Drilling Riser Flanges with Contoured Bearing Surfaces
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Solution Overview
Problem
Flange assemblies in sub-sea drilling operations face issues with radial displacements and deflections due to manufacturing variances and operational motions, leading to significant bending moments and shear forces on fasteners, which can result in bolt breakage and flange failure.
Innovation Solution
The use of pivotable members within counterbored bolt holes allows for flange displacement without transferring shear forces or bending moments to the fasteners, utilizing washers and nuts with convex and concave bearing surfaces to maintain contact and absorb movements, thereby reducing stress on bolts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flanges are tightened to ensure face-to-face contact, then leakage prevention is improved, but radial displacements and deflections transfer significant bending moments and shear forces to fasteners, reducing the allowable tightening force and potentially causing bolt breakage
Solution Approach 1:
The patent introduces spherical bearing surfaces (concave in flanges, convex in washers/nuts) that allow pivotable movement. This curvature enables the connection to accommodate radial displacements and deflections through rotational movement rather than transferring shear forces to the fasteners, thus maintaining face-to-face contact for leakage prevention while protecting bolt strength
Solution Approach 2:
The invention changes the geometric parameters of the bearing surfaces from flat to spherical, and modifies the fastener configuration to include pivotable members. This parameter change allows the system to transform from a rigid connection that transfers shear forces to a flexible connection that accommodates movement through pivoting, resolving the contradiction between maintaining contact pressure and protecting fastener strength
2Ease of operation
If flanges are subjected to operational motion (ocean currents, vibrations), then operational functionality is maintained, but relative displacements and deflections transfer significant bending moments and shear forces to fasteners, potentially resulting in fastener breakage and flange failure
Solution Approach 1:
The patent transforms the static rigid flange connection into a dynamic system with pivotable members. The spherical bearing surfaces enable the connection to move and adapt during operational motions, allowing the flanges to accommodate ocean currents and vibrations through controlled pivoting rather than transferring damaging forces to the fasteners
Solution Approach 2:
The pivotable members (washers with convex surfaces and nuts with concave surfaces) act as intermediaries between the flanges and the external environmental forces. These intermediaries absorb and accommodate the relative movements caused by ocean currents and vibrations, protecting the fasteners from direct exposure to shear forces and bending moments
Data Source
AI summary
This disclosure includes riser flange assemblies and related methods. Some assemblies include first and second flanges each defining a plurality of counterbored bolt holes and having a plurality of concave bearing surfaces each disposed around one of the counterbored bolt holes, a plurality of bolts each having a head and a male threaded portion, a plurality of washers each having a convex bearing surface configured to correspond to the concave bearing surface of a bolt hole when one of the bolts extends through the washer and the bolt hole and a plurality of nuts each having a convex bearing surface and a female threaded portion configured to receive the male threaded portion of one of the bolts, the convex bearing surface configured to correspond to the concave bearing surface of a bolt hole when one of the bolts extends through the bolt hole and is received in the nut.