U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
|Accelerating Infrastructure Innovations|
Publication Number: FHWA-SA-96-014
Date: March 1996
Many State highway agencies are eager to try anti-icing technologies, but find their plans hampered by the high cost of commercially available liquid spreaders. In response, many agencies are building their own liquid spreaders. Here's how one State did it.
The Oregon Department of Transportation (DOT) built its first liquid spreader in 1989. The first unit was simple, consisting of a 5,680-liter (1,500-gallon) polyethylene tank, a spray bar, plastic piping, and a pump mounted on the back of a 3.8-cubic meter (5-cubic yard) dump truck. Parts were purchased from a local farm supply store, at a cost of about $1,500.
Dick Parker, then research coordinator for Oregon DOT, says crews calibrated the homemade spreaders by measuring the liquid left in the tank after traveling a specific distance at a certain speed, and then calculating how much liquid had been applied to the road. "This is extremely low tech," he says, "but it works."
Oregon DOT's fabrication shop in Salem, which built the prototype, built several more to be used by various maintenance stations throughout the State. Later, the shop used modified agricultural herbicide sprayers to make more sophisticated units. As word spread about the effectiveness of these homemade devices, demand for them grew.
Mel Chaput, equipment repair manager for the fabrication shop, says the shop crew has built all types of systems, ranging from the simple dump truck version to more complex computerized systems that run from $35,000 to $45,000. The computerized liquid spreaders are able to monitor ground speed and chemical flow to calculate the application rate.
Crews have also built spreaders as small as 1,900 liters (500 gallons) for use on pick-up trucks. These scaled-down devices employ gasoline-powered pumps and spraybars.
"We can produce just about any type of spreader that is requested," says Chaput. "Our products are as good as any that are commercially manufactured."
Chaput says building the liquid spreaders has been a learning experience for the Oregon DOT. For example, crews learned that polyethylene tanks and plastic spray systems work best with anti-icing and deicing chemicals. The first herbicide sprayer that the shop converted had bronze valves and nozzles, and the bronze reacted with the deicing chemicals, causing premature corrosion of the valves and nozzles. Chaput also says that weight limitations of the vehicle should be considered because the chemicals can be quite heavy--as much as 1.3 kilograms per liter (11 pounds per gallon). In addition, the size of the tank should be taken into account when it is installed on the back of a truck. For example, Chaput says he wouldn't recommend anything larger than a 1,900 liter (500-gallon) tank for a pick-up truck.
After using homemade devices to experiment with anti-icing strategies, most districts in Oregon will eventually invest in commercial spreaders. The reason: the commercial spreaders more accurately measure chemical application rates. The homemade spreaders are then used for smaller jobs, such as parking lots and residential streets.
"Before we built the homemade spreaders, we were just plowing and applying sand," says Parker. "By being innovative we opened the door to some very effective technology."
For more information contact Dick Parker at 503-239-5094 (phone and fax), or Salim Nassif at FHWA at 202-366-1557 (fax: 202-366-9981).