I was on my patio the other day, soaking up what is left of autumn in Illinois, and I noticed something was missing -- and not just the leaves off the trees. It was the absence of the loud buzzing noise I had heard at the beginning of summer. Until recently, I thought this noise came from a bird. I learned, however, that an insect, a cicada, is responsible for the long-lasting background buzz many of us hear from May through July.
According to the University of Michigan Museum of Zoology Insect Division, cicadas have multiple-year life cycles and come in many varieties, some of which appear each year and others that appear periodically in 13- and 17-year cycles. Those that appear every 13 years generally can be found in the Midwest and South while the 17-year cicadas are found mostly in the North.
To the average Joe (and unless you are a tree branch!), cicadas are harmless insects. But to the engineer whose manufacturing process requires a cooling tower, cicadas in large concentrations -- such as the periodic cicadas that emerge every 13 or 17 years -- can wreak havoc on a manufacturing process and on a company's pocketbook. The population of the insects upon their emergence can reach as high as 1.5 million per acre, with several hundred thousands per acre being usual.
Living woody vegetation is necessary for the male insects to survive. Take a look outside your plant. Are you located within a mile of a natural forestry area? If so, are your cooling towers equipped to handle airborne debris? If not, cooling tower fill material can plug up quickly and the cooling water will load with massive numbers of these insects. If that happens, you will face frequent downtime for cleaning strainers and fill.
This coming spring, the 17-year cicada will emerge in parts of Alabama, Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia. Check with your local department of entomology to determine what regions in your state will be affected.
If your plant is in an area where periodical cicadas are expected to emerge, consider now what steps to take to prepare. Consider whether cooling tower filters, changes to water treatment programs, supplemental cooling systems or other means will be necessary. Although the infestation should be a fairly short event -- 17-year cicadas live little more than a week -- if your plant is in a heavily infested area, the effects on your process cooling equipment could be longer lasting.
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