Plant Services - March 2008 - (Page 37)

ood sheave alignment increases drive train efficiency and reduces premature wear or failure of belts, pulleys and bearings. You can achieve this state of high alignment two ways: the common, but laborintensive, string-and-straightedge method, or by laser. The latter approach is now well established in the sheave alignment field, and has proved to reduce downtime and labor while achieving much higher accuracy. This results in significant savings and increased production uptime. A V-belt drive is an efficient power transmission method, exhibiting efficiencies from 90% to 98%, and has traditionally been thought of as forgiving. However, proper alignment and belt tension are critical variables that can make a difference in mean time between repairs (MTBR). Good drive maintenance involves a number of steps. Roughly half involve aligning the drive – removing belts, inspecting components for wear and damage, checking for bent shafts, correcting sheave runout, installing belts, alignment and tensioning the belts. Your foremost concern always should be safety. Never allow loose clothing or long hair anywhere near belt-driven machinery, and ensure that the equipment is locked out and tagged out. G First, seek the root cause Before beginning the sheave alignment, try to determine the cause of the belt or sheave failure and correct it to prevent a recurrence. The root cause of the failure might be associated with poor drive maintenance (improper belt tension, poor sheave alignment), environmental factors (ultraviolet degradation, harsh temperature fluctuations), improper installation (wrong belts/sheaves, belts pried on by force) or operating factors (overload, shock load). Closely inspect the belts, each sheave and its grooves. Look (and feel) for cracks, chips and excessive groove wear (Figure 1). Check for proper contact between the belts and the sheaves. Correct any such mechanical and structural problems before proceeding with alignment to prevent premature or catastrophic failure. Change belts any time you detect undue wear. Inspect the used belt for any noticeable cracking, gouges or crumbling, and watch for glazing, which indicates belt slippage. The belt’s wear pattern can be a good indication of the type of misalignment or other problem that might be in play (Figure 2). Removing belts only requires slackening the tension by moving one sheave toward the opposing sheave. March 2008 www.PLANTSERVICES.com 37 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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