Orkot 'TLM Marine' Provides Exact Rudder Post Bearing Solution in MV "Stena Felicity" Refit
Orkot 'TLM Marine' is fast becoming the marine industry standard for reduced maintenance, robust marine bearings, for above or below the water applications. In 1994 'TLM Marine' was specified for repairs to the rudder post bearings of the Stena Sealink Line, multipurpose passenger ferry, MV "Stena Felicity". The 23,500 tonne ferry, which has been operating between Fishguard and Rosslare since 1989, was built in Sweden in 1980 and has a passenger certificate for 1,800 passengers, a crew of 110 and can load 45 articulated lorries and 210 cars.
"Stena Felicity" dry-docked at A & P Appledore's Falmouth yard for repairs to her rudder post bearings and other routine dry-dock maintenance. Steve Rooke is the Senior Chief Engineer of MV "Stena Felicity" and he commented on the incorporation of 'TLM Marine'.
"Each rudder post is supported by an upper and lower bearing in the vertical plane. These were fitted with the original design of segmented Tufnol staves that were locked in the bearing house with stainless steel strips. Excessive corrosion of the lower landing face and the housing at the back of the necessitated the line boring in place of the lower bearing housings, to allow new bearings to be fitted."
The Senior Chief Engineer continued, "The owners, Det Norske Veritas, the classification society and Stena Sealink the charters, agreed not to refit the old obsolete type of bearing, but to replace the upper and lower bearings on both rudder posts with a modern composite type bearing. A & P Appledore presented us with technical literature on Orkot blanks which met our specifications exactly.
A telephone call ensured that 'TLM Marine' blanks of the correct sizes were available for immediate despatch. Whilst the bearing housings were being line bored, the rudder posts had new bronze liners fitted in way of the bearings and the Orkot blanks were machined to size, ready to be shrunk into place. This has allowed us to bring all the clearances back to the manufacturer's tolerances."
Steve Rooke concluded, "To date, we are very satisfied with the performance of the bearings. They will, of course, have a thorough examination when next we dry-dock, which is planned for April 1996."
Orkot, based in Rotherham, England, has monitored closely the success of 'TLM Marine' in many, proven marine applications. The moisture absorption and swell of Orkot is as little as 0.1% after 12 months immersion in sea water, at 23° C, with no change in hardness or mechanical properties. Regular mechanical testing is carried out on production material to ensure uniformity of properties throughout the material, which contributes significantly to the high levels of safety requirements in the working strength for applications such as rudders where the maximum design load approval is only 10 N/mm2. Orkot's ultimate compressive load is in excess of 30 times greater than this value.
One of the particular characteristics of Orkot is a level of elasticity uncommon in other composite materials. It is possible to compress the Orkot composite by as much as 15% of its wall thickness before any permanent set will occur. This value relates to a bearing load in the region of 110 N/mm2 and recovery from this deformation is almost immediate, giving Orkot the unique ability to withstand any significant wear or extrusion from high edge loading and misalignment. The bearing is able to physically deform under stress and increase the load footprint preventing high line or point contact compaction.
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MR JOHN CHER TONSTERN
INDUSTRIAL SUPPLIES
TEL: 741 0733
FAX: 741 0332
