Roller
chain consists of a series of connecting traveling metallic bearings, which
must be properly lubricated to obtain the maximum service life of the chain.
Although many slow speed drives operate successfully with little or no
lubrication beyond the initial factory lubrication, proper lubrication
will greatly extend the useful life of every chain drive. The chain drive
requires lubrication for six purposes.
-
To resist wear of the pin-bushing
joint.
-
To cushion impact loads.
-
To dissipate any heat generated.
-
To flush away foreign materials.
-
To lubricate chain-sprocket
contact surfaces.
-
To retard rust or corrosion.
A good grade of clean petroleum
oil without additives, free flowing at the prevailing temperatures, should
be used. Some additives leave a varnish or gum deposit which prevents the
oil from entering chain joints. Heavy oils and greases are generally too
stiff to enter the chain joints and should not be used.
With proper lubrication,
a separating wedge of lubrication is formed between the pins and bushings
in the chain joints much like that formed in journal bearings. The viscosity
of the lubricant greatly affects its film strength, and its ability to
separate moving parts. The highest viscosity oil which will flow between
the chain linkplates and fill the pin-bushing areas will provide the best
wear life. This is essential to minimize metal to metal contact and, if
supplied in sufficient volume, the lubricant also provides effective cooling
and impact dampening at higher speeds.
Note:
Rotative speeds beyond the maximum recommended for chain operation are
indicated in the horsepower rating tables with zero horsepower.
Operation at these or higher
speeds will result in excessing galling of the chain pins and bushings
regardless of the volume of oil applied.
Chain drives should be protected
from abrasive and corrosive conditions, and the oil supply kept free of
contamination. Periodic oil change is desirable.
Chain Cross-Section
Showing Exaggerated Clearances
|
Note:
Oil should be applied to the lower span of chain on the upper edges of
linkplates since access of oil to pin-bushing joints is possible only through
the clearances between the roller chain linkplates. |
|
Oil
applied to rollers only cannot reach pin-bushing joints, and therefore,
cannot retard chain elongation due to wear. The lengthening of chains in
service results from wear on pin and bushing surfaces, not rollers.
When lubricating multiple
strand chain, it is important that lubricant be directed to each row of
chain linkplates.
In conveyor applications
oil should be directed between the rollers and bushings as well as between
the chain linkplates.
The following table indicates
the lubricant viscosity recommended for various surrounding temperatures:
| Recommended
Grade |
Temperature,
oF |
| SAE 5 |
-50 to + 50 |
| SAE 10 |
-20 to + 80 |
| SAE 20 |
+10 to +110 |
| SAE 30 |
+20 to +130 |
| SAE 40 |
+30 to +140 |
| SAE 50 |
+40 to +150 |
There are three
basic types of lubrication for roller chain drives. Close adherence to
the recommended type of lubrication is essential to obtaining maximum service
life of a chain drive.
The recommended type of lubrication
as shown in the horsepower rating tables is determined by the chain speed
and the amount of power transmitted.
Manual
or drip lubrication. (Type A)
Oil should be applied periodically
between the chain linkplate edges with a brush, spout can, or drip lubrication.
Oil
bath or oil slinger. (Type B)
With bath lubrication the
lower strand of chain runs through a sump of oil in the drive housing.
The oil level should reach the pitch line of the chain at its lowest point
while operating. Only a short length of chain should run through the oil.
A typical drive arrangement
for bath lubrication is shown in the illustration below.
Drive arrangements which permit
long length of chain to travel through the oil should be avoided as overheating
or foaming may result. |
