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Preventive maintenance and inspection can not only help prevent costly shutdowns but eliminate potentially catastrophic failures
Industrial fans used in pulp and paper processing applications face the potentially dangerous condition of imbalance. Imbalance can cause breakdowns, costly operation shutdowns and catastrophic failures, which could result in injury or damage to other equipment. Therefore, it is important for plant managers and engineers to understand what imbalance is, how to detect it, what causes it and how it can be addressed. Early detection may mean less damage to equipment and therefore reduced repair costs. Sometimes improper manufacturing processes cause imbalance. However, this article will review a number of causes that may originate at the site of operation.
There is an important distinction between the terms imbalance and vibration. To explain let's look at a fan rotor, which is generally comprised of a welded, riveted or cast fan impeller mounted on a shaft. Even if the manufacturer carefully locates the blades and weighs the component parts, one can be sure the weight center will be separated from the axis of rotation by at least a small amount. This differential is referred to as imbalance. Because imbalance is not a function of rotating speed, it can be assessed and measured when the fan is not in operation. Imbalance can be calculated by multiplying the weight of the fan rotor by the radial distance between the...