By Scott Zorno, CSP
Too often companies assume that because an equipment operator is adept at one area of operations that their skill set and knowledge automatically translates to others. This is not true when it comes to effectively and efficiently using liquids for ice control. When an operator has been using a plow truck with a salt spreader for a while but now has to learn to use liquid deicers, it can be challenging. Following is some guidance to help reduce the stress of that transition.
Determine plan of action
First, determine what action the contracted service level requires. With liquids, the strongest benefit is in anti-icing: spraying a film of deicer liquid on a designated portion of a lot or road before a storm starts. The liquid will dramatically reduce the snow bonding to the pavement, making plowing cleaner. Post-treatment is similar to salting after the plowing is done. The goal is to melt the snow/ice residue after plowing. With a low tolerance level of service, anti-icing and post-treat can be used, which creates a top and bottom or “sandwich melting” effect. Liquid deicers melt residual snow faster than salt or most dry products, making them desirable to use when quick, visible results are needed. Understanding the service level and corresponding plan of action are important. Your supervisor can provide additional details.
Know your rates
As an operator, there are several facets of quality control to understand. Liquids are normally distributed either in square feet per gallon, gallons per acre or gallons per lane mile. A lane mile generally means a 1-mile long, 10-foot wide path. So a lane mile has approximately 52,800 square feet. An acre is rounded off to 43,000 square feet. If you are instructed to spray liquid at a rate of 1,000 square feet per gallon (a typical anti-icing coverage rate), then you know you should spray about 43 gallons per acre, or about 50 to 55 gallons per lane mile. Coverage rates are most easily adjusted by changing the truck’s speed. To put liquid down thicker, slow the truck. For newer pavement or good surfaces, thin out the application by speeding up a little.
Truck speed will influence application rates, with heavier flow at slower speeds.
Calibration of a spray system is important and easy if you have a flow meter, which measures the quantity of liquid flowing past it (usually independent of the pressure). As an example, assume you have a flow meter, a gas engine pump, and a boom (or spray bar) that leaves an 8-foot path. The anti-icing coverage is targeted to be 1,000 square feet per gallon of liquid. To start, set the motor to a high idle, turn on the sprayer and drive a consistent speed over a known area (say 10 mph to start). If that known area is about an acre, then stop when coverage is done to check the flow meter. If you have used approximately 42 to 45 gallons, you know your match between truck speed and pump engine speed/pressure is about right. If you have used over 46 gallons, then you know you can either speed up the truck or slow the pump motor to drop the pressure.
If you do not have a flow meter, then manual calibration will be needed:
- Set the pump engine to a high idle speed
- Turn on the boom
- Get a calibrated pitcher or bucket and put it under a single spray head for exactly 15 seconds to collect the liquid
- Shut down the motor, turn off the flow to the boom and remove the bucket
- Measure how many ounces of liquid are in the bucket
Then multiply the ounces by 4 to get the ounces per minute coming out of a spray head. Divide the total ounces by 128 to get the gallons per minute (gpm) coming out of that single spray head (typically 1 to 1.5 gpm). Multiply that gpm by the number of spray heads to calculate how many gpm the truck is spraying.
Next, measure the width of the spray path (e.g., 8 feet wide). At 10 mph, a truck covers 880 feet per minute (mph x 88). At 12 mph, the truck goes 1,056 feet per minute. In our example, the sprayer covers 8 feet wide x 880 feet long or 7,040 square feet per minute. If you have six spray heads spraying 1 gpm each, you’re putting down 1,173 square feet per gallon (7,040 / 6). If your supervisor told you to aim for 1,000 square feet per gallon, the simple thing to do is slow the truck down a little. If you slow the truck to 9 mph, your coverage will be 1,056 square feet per gallon. That’s very close to the target.
Using a flow meter is an easy way to ensure your equipment is dispensing the correct amount of liquids based on your application rates.
Document your operations
Recordkeeping is an important part of sustainability. Make sure you log the gallons used from either the flow meter, careful observation of the markings on the tank, or the gallons used by calculating the calibration. The driver’s final responsibility is to look at the job before leaving. Does it look right? Is the coverage good and even? Are special needs for the site completed (loading docks, intersections, etc.)?
The last but most critical item for a new operator to heed is safety. Is your truck equipped with reasonable warning lights? Do you know how to turn them on and understand regulations in your area for driving with warning lights on? Does your truck have work lights for backing and lighting up the sides of your truck? Are they aimed well? Seeing and being seen are critical to safe operations at all times.
Not overloading your truck is also critical to safety, particularly when transporting on main highways. Salt brine is only slightly heavier than water (just over 8.5 pounds per gallon). However, magnesium or calcium chloride solutions and many well brines are up to 11 pounds per gallon. You cannot put 350 gallons of magnesium chloride safely in a ¾-ton truck with a sprayer system. You will likely break something in the driveline or suspension. Know what chemical you are using and how much can be safely loaded onto your specific truck.
When you know what chemical you are using and receive specific application instructions, you can apply liquids with confidence. Ask questions. Caution and product knowledge are needed to prevent issues like adding slickness to a road or spraying a deicer with an odor near a populated building during business hours.
With training from your company and this information, you can become a very effective spray operator in a shorter period of time.
Rookie mistakes during spraying operations
- Backing up to make a pass and hitting a snow bank or post with the boom
- Not verifying the function of the cab control before spraying
- Not putting the top back on firmly and straight, allowing the liquid to splash over the truck bed
- Running a tank dry with the pump still on and burning up the pump seal from overheating
- Not recording each job’s product usage and running out of product
Scott Zorno, CSP, owns HighCountry Spray Systems in Conifer, CO. He is a retired snow contractor and is a member of the Snow Business Editorial Advisory Committee. Contact him at scott@HighCountryIS.com.