Medium- and large-size bearings
Because larger bearings (d > 120 mm) require considerably more force to mount, SKF hydraulic nuts should be used. Where applicable, SKF also recommends preparing the shaft for the oil injection method prior to mounting. When combining the two methods, bearing mounting and dismounting becomes much faster, easier and safer. For additional information about the oil injection equipment required for both the hydraulic nut and the oil injection method, refer to Maintenance products.
Mounting with SKF hydraulic nuts
The hydraulic nut can be positioned onto a threaded section of the shaft (fig. 1), or onto the thread of a sleeve (fig. 2 and fig. 3). The annular piston abuts the inner ring of the bearing (fig. 1 and fig. 2) or a stop on the shaft, which can be either a nut on a shaft thread (fig. 3) or a plate attached to the end of the shaft. Pumping oil into the hydraulic nut displaces the piston axially with the force needed for accurate and safe mounting.
Oil injection method
With the oil injection method, oil under high pressure is injected via ducts and distribution grooves between the bearing and bearing seat to form an oil film. This oil film separates the mating surfaces and considerably reduces the friction between them. This method is typically used when mounting bearings directly on tapered shaft seats (fig. 4). The necessary ducts and grooves should be an integral part of the shaft design. This method can also be used to mount bearings on adapter or withdrawal sleeves if they have been properly prepared.
A spherical roller bearing mounted on a withdrawal sleeve with oil ducts is shown in fig. 5. Oil is injected between all mating surfaces so that the withdrawal sleeve can be pressed into the bearing bore as the bolts are tightened.