Hold-Back Bushing Grooves for Reliable Subsea J-Lay Pipe Restraint
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Solution Overview
Problem
Current hold-back systems for J-lay operations in subsea pipeline installation, such as friction clamps and J-lay collars, are either costly, complex to implement, or compromise thermal insulation, posing safety risks and inefficiencies in deep water installations where high hold-back capacity is required.
Innovation Solution
A hold-back bushing or travelling clamp with radially inner surfaces featuring circumferentially-extending grooves and frusto-conical faces engages with external hold-back formations integral to the pipeline's thermally-insulating coating, providing a reliable and cost-effective mechanical connection without disrupting thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If friction clamps are used to hold back the pipeline, then hold-back capacity is improved, but reliability deteriorates because there is nothing to hold the pipeline if it starts to slip
Solution Approach 1:
The patent replaces the friction-based mechanical holding system with a geometric interlocking system. The bushing features frusto-conical faces that engage with complementary frusto-conical hold-back formations on the pipeline, creating a mechanical lock that prevents slipping without relying on friction forces.
2Reliability
If J-lay collars are used to provide mechanical connection, then reliability is improved, but device complexity and cost increase due to forged collars and subsequent coating operations
Solution Approach 1:
The patent merges the thermal insulation coating function with the mechanical hold-back function by integrating the hold-back formations directly into the coating structure. This eliminates the need for separate forged collars and subsequent coating operations, reducing device complexity while maintaining reliability.
Solution Approach 2:
The thermal insulation coating serves dual functions: providing thermal insulation and providing mechanical hold-back engagement features. The hold-back formations are formed as integral parts of the coating, allowing the coating to perform both its traditional insulation role and the new mechanical engagement role.
3Reliability
If forged collars are used for mechanical engagement, then reliability is improved, but manufacturing cost and time increase due to expensive forged pieces and welding operations
Solution Approach 1:
The patent replaces expensive forged steel collars with hold-back formations made from the thermal insulation coating material, which is relatively inexpensive and already present on the pipeline. The formations are created through molding or shaping the coating material rather than expensive forging and welding operations.
4Force
If friction clamps with embedded pads are used to increase contact area, then hold-back capacity is improved, but the system remains vulnerable to slipping on poor surface finishes
Solution Approach 1:
The patent replaces the friction-based mechanical holding system with a geometric interlocking system. The bushing features frusto-conical faces that engage with complementary frusto-conical hold-back formations on the pipeline, creating a mechanical lock that prevents slipping without relying on friction forces.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the load-carrying capacity of the hold-back system, reduces offshore fabrication complexities, ensures continuous thermal insulation, and improves safety by eliminating the need for expensive forged collars and subsequent coating operations, while maintaining high frictional engagement and load distribution.
Implementation Method 1
The faces are frusto-conical and engage with frusto-conical hold-back formations that are integral to a thermally-insulating coating of the pipeline. The grooves are arranged to receive the hold-back formations.
Data Source
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AI summary
A hold-back bushing (50) or travelling clamp for use in J-lay operations. The bushing (50) or clamp is annular and has a radially inner surface that comprises at least one circumferentially-extending groove arranged to receive one or more external hold-back formations (36) projecting radially from a pipe joint (32). The or each hold-back formation (36) is a ring that extends continuously around the pipe joint (32) circumferentially. The or each groove (54) is defined by a pair of oppositely-inclined generally frusto-conical faces (56, 58) that converge with each other in a radially outward direction.