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Book Bits
Here's a bit from "The Practical Handbook of
Lubrication":
"Cost cutting by machine design engineers, incomplete
commissioning
and plant start up procedures and inadequate
equipment
condition monitoring and maintenance practices, are
the
major reasons for initial seal failure and fluid leakage.
"Once a seal has failed and fluid leakage results, the problem
is
perpetuated by bad purchasing department policies of
purchasing
and restocking low quality (read less expensive),
or
incorrect seals, or by careless installation practices used
during
replacement procedures.
"The subsequent leaks, while not considered excessive, go on
and
on and soon, plant operating and maintenance personnel
accept
the leakage as normal.
"The lack of attention to a few basic details cost millions of
dollars
annually in external fluid wastage, unnecessary
maintenance
downtime and environmental damage."
Daily Tips
- One way to choose the correct viscosity for a
rolling contact
bearing
is to find its dN or dmN. The dN is the speed of the
bearing
multiplied by its inside diameter in mm. dmN is the
speed
of the bearing multiplied by its pitch diameter. This
is
a more accurate method because it takes into account the
difference
in the inside and outside diameter of the bearing.
There
are charts available in most books on lubrication that
show
dN of dmN values at different operating temperatures for
determining
the viscosity.
-
Enclosed gears can be lubricated by a many methods including
bath/splash,
spray, circulating system, drip or mist. AGMA
recommends
changing gear lubricants every 2,500 hours or
six
months, whichever comes first.
Correction
to Tuesday's Lube Tips on Lubrication of Piston
Compressors:
Most
industrial and commercial piston compressors in use today
are
of the single acting, air-cooled type and are splash-
lubricated.
Only a few manufacturers use a pressure lubrication
system
and of these, only two use pressure in other places than
the
crankshaft. In fact, lubricating oil passing at the rings
can
be a problem with pressure lube designs-it can cause
premature
ring and discharge valve failure. In one case, excess
oil
down-stream led to coking of discharge air lines at a soft
drink
bottling facility and ignition of the "coke" in the air
line.
Only double acting compressors use positive-pressure
injection-type
piston lubrication. These compressors have been
widely
replaced by rotary screw compressors due the high initial
installation
and maintenance costs associated with double-acting, water
cooled compressors. Information supplied by a Lube-Tips
reader.
Daily Tips
-
Additives that might be depleted when an engine oil ages are:
-
Three ways to test for glycol in engine oils are:
More
Great Tips
Today
we are going to look at a passage from "The Practical
Handbook
of Lubrication." Lloyd (Tex) Leugner has done a wonderful job
making this book easy to read and extremely useful to anyone involved
in lubrication. The following excerpt discusses turbine lubrication
systems.
"Circulation
oiling systems vary widely as to detail, the particulars
of each design depending on the make, size, type and
purpose of the turbine.
"Oil
is taken from a reservoir and delivered at full pump pressure
to
a header that supplies oil to the governing and control
mechanisms.
The oil pressure ranges from about 50 psi in some
systems
to 450 psi in others (3.5 to 31.6 kg/sq cm). Oil from the
bearings
and governor mechanism drains back to the reservoir.
"A
reservoir capacity of five to ten times the volume of oil
circulated
per minute is recommended. Sizes therefore range from a
few, to several thousand gallons. Large reservoirs are
fabricated
from steel plate and are provided with manholes to
permit
entrance for cleaning.
"Reservoirs
should have a bottom that slopes slightly (1 unit in
24)
toward a drain connection through which contaminants may be removed.
To prevent foaming, oil return lines are generally
arranged
so that they enter the tank horizontally just above, or
at
the oil level and at a point above the lowest part of the
sloping
tank bottom."
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