VI balance grades 12 2006

Motor Repairs Motor Repair Specification  Balance Grades  Initial Balance with Shop Balance Machine  Final Balance with Motor Assembled... Motor Repair Specification... Balance Grade

Schenck Trebel Corporation

535 Acorn Street Deer Park, NY 11729 Toll Free: 1-800-873-2352 http://www.schenck-usa.com

http://www.mpta.org/MPTABalancingPrimer.pdf

http://www.irdbalancing.com/downloads/TechPaper1BalQualityReqmts.pdf

Motor Repairs

 Motor Repair Specification

 Balance Grades

 Initial Balance with Shop Balance Machine

 Final Balance with Motor Assembled

Motor Repair Specification

Balance Grades

imbalance for rotating machinery

different classes of machinery (Rigid Rotors Only*)

Steam Turbines, Machine Tools and Small Electric

Armatures

* ISO 11342 defines the balance quality requirements for rotors in a flexible state

Balance Grades: Sample Chart

Balance Grades

(Velocity) if freely suspended while rotating at servicespeed (2.5 mm/sec = 0.10 IPS)

V(mm/sec) = 2p e(mm)*RPM

60sec/min

e(mm) = Residual Imbalance (g-mm)

Rotor weight(g)

Initial Balance with Shop Balance Machine

It is difficult if not impossible to achieve Balance Grades G1.0 or G0.4 in a balance machine only

Balance Grades G1.0 and G0.4 have special requirements.

 The rotor must be mounted in its own service bearings

 No end drive (for balance machines)

 The rotor must be mounted in its own housing and bearings

 Must be run under normal service conditions: Load,

Temperature

 Self driven

Initial Balance with Shop Balance Machine : Roller Size

“…the roller diameter should differ from the journal

diameter by at least 10%, and the roller speed should never differ less than 60 rpm from the journal speed… “

p.54 Fundamentals of Balancing, 2 nd Ed 03/1983; Schenk Trebel

Final Balance with Motor Assembled

2-pole Motor phase readings

Motor Setup

Final Balance with Motor Assembled

Flexible or Rigid Rotor – Large 2-pole motors

In test runs at service speed, moving two test

masses from the end planes to the center plane,

results in a vibration change of less than 20%.

pp.21-22 Fundamentals of Balancing, 2 nd Ed 03/1983; Schenk Trebel

Graphic: http://www.schenck-usa.com/lib_101_types_unbal.asp

Effect of startup heating

60 Hz

Trial 1 (1:25 PM)

Trial 2, 3, 4, 5 … 6 (9:00 PM)

As low as reasonably achievable.

Before and After MOV Spectrum

2 Year Overall Trend