Efficient Plant February 2018 - 29
feature | lubrication strategies
surized crankcase ventilation (PCV) system
in use today.
An automotive crankcase is, of course, a
reservoir similar to any gearbox or hydraulic-oil reservoir. In all cases, the reservoir
is an enclosed container used to house oil
that is pumped through the machine to
lubricate bearing surfaces and return to the
reservoir within the closed-loop system.
When designed correctly, the reservoir will
always have an air space (headspace) above
the oil level designed to permit thermal
expansion of the oil and allow the fluid to
de-aerate (aerated fluids cause pump cavitation). To equalize the internal pressure
build up created through the resulting
changes in the oil level as the machine
moves from rest to full operation, and vice
versa, air must be allowed to enter and
exit the reservoir through a device known
simply as a breather.
If air is allowed to freely move in and out
of the reservoir through the breather, so
is everything contained within that air exchange. This can include contaminants and
moisture, both detrimental to the oil and
the very bearings surfaces oil is designed
to protect. This now requires the reliability
engineer and/or maintainer to recognize
the ambient working conditions and choose
the appropriate breather style and type for
the conditions and, furthermore, exercise
diligence, through preventive-maintenance
procedures, to ensure that the breather is
always in place in the reservoir, is clean,
and is unencumbered, allowing it to work
the lubrication system preventive-maintenance program. The change-out
schedule is based on application and
ambient conditions. If the breather is a
less-sophisticated design that does not
display its condition to the operator or
maintainer, the rule of thumb is change
out every three months in dirty environ-
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ANATOMY OF A BREATHER
Breathers come in all configurations,
shapes, and sizes, and different styles
accommodate different airflow, particulate size, and working conditions. Most
breathers are consumable devices. As such,
they must be changed regularly as part of
If air is allowed to freely
move in and out of
the reservoir through
the breather, so is
within that air exchange.
EPRS Maintenance Tech.indd 1
1/3/18 9:06 AM