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AMCA International Technical Seminar 2009

AMCA International Technical Seminar 2009. Equipment Vibration Presented by: Bill Howarth, Illinois Blower Inc.

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AMCA International Technical Seminar 2009

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  1. AMCA International Technical Seminar 2009 • Equipment Vibration • Presented by: • Bill Howarth, Illinois Blower Inc.

  2. The Air Movement and Control Association International (AMCA), has met the standards and requirements of the Registered Continuing Education Providers Program. Credit earned on completion of this program will be reported to the RCEPP. A certificate of completion will be issued to each participant. As such, it does not include content that may be deemed or construed to be an approval or endorsement by NCEES or RCEPP.

  3. Describe the distinction between balance and vibration • Know the levels of balance quality • Know the levels of installed vibration • Understand the importance of an adequate foundation • Recognize symptoms and causes of problems • Know how to avoid vibration problems Learning Objectives

  4. Equipment Vibration Presented by Bill Howarth Hartzell Fan, Inc.

  5. ANSI / AMCA 204-96 • Balance Quality and Vibration Levels for Fans • Balance • Vibration

  6. BALANCE • Balance • Synonymous with Unbalance. A physical property results in centrifugal force being applied to the fan impeller. • Measured as the product of unbalance mass and distance from axis of rotation (oz-in).

  7. UNBALANCE • EXAMPLE: • ROTOR WEIGHT = 300 LBS • RADIAL SEPARATION OF CENTER OF MASS FROM AXIS OF ROTATION=0.0052 INCHES • UNBALANCE =300 LBS * 16 OZ/LB *0.0052 IN.=25 OZ-IN. Center of Mass Shaft Axis of Rotation Fan Impeller

  8. UNBALANCE A. Particulate builds up uniformly on the rotor. Sticky-wet particulate in gas stream Scrubber B. A piece of particulate flies off. Fan C. Center of mass shifts so that it no longer coincides with the axis of rotation.

  9. UNBALANCE Dead spot 250F at top of housing 250F Top of shaft = 188F Bottom of shaft = 187F 120F Fan wheel weight = 8500 lbs. Differential Expansion: (188 - 187) * (6.5E-6in/in-F) * (200 in) = 0.0013 in Shaft Bows Upward! 120F at bottom of housing  = Displacement from axis of rotation = 0.36” Then Unbalance = (8500)*(16)*() = 49,000 oz-in 200.0013  200.0000

  10. UNBALANCE Dust accumulation inside hollow airfoil blade. Rotation

  11. UNBALANCE Buildup of dust on the backside of backward curves blades. Rotation

  12. UNBALANCE Hub Shaft Setscrews initially hold hub tightly in position on the shaft. Setscrew tips are corroded or worn by fretting over time. This allows the hub and entire fan wheel to be displaced relative to the axis of rotation causing unbalance. Interference fit eliminates the possibility of the hub being displaced relative to the shaft in most systems.

  13. Conclusion: Initial interference fit should be in excess of 0.002 inches to allow for thermal expansion plus an allowance for hub expansion due to centrifugal force. Example: Shaft dia. = 3.9375 in. Hub average temp = 215 F Shaft average temp =80 F Then hub growth relative to shaft: (3.9375) * (80) * (6.5E-6) = 0.002 in. Fan impeller weight = 250 lbs.. (250 lbs. x 16 oz/lb. x 0.002 inches) Resulting unbalance = 8.0 oz-inches EFFECT OF TEMPERATURE CHANGE Fan impeller initially operating at 70 F. Process gas temperature increases rapidly. Weld Integral hub and shaft for very rapid temperature change applications. Fan impeller and hub heat up more quickly than the shaft.

  14. ANSI / AMCA 204, TABLE 4-1

  15. ANSI / AMCA 204, TABLE 5-1

  16. ANSI / AMCA 204, APPENDIX C.2

  17. VIBRATION • Vibration • The alternating mechanical motion of an elastic system, components of which are amplitude, frequency and phase. • In general practice vibration values are reported as: • Displacement - mils • Velocity - inches/second • Acceleration - peak g’s

  18. VIBRATION VELOCITY 1780 RPM Uper = 12.72 oz-in Maximum Vibration (in free space) =2.5 mm/sec (or 0.10 in.sec)

  19. Small Diameter, Light Rotor Vibration Pickup Massive Bearing Housing High Stiffness Pedestal VIBRATION • Note that the bearing housing is considerably lower than the expected vibration of the rotor in free space.

  20. SLEEVE BEARING Proximity Probe measures shaft surface movement relative to the bearing housing. Shaft (rotating) Bearing Liner (static) Bearing Housing Oil Film supports shaft

  21. EFFECT OF STRUCTURE Mass Fan Mass Cyclic Forces Structural Steel acts as a spring Circus Flagpole cyc/min Fn = 1200 Fan operating Acrobat speed = 1180 RPM Flagpole acts as a spring cyc/min Fn = 30 Foundation

  22. Normal Fn = 1680 cyc/min Operating speed (F) Vibration (in/sec) 0.10 in/sec 1180 Speed (RPM) Fn >1.4 * F SOLID FOUNDATION

  23. Normal Fn = 1200 cyc/min Operating speed (F) 0.70 in/sec Vibration (in/sec) 1180 Speed (RPM) STRUCTURAL STEEL MOUNTING

  24. FLEXIBLE MOUNT Expansion Joint Expansion Joint Discharge Duct Inlet Duct Rigid Sub-Base (Often concrete filled) Spring Isolation with static deflection of 1.0 inches Fn = 187.7/1.5 =187.7 cyc/min Structural Steel Platform

  25. ANSI / AMCA 204, TABLE 6-3

  26. VIBRATION UNITS

  27. Vertical Axial Horizontal TRANSDUCER MOUNTING • SWSI Centrifugal Fans

  28. Vertical Axial Horizontal TRANSDUCER MOUNTING • DWDI Centrifugal Fans

  29. TRANSDUCER MOUNTING Vertical Axial Horizontal • Axial Fans Vertical

  30. VIBRATION SPECTRUM 0.20 Filter Out Filter In 0.15 Velocity (In./sec.) 0.10 0.05 0.00 0 500 1000 1500 2000 2500 Speed (RPM)

  31. ANSI / AMCA 204, TABLE 6-4

  32. Questions?

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