Plant Services - June 2008 - (Page 39)

Heating & Cooling safety Table 1. ANSI/AMCA vibration limits (in./sec.) Factory mechanical run testing Mounting Type Shop Test BV-3 Shop Test BV-4 Start-up Condition BV-3 Start-up Condition BV-4 Alarm Condition BV-3 Alarm Condition BV-4 Emergency Shutdown BV-3 Emergency Shutdown BV-4 Rigidly mounted 0.15 0.10 Flexibly mounted 0.20 0.15 Normal operation in situ Rigidly mounted 0.25 0.16 0.40 0.25 0.50 0.40 Flexibly Mounted 0.35 0.25 0.65 0.40 0.70 0.60 Lapp Group's New Full-Line Product Catalog Notes: • Alarm – action should be taken immediately to determine the cause of the high vibration and to take steps to correct it. • Shutdown – the fan should be shut down immediately. • Rigidly mounted – fan mounted by means of anchor bolts and epoxy grout on a heavy concrete foundation in a properly prepared soil or bedrock; fan operates well below the system’s first natural frequency. • Flexibly mounted – fan mounted on elevated structural steel or on a spring-isolation system; fan operates well above the system’s first natural frequency. The Lapp Group of North America is pleased to announce the release of our new 728 page product catalog. Included in the new catalog is our full range of OLFLEX®, UNITRONIC®, and ETHERLINE® cables, EPIC® connectors, SKINTOP®, SILVYN®, and FLEXIMARK® accessories, value-added and custom services. Many enhancements have been made to this new edition. New features include: • Complete your installation guides • Standard put-ups • Technical comparison charts in the front of each section. New products include: • OLFLEX® Tubing & Sleeving • EPIC® M23 Connectors • EAB, EAC & EPT Mil Style connectors • NFPA 79 2007 compliant cables. For additional information or to request a catalog visit www.lappusa.com. These bearings have a direct mechanical link from the shaft, through the rolling elements and the races, to the bearing housing. Therefore, for these bearings, it’s best to mount seismic probes on the bearing base (or better, mount directly to the fan bearing housing), to monitor the bearing housing vibration level. These seismic vibration pick-ups are available as: • Accelerometers, which measure vibration in acceleration units, typically Gs • Velocity pick-ups, which measure vibration in velocity units, typically in./sec. or mm/sec. Using velocity output units, the recommended alarm and shutdown vibration levels are independent of the shaft operating speed. Therefore, regardless of which type of seismic probe you use, the output usually is converted to velocity units for monitoring and recording vibration levels. Suggested vibration limits are specified in ANSI/AMCA Standard 204, “Balance Quality and VibraJune 2008 tion levels for Fans.” In this standard, fans are categorized over a wide range of applications and motor sizes. For most industrial applications, balance-vibration categories BV-3 and BV-4 apply. The maximum recommended vibration levels (peak velocity, in./sec.) in these are shown in Table 1. For sleeve-type bearings Many larger fans use hydrodynamic sleeve-type bearings, such as plane cylindrical bore, elliptical bore and tilting pad units (Figure 5). The rotating shaft rides on a thin film of oil inside the bearing liners. Typically, the bearing housings are robust with high rigidity and are mounted on equally rigid steel pedestals or concrete piers. Significant bearing housing vibration requires a tremendous amount of vibratory force. Therefore, when these bearings are used, monitor the shaft vibration, as opposed to the bearing housing movement. This can be done by means of eddy-current www.PLANTSERVICES.com 888-456-3539 www.lappusa.com 39 http://www.lappusa.com http://www.lappusa.com http://www.PLANTSERVICES.com

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Plant Services - June 2008

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