Fans are used to move air and process gas in many industries, including cement plant applications. Large fans are typically put on substantial foundation blocks at ground level and, for other fans, there are a variety of solutions ranging from bolting a fan to steelwork, bolting a fan to the floor, and bolting a fan at ground level to a thicker floor section. The location of the fan will depend on customer requirements and knowledge of how the fan will interact with the structure supporting it.
Foundation blocks can represent a substantial cost and a substantial impact on the installation time. Fans are most often installed in existing plants, typically for new processes or replacing existing fans at an available outage. However, on existing plants, there is often a lack of construction drawings and the potential deterioration of structure. This deterioration would not be significant enough to affect the structural integrity, but may affect the structure’s stiffness. There is also often a lack of accurate underground cable and pipe details. This means that digging a substantial hole in the ground can represent a major risk. At a minimum, there may be substantial cost over runs associated with rerouting cables or pipes. Of more significance, there could be an unplanned plant shutdown associated with a cable or pipe being broken.
The location of a fan can also be an issue. Where there are constraints on the fan location, there may be implications on the length of duct runs. Extensive duct runs can be a substantial installation cost, especially with the highly erosive dust seen in the cement industry. In addition to installation cost, there can be cost associated with heat loss. Another aspect to consider, especially with large dust loads and high temperatures, is that it might not be possible to install in-duct silencers. With no in-duct silencers, duct breakout noise (the noise coming out of the duct), can become an issue. The larger a noise source, i.e. the longer the duct, the larger the noise effect for a given breakout sound pressure. This means that, especially with no in-duct silencer, ducting can be a substantially greater noise source than the fan itself. This is often the case in plants where there is high work level noise.
With the desire to avoid foundation blocks and long duct runs, many fans are installed on anti-vibration mounts.
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Read the article online at: https://www.worldcement.com/special-reports/04102019/designed-for-good-vibrations/