Wiper Seal Assembly for Hydraulic Blowout Preventer
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Solution Overview
Problem
Conventional pressure seals in blowout preventers (BOPs) are prone to damage and degradation from wellbore fluid contaminants, leading to frequent inspection, repair, and replacement due to leakage issues, as they fail to effectively seal the interface between the hydraulic fluid system and the wellbore fluid.
Innovation Solution
A modified annular seal assembly at the piston interface featuring a U-shaped lower housing with an adapter ring, discrete wiper seals, pressure seals, and retainer members to prevent radial and axial movement, forming an annular hydraulic fluid chamber that isolates the hydraulic fluid system from contaminants and pressurized wellbore fluid, using extruded nitrile rubber wiper seals and Polypak™ pressure seals to reduce rolling and twisting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pressure seals are used to separate hydraulic fluid from wellbore fluid, then fluid separation is achieved, but the seals suffer damage and degradation from contaminants leading to frequent replacement
Solution Approach 1:
The sealing function is divided into two separate components: a wiper seal that contacts the rod to remove contaminants, and a pressure seal that seals the hydraulic chamber. This segmentation allows each seal to perform its specific function optimally without the wiper seal degrading the pressure seal through contaminant exposure.
Solution Approach 2:
The wiper seal acts as an intermediary element between the contaminated wellbore environment and the clean hydraulic system. It removes contaminants from the rod surface before they can reach the pressure seal, thereby protecting the pressure seal from damage and degradation.
2Device complexity
If dual-functioning wiper seals are used to provide both pressure sealing and wiping, then both functions are attempted in one component, but the seal is still prone to degradation and frequent replacement
Solution Approach 1:
Instead of using a single dual-functioning seal, the invention segments the sealing system into two distinct seals: a wiper seal for contaminant removal and a pressure seal for hydraulic sealing. This segmentation improves reliability by allowing each seal to be optimized for its specific function rather than compromising performance by attempting to do both functions in one seal.
3Reliability
If conventional pressure seals are used, then fluid separation is provided, but the seals can roll or twist releasing sealed engagement and allowing leakage
Solution Approach 1:
The pressure seal is positioned in a specific location within the hydraulic chamber where it is protected from rolling or twisting movements. The seal groove and retaining structures provide local constraints that maintain the seal's proper orientation and engagement, ensuring stable sealed engagement under varying operating conditions.
Data Source
AI summary
A hydraulically-operated annular blowout preventer, for controlling a wellbore and comprising a wiper seal assembly, is described. The wiper seal assembly comprises a discrete wiper seal, for preventing debris and/or contaminants from the wellbore from entering the hydraulic fluid chamber of the blowout preventer, a discrete pressure seal, positioned below and abutting the wiper seal in the same seal groove, for isolating the hydraulic chamber, and a retainer member for preventing both radial and axial movement of the wiper seal.