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Take care when using and storing poly tanks on the farmPosted Monday, December 20, 2010, at 6:13 PM
Poly tanks are used by many farmers and commercial operations to store various liquids. Whether a tank is a few years old or 20 years old, the only way to be sure it is structurally sound is to perform inspections before use in spring and again at the end of the application season.
Just looking at a tank to determine if it is good or bad is very difficult. There are three inspection techniques to pin-point weakened areas and stressed areas around fittings.
1. Mark the tank with a water soluble marker. The inspection is performed by rubbing the marker over several six-inch by six-inch sections on the sides of the tank exposed to sun, on its top, and around fittings. Quickly rub off the ink with a dry cloth or paper towel.
The ink left behind has penetrated the surface of the tank. Crazing is one of the first signs of deterioration, so tanks with crazing should be checked often. Crazing is the development of very fine cracks within the tank wall, usually appearing as a network of fine lines that cannot be felt with a fingernail. Cracks can be felt with a fingernail.
2. Candling consists of placing a bright light source inside a poly tank while conducting a visual inspection from the outside. Defects and cracks usually show up as areas or lines of different light intensity
3. Hitting an empty tank with a baseball bat can be done to further evaluate the condition of the tank. This would be best done when the temperatures are warmer.
A good tank has the flexibility to bend outward when filled and inward as it is emptied. Tanks that are brittle have lost the ability to flex under pressure and to rebound when impacted. The brittleness of an empty tank can be tested with a solid swing of a baseball bat where signs of cracking were discovered.
Hit the tank along the sides and top where they receive the most sunlight; then check the tank for signs of breakage. It is impossible to crack a good tank using this method because the polymer is strong and resilient.
Another concern with storage tanks is spill coverage on your insurance policy. Many farm and commercial business policies do not cover pollution from fertilizer or pesticide spills.
It is critical for business owners and farmers to consult with their insurance representatives to confirm what is and is not included in their coverage.
Your insurance agent can tell whether cleanup and product replacement cost resulting from a ruptured stationary or vertical poly tank are covered under your property or vehicle policy. Policy discounts may be available for things like conducting and documenting annual and biannual inspections and for diking your storage tanks.
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As our local University of Missouri Agronomy Extension Specialist, Crook has been writing a column for the print edition Agriculture page for the past three years and we will now be sharing it on our web version. Crook has a bachelor and masters degree in agronomy from University of Missouri and received his doctorate in Agronomy from Kansas State University. He was in soybean variety development research for 22 years for various seed companies and has been Saline County's agronomy specialist for 10 years.