A V-box style spreader has hoses leading to the tank that holds the brine near the truck's cab. The nozzles spray in a fan
pattern directly onto the driving surface.
|
When it comes to winter maintenance, most private contractors have the "standard" equipment – a plow on the front of their
pickups and a spreader on the back. For years, this combo has been all a contractor needed to cater to most customers. In
recent years, there has been a trend toward understanding the science of snow and ice control.
At one time, it was enough for contractors to simply push the snow out of the way and spread a layer of rock salt down on
the ice layer below. And if that didn't do the trick, the answer was more rock salt. Little thought went into the chemical
reaction that occurred between the deicing agent and the ice.
A closeup shot of the pencil-spray nozzle setting.
|
In recent years, with increasing customer demands for more effective ice control, the trend has been toward more scientific
responses. The plow and spreader are still staples of the industry, but it's the materials being spread that are more sophisticated.
Each material offers different benefits in terms of the application, weather conditions and the spreader being used, which
requires the contractor to be more sophisticated. This trend toward a more scientific response continues with the growing
use of liquid deicing agents for pre-wetting spreading materials and anti-icing surface treatments.
What is pre-wetting and anti-icing? The practice of pre-wetting and anti-icing could be deemed the newest "old" technology used to combat snow and ice. The idea
has been in practice for years by municipalities, but its implementation has yet to become common amongst the private sector.
The principles are simple. Pre-wetting involves the use of a liquid chemical or salt brine solution applied to a deicing material
before it is spread.
A pre-wetting system can be used to wet the spreading material in the chute before it hits the distribution pinner on a spreader.
|
Anti-icing is similar, but the brine solution is sprayed directly onto the driving or walking surface. These practices are
relatively basic, but the benefits are considerable.
Pre-wetting material
One big problem associated with spreading bulk materials is its tendency to bounce off the roadway during application or to
be swept away by wind or traffic before taking effect. Some people address this by spreading much more than is typically necessary,
assuming that enough will remain to do the job. This is crudely effective, but it wastes material, is expensive and is not
good for the environment.
Continued application problems eventually led to the practice of pre-wetting the spreading material.
The logic behind this approach is quite simple. If the salt is wet, it's more likely to cling to the target surface instead
of bouncing or blowing away.
When first tried, operators used water to saturate the materials after they were loaded into the spreader's hopper. Given
the hazard of the load freezing, most now use a part-brine, part-water solution to wet the material. Some people still wet
the material as it's loaded into the hopper, but most use equipment that sprays the brine onto the material as it hits the
spreader's spinner. This results in a more uniform application of brine.
Also, pre-wetting deicing materials results in faster dissolving of snow/ice. Generally, the melting potential of deicing
materials is determined by the agent's ability to attract sufficient moisture from the environment, which then forms a liquid
brine. Simply, a mixture of water and the active deicing material, brine lowers the freezing point of water and then begins
to melt the surrounding snow/ice.
