Fleet Maintenance - 31

Grading the grease

The National Lubricating Grease Institute (NLGI)
classifies the "grade" of a grease based on its
texture. To determine the grade of the grease,
the NLGI utilizes a penetration test - ASTM
D217. The American Society for Testing and
Materials (ASTM) penetration test places a cone
over a container of grease and drops the cone
into the grease. The cone's penetration into the
grease is measured and the depth of penetration
is compared to a reference standard wherein the
NLGI assigns the grade of the grease according to
the depth of penetration.
"The penetration or stiffness of the grease is a
function of the thickener type and the thickener
concentration in the formulation," LeBlanc says.
"Although the [NLGI] scale ranges from the softest
#000 grade to the stiffest #6 grade, most greases
for fleets are between NLGI #00 to NLGI #2."
LeBlanc explains that heavily loaded, slow

"When the grease is
subjected to mechanical
work, it releases the
base oil and additives to
lubricate the components,
whether it's rolling
elements of wheel bearings,
sliding surfaces of a
fifth wheel, et cetera."
Ron LeBlanc Sr., senior technical services
advisor, Petro-Canada Lubricants

»Heavily loaded, slow-speed applications
such as a fifth wheel require a stiffer
grade of grease to properly lubricate.
Photo courtesy of Cummins

speed applications such as a fifth wheel generally require a stiffer grade of grease to properly
lubricate. In applications such as trailer wheel
bearings, a common grease of choice is a softer,
semi-fluid NLGI #00 synthetic base oil grease.

Lubrication and
anti-contamination
Simply put, grease lubricates vehicle components.
However, depending on its grade, composition,
and application, grease can serve a multitude of
purposes on the commercial vehicle.
"Grease is a lubricant," Mistry says. "Its primary goal is to separate the mating surfaces within
the bearing or within the engineering component
by creating a lubricant film under high contact
stresses. The lubricating film helps to reduce the
friction, the wear, and prevent corrosion."
Not only does grease lubricate, but it also seals
and protects components.
"Greases are excellent sealants and thus they aid
in minimizing contamination," Mistry explains.
"Grease is preferred for equipment operating under
extreme conditions, such as high temperature and
pressure, or contact stresses, shock loads, as well
as slow speed under heavy load."

Best practices for greasing

A fleet should consult the vehicle owner's manual
or with the vehicle OEM to best understand application recommendations for greasing components.
This should present a guide to lubrication intervals per component. This research may or may not
reveal how much grease to utilize per application;
technicians should proceed with caution, consult
with OEMs, consult with lubrication suppliers, and
consult the Technology & Maintenance Council's
Recommended Practices to understand the quantity of grease per application to avoid over- or
under-greasing.
"In a lot of the typical grease applications, you
like to put in enough grease until you see it come
out a little bit, and you know you've filled the joint
up," Shell's Granger explains. "There are certain
applications where you don't want to do that. If
the joint is a sealed joint, you don't want to put too
much grease in there because if it has a rubber boot
on it, you can actually damage that rubber boot."
Applying too much or too little grease can yield
component damage, and in some cases cause catastrophic failure.
"Too much grease causes friction within the
bearing housing, leading to seal failure due to
higher-than-normal temperatures which causes
the grease to thin and run out of the bearing,"
LeBlanc says, adding that this can also allow
contaminants to penetrate the bearing. "When
too little grease is applied, the bearing or component can get hot and cause damage. Once a grease
starts to get hot, it continues to build heat and
takes longer to cool because it is not moving
through the component rapidly. Ultimately, the
heat builds to a point where the component begins
to fail. Sometimes when the component gets hot
enough, a catastrophic failure occurs, or a fire
breaks out from the heat."

LeBlanc recommends an automatic lubricator
for tough-to-lubricate components in order to
increase safety and efficiency.
Fleets and technicians should routinely monitor greased components to ensure proper lubrication has been completed and to spot any damage
from mis-lubrication. There are different tools
and methods available to monitor such conditions, such as thermal sensing systems, suggests
Ean Howard Dickerhoof, application engineer at
Timken. "An operator or a technician can use a
heat gun to see what temperature the wheel end is
operating at," Dickerhoof says. "Also, hot dots are
very common in the industry to see if the wheel
end rises above a certain temperature."
Timken offers hot dots, visual indicators that
change from white to black when the wheel end
temperature exceeds 250 degrees F, to monitor
wheel end temperature and alert the fleet should
the components reach unwanted temperatures.
"Nominal temperature for grease is right around
70 degrees Celsius or 160 degrees Fahrenheit,"
Dickerhoof continues. "Either 10 degrees Celsius
or 18 degrees Fahrenheit, every increment of that,
your grease life is cut in half. The higher temperature that you're running at will further degrade
that grease life."
Storage of grease is another important aspect
fleets must monitor.
"Typically, greases can have a shelf life of up to
five years," LeBlanc says. "The softer NLGI grades
of #0, #00, and #000 typically have a shorter shelf
life of around two years."
Timken's Mistry provides the following storage
recommendations for greases:
Ü Products should be kept in their original packaging before being placed into service.
Ü Fleets should not remove or alter labeling.
Ü Grease should be stored in a manner in which
the packaging is not damaged.
Ü Storage area temperature should maintain a
range from 32 degrees F to 104 degrees F (0
degrees C to 40 degrees C).
Ü Relative humidity of the storage area should be
maintained below 60 percent.
Ü Storing inside is preferred to avoid contaminants such as dust, dirt, and moisture.
Ü Packaging should be isolated from undue
vibration.
Dispensing grease from its container will require
specific equipment. Granger recommends that
pumping and dispensing systems have adequate
pressure to dispense grease from its container, as
well as utilizing a follower plate within the container to reduce contamination and reduce waste.
The adage of "greasing the squeaky wheel" is
not suitable for an efficient fleet of commercial
vehicles. Proper maintenance procedures, adherence to recommended greasing intervals, and due
diligence are essential in the effort to increase
uptime and keep vehicles moving. When it comes
to selecting greases for a fleet, there are many
variables to take into consideration; understanding the climate in which the vehicles will be operating, understanding the different components
that will require grease, and deciphering the best
suited properties for such instances will allow a
fleet to successfully acquire the right grease for
their business.

August 2020 | VehicleServicePros.com

http://www.VehicleServicePros.com

Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance