Milnor 72044 WP2, Service, Page: 37 / 202

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—The useful life of antifriction bearing
grease can be estimated, based on service conditions, frame type, and motor rpm. An example of
determining the correct lubrication interval is provided below.
Ex: A fan motor, operating at an ambient temperature of 109
o
F (43
o
C) in a moderately corrosive
atmosphere. The motor has a NEMA 286T/(IEC 180) frame and is rated at 1750 rpm.
Table 1 classifies the service condition as “severe.”
Table 2 specifies a 0.5 service condition multiplier value for “severe” service condition.
Table 3 specifies 9500 hours as the recommended lubrication interval for frame sizes 254 to 286
(see nameplate), given standard service conditions.
Multiply .5 (service condition multiplier value) by 9500 hours (recommended lubrication interval)
= 4750 hours (calculated lubrication interval).
Table 4 shows that the amount of grease to be added is 0.32 ounces (9.1 grams).
Table 1 — Determining the Service Condition
Severity of Service Maximum Ambient
Temperature
Atmospheric
Contamination
Type of Bearing
Standard 104
o
F (40
o
C) Clean, little corrosion Deep groove ball
bearing
Severe 122
o
F (50
o
C) Moderate dirt, corrosion Ball thrust, Roller
Extreme >122
o
F (>50
o
C) or
Class H Insulation
(Note 1)
Severe dirt, abrasive dust,
corrosion
All bearings
Low Temperature -22
o
F (-30
o
C)
(Note 2)
Note 1: Special high temperature grease is recommended.
Note 2: Special low temperature grease is recommended.
Table 2 — Service Condition Multiplier Value
Operating
Condition
Multiplier
Standard 1.0
Severe 0.5
Extreme 0.1
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