Marine Riser Mechanical Connections High Strength Steel
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Solution Overview
Problem
Traditional marine risers face challenges in achieving pressure level ratings above 15 ksi due to component heaviness, handling issues, and difficulty in achieving uniform weld properties, while also requiring corrosion resistance and compliance with regulatory standards.
Innovation Solution
The use of higher strength steels like API grade C110 and C125, which are NACE certified, allows for the creation of marine riser components with threaded or mechanical connections, eliminating the need for welding and enabling pressure ratings up to 20 ksi or more, while maintaining corrosion resistance and improved handling and assembly efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If components are scaled up to achieve pressure ratings above 15 ksi, then pressure rating is improved, but weight increases significantly and handling becomes difficult
Solution Approach 1:
The riser system is divided into multiple modular components (riser joints, collars, auxiliary lines, receptacles, stabs) that can be assembled together. This segmentation allows each component to be optimized independently for strength-to-weight ratio while maintaining overall system pressure integrity above 15 ksi.
Solution Approach 2:
The patent employs composite construction combining high-strength steel materials (grade C110 or C125) with optimized geometric designs. This composite approach achieves the necessary pressure ratings above 15 ksi while reducing component weight compared to traditional solid thick-walled constructions.
2Strength
If component thickness is increased to achieve higher pressure ratings, then pressure rating is improved, but weld uniformity becomes difficult to achieve
Solution Approach 1:
The patent extracts the welding process from the assembly methodology and replaces it with mechanical threading and bolting operations. By removing welding from the construction process, the difficulty of achieving uniform welds through thick components is completely eliminated, while maintaining pressure integrity above 15 ksi through precision-machined threaded connections.
Solution Approach 2:
The patent substitutes thermal welding processes with mechanical fastening systems (threaded pins, boxes, and bolts). This mechanical substitution eliminates the welding uniformity problem entirely, as the precision-threaded connections provide consistent, controllable, and verifiable joint strength without the variability inherent in welding thick materials.
3Ease of manufacture
If traditional welding is used for assembly, then manufacturing simplicity is maintained, but corrosion resistance and regulatory compliance become problematic
Solution Approach 1:
The patent changes the material parameters by selecting high-grade corrosion-resistant steels (C110 or C125) and changes the connection parameters by using mechanical fastening instead of welding. This dual parameter change maintains manufacturing simplicity while achieving the required corrosion resistance for marine environments and compliance with regulatory standards.
Solution Approach 2:
The patent uses composite material construction combining corrosion-resistant steel alloys with protective coatings and cathodic protection systems. This composite approach maintains ease of manufacture through standardized components while providing superior corrosion resistance compared to traditional welded structures, ensuring regulatory compliance in marine environments.
Data Source
AI summary
A marine riser having a pressure level rating of twenty ksi or more includes riser tubulars and auxiliary lines that are made of steel having an API grade C110 and C125 and is NACE certified. The riser tubulars and auxiliary lines are not welded, but are assembled via threaded, clamped, stabbed or other mechanical and/or hydraulic connections. Some of the connections may be pre-assembled to reduce assembly time on the drill ship.