Page 234 - Rollingbearings

Bearing execution
Given:

NU 311 ECP 7312 BECBP

Condition of rotation rotating inner rotating inner ring load
ring load
P/C ratio 0,02 0,07 Checking the initial internal clearance
Bore diameter 55 mm 60 mm The current design uses bearings with Normal initial clearance. The
its for the inner and outer rings, and a temperature difference
between the inner and outer rings of 10 °C (20 °F), reduce the intern-
Results: al clearance. Other inluences on the internal clearance are
negligible.
Bearing seat
1. Initial internal clearance
Bearing Dimensional Total radial run- Total axial Ra
tolerance out tolerance run-out tolerance
NU 311 ECP Pair of 7312 BECBP
NU 311 ECP k6� IT5/2 IT5 0,8 µm
min./avg./max. 40 / 55 / 70 μm 22 / 32 / 27 μm
7312 BECBP k5� IT4/2 IT4 0,8 µm
Refer to Bearing data, Refer to Bearing data,
page 504. Values page 392. Axial val-
Housing tolerances obtained from table 3, ues obtained from
page 506. table 4, page 394,
converted to radial
Any wear developing during service may lead to imbalance of the (axial × tan 40°).
impeller, leading to an indeterminate direction of load on the outer
rings of both bearings. 2. Clearance reduction caused by interference its
You can ind tolerances for seats for cast iron and steel housings, Use:
for radial ball bearings, in table 8, page 151. Δr = Δ f + Δ f (Clearance reduction caused by interference its,
2 2
1 1
it
page 184)
Given:
Obtain values for:
NU 311 ECP 7312 BECBP
• factors f and f (diagram 2, page 184)
1
2
Condition of rotation indeterminate direction indeterminate direction • probable its for shafts, Δ (table 14, page 160)
1
of load of load • probable its for housings, Δ (table 20, page 172)
2
P/C ratio 0,02 0,07
Results:
Outer diameter 120 mm 130 mm
NU 311 ECP Pair of 7312 BECBP
Results:
d/D 0,46 0,46
Bearing Dimen- Total radial Total axial Ra
sional run-out run-out f 1 0,78 0,78
tolerance tolerance tolerance
f 2 0,86 0,86

NU 311 ECP K7� IT6/2 IT6 3,2 µm Δ 1 min./avg./max. –32 / –19 / –6 μm –26 / –16 / –6 μm
7312 BECBP K7� IT6/2 IT6 3,2 µm Δ 2 min./avg./max. –20 / 0 / 20 μm –21 / 1 / 23 μm
min./avg./max. –42 / –15 / –5 μm –38 / –12 / –5 μm
Δr it
Axial location
C.3 Centrifugal pump The current design has adequate axial location. Make sure that the difference between shaft, bearing rings and housing, page 184)
3. Clearance reduction caused by temperature difference
lock nut that locates the inner rings of the angular contact ball bear-
Use:
ings is suficiently tightened. Apply the clamp force uniformly around
= 0,012 ΔT d (Clearance reduction caused by temperature
Δr
m
temp
the circumference and respect the abutment dimensions (product
data for 7312 BECBP is on page 414). To avoid distortion of the inner
rings and to achieve the desired axial clearance in the bearing pair,
limit the clamping force. For centrifugal pumps, a clamping force of
C /4 (19 kN) is recommended.
0
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