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Fluid Journal : Fluid Journal 2008-2009
Consider installing a tank liner or applying a protective coating. Evaluate these options carefully, as these components can also fail, potentially resulting in an even larger problem. Operational Check the pH of incoming UAN. Measurement of pH is a good indication of how much excess ammonia is contained in the UAN. Most producers ship product with a pH above 7.0.ApHaslowas6.5isquite acceptable, but much below that there is a risk of stressing all the corrosion management systems. Discuss with your supplier a desire to receive product with a pH no lower than 6.5. UAN purchasers can check the pH of incoming UAN with something as inexpensive as pH paper tape (less than $50), or consider the purchase of a pH meter (less than $500). This is highly recommended if you are purchasing imported product, which has been known to lose allows for the buildup of "pockets of corrosive ions" under the corrosion sludge. Many UAN producers now have adopted a best practice of installing an inlet recirculation pipe across the entire diameter of their tank bottom. This header pipe has several outlet spouts that point toward the floor at a 45o angle. Recirculation of the UAN allows tank sludge to keep moving across the tank bottom. This helps to greatly reduce pitting corrosion. Some new tank builders are now recommending installation of a sloped tank bottom with a center outlet. This design is great for corrosion prevention, as sludge is constantly removed from the tank so buildup is always minimal. Figure 7. Pitting under UAN tank sludge. Figure 8. UAN rail car sludge. Figure 9. Pitting under UAN rail car sludge. excess ammonia during the long transport time. If available, ask the supplier to include excess ammonia levels on the Certificate of Analysis for each load. Excess ammonia should be no less than 0.010 weight percent (100 ppm), and preferably should be at least 0.020 to 0.050 weight percent (200-500 ppm). Another important quality of the UAN is known as the AN/ Urea Ratio. This is a simple mathematical calculation of the
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