Subsea Pressure Compensation Piston with Differential Area
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Solution Overview
Problem
Existing pressure compensation systems for underwater hydraulic systems face challenges in maintaining sufficient pressure at great depths without requiring excessively strong and cumbersome mechanical components, especially when dealing with large volumes of hydraulic fluid and significant pressure differentials.
Innovation Solution
A pressure compensation system using a piston with a larger exterior surface area exposed to seawater pressure and a smaller interior surface area, where the pressure differential is balanced by a gas or hydraulic fluid under pressure applied to a piston rod, allowing for efficient overpressure of the hydraulic fluid within the reservoir, enabling the use of lighter materials and reducing the need for high-strength components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gas charged accumulator is used with high gas pressure to provide motive force, then the accumulator can operate at depth, but the accumulator becomes excessively large and cumbersome requiring high-strength materials
Solution Approach 1:
The accumulator is divided into two separate chambers: a first chamber containing hydraulic fluid and a second chamber containing gas. This segmentation allows each chamber to be optimized independently - the hydraulic fluid chamber can be larger for volume storage while the gas chamber provides pressure compensation, avoiding the need for a single oversized accumulator
Solution Approach 2:
A movable partition wall is introduced as an intermediary between the hydraulic fluid chamber and the gas chamber. This partition wall moves in response to pressure differential changes, automatically balancing the pressures in both chambers and enabling the system to compensate for depth variations without requiring excessive structural strength
2Reliability
If the accumulator is precharged to full gas pressure at the surface, then depth compensation is achieved, but the system becomes complex and requires high-strength sealing over long periods
Solution Approach 1:
The movable partition wall automatically adjusts the gas pressure in the second chamber to match the hydraulic fluid pressure in the first chamber. This self-regulating mechanism eliminates the need for complex external sealing systems and maintains pressure balance without requiring high-strength seals, as the system self-compensates for pressure variations
3Reliability
If a piston with equal interior and exterior surface areas is used, then pressure compensation is achieved, but the system cannot handle large fluid flows and requires excessive spring force
Solution Approach 1:
The partition wall is designed with non-uniform thickness, creating different effective surface areas on either side. The first surface area (facing hydraulic fluid) is larger than the second surface area (facing gas), allowing the system to handle larger fluid flows while maintaining pressure compensation. This local variation in geometry optimizes both flow capacity and pressure balance
Solution Approach 2:
The system changes the geometric parameters of the partition wall to optimize performance. By varying the thickness and surface area distribution, the system achieves both pressure compensation and high fluid flow capacity, eliminating the need for excessive spring force while maintaining reliability
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 effectively maintains internal overpressure in subsea hydraulic systems, allowing for large fluid flows and operation of equipment like BOPs and coiled tubing units, while minimizing the use of high-strength materials and reducing the size and weight of mechanical components.
Implementation Method 1
The outer surface of the piston is greater than the inner surface of the piston and the outer surface is positioned for pressure thereagainst by fluid exterior to the body so that a pressure differential exists due to the pressure exerted by the operational hydraulic fluid and the fluid exterior to the body
Implementation Method 2
A fluid system in fluid communication with the interior of the rod chamber applies fluid under pressure to the piston rod sufficient to adjust the pressure of the operational hydraulic fluid within the reservoir
Data Source
AI summary
Systems and method for operating subsea devices and pressure compensated reservoir systems useful therewith which in certain aspects, include a chamber with a piston therein acted on an exposed side by water, e.g. sea water, to provide operational hydraulic fluid for operating a subsea device, with a piston rod having an end in a separate chamber acted on by a fluid to compensate for a pressure differential between the pressure of the water on one piston side and the pressure of the operational hydraulic fluid on the other piston side.