Lubrication plays a vital role in
the performance and in the life of
bearings. The functions of the lubricants are
to reduce friction and wear, to dissipate heat, and
for ferrous-based bearings, to prevent rusting.
There are bearings that are “lubricated for
life” and bearings that need to be re-lubricated.
“Lubricated for life” bearing is a bearing that
does not need re-lubrication over its normal
service life.
For a maintenance crew, it is important to
know which bearings need re-lubrication and
make sure they are lubricating those bearings.
The bearings can be lubricated manually or
by automatic lubrication systems. This article
will review each method and discover its pros
and cons.

Manual Lubrication
Pros

? Easy access. This method is good, when your
bearings are easy to access and it is safe for
the operator. These types of applications are
not time consuming and will cost much less
than automated systems.

? Inspection while greasing. Many
maintenance managers prefer manual
greasing to make sure their equipment is
getting inspected. Having an automatic
lubrication device doesn’t mean that the
system won’t require any inspection, but a
lot of places don’t have proper inspection
procedures, so lubrication is a reason to go
and check the equipment as well.
Cons
The cons of manual lubrication are many.
Since it is done by human beings, there are
many things that can go wrong:

? The No. 1 reason that bearings fail
prematurely is the improper amount of
grease (overgreasing and undergreasing).
Certain parts of equipment that are easy to
access may get greased too many times and
hard-to-reach areas may never get greased.
The lubrication team must have proper
training on how often and how much the
equipment should be greased.

? Using the wrong lubrication can cause
a premature failure because of grease
incompatibility (not all greases are
compatible with each other) or the incorrect
grease for the application. Proper training
and procedures are necessary for lubrication
teams to know which grease goes where.

? Safety is an issue of concern, when doing a
manual lubrication. In a lot of instances the
lubrication points are in places where people
can easily hurt themselves. For this reason,
safety training is a must, when doing manual
lubrication.
? Hard-to-reach lubrication points can be
very time-consuming. Sometimes to reach
certain lubrication points the technicians
have to disassemble the equipment. This
increases the cost of lubrication. For certain
places lubrication tubes can be used, but not
always.

? In many applications, grease fittings can
be covered in contaminants, and you can
never perfectly clean them up, which causes
the contaminants to get injected into the
bearing along with the grease. It is very easy

to damage or break the seals with grease
guns (due to high pressure generated by
grease gun). Also, contaminants can easily
penetrate into damaged seals.

Automatic lubrication systems
Pros

? Protection from overgreasing and
undergreasing. With automatic lubricators,
the amount of grease is set over a period of
time. The bearings are getting the grease and
they are getting the right amount. This way
no lubrication point is missed or forgotten.

? The chances of confusing the lubricants are
less than with manual greasing.

? Increased safety. With automatic lubrication,
the technicians don’t have to get to unsafe
places like in the case of manual greasing.

? Labor Savings. Automatic lubricators can
save a lot of time, especially for hard-toreach
lubrication points.

? Less contamination is introduced, due to
increased maintenance intervals. Most of
the automatic lubricators don’t have enough
pressure to damage the bearing seals. This
reduces the chance for contaminants to
enter into the bearing due to damaged seals.

? Optimized lubricant delivery (Fig.2).

Cons

? Investment cost. Of course, implementing an
automatic lubrication system requires some
level of investment. To maximize the return
on that investment, the key is to choose the
right solution based on the requirements
and criticality of the application. Typical
solutions range from inexpensive singlepoint
automatic lubricators to very complex
centralized systems with various options for
online monitoring.
Let’s take a look at the pros and cons of single-point
lubricators and multi-point systems.

Single-Point Lubricators
Pros

? Single-point lubricators are suitable for
remote locations.

? They don’t require initial high investment
cost as for centralized systems.

? They are easy to install and maintain.

? No long lubrication lines Cons

? Most of the single point lubricators are of
single use, so after they dispense the grease
you need to purchase again.
Multi-Point Lubricators
Pros

? Some production plants have many
lubrication points in one area. In such cases,
it is more effective to have one centralized
system to lubricate all the bearings in the
area.

? Over time the cost may be less than singlepoint
installation. After initial setup,
technicians just have to fill the reservoir.

? Multi-point can generate much higher
pressure than single-point, hence it can have
longer tube lines to lubrication points. This is
convenient in hard-to-reach areas.

Cons

? Much higher initial cost than with singlepoint
lubricators.

? Proper inspections are needed. For hardto-reach
points, sometimes lines may break
under high pressure. The bearing will not
receive any lubrication and eventually will
fail. The grease from a broken line may drip
on the product or somewhere else where it
not should be.
In summary, there is no perfect answer
regarding which method is better. It all depends
on application, maintenance crew, industry
and other conditions. There are plants that use
single-point lubricators, multi-points and still
do manual greasing as well.