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The ROYAL NAVY decided to upgrade their Trafalgar class of nuclear powered attack submarines in a major refit programme, which included the propulsor systems and stator shrouding. The aim was to improve performance and lengthen serviceability for many years to come.When looking at the propulsor blading and stator shrouding, the need for controllability and accuracy of residual load was critical when considering the choice of bolts. PILGRIM already had a long history of supplying high integrity bolting solutions to both the ROYAL NAVY and BAE SYSTEMS from the early 1970’s onward. So it was an obvious choice to contact PILGRIM for support.
PILGRIM selected their Radial Fit Bolts which comprised of a 90mm Ø and 60mm Ø bolts to secure each of the new propulsor blades to the hub. The 90mm Ø bolts provide radial location and axial clamping forces while the 60mm Ø are to function as locating dowels and provide additional clamping forces. Bolts of the same design are being used on the stator shroud assembly securing it to the hull.
The bolts are fitted in a clearance condition and then hydraulically installed to provide a perfect interference fit by drawing the bolt body into a matching tapered sleeve, expanding the sleeve. The bolt is finally tensioned.
