When the days get shorter and that fall bite is in the air, public works officials and fleet managers realize their daily battlefield will change drastically. Instead of mowers and sweepers, plows and spreaders will be their weapons of choice. The annual cold war is on—are you prepared for battle?
Large plow trucks and massive sand/salt spreaders can handle highways, interstates, and major arterials, but what about smaller jobs? Though public parking lots, sidewalks, and other areas typically get less attention, the potential for slip-and-fall injuries (and lawsuits) is forcing officials to take closer notice and address these areas with more zeal. All it takes is a basic understanding of the enemy (ice and snow), something to melt it, and a few smaller-scale spreaders in your arsenal.
Knowing the basics about how deicing materials interact with ice can make a big difference. The melting potential of most deicing materials is determined by the agent's ability to attract moisture from the environment, which then forms a liquid brine. A mixture of water and active deicing material, brine lowers the freezing point of water—melting the ice and snow.
The deicer breaks down the hydrogen bond that forms when water freezes. As it absorbs moisture, the brine solution increases and bores its way toward the pavement. Once the brine reaches the surface, it fans out underneath the ice and snow, breaking the bond formed with the pavement. Sufficiently applied deicer will weaken the bond so that snow and ice can be removed easily.
There are more than 100 different deicers available. All offer performance characteristics, such as melting speed and varying levels of temperature effectiveness, and 95% of all available ice melters are made from one or more of six basic ingredients: sodium chloride, urea, potassium chloride, magnesium chloride, calcium chloride, and calcium magnesium acetate. Knowing the characteristics of these ingredients can determine how a particular product will work for individual applications. Refer to the sidebar on the next page for detailed descriptions.
After choosing the agent, decide what equipment to use to deliver the material. For smaller applications such as sidewalks, a walk-behind spreader may be used. Though a larger capacity option could better handle the demanding applications typically faced by a municipality, often site constraints or other limitations prevent the use of a vehicle-mounted spreader.
There are two basic types of walk-behind spreaders: drop and rotary. A drop spreader simple “drops” material directly under the hopper, limiting application to the width of the spreader. These work best when applying to a surface that matches the spreader width such as a sidewalk. Rotary spreaders include a controlled opening that drops material onto a spinner, which distributes laterally in all directions. Rate of delivery is determined by the amount of flow allowed to the spinner and how fast the operator walks. Rotary spreaders typically handle 50 to 200 pounds of material.
Walk-behind application options are essential, but the true workhorse of a spreading operation is a larger tailgate or vee-box spreader. Used for parking lots, driveways, roadway applications, and narrow bridge decks, tailgate and vee-box spreaders range in capacity from 200 pounds to more than 3500 pounds. Choice of style can depend on several different factors, including size of application, size of vehicle, and ability to load bulk materials.
Tailgate spreaders attach to the back of a truck or single-utility vehicle tailgate, allowing for spreading without limiting the vehicle payload. This is of particular interest to the user who must use the truck to carry other winter-maintenance equipment such as a snowblower or powered sidewalk sweeper. Conversely, though a vee-box spreader typically fills the entire truck bed, the benefit is much longer spreading intervals to accommodate larger applications.
One spreader development that has grown in recent years is the availability of units with hoppers constructed entirely of polyethylene. For years, tailgate and vee-box spreaders had only been available in steel-built designs. Of course, combining a material like sodium chloride with a metal delivery device is a recipe for corrosion. All it takes is a slight chip or scratch in the paint, and corrosive elements like water, salt, and air are directly exposed to the metal. Though typically 10% to 20% higher in price, poly-built equipment is completely noncorrosive and will not scratch, bend, dent, pit, or scale. Additionally, poly offers nonstick characteristics, which keeps material flowing.
Also, poly-constructed spreaders are typically half the weight of steel-built units but do not sacrifice strength or durability. Lighter weight makes them easier to install, handle, and store than steel units. A typical poly spreader or plow can be installed by two people, whereas steel options require additional personnel or mechanical assistance, such as a forklift.
Lighter weight is an obvious benefit with installation, but it also makes vehicles more flexible. Because of the excessive weight of steel spreaders, shop personnel tend to avoid multiple installs and removals. The unit is installed once at the beginning of the season and removed and stored once at the end. Once a vehicle receives the spreader, it is dedicated to spreading—effectively eliminating the truck's payload capabilities. Poly-constructed vee boxes do not require the same dedication. Because the units can be installed and removed by two people, a vehicle can spread deicer in the morning, then haul equipment in the afternoon.
There will never be a shortage of snow and ice—and the demand for effective and speedy removal will only increase. Fortunately, equipment and material producers recognize this demand and continue to provide better tools. If you take the time to understand the problem and evaluate the tools available to counter it, there is no reason you can't be a “cold warrior,” instead of waving the “white” flag.
— Jon Thorp is public relations director for TrynEx International, Warren, Mich.
Six basic ingredients of deicers
1. Sodium chloride (rock salt)
Advantages: most readily available, least expensive
Disadvantages: highly corrosive, potentially damaging to plants and soils
Practical effectiveness temperature: 12º F
2. Potassium chloride
Advantages: more environmentally safe than sodium chloride, less corrosive
Disadvantage: requires higher temperatures for effectiveness
Practical effectiveness temperature: 20º F
Advantage: only 10% as corrosive as sodium chloride
Disadvantages: can contaminate groundwater and runoff collection ponds with nitrates
Practical effectiveness temperature: 20º F
4. Magnesium chloride
Advantages: very hygroscopic salt (readily absorbs moisture)
Disadvantages: easily tracked into buildings (results in slippery floors); requires careful storage
Practical effectiveness temperature: -25º F
5. Calcium magnesium acetate
Advantages: noncorrosive, environmentally friendly, practical effectiveness temperature comparable with sodium chloride; also works as an anti-icer (applied before snowfall and ice development)
Disadvantages: extremely expensive compared with sodium chloride
Practical effectiveness temperature: 15º F