SKF delivers clever shaft connection
by SKF Australia Pty Ltd on 14/02/2020 7:30 AM
The lifeline of any machine is the effective transfer of energy. The transmission of energy in a propeller shaft is fundamental to the performance of a vessel. A simple and efficient method of connecting the shaft segments is the key to successful power transmission.
SKF OK couplings provide benefits impossible to achieve with traditional couplings. Their simplicity of installation & removal and high torque transmission capacity
are achieved using a powerful friction joint.
The SKF OK concept
When working with OK couplings for shaft connections, you benefit from the advantages of the well-proven SKF oil injection method.
Preparation of the shaft is simple. There are no keyways to machine, no taper and no thrust ring. When mounting an OK coupling, a thin inner sleeve with a tapered outer diameter is slid onto the shaft. A thick outer sleeve with a matching tapered inner surface, then fits onto the inner sleeve.
Ordinary mineral oil is then injected between the sleeves. A built-in hydraulic jack drives the outer sleeve up the taper of the inner sleeve. After the pressurised oil has been released, the residual contact pressure & resulting friction enables the OK coupling to transmit torque and axial loads over the entire area of the shaft. There are no stress raisers due to the absence of a keyway; as a consequence, no fretting occurs when high shock or reversing loads are applied.
SKF’s new development
The OKCX and OKFX are friction-coated couplings that facilitate creative new solutions for the shaft line, while taking full advantage of time-saving SKF oil injection technology, in applications where previously this has not been possible.
The couplings are a milestone in the development of advanced technology and have strengthened SKF Coupling Systems' position as the world leader in shaft connections based on the SKF oil injection method.
Thanks to the increased transmission capacity, it is possible to make substantial cost-savings in the shaft line using the OKCX or OKFX. Large flanged couplings can be replaced Costly reinforcement sleeves can be avoided These are just two examples demonstrating that the OKCX and the OKFX are clever connections with a quick payback.
The inner sleeve of each coupling is coated with carbides utilizing advanced plasma technology This coating increases the friction considerably and gives the OKCX and OKFX couplings a number of advantages over other techniques.
Increased torque capacity means safer connections:
Since the torque capacity is some 50% higher, these new couplings can withstand heavy shock forces and fast rotation switches. It is therefore possible to take advantage of the time-saving, oil injection method in transmissions where previously it was difficult, for instance, in large heavily loaded shafts.
A compact coupling optimizes shaft design:
OKCX and OKFX are robust couplings transferring higher torque, which makes it possible to optimize the design of shaft lines. The shaft diameter can be reduced at the same time as the coupling diameter and length.
Reduced coupling pressure creates opportunities for innovative solutions:
Since the friction is higher, the surface pressure of the coupling can be reduced, if desired as another route to design optimisation. This is particularly valuable when hollow shafts are connected. And because reinforcement sleeves are therefore not necessary, significant cost and production savings can result.