AMCA International Technical
Seminar 2009
Equipment Vibration
Presented by:
Bill Howarth, Illinois Blower Inc.
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.
Learning Objectives
•
•
•
•
•
•
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
Equipment Vibration
Presented by
Bill Howarth
Hartzell Fan, Inc.
ANSI / AMCA 204-96
Balance
Quality and
Vibration
Levels for
Fans
• Balance
• Vibration
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).
UNBALANCE
EXAMPLE:
Center of Mass
Shaft
Axis of
Rotation
Fan Impeller
• 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.
UNBALANCE
A. Particulate builds
up uniformly on the
rotor.
Sticky-wet
particulate in
gas stream
Scrubber
B. A piece
of
particulate
flies off.
C. Center of mass shifts so
that it no longer coincides
with the axis of rotation.
Fan
UNBALANCE
Dead spot
250F at top
of housing
250F
Top of shaft = 188F
Bottom of shaft =
187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
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
UNBALANCE
Dust accumulation inside
hollow airfoil blade.
UNBALANCE
Buildup of dust on the
backside of backward curves
blades.
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.
EFFECT OF
TEMPERATURE CHANGE
Fan impeller initially
operating at 70 F.
Process gas
temperature increases
rapidly.
Fan impeller and hub
heat up more quickly
than the shaft.
Weld
Integral hub and shaft
for very rapid
temperature change
applications.
Example:
Conclusion:
Shaft dia. = 3.9375 in.
• Initial interference fit should
Hub average temp = 215 F
be in excess of 0.002 inches
Shaft average temp =80 F
to allow for thermal
expansion plus an allowance
Then hub growth relative to shaft:
for hub expansion due to
(3.9375) * (80) * (6.5E-6) = 0.002 in.
centrifugal force.
Fan impeller weight = 250 lbs..
(250 lbs. x 16 oz/lb. x 0.002 inches)
Resulting unbalance = 8.0 oz-inches
ANSI / AMCA 204, TABLE 4-1
Table 4-1 Fan Application Categories
APPLICATION
EXAMPLES
DRIVER
POWER
kW (HP)
LIMITS
FAN
APPLICATIO
N
CATEGORY,
BV
RESIDENTIAL
Ceiling fans, attic fans,
window AC
<= .15 (0.2)
>.15 (0.2)
BV-1
BV-2
HVAC &
AGRICULTURAL
Building ventilation and
air conditioning;
commercial systems
<=3.7 (5.0)
>3.7 (5.0)
BV-2
BV-3
INDUSTRIAL
PROCESS& POWER
GENERATION, ETC.
Baghouse, scrubber,
mine, conveying, boilers,
combustion air, pollution
control, wind tunnels
<=300
(400)
>300 (400)
BV-3
BV-4
TRANSPORTATION &
MARINE
Locomotives, trucks,
automobiles
<= 15 (20)
> 15 (20)
BV-3
BV-4
TRANSIT/TUNNEL
Subway emergency
ventilation, tunnel fans,
garage ventilation,
Tunnel Jet Fans
<=75 (100)
> 75 (100)
ANY
BV-3
BV-4
BV-4
PETROCHEMICAL
PROCESS
Hazardous gases,
process fans.
<= 37 (50)
> 37(50)
BV-3
BV-4
COMPUTER CHIP
MANUFACTURE
Clean room
ANY
BV-5
ANSI / AMCA 204, TABLE 5-1
Table 5-1
FAN
APPLICATION
CATEGORY
BALANCE QUALITY
GRADE
FOR RIGID
ROTORS/IMPELLER
BV-1*
G 16
BV-2
G 16
BV-3
G 6.3
BV-4
G 2.5
BV-5
G 1.0
*Note: In FAN APPLICATION CATEGORY
BV-1 there may be some extremely small
fan rotors weighing less than 227 grams (8
ounces). In such cases, residual unbalance
may be difficult to determine accurately.
The
fabrication process must ensure
reasonably equal weight distribution about
the axis of rotation.
ANSI / AMCA 204, APPENDIX C.2
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
VIBRATION VELOCITY
1780 RPM
Uper = 12.72 oz-in
Maximum Vibration
(in free space)
=2.5 mm/sec
(or 0.10 in.sec)
VIBRATION
Small Diameter,
Light Rotor
Vibratio
n
Pickup
Massive
Bearing
Housing
High
Stiffness
Pedestal
Note that the
bearing housing
is considerably
lower than the
expected
vibration of the
rotor in free
space.
