producing railroads in North America.

Amburgey retired in 2009 after 30 years of service, but his vision for long-lasting railroad ties is still being pursued at the land-grant university. MSU Forest and Wildlife Research Center assistant professor Shane Kitchens has continued the research program, collaborating with Amburgey to develop supplemental treatments for in-track wooden crossties.

"There are more than 400 million crossties in use, with an estimated 23 million replaced each year," Kitchens said. "The system developed by Amburgey and Williams will provide long lives for railroad ties. Through education and demonstration, we hope to increase the number of railroads using the system."

Norfolk Southern and the Railway Tie Association recently demonstrated the advantage of the dual borate-creosote treatment in Cordele, Ga. More than 50 railroad engineers, purchasers and quality control staff were in attendance.

"When people see how well the crosstie performs and looks, they are immediately sold on the concept," Kitchens said.

The technology to extend the life of railroad crossties, which began at Mississippi State, is still on the move.


Forest Products