SKF OKC Hydraulic Muff Couplers – Handle with Care

2009 August 17
by Chris Brown
An installed SKF Hydraulic Muff Coupler on  5.5" Shaft for a 131' Feadship

SKF Hydraulic Muff Coupler on 5.5" Shaft

Over the past few weeks we have had the pleasure of working on a classic 131′ Feadship.  This yacht has 5.5″, three-section shafts with two sets of hydraulic muff couplers (four total).  The hydraulic muff coupler manufactured by SKF can be incredibly simple if everything goes well.  Removing or installing a hydraulic coupler requires two different hydraulic pumps – one high pressure and one low pressure.  The high pressure pump is unique – up to 40,000 psi which requires special high pressure fittings and a great deal of safety precautions.   High Seas has the right tools for this job.

The hydraulic coupler installation requires an exact fit and a light touch between the steel coupler sleeve and the shaft ends.   There are no fasteners in this system – no bolts, no keys or key-ways.  Approximately 7″ of shaft ends that are inside the coupler must be machined to within tenths of a millimeter to the coupler sleeve.  This particular sleeve was manufactured to 139.7mm (not 140mm) to give you an idea of the tolerances.  No burs or other imperfections are allowed.  Mistakes during installation can result in small burs that will destroy the coupler when the next yard tries to remove it.  

Our thanks to Steve at SKF for his outstanding customer support.  Steve coordinated the expediting of SKF parts for this project and was a wealth of knowledge on a few technical questions.  While we have experience working with hydraulic couplers we are also always open to speaking to the company experts to make sure we are taking advantage of all the tricks and knowledge in highly unique parts.

The SKF Hydraulic Muff Coupler from another view.

Hydraulic Muff Coupler - the long view

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