Polyurea greases typically perform well in
smaller ball bearings.
Solid lubricants can be used in very
demanding applications. These are oil-filled
polymers, or grease and polymer mixtures
that solidify once heated and cooled. Solid
lubricants can eliminate problems with
grease leakage and emulsification when
water is present.
Due to the wide array of products along
with price and availability, both a lubrication specialist and the bearing manufacturer should be consulted before making a
final lubricant selection.
All bearings should be manufactured
using components produced from high
purity material. While bearings are most
commonly produced from SAE 52100
chrome steel, for most food processing
applications, martensitic stainless steel,
similar to AISI 440C, is recommended.
400 series stainless steel offers the best
combination of corrosion resistance and
For certain sizes of ball bearings,
nitrogen-enhanced martensitic stainless
steel is also available. This material is
more expensive, but offers up to five times
the corrosion resistance when compared
to traditional “440C type” materials. This
material also exhibits very low noise levels
and extended fatigue life due to its fine
structure that contains smaller chromium
nitrides (as opposed to chromium car-
Bearing components such as shields,
slingers and cages should be manufactured from AISI 302 or 304 stainless steel.
While deep groove ball bearings can be
manufactured from AISI 300 series steel,
which has outstanding corrosion resistance
when compared to martensitic 400 series
steels, they typically are not used in food
processing applications due to their compromised fatigue strength. Load ratings
for ball bearings manufactured from 300
series austenitic steel are approximately
20% of the ratings for 400 series. However,
if the applied loads are very light they
could be considered.
If bearings are required to operate
immersed in water or resist chemical
attack, hybrid ball bearings can be used.
The rings are produced from martensitic
stainless steel, and the balls are ceramic-silicon nitride. The bearing cage can be
produced from a fluoro-resin or Teflon,
which provides lubrication. These bearings
are maintenance-free and extend life in
these severe conditions.
Mounted bearings are used extensively
in food processing equipment and conveyors. This type of bearing usually consists
of a radial ball bearing, sometimes a roller
bearing, mounted and held within a housing. The bearing inside is known as an
insert. Various housing styles allow for different mounting arrangements. One of the
more common housing configurations is
known as a pillow block.
Insert bearings should be produced
from 440C stainless steel. Other options
to consider for the insert are AISI 52100
chrome steel bearings that are either zinc
chromate plated or black oxide coated.
Several options are available for corrosion-resistant, food-safe housings.
In the meat and poultry sectors, high
strength housings are often required. Cast
or ductile iron housings with electro less
nickel plating offer strength and can withstand most wash downs with the added
benefit of being cost effective. However,
cast stainless steel, 300 series, is the best
choice when facing high concentrations
of chlorine or other chemicals in the wash
down solutions. Thermoplastic housings
are an effective alternative in high moisture
environments with caustic wash down
solutions. While they are not as strong, they
are light weight and do not chip or flake as
compared to a housing with plating.
Housing surfaces should also be smooth
with flat mounting bases without recessed
areas. This assists with effective wash
down and eliminates the possibility of food
by-products or debris getting caught under
the mounting surfaces which can lead to
In food processing plants, bearings are
continuously exposed to liquids and various types of particulate debris. Sealed or
shielded bearings are the best option for
keeping foreign debris out of the interior of
the bearing and keeping lubricant in.
The most common bearing seal material is a nitrile rubber. This type of seal is
typically Buna-N bonded to a steel insert.
The seal is fixed into a groove in the outer
ring. The maximum operating temperature
…equipment must be designed to withstand the rigors and
safety constraints of the food processing industry.