SLEEVE BEARING
Shaft
(rotating)
Bearing
Housing
Proximity Probe
measures shaft surface
movement relative to the
bearing housing.
Bearing Liner
(static)
Oil Film
supports shaft
EFFECT OF STRUCTURE
Fan Mass
Mass
Cyclic Forces
Fan operating
speed = 1180
RPM
Structural Steel
acts as a spring
Fn = 1200 cyc/min
Flagpole acts as
a spring
Fn = 30 cyc/min
Foundation
Circus Flagpole
Acrobat
SOLID FOUNDATION
Normal
Fn = 1680
cyc/min
1.6
1.4
Operating
speed (F)
Vibration
(in/sec)
1.2
1.0
0.8
0.6
0.10 in/sec
0.4
0.2
0.0
0
500
1000
1180
Speed (RPM)
Fn >1.4 * F
1500
2000
STRUCTURAL STEEL MOUNTING
1.4
1.2
Vibration
(in/sec)
Normal
Fn = 1200
cyc/min
Operating
speed (F)
1.6
0.70 in/sec
1.0
0.8
0.6
0.4
0.2
0.0
0
500
1000
1180
Speed (RPM)
1500
2000
FLEXIBLE MOUNT
Expansion
Joint
Expansion
Joint
Inlet
Duct
Structural Steel
Platform
Discharge
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
ANSI / AMCA 204, TABLE 6-3
Table 6-3 Seismic Vibration Limits for Tests Conducted in the Factory
Values shown are peak velocity, mm/s (inches/s),
Filter-In, at the factory test speed.
FAN
APPLICATION
CATEGORY
RIGIDLY
MOUNTED
mm/s (in./s)
FLEXIBLY
MOUNTED
mm/s (in./s)
BV-1
12.7 (0.50)
15.2 (0.60)
BV-2
5.1 (0.20)
7.6 (0.30)
BV-3
3.8 (0.15)
5.1 (0.20)
BV-4
2.5 (0.10)
3.8 (0.15)
BV-5
2.0 (0.08)
2.5 (0.10)
VIBRATION UNITS
TRANSDUCER MOUNTING
Vertical
Axial
Horizontal
SWSI Centrifugal Fans
TRANSDUCER MOUNTING
Vertical
Axial
Horizontal
DWDI Centrifugal Fans
TRANSDUCER MOUNTING
Vertica
l
Axial
Horizontal
Vertical
Axial Fans
VIBRATION SPECTRUM
Velocity (In./sec.)
0.20
Filter Out
Filter
In
0.15
0.10
0.05
0.00
0
500
1000
1500
Speed (RPM)
2000
2500
ANSI / AMCA 204, TABLE 6-4
Table 6-4 Seismic Vibration Limits for Tests Conducted In-Situ
Values shown are peak velocity, mm/s (inches/s), Filter out.
Condition
Fan
Application
Category
Rigidly
Mounted
mm/s (in./s)
Flexibly
Mounted
mm/s (in./s)
Start-Up
BV-1
BV-2
BV-3
BV-4
BV-5
14.0 (0.55)
7.6 (0.30)
6.4 (0.25)
4.1 (0.16)
2.5(0.10)
15.2 (0.60)
12.7 (0.50)
8.8 (0.35)
6.4 (0.25)
4.1 (0.16)
Alarm
BV-1
BV-2
BV-3
BV-4
BV-5
15.2 (0.60)
12.7 (0.50)
102 (0.40)
6.4 (0.25)
5.7(0.20)
19.1 (0.75)
19.1 (0.75)
16.5 (0.65)
10.2 (0.40)
7.6 (0.30)
Shut-Down
BV-1
BV-2
BV-3
BV-4
BV-5
NOTE 1
NOTE 1
12.7 (0.50)
10.2 (0.40)
7.6 (0.30)
NOTE 1
NOTE 1
17.8 (0.70)
15.2 (0.60)
10.2 (0.40)
Note 1: Shutdown levels for fans in Fan
Application Grades BV1 and BV2 must be
established based on historical data.
Questions?