Plant Services - March 2008 - (Page 39)

Power transmission Reliability Store belts carefully While you’re getting new belts, make sure your maintenance storeroom knows that belts are to be stored in a cool, dry place with no exposure to direct sunlight or near any source of heat, including HVAC systems. Don’t hang belts from a single peg; this can damage the tensile members and distort the belt over time. Hang them from two pegs or, better yet, stack them flat on shelves. Coil the long ones, and don’t make your piles so big or heavy that they distort the bottommost belts. Place the new belt(s) into the sheave grooves, reposition the sheaves to rough alignment, and check that the belts are properly seated within the grooves. Misalignment consists of three types: vertical angularity (twist), horizontal angularity and axial offset, all of which can be present in any combination and severity (Figure 4). The most common alignment method is the straightedge and string method. It requires that both straightedge New string be able to touch each Timeand projected life curve sheave at two diametrically opposite points simultaneously (a total of four New projected contact points) (Figure 5). Rotate life curve the sheaves half a turn and recheck. Because a string can bend around corners, you can’t easily differentiate between an offset and a horizontal angle when only three-point contact is made. Nor will a straightedge or string detect twist angle under certain conditions. The approach is labor- and time-intensive. A fan-type laser overcomes these problems (Figure 6). One such system mounts magnetically to the face of sheaves as small as 2.5 in. in diameter and projects a laser fan line onto three targets magnetically attached on the other pulley(s). Alignment requires nothing more than ensuring that the projected laser line cuts across the center of each target simultaneously. With additional targets, other pulleys in the drive (such March 2008 Equality counts Figure 3. When multiple-belt systems need replacements, always use matched sets, not a one-byone retrofit. Stay straight Laser versus string Improper belt storage or handling Angle Twist Improper belt or pulley installation Poor drive design Imprope belt stora or handli Poor drive design Angle Twist Environmental factors ime Figure 4. There are three types of misalignment that can be present in any combination. Improper belt or pulley Improper installation drive maintenance Environmental factors Defective drive components Improper drive maintenance The low-tech way to align 1 2 3 4 Defective compone 1 2 Tie string 3 Pull string 4 Figure 5. Stretching a string across the sheave faces works, but takes time. as inside or outside idlers) can be Pull string aligned simultaneously. Green lasers provide greatly increased visibility suitable for bright-light conditions, especially outdoors on a sunny day, where red laser light can be harder to see. Whatever you use, though, in www.PLANTSERVICES.com 39 Tie string http://www.mactekcorp.com http://www.mactekcorp.com http://www.PLANTSERVICES.com

Table of Contents Feed for the Digital Edition of Plant Services - March 2008

Plant Services - March 2008 Contents From The Editor Letters The PS Files Up and Running Crisis Corner What Works Asset Manager: Enterprise Thinking Technology Toolbox: Hydrogen In Action Cover Story: Get Real Electrical: Reliable Distribution Power Transmission: When the Belt Breaks Web Hunter: Tooting Horns In the Trenches Product Picks Classifieds Fast Facts Energy Expert: Energy versus Sustainability

Plant Services - March 2008

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