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126 KRW
Speeds
According to DIN 732 - 2 (draft), the rotational speed factor f n will be found.
To the cylindrical roller bearing NJ220E (single row cylindrical roller bearing of size series 02) the following applies:
f o = 2
f 1 = 0,0003
P 1 = F r , insert according to DIN 732 – 2 (draft) [kN]
n th thermal reference rotational speed [rpm]
d m average bearing diameter [mm]
Q heat energy that can be removed [kW]
If using the lubricating oil ISO VG 100 ithe kinematic viscosity at operating temperature of t = 70 °C
ν = 27 mm²/s
The heat that can be removed from the bearing is estimated by setting, for the bearing seat, Ar from DIN 15312
(draft):
Ar = π · (D + d) · B = π · (180 + 100) · 34 = 29.908 mm²
Using the approximated heat transfer coefficient k q = 0,4 at an ambient temperature of t U = 20 °C , the heat
capacity that can be removed by convection can be estimated with
Q s = k q · A r + (t B - t U ) = 0,4 · 29.908 · 50 · 10 -6 = 0,6 kW
Generally, oil lubrication is used to remove heat. The following rough equation applies under the assumptions below:
t operating temperature 70 °C
t u temperature 20 °C
t ab temperature of the outgoing oil flow 72 °C
t zu temperature of the incoming oil flow 5 °C
VL quantity of the oil flowing through 1,2 l/min
L
QOil = 0,03 · (tab - tz ) · VL = 0,03 · (72 – 65 ) · 1,2 = 0,24 kW
If no process-dependent heat flows are to be considered, the following applies:
Q = Q L + Q
the equation:
L Oil
For the equation of the lubrication film parameter (page 124) ist to be used:
L
= 0,6 + 0,24 = 0,84 kW, thus, the following values are to be used in
-6 -7 2/3
KL = 10
· π/30 · 3600 · 10 · 2 · (27 · 3600) · 140³ · 1/0,84 = 0,52
L
For the load parameters (page 125) ist to be used:
K P = 10 -6 · π/30 · 3600 · 0,0003 · 30 · 10 3 · 140 · 1/0,84 = 0,565
The following approximation equation applies for the rotational speed factor:
(-0,6) (-0,45) (0,77)
fn = 0,98 · KL · (exp(-0,64 · KL · KP ) + 0,072)
f n = 0.98 · 0,52 (-0,6) · (exp(-0.64 · 0.52 (-0,45) · 0.565 (0.77) ) + 0.072) = 0.938
The thermally permissible speed for the cylindrical roller bearing NJ220E under the selected operating conditions is
n zul = f n · n th = 0.938 · 3600 = 3377 rpm
The limiting rotational speed n g = 3900 rpm isn‘t achieved.