Ram Blowout Preventer Backup Ring for Seal Extrusion Gaps
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Solution Overview
Problem
Ram-style blowout preventers face challenges in maintaining seal integrity at high wellbore pressures due to extrusion gaps and material susceptibility, leading to potential leakage and failure.
Innovation Solution
An anti-extrusion apparatus featuring a backup ring with a compressible cross-sectional profile that reduces the extrusion gap by flattening and decreasing its inner diameter upon axial loading, supported in an annular groove adjacent to the primary seal, effectively minimizing or eliminating the gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the extrusion gap is decreased by making the inner diameter of the ram block recess close to the outer diameter of the tubular, then seal extrusion resistance is improved, but the risk of metal-to-metal contact and damage increases due to tolerance variations and misalignment
Solution Approach 1:
A backup ring is introduced as an intermediary component between the primary seal and the ram block recess. The backup ring has an inner diameter that is larger than the tubular outer diameter, creating a buffer zone. This intermediary structure prevents direct metal-to-metal contact while providing mechanical support to the seal, resolving the contradiction between reducing extrusion gap and preventing damage.
Solution Approach 2:
The backup ring is positioned in advance within the ram block recess to provide protective cushioning for the primary seal. By having this protective structure in place before pressure events occur, the system preemptively prevents seal extrusion and metal-to-metal contact damage, addressing the contradiction between seal protection and tolerance accommodation.
2Ease of operation
If larger tolerances are used for the inner diameter of the ram block recess to accommodate off-center tubulars, then ease of operation is improved, but the extrusion gap size increases leading to seal failure
Solution Approach 1:
The backup ring acts as a mediator that decouples the tolerance relationship between the ram block recess and the tubular. The backup ring's inner diameter is intentionally larger than the tubular, absorbing the tolerance variations and misalignments. This allows larger recess tolerances for ease of operation while maintaining seal integrity through the backup ring's protective presence.
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
The solution enhances seal integrity and pressure capability, allowing blowout preventers to maintain sealing effectiveness even at high pressures up to 10,000 psi by minimizing extrusion gaps and preventing seal failure.
Implementation Method 1
the ring profile flattens and the inner diameter diminishes to reduce the extrusion gap
Implementation Method 2
The backup ring is flexible, having a cross-sectional ring profile axially compressible between a resting position and compressed position
Data Source
AI summary
A blowout preventer (BOP) and a seal anti-extrusion apparatus is provided for well control about a tubular such as a polish rod. Each of opposing ram blocks support a semi-circular primary seal and at least one downstream backup ring. An extrusion gap is formed between the ram block and the rod. The backup ring has profile that is axially compressible by the primary seal when activated, causing an inner diameter diminish, and closing the extrusion gap for improved sealing integrity of the primary seal.