Page 190 - Rollingbearings

B.7 Bearing execution
Steel cages dependent and subject to ageing The factors Polyamide 46
that most inluence the ageing process are Glass ibre reinforced polyamide 46 (PA46) is
Steel cages can be used at operating tem- temperature, time and the medium (lubri- the standard cage material for some small
peratures up to 300 °C (570 °F) cant) to which the polymer is exposed The and medium- size CARB toroidal roller bear-
relationship between these factors for glass ings The permissible operating temperature
Sheet steel cages ibre reinforced PA66 is shown in diagram 5 is 15 °C (25 °F) higher than for glass ibre
Cage life decreases with increasing tempera- reinforced PA66
Stamped sheet steel cages are made of low ture and the aggressiveness of the lubricant
carbon steel These lightweight cages have Therefore, whether polyamide cages are Polyetheretherketone
relatively high strength and, for some bear- suitable for a speciic application depends on
ing types, can be surface treated to further the operating conditions and life require- Glass ibre reinforced polyetheretherketone
reduce friction and wear in critical ments The classiication of lubricants into (PEEK) is more suitable for demanding con-
conditions “aggressive” and “mild” is relected by the ditions regarding high speeds, chemical
“permissible operating temperature” for resistance or high temperatures than PA66
Machined steel cages cages made of glass ibre reinforced PA66 and PA46 The exceptional properties of
with various lubricants (table 1) The per- PEEK provide a superior combination of
Machined steel cages are normally made of missible operating temperature in table 1 is strength and lexibility, high operating tem-
non-alloyed structural steel To reduce fric- deined as the temperature that provides a perature range, and high chemical and wear
tion and wear, some machined steel cages cage ageing life of at least 10 000 operating resistance Because of these outstanding
are surface treated hours features, PEEK cages are commonly availa-
Machined steel cages are not affected by Some media are even more “aggressive” ble for hybrid and/or super- precision ball
the mineral or synthetic oil-based lubricants than those speciied in table 1 A typical and cylindrical roller bearings The material
normally used for rolling bearings, or by the ex ample is ammonia, used as a refrigerant does not show signs of ageing by tempera-
organic solvents used to clean bearings in compressors In those cases, cages made ture or oil additives up to 200 °C (390 °F)
of glass ibre reinforced PA66 should not be However, the maximum temperature for
used at operating temperatures above high -speed use is limited to 150 °C
Brass cages 70 °C (160 °F) (300 °F) as this is the softening temperature
Polyamide loses its elasticity at low tem- of the polymer
Brass cages can be used at operating tem- peratures Therefore, cages made of glass
Bearing execution Sheet brass cages applications where the continuous operating
peratures up to 250 °C (480 °F)
ibre reinforced PA66 should not be used in
temperature is below –40 °C (–40 °F)

Stamped sheet brass cages are used for
some small and medium -size bearings In

sors that use ammonia, machined brass or
B.7 applications such as refrigeration compres- Cage ageing life for glass ibre reinforced PA66 Diagram 5
steel cages should be used
Cage ageing life [h]
Machined brass cages
100 000
Most brass cages are machined from cast or 2)
wrought brass They are unaffected by most
common bearing lubricants, including syn- 10 000 1)
thetic oils and greases, and can be cleaned
using organic solvents
1 000
Polymer cages

100
Polyamide 66 50 100 150 200
(120) (210) (300) (390)
Polyamide 66 (PA66) is the most commonly Bearing temperature [°C (°F)]
used material for injection moulded cages
Mild lubricants
This material, with or without glass ibres, is Aggressive lubricants
characterized by a favourable combination of
strength and elasticity The mechanical 1) The permissible operating temperature is deined as the temperature that provides a cage ageing life of at least 10 000 operating
properties, such as strength and elasticity, 2) Generally, “aggressive” lubricants have a permissible temperature that is less than 120 °C (250 °F)
hours
of polymer materials are temperature
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