SnowEx PWS-225 - Manual (Page 28)

© Trynex International 2010 L1217 AS — 28
Pre-Wetting System
Pre-Wetting is the process of spraying de-icing salt with a solution of liquid chemical before spreading the salt on the roadway.
Pre-Wetting the salt helps it work more effectively as a de-icing agent for two reasons: First, wet salt clings to the road instead of
bouncing off or being swept off by traffi c. The result is that less salt is spread, saving money and minimizing the threat to the
environment. Second, to be effective as a de-icing agent, salt requires moisture. Moisture dissolves the salt, releasing heat and
thereby melting the ice and snow, as well as breaking the ice-road bond. When temperatures drop below freezing, there is no
moisture on the road, and salt alone is ineffective. Pre-Wetting the salt, however, ensures that there will be enough moisture
to facilitate the melting process. Then, pre-wetted salt works faster and at lower temperatures than does dry salt, with
less waste. As a pre-wetting agent sodium chloride (salt) brine is a low-cost, effective alternative to liquid calcium.
WHY PRE-WET WITH SALT BRINE?
Sodium chloride has been used as a pre-wetting agent primarily because of its low cost and ready availability, but the real benefi ts
from pre-wetting occur when the brine is mixed with the dry materials. Sodium chloride must fi nd moisture from some source
before it can generate the heat needed to begin the melting process. Under past operations, dry sodium chloride could not
generate heat until it came into direct contact with the snow or ice on the surface. As the sodium chloride found the moisture in
the snow or ice, it began to generate heat which melted more snow and ice, accelerating the melting process. During snow storms
and temperatures and low humidity, sodium chloride had diffi culty fi nding available moisture, which slowed the melting process
cold air considerably. Adding sodium chloride brine to dry sodium chloride at the spinner before it struck the road surface
provided extra moisture to quicken the melting process.
BENEFITS
We are pleased with the results and have found the following benefi ts in using pre-wetted materials:
• Materials readily adhere to the roadway better than with dry materials.
• Pre-wetted materials begin dissolving snowpack and ice faster than dry materials.
• The quantity of materials can be reduced when pre-wetted, since less materials leave the roadway during spreading.
• Corrosion of equipment is minimized by spraying the liquid salt at the spinner.
• Operators report quicker melting with the pre-wetting process, which means better service to the traveling public.