Pilgrim Eliminates Bolts From the Blue
Removing the tail shafting from Caledonian MacBraynes Isle of Lewis ferry, which runs from Ullapool to Stornaway, is a regular operation at overhaul and for survey. Recognising that the time consuming task would be necessary a number of times over the ships remaining 20 to 25 year operational life, the owners wanted a solution installed that would overcome the unpredictable characteristics of conventional coupling bolts.
Reviewing the bolting problems experienced each time the shafting had been removed, the remedy decided upon was the installation of hydraulically actuated radial fit coupling bolts from Oldham UK based Pilgrim International. This course of action has eliminated all problems encountered with conventional bolting and means any future splitting of the flanges and their re-assembly can be carried out to a reliable and predictable schedule.
Through their design and hydraulic operation, the Pilgrim bolts also help achieve accurate alignment and concentricity of the coupling which in turn contributes to maintaining optimum balance and smoother running.
Caledonian MacBrayne’s Fleet Technical Manager, Scott Ure, said, ‘The annual inspection and survey at the River Dee Ship Repairers Dry Dock in Aberdeen was the ideal opportunity to install the Pilgrim bolting.
This was completed well within the planned schedule, demonstrating the serious benefits of the bolt design.
This will now help maintain planned project time scales and therefore cost schedules whilst in dry dock.’
Being hydraulically actuated, the Pilgrim bolt design provides a taper shaft bolt and matching sleeve with parallel outer diameter. These are installed and removed in a clearance condition. Using hydraulic power to draw the bolt into the sleeve, the sleeve expands with tremendous force to give a true interference fit, accurately aligning the bolt holes and preventing slippage in operation.
The bolts are then further tensioned to achieve the clamp load required. This, together with the interference fit, ensures a coupling maintains its optimum alignment and balance.
The bolts can be re-used indefinitely and there is no requirement to re-machine coupling bolt holes damaged while removing seized conventional bolts, saving time and reducing cost compared to conventional force fitted bolting. Fitting the Pilgrim bolts to a relatively small ferry like the Isle of Lewis demonstrates their benefits are not exclusively reserved only for larger vessels.
MJ Information No: 17925
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