The freeze-thaw cycle can do a number on wash plants and their components. Photo: P&Q Staff
Bringing a wash plant back to life after a winter shutdown requires more than a flip of switch.
A lot more, in fact.
The freeze-thaw cycle can do a number on components that are critical to effectively run a plant. Operators, therefore, have plenty to consider as spring start-up arrives.
“Make sure you change all of your oils and things are properly lubricated,” says John Bennington, product manager of washing and classifying at Superior Industries. “With the freeze-thaw cycle, you can get water in the gearbox [and] damage the oil.”
Because of this possibility, Bennington always recommends operators follow one key guideline before shutting plants down for the winter.
“Leave last year’s oil in the gearbox until the spring,” he says. “The oil is going to take some abuse because of cold temperatures. Overnight, they may get down to 0 degrees and then the sun comes up. With the up and down of temperatures over the winter, drain all of the old oil in the spring that took that abuse.”
Of course, an operator’s wash plant checks ahead of spring start-up extend beyond the oil. Neil Rooney, engineering manager at Terex Washing Systems, offers another perspective.
“Any component that delivers water, oil or power should be carefully checked for damage caused by freezing temperatures before gently ramping the plant up to capacity,” Rooney says.
Once checks for temperature damage are complete, Rooney advises operators to follow their standard daily wash plant inspections.
“This involves testing the oil and making sure no obstacles are trapped within the media decks or log washer blades.”
Additionally, Rooney says conveyor rollers can be susceptible to seizing over winter due to lack of movement.
“These need a visual inspection and intervention if required,” he says. “Grease lines to the head and tail drums should be topped up, and we should listen to the motors and gearboxes for anything untoward.”
When operators are finally ready to start up, plants should be given the necessary time to warm up. According to Rooney, initially running plants at low capacity will provide operators the time to inspect equipment such as thickener tanks and filter presses as they’re in action.
“Some components, including Terex Washing filter presses, have oil heater plugs and optional insulated housing, making the start-up process easier,” Rooney says. “Our deep cone thickeners contain drain-down technology that gives less opportunities for standing water to enter and freeze which, again, helps to simplify the start-up procedure.”
With equipment such as log washers, Bennington is an advocate of safety covers that prevent people from falling or climbing into them.
“One of the problems you run into being human beings is we tend to be curious,” he says. “If you make a cover that you can’t see through, then the first thing everybody wants to do is open it up and see in.”
For that reason, Bennington says his company provides bar grade covers.
“They don’t have to be overly complicated,” he says.
One other recommendation Bennington issues ahead of wash plant start-up is to purge the water lines feeding spray bars on dewatering screens.
“Purge the line so that the nozzles aren’t clogging,” he says. “If you have sedimentation in there after a shutdown for any reason, you might find that you turn the spray bars on and half the spray bars aren’t working.”
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