Gas Pipeline Flow Measurement With Liquid Presence Correction
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Solution Overview
Problem
The presence of liquid in gas pipelines leads to inaccuracies in gas flow rate measurements, causing over or under readings, which can significantly impact revenue determination.
Innovation Solution
A system utilizing flow restriction differential pressure and a third tap differential pressure to determine a pressure loss ratio, detecting liquid presence, and iteratively correcting gas flow rate measurements by accounting for over or under readings using Lockhart-Martinelli parameters and gas Froude numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If liquid is present in the gas pipeline, then the gas flow rate measurement is affected, but the measurement accuracy deteriorates causing over or under reading
Solution Approach 1:
The patent uses a third tap differential pressure measurement as an intermediary indicator to detect liquid presence. By measuring the pressure difference between the first tap (upstream of flow restriction) and third tap (downstream of flow restriction), the system can identify liquid presence without directly interfering with the gas flow measurement process. This intermediary measurement enables the system to distinguish between liquid-present and liquid-absent conditions, allowing for appropriate correction of the gas flow rate measurement.
Solution Approach 2:
The patent changes the measurement parameters by introducing a pressure loss ratio calculation that compares the third tap differential pressure to the flow restriction differential pressure. This parameter transformation allows the system to detect liquid presence through changes in pressure distribution patterns. When liquid is present, the pressure loss ratio deviates from expected values, triggering correction mechanisms that adjust the gas flow rate measurement to compensate for the liquid's effect.
2Reliability
If traditional flow measurement methods are used without liquid detection, then the device complexity is low, but the measurement reliability deteriorates due to over or under reading
Solution Approach 1:
The patent makes the flow measurement system multi-functional by enabling it to perform both gas flow rate measurement and liquid presence detection using the same pressure measurement infrastructure. The third tap differential pressure measurement serves dual purposes: it characterizes the flow restriction performance and simultaneously detects liquid presence. This universality allows the system to maintain reliability improvements without proportionