It’s Time To Start Planning Now For The Fall And Winter Freeze.
By Steve Dixon
It is talked about a lot in early fall but not much gets done until the pain starts at the onset of the first big freeze, then it is an emergency.
Fighting freezing issues with temporary makeshift remedies is a way of life for most operators. Morale dips, labor gets strained, fires break out and people get hurt, even fatally. The labor expenses and lost production costs are staggering for some operators. The mindset is: This is the way it is in the winter and this is the way we have always dealt with it.
Freezing issues are around every corner when moving bulk solids with conveyor belts. The following is a brief description of the daily encounters that are prevalent when moisture-laden materials move on conveyor belts that can virtually be eliminated with the technology that is now available.
Fast Freeze
Bulk material being fed to conveyor belts from bins and hoppers and being transferred from one belt to the next via chutes creates a lot of areas where even a small amount of moisture in the material causes it to freeze fast to sub-freezing surfaces, like the tongue on the pump handle. This is especially problematic in chutes, bins and hoppers.
The buildup eventually leads to blockages that stop the material flow from one end of the operation to the other, including the entire processing plant in most instances. A single blockage in a chute or transfer point, or one conveyor belt goes down due to some freezing issue, causes a chain reaction.
When chutes sit idle with material inside that freezes, the material in bins and hoppers will start to freeze which may not otherwise be a problem as long as a constant flow is present. Material will freeze on the belts as well as on the belts when movement stops.
Ice, frost and snow that accumulates on belts and pulleys when setting idle between shifts and over weekends causes issues with getting the belts in motion due to drive roll slipping. The loss of traction is compounded by the belts being cold and stiff. Belts get damaged, lagging on drive rolls get damaged and production gets delayed.
Frost or frozen material on the carrying side of the belt causes the material to slip or slide back, primarily on inclined belts, but slipping also occurs on flat belts. In the case of an inclined belt, the material will slide back down the belt which has in effect become a lubricated chute or sliding board.
The material piles up at the bottom of the conveyor stopping the operation until said material is removed. In the case of a long and wide inclined belt, this can be many tons. Flat belts such as those used under hoppers as feeder belts can lose traction and be rendered totally ineffective or cause sporadic feed rate with some materials.
Cleated Concerns
Inclined belts are often replaced with cleated belts during cold weather operations. Cleated belts work for inclines but they have many drawbacks. To start with, they are expensive to buy and change out seasonally. The major issue is they are impossible to scrape and keep clean, which causes the material that is conveyed to be carried back along the return, causing a constant cleanup nightmare.
Scrapers at the discharge end of the conveyor, designed to remove fines and even water from the belt to prevent it from being carried along on the return, are rendered useless when even a small amount of frozen material builds up on the cutting edge. Since scrapers are very rigid in their construction, a very small amount of frozen material the size of a pea can lift the blade and render the scrapper useless.
When the belt doesn’t get scraped clean, the material gets carried along, building up on idler rolls and pulleys, causing belt misalignment, and sometimes it falls off along the way. What remains on the belt freezes to the surface, causing more problems. Once material freezes to the belt, scrappers cannot remove it. If enough pressure is applied to a scraper to remove ice, it will eventually start cutting into the belt cover.
Bend pulleys or turn-down pulleys at gravity take ups on counterweights are subject to freezing material buildup that causes belt misalignment. When the belt misaligns, it can be severely damaged as it comes into contact with the surrounding structure.
Typically, the edge of the belt is worn away, sometimes to the point it is ruined or has to be trimmed and used as a narrower belt, reducing the amount of material it is able to carry. In extreme cases, the belt can be totally destroyed.
Blinded Off
Classifying screens and grizzlies freeze over, get plugged or, as the industry says, “They get blinded off.” When classifying screens get “blinded off,” the material goes to the reject pile instead of the stockpile. When grizzlies on feed hoppers get plugged, the operation ceases.
In most instances, the remedy for the situations as described is tarps, torpedo heaters, weed burners, antifreeze, jack hammers, digging bars, picks and shovels, and enough manpower to apply these time-tested remedies. Operators will literally buy every torpedo heater in town and dispatch every able-bodied man that is available armed with the aforementioned when the system goes down. This despite the fact that it happens every winter.
Some operators do plan ahead and literally buy a truckload of torpedo heaters and thousands of gallons of antifreeze and have them on the ready. Tarps and portable heaters, and labor is the staple of emergency winterization.
With all of this being said, everything described above is what I have experienced, dealt with, been involved in or read about.
There is technology available to make a vast majority of these problems a thing of the past. Over the past 40 years, Thermo-Tech has developed and field-proven a wide variety of heating solutions available nowhere else. Everything we build has a proven history in some of the most severe operating conditions on the planet such as the Gobi Desert, Mongolia and Baffin Island, NU, Canada.
Steve Dixon is chief operations and engineering officer at Thermo-Tech Inc. For more information, go to www.thermotechinc.com, or call 877-693-7693.
