Describe about Muff Coupling.

Muff coupling is the conventional flange couplings for the tailshaft. Muff coupling allows the shaft to be withdrawn outboard.

The SKF coupling basically consists of two steel sleeves. The thin inner sleeve has a bore slightly larger than the shaft diameter and its outer surface is tapered to match the taper on the bore of the outer sleeve. The nut and sealing ring close the annular space at the end of the sleeves.

 

When the coupling is in position, the outer sleeve is hydraulically driven on to the tapered inner sleeve. At the same time, oil is injected between the contact surfaces to separate them which overcome the friction between them. Oil is supplied in three places. Two are the forced lubrication and one is by hand pumps or power pump for the driving oil pressure.

When the outer sleeve reaches on to a predetermined position, the forced lubrication pressure is released and drained. Only oil pressure is maintained in hydraulic space until the oil drained from the sleeve drain. After disconnecting the lubrication point, plugs are fitted and rust preventive are applied to protect exposed seatings. A sealing strip is pressed into the groove between the end of the sleeve and the nut.

The grip of the coupling is checked by measuring the diameter of the outer sleeve before and after tightening. To disconnect the coupling, oil pressure is raised to a set pressure in the hydraulic space. Now oil is forced between the sleeves and then outer sleeve slides on the inner sleeve with a rate controlled by release of the hydraulic oil pressure.