Page 220 - Rollingbearings

3. Life modiication factor, a SKF
SKF LGEP2 is a suitable choice provided a viscosity ratio, κ, of 4 is
Given: conirmed.
LGEP2 has the following properties:
• κ = 4
• η P /P = 0,2 × 132/186 = 0,14 • ν = 200 mm 2 /s at 40 °C (105 °F)
c
u
• 22328 CCJA/W33VA405 is an SKF Explorer bearing • ν = 16 mm 2 /s at 100 °C (210 °F)
• operating viscosity at 75 °C (165 °F) is around 40 mm 2 /s, based on
then, using diagram 10, page 97, for radial roller diagram 13, page 100.
bearings, a SKF = 1,3 • κ = ν/ν = 40/10 = 4 is conirmed
1

⎛ 10 6 w ⎛ C w 10/3 Relubrication interval and quantity
L 10mh = a SKF J J J
⎝ 60 n⎠ ⎝ P ⎠
Experience suggests relubricating the bearings in the vibrating
screen every 75 h with 30 g of grease. The short intervals are needed
= 1,3 × (10 6 /(60 × 756)) (7,3) 10/3 = 21 500 h > 20 000 h to push out contamination, while the reduced quantity limits heat
generation caused by high grease volumes.
Conclusion Using the standard relubrication interval from diagram 2,
SKF bearing 22328 CCJA/W33VA405 is a suitable size to meet the page 112, and input values gives:
rating life requirements.
• n d b = 166 320 × 2 ≈ 330 000
m f
• C/P ≈ 8
Lubrication The relubrication interval is 1 700 h. This needs to be reduced, with
contamination and vibration considered (table 2, page 115), con-
irming approximately the experienced values used for vibrating
screen bearings.
Relubrication quantity is:

Selecting grease or oil G = 0,002 D B = 0,002 × 300 × 102 = 61 g
p
On page 113, table 1 provides limits for the nd value, up to which Standard relubrication of the bearings every 75 h with 30 g of grease
m
grease lubrication is normally a suitable solution in terms of relubri- will maintain adequate lubrication condition.
cation intervals at normal temperatures.
Input values: Initial grease ill

• spherical roller bearing in the 223 series The free volume in the bearing, which should be illed with grease, is
• C/P = 7,3 approximately:
• n d = 756 × (140 + 300)/2 = 166 320
m
π M
From table 1, page 113, the recommended nd limit for C/P ≈ 8 is V = J B (D 2 – d 2 ) × 10 –3 – J J J J
m
150 000, which is somewhat below the actual nd value. The oper- 4 7,8 × 10 –3
m
ating conditions are at the limits where grease lubrication is suitable,
and you can expect short relubrication intervals. But this is not an V = 3,14/4 × 102 × (300 2 – 140 2 ) × 10 -3 – 36,5/0,0078 = 957 cm 3
issue for vibrating screens, and you can select grease lubrication.
For a illing degree of 50%, you need about 430 g of grease per
Grease selection bearing.
You can ind a suitable SKF grease using the SKF bearing grease
selection chart, page 124. Grease selection criteria are:
C.1 Vibrating screen • speed: n d ≈ 166 000 → M to H
• temperature: 75 °C (165 °F) → M
m
• load: C/P ≈ 8 → M
• severe vibrations
• humid outdoor conditions → good rust inhibiting properties

218