Flexible Pipe Annular Space Free Volume Measurement
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Solution Overview
Problem
Current methods for determining the free volume of an annular space in flexible pipes are inefficient, often requiring significant gas diffusion and leading to imprecise measurements, which can result in errors and increased corrosion risk due to the accumulation of corrosive gases.
Innovation Solution
A method involving a regulation and control system that uses a vacuum pump to depressurize the annular space and inject a measuring gas to calculate the free volume using pressure and flow measurements, allowing for precise determination without relying on natural gas diffusion, thus reducing corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gas diffusion is used to fill the annular space for measurement, then the measurement can be performed, but the process becomes long and tedious for impermeable inner sheaths
Solution Approach 1:
The patent applies preliminary action by pre-filling the annular space with a controlled amount of gas before measurement begins. This eliminates the need to wait for slow natural diffusion through impermeable inner sheaths, immediately establishing conditions suitable for accurate free volume measurement without time loss.
2Measurement precision
If a significant quantity of gas is allowed to diffuse into the annular space, then measurement can be performed, but the measurement becomes imprecise due to small pumped gas quantity
Solution Approach 1:
The patent pre-introduces a controlled quantity of gas into the annular space before pumping begins. This preliminary action ensures that sufficient gas is available for measurement while maintaining precise control over the total gas quantity, avoiding the imprecision that arises from attempting to pump out large diffuse quantities.
Solution Approach 2:
The patent changes the parameter of gas introduction from passive diffusion to active controlled injection. By controlling the amount and timing of gas introduction, the system optimizes the balance between having enough gas for measurement and maintaining measurement precision, regardless of the inner sheath's permeability characteristics.
3Measurement precision
If gas is allowed to accumulate in the annular space before pumping, then measurement can be performed, but corrosion risk increases due to corrosive gas accumulation
Solution Approach 1:
The patent performs preliminary gas introduction and immediately follows with pumping operations. This preliminary action sequence minimizes the time that corrosive gases can accumulate in the annular space, reducing corrosion risk while still providing sufficient gas for accurate measurement.
Solution Approach 2:
The patent rushes through the measurement process by introducing gas and immediately performing pumping and measurement without prolonged accumulation phases. This approach skips the harmful intermediate state where corrosive gases could cause damage, transitioning quickly from gas introduction to measurement while maintaining measurement accuracy.
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 approach enables precise and timely evaluation of the free volume, extending the lifespan of flexible pipe components by reducing corrosion and providing accurate integrity monitoring.
Implementation Method 1
a vacuum pump to depressurize the annular space
Implementation Method 2
by diffusion of gases from the fluid circulation passage
Implementation Method 3
condensation of water vapor diffused through the annulus
Data Source
Figure 1
Figure 2~3
AI summary
A method for determining the free volume of an annular space of a flexible pipe and associated system comprising the following steps: • depressurising and isolating the annular space (24); • recording a first pressure and the temperature prevailing in the annular space (24); • injecting a given amount of a measuring gas into the annular space (24) and isolating the annular space (24), the annular space (24) remaining under negative pressure following the injection and isolation; • measuring the given amount of measuring gas; • recording a second pressure prevailing in the annular space (24), following isolation of the annular space (24); • determining the free volume of the annular space (24), on the basis of the first pressure, the second pressure, the temperature and the measurement of the given amount of measuring gas.