Fan Bearing Maintenance Troubleshooting Fe 1300
Fan Bearing Maintenance Troubleshooting Fe 1300
Fan Bearing Maintenance Troubleshooting Fe 1300
FE-1300
Fan Bearing
Maintenance & Troubleshooting
Lubrication
Proper lubrication and maintenance are essential for long
bearing life. An adequate supply of clean lubricant must
be present at all times to prevent damaging, metal-tometal contact.
Twin City Fan Companies experience has shown that
grease is the best type of lubricant for fan applications.
For ball and spherical roller bearings a NLGI Grade 2
or 3 grease is recommended. Special high temperature
greases are recommended if the bearing temperature
exceeds 160F.
Avoid mixing greases with different bases. This can
cause hardening of the grease and inadequate lubrication. The grease used at the factory is a lithium-based
grease. When using a grease constructed with a different
base (such as sodium or a synthetic base), keep adding
the new grease until all of the lithium based grease
purges out of the bearing.
Fans are shipped with labels on them showing the
relubrication schedule for normal operating conditions. If
the operating condition is relatively clean and at ambient
temperature, use the relubrication interval shown on the
sticker as a starting point. Frequently, however, operating conditions are dirty or humid and require more frequent relubrication. If there is high moisture, high temperature, or if the shaft is in the vertical position, start
out relubricating twice as often as shown on the sticker
and adjust the interval as required. The best way to see
if a relubrication interval is adequate is to check the
condition of the grease purged from the bearing when
adding new grease. If darkened and badly oxidized
grease purges, relubricate more frequently. If the purged
grease looks about the same as new grease, a longer
interval may work.
High ambient temperatures can make bearing and
lubricant selection difficult. The viscosity of the oil contained in the grease is the property that prevents metalto-metal contact. With most common lubricants, the
viscosity starts to fall at temperatures over 200F.
Because the temperature inside the bearing is always
higher than the ambient temperature, bearing and lubricant selection is difficult if the ambient temperature rises
over 125F. External means of cooling the bearing may
be required in these situations.
Static or circulating oil should only be used with split
pillow block bearings on high speed or high temperature
applications where grease is unsuitable. Oil lubricated
bearings require more rigorous maintenance. High oil
levels can prevent the bearing from venting the air inside
the bearing as it heats up. The built-up pressure can
blow all of the oil out of the bearing in only a few
minutes. Low oil levels do not provide adequate lubrication. If sight gauges are used to monitor the oil level
they must be adjusted to read properly. Since the indicated level changes when the fan is turned on, it is best
to check the oil levels when the fan is off. If this is not
A B C
SHEAVE
DIA.
3.5
200 BC SWSI
CLASS II
2490 RPM
15 HP MOTOR
6" SHEAVE
7
1 /16" HEAVY DUTY
BALL BEARING
SHEAVE
POSITION
A
B
C
AS SOLD
AS INSTALLED
200 BC SWSI
CLASS II
2490 RPM
15 HP MOTOR
17/16" HEAVY DUTY
BALL BEARING
L-10 LIFE
32,000 HRS.
40,000 HRS.
50,000 HRS.
DIA.
4.2"
4.8"
5.0"
5.2"
HRS.
19,000
5.6"
27,000
6.4"
31,000
8.2"
34,000
43,000
62,000
90,000
36%
34%
14%
16%
Inadequate Lubrication
Normal Fatigue
Contamination
Other Causes Such as:
Faulty Mounting
Static Vibration
Electric Currents
Incorrect Fits
Source: Rolling Bearing Digest, 1985
Figure 6. Spall
Allowing electrical current to pass through a bearing can cause damage. Figure 26 shows a spherical roller with
pits in its surface caused by electrical current. This type of damage commonly occurs when welding balance weights
on a fan wheel with improper grounding. To avoid having the welding electrical current pass through the bearings,
attach the grounding clamp to the wheel or shaft when adding balance weights.
Summary
There are several different types of rolling element bearings used for fan applications. The best choice is the one
that provides adequate L-10 life with reasonable cost. Proper care during mounting, shipment, storage, and operation
is required in order for the bearings to achieve the theoretical L-10 life they were selected for.
References
Bearing Installation and Maintenance Guide, SKF USA Incorporated, King of Prussia, Pennsylvania, 1992
SKF General Catalog, SKF USA Incorporated, King of Prussia, Pennsylvania, 1991
Bearing Technical Journal, PTC Components Incorporated, Indianapolis, Indiana, 1982
Bearing Failure: Causes and Cures, The Barden Corporation, Danbury, Connecticut, 1992
Dodge Engineering Catalog, Volume 1.1R, Reliance Electric Industrial Company, Greenville, South Carolina, 1993
Sealmaster Bearing Products, Morse Industrial, Emerson Power Transmission Corporation, Ithaca, New York, 1988
Eugene R. Hafner, Selecting Bearings for Fans and Blowers Machine Design, April 29, 1990
Photographs in Figures 5 through 26 are courtesy of SKF USA Incorporated