Efficient Plant March 2020 - 19

feature | lubrication strategies
APPLYING GREASE
Pumping grease into a motor bearing is not complicated. However, a few basic precautions should
be taken. First, any tubing that connects the grease
fitting to the motor bearing should be pre-charged
with grease. Failure to do so could result in no grease
getting to the bearings for the first few shots as any
grease that is ejected from the gun is simply filling
the supply tube. Second, don't rush. Rapidly filling a
bearing with grease can cause sudden shock. Three
to five seconds per shot, ensuring that a full shot is
dispensed each time, is preferred.
If equipped, it is also good practice to remove the
purge port, but do not necessarily expect grease to
purge out. All too often, mechanics pump grease into
a motor, intent on seeing grease exit the purge port.
Never apply more than the calculated quantity of
grease. Though not always practical, some motor
experts recommend applying grease when the motor
is not running. Since many bearing failures are
induced by particle contamination, it is also best
practice to clean the grease fitting and the end of the
grease gun prior to applying grease to the motor.

ULTRASONIC-ASSISTED LUBRICATION
In the past 10 to 15 years, many companies have used
ultrasonic devices to assist in correctly lubricating
motors. By measuring ultrasonic energy in the 20- to
50-kHz range, metal-to-metal contact and churning,
caused by too much grease, can be measured as an
increase in the amount of ultrasonic energy emitted
by the bearing. With this technique, the right quantity
and frequency of re-grease calculated using the Leugner formula can be refined simply by observing the
ultrasonic response of the bearing to the addition of
grease.
In most industrial facilities, motors make up a
third to a half of all lubrication points. As such, they
are critical to uptime and machine reliability. Do not
take a shotgun approach to motor lubrication. Add
precision by making sure you use the right grease,
calculate the correct quantity and frequency of
re-grease, and leverage technologies such as ultrasound, shock-pulse monitoring, or high-frequency
vibration analysis to ensure your motors are properly
lubricated. EP

MARCH 2020

EP2003flube.indd 19

Leugner Equation Correction Factors
Condition

Adjustment

Operating
temperature

Reduce the re-grease interval by half for
every 25 degrees above 150 F.

Moisture

Reduce the interval by as much as
95%, based on the severity of moisture
ingression.

Particle
contamination

Reduce the interval by as much as
70%, based on the severity of particle
contamination.

Bearing orientation

Reduce the interval by half for vertically
mounted motors.

Fig. 2: Re-grease quantity is also affected by operating conditions. Apply these correction factors to refine the results of your Leugner-equation calculations.

Grease Application Procedure

1. When possible,
remove the vent plug.
2. Wipe the grease fitting, purge a
shot of grease from the gun nozzle,
and wipe it.
3. Slowly apply the requisite amount
of grease. If, at any point, grease
emerges from the seal or vent,
or if there is an increase in
backpressure,
STOP adding grease.
4. Leave a bit of grease on
the grease fitting to protect
it and facilitate cleaning at the
next application.
5. Come back in 10 to 20 min. and
replace the plug.

Mark Barnes, CMRP, is Senior Vice President at
Des-Case Corp., Goodlettsville, TN (descase.com). He
has 21 years of experience in the fields of lubrication
management, oil analysis, and contamination control
and has published more than 150 technical articles and
white papers.
EFFICIENTPLANTMAG.COM |

2/17/20 11:43 AM

http://www.descase.com http://www.EFFICIENTPLANTMAG.COM

Efficient Plant March 2020

Table of Contents for the Digital Edition of Efficient Plant March 2020