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Mounting Bearings Using Hydraulic Techniques
SKF pioneered hydraulic mounting
techniques
SKF invented hydraulic techniques for
mounting bearings in the 1940 s. Since then, the SKF hydraulic methods
have been further developed to become the preferred mounting methods for
larger bearings as well as other components. These techniques have
helped to simplify bearing arrangements and facilitate correct and easy
mounting.
With the SKF hydraulic mounting techniques
you can achieve:
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More control, allowing precision,
accuracy and repeatability to be maintained
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Minimum risk of damaging the bearings
and shafts
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Less manual effort
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Greater operator safety
The SKF Oil Injection Method
Makes bearing mounting an easy task
The SKF Oil Injection Method allows
bearings and other components with an interference fit to be fitted in a
safe, controllable and rapid manner. The method does not require keyways
to be machined on the shaft, saving valuable time and money in materials
and production. Interference fits (also known as shrink fits) have long
been recognised for their reliability in transmitting large torsional
loads. Very often interference fits offer the only solution when
connecting hubs to shafts with intermittent or fluctuating loads.
The SKF Oil Injection Method is used to
mount bearings on tapered seatings in combination with a hydraulic nut.
The method, which is used for many bearing applications, can also be
found in other applications, such as:
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Couplings
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Gear wheels
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Railway wheels
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Propellers
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Built-up crankshafts
Tapered shafts
The concept
Injecting oil between two tapered surfaces creates a thin oil film,
which reduces the friction between them, thereby significantly reducing
the mounting force required. The thin oil film also minimises the risk
of metallic contact when mounting, reducing the risk of
component damage.
The preparation
During manufacture the shafts are prepared with oil ducts and grooves.
For technical information on how to prepare the shafts, consult an SKF
application engineer.
The action
Bearings are mounted by pushing them up the shaft with the aid of an SKF
HMV .. E nut.
The force to mount the bearing is reduced
if oil is injected between the shaft and the bearing. This is often done
with larger size bearings.
The SKF Oil Injection Method
Easy, quick and effortless bearing
dismounting
When using the SKF Oil Injection Method
the mating surfaces are separated by a thin film of oil injected under
high pressure, thereby virtually eliminating the friction between them.
The method is versatile as it can be used for dismounting bearings and
other components mounted on either cylindrical or tapered seatings. When
dismounting bearings mounted on cylindrical seatings, the injected oil
can reduce the required pulling forces by up to 90%.
Subsequently, the physical effort required
when using a puller to remove the bearing from its seating is reduced.
When using the Oil Injection Method to dismount bearings mounted on
tapered seatings, the interference fit is completely overcome by the
injected oil. The bearing is then ejected from the seating with great
force, making the use of a puller unnecessary.
In this case, a stop-nut must be used to
control the ejection of the bearing.
The method, which is used for many bearing
applications, can also be found in other applications, such as:
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Couplings
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Gear wheels
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Railway wheels
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Propellers
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Built-up crankshafts
Cylindrical shafts
The concept
By injecting oil of a certain viscosity between two shrink fitted
surfaces, the mating surfaces will be separated by a thin oil film.
The dismounting force required is thus
greatly reduced. The thin oil film also minimises the risk of metallic
contact when dismounting, reducing the risk of component damage.
The preparation
During manufacture the shafts are prepared with oil ducts and grooves.
For technical information on how to prepare the shafts, consult an SKF
application engineer.
The action
Dismounting the bearing is made easy by pumping oil under pressure
between the mating surfaces. Once the oil pressure has built up, the
component can be removed from the shaft with a minimum of effort.
Tapered shafts
The concept
Injecting the oil between two tapered surfaces will create a reaction
force which could be quite substantial as the oil will also act as a
"hydraulic cylinder" which can push the outer component off.
The preparation
During manufacture the shafts are prepared with oil ducts and grooves.
For technical information on how to prepare the shafts, consult an SKF
application engineer.
The action
Bearings are dismounted by injecting oil between the mating surfaces and
when sufficient pressure is reached, the bearing will be pushed off. A
nut is required to keep the bearing from sliding off the shaft.
The SKF Drive-up method
Accurate axial drive-up of
spherical roller and CARB® bearings
The SKF Drive–up Method is a well–proven
method of accurately achieving the adjustment of spherical roller and
CARB® bearings, mounted on tapered seatings, which is unique
to SKF. The correct fit is achieved by controlling the axial drive–up of
the bearing from a predetermined position. The method incorporates the
use of an SKF HMV ..E hydraulic nut fitted with a dial indicator, and a
high accuracy digital pressure gauge, mounted on the selected pump.
Special hydraulic pressure tables have
been developed, providing the required pressures, for each bearing type.
This enables accurate positioning of the bearing at the starting point
from where the axial drive–up is measured.
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Reduces the use of feeler gauges
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Greatly reduces the time to mount
spherical roller and CARB® bearings
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A reliable and accurate method of
adjustment
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The only suitable way to mount sealed
spherical roller and CARB® bearings
The SKF Drive-up Method -
Patent protected
Fig. 1
Fig. 2 One sliding surface
Fig. 3 One sliding surface
Fig. 4 Two sliding surfaces
Fig. 5 Two sliding surfaces
Step by step procedure
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Ensure that the bearing size is equal
to the HMV E-nut. (Otherwise the pressure in the table must be
adjusted.)
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Determine whether one or two surfaces
slide during mounting; see figures 2 - 5.
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Lightly oil all mating surfaces with a
thin oil, e.g. SKF LHMF 300, and carefully place the bearing on the
shaft.
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Drive the bearing up to the starting
position by applying the HMV E-nut pressure found in the table.
Monitor the pressure by the gauge on the selected pump.
SKF hydraulic pump 729124 SRB is suitable for hydraulic nuts smaller
than or equal to HMV 54E. SKF TMJL 100SRB is suitable for hydraulic
nuts smaller than or equal to HMV 92E while TMJL 50SRB is suitable
for nuts smaller than or equal to HMV 200E.
As an alternative the SKF digital pressure gauge TMJG 100D can be
screwed directly into the hydraulic nut.
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Drive the bearing up the taper by the
required distance Ss.
The axial drive-up is best monitored by a dial indicator. The SKF
hydraulic nut HMV E is prepared for dial indicators.
Normally, the bearing is now mounted with
a suitable interference on the shaft and a suitable residual clearance.
For abnormal operating conditions, hollow
shaft, very accurate requirements on residual clearance etc., the
drive-up must be adjusted. The SKF Drive-up Method CD-ROM can calculate
the correct drive-up for such conditions. Otherwise please contact SKF
or skf.com/mount. |
