Steel Catenary Riser Connector Tooth Alignment via Pre-Compression
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Solution Overview
Problem
Current designs for small-diameter Steel Catenary Riser (SCR) connectors fail to withstand high pressures and depths due to tooth misalignment caused by Poisson's effect and limited strain, leading to engagement issues and potential disengagement under tension and bending loads.
Innovation Solution
A coaxial parallel-thread connector design that minimizes tooth contact stresses by maintaining constant tooth spacing and increasing engagement depth through external metal addition to the box member, along with methods like using pressurized fluid and strategic groove placement to align teeth and reduce make-up pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coaxial parallel-thread connector design is used for small-diameter SCRs, then connector engagement is achieved, but tooth misalignment occurs due to Poisson's effect causing engagement issues
Solution Approach 1:
The patent applies preliminary anti-action by pre-compressing the pin member before connector engagement. This pre-compression counteracts the Poisson's effect that would otherwise cause tooth misalignment during engagement. The pre-compression is achieved through a compression device that applies axial force to the pin member, reducing its length and adjusting tooth spacing before the pin and box members are forced together, thereby preventing tooth misalignment from occurring during the engagement process.
Solution Approach 2:
The patent utilizes parameter changes by modifying the physical state of the pin member through compression. By changing the length and tooth spacing parameters of the pin member through pre-compression, the system compensates for Poisson's effect. The compression ratio and pre-compression force are controlled parameters that are adjusted to achieve proper tooth alignment while maintaining reliable engagement under high pressure and tension conditions.
2Strength
If high pressure and depth conditions are withstood, then connector strength is sufficient, but tooth contact stresses increase causing potential disengagement
Solution Approach 1:
The patent applies preliminary anti-action by pre-compressing the pin member to reduce tooth contact stresses during operation. The pre-compression creates initial contact pressure that distributes loads more evenly across the tooth interface, preventing excessive stress concentrations that would lead to disengagement under high external pressures and tension loads.
Solution Approach 2:
The patent introduces an intermediary compression device that acts as a mediator between the pin member and external loading conditions. This device applies controlled pre-compression to the pin member, creating an intermediate stress state that protects the tooth interface from excessive contact stresses during connector operation under high pressure and depth conditions.
3Ease of operation
If strain is increased to allow sufficient expansion for teeth engagement, then connector engagement is achieved, but connector diameter increases
Solution Approach 1:
The patent utilizes parameter changes by controlling the compression ratio of the pin member. Instead of requiring large strain values that would increase connector diameter, the system uses optimized pre-compression parameters that achieve sufficient tooth engagement with minimal dimensional changes. The compression ratio is carefully controlled to balance engagement requirements with compact connector geometry.
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
Enables reliable engagement and stability of small-diameter SCR connectors under high pressure and depth conditions, preventing disengagement and ensuring a secure connection.
Implementation Method 1
a system of using a pressurized fluid between the teeth to minimize the contact pressure may be used
Implementation Method 2
Poisson's ratio, also known as the coefficient of expansion on the transverse axial, is the negative ratio of transverse to axial strain. When a material is compressed in one direction, it usually tends to expand in the other two directions perpendicular to the direction of compression.
Data Source
AI summary
Methods that may be employed to help to equalize the length of the teeth on a pin-and-box SCR connector during make-up include locating the make-up groove on the box at the far box end away from the pipe end. This causes the make-up force to tension and stretch the box to make it longer. Additionally or alternatively placing grease or other fluid in the nib groove creates a resistance force to nib entry. The grease or fluid exits through a nib vent port in the box while creating a resistance that compresses the pin and stretches the box causing the tooth spacing of the pin and the box to be similar. Providing a ring groove at both ends of the box allows a tensioning device to be used to tension the box causing box elongation, which equalizes the tooth length of pin and box members during connector make up.