Hydraulic bolts are a very simple method of flange connection. They reduce the requirement of flange hole preparation and eliminate the need for onsite machining requirements. Also ensures a safe transmission of torque to the propeller by shear and/or by friction force.
Hydraulic bolts consist of an externally tapered bolt which presses over an internally tapered sleeve during its axial displacement. This contact forms the shrink pressing force. A good combination between bolt, sleeve and flange hole, in conjunction with the hydraulic injection method, allows clearance for the bolt until it fits in the flange hole.
Once it is installed in the flange hole, the bolt is tensioned with the tensioning tool providing a very high contact force between the flange faces with minimum effort.