Alan S Yarrow

1
ISSCT WorkshopIn-field balancing of machines.by
Alan S Yarrow
ISS Machine Health (Esper Pty Ltd)
machinehealth.com

• Presentation
• by
• Alan S Yarrow

2
Machine Unbalance
Unbalance occurs when the center-of-gravity of a
rotating object is not aligned with its
center-of-rotation. By analysing the change in
amplitude and phase of the vibration at the
bearings it is possible using a test weight run
to establish what correction weights are required
and where they must be placed.
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
3
Why Hand Balancing or balancing on a Knife Edge
nearly always fails
Dynamic Unbalance If weight A B Then machine
only balanced when not running.
Static Unbalance If weight A B Then machine
balanced when stationary and running.
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
4
There are some simple rules about fan geometry to
help make that decision However, it is better to
analyse the phase angles before deciding. It may
save you time.
How many planes do I balance?
1 - Plane as Phase Angles are the same
2 - Plane as Phase Angles are different
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
5
Basic Considerations before you start Balancing.

• Examine the Fan -
• Structural Integrity OK?
• Is the rotor clean?
• Are there any aerodynamic problems?
• Have any correction weights been lost?
• Are there any safety hazards?

ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
6
Next Analyse the Vibration Data before you start.
Balancing.

• Does the vibration data present only unbalance?
• Any harmonics - how much misalignment vibration
  is there?
• Measure vibration and phase during run up does
  the vibration increase exponentially with speed
  and are there any resonances?
• Move the accelerometer mounting radially 180 or
  90, does the phase angle move by a similar
  amount?

ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
7
In-field Balancing Setup
Accelerometer 1
Accelerometer 2
Note For Illustration only. Balancing is done
with the fan casing closed.
Laser Tachometer
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
8
Fan Vibration Trend
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
9
Balancing Records Indicate a Changing Structure
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
10
Common Defects found by Vibration Analysis

• The majority of excessive vibration found by ISS
  can be divided into three groups -
• Unbalance.
• Alignment.
• Mechanical Looseness
• Resonance

ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
11
ISSCT WorkshopLaser alignment of machine
position or coupling.by Alan S Yarrow
ISS Machine Health (Esper Pty Ltd)
machinehealth.com

• Presentation
• by
• Alan S Yarrow

12
Alignment Errors

• Misalignment of machine couplings cause -
• bending forces on the machine shafts.
• premature bearing failures.
• premature seal failures.
• premature coupling failure.
• vibration.
• energy losses.

ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
13
The Myth of the Flexible Coupling.

• Flexible couplings are deceptive they seem nice
  and free and compliant when stationary or hand
  rotated. 
• However, imagine the tension/distortion in a pin
  type coupling when transmitting 100 hp across it.

Loaded behaves like a V-block
No Load flexible
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
14
Basic Alignment of Couplings
Parallel Error Measurement
Angular Error Measurement
What about the effect of axial shaft movement on
the accuracy
What about when the coupling halves are not equal
diameter or perish the thought not concentric
with the shaft?
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
15
Face and Edge Alignment of Couplings
However, you must still consider the effect of
shaft end float with this method.
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
16
Reverse Rim Alignment of Couplings
This is the basis for most Laser Aligning tools
it is not effected by axial shaft movement nor
eccentric coupling halves. However, it is quite
complex to do with dial guages and to calculate
the required corrections.
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
17
Before starting alignment.

• Cleanliness of footings
• Jacking bolts
• Try to use no more than three shims under each
  foot.

ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
18
Alignment in steps

• Remove soft-foot (uneven feet)
• Get rid of the vertical angular error.
• Raise/lower the machine parallel.
• Get rid of the horizontal angular error.
• Move machine sideways parallel.

ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
19
Laser Alignment of couplings
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
20
Laser Alignment of Couplings

• Fast correction speed is only limited by ease
  of moving/shimming the machine.
• Accurate can correct for soft foot and allow
  for axial movement of shaft.
• No beam sag can align over large distances, eg.
  gt5m
• Records - produces hard copy of results
• Adaptable can cope with thermal growth or
  torque distortion.
• Not expensive at approx 18K, compared to saved
  downtime

ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
21
The End. Thank you for your attention. Any
questions?
ISS Machine Health
Innisfail Scientific Services (Esper Pty
Ltd)
alan.yarrow_at_machinehealth.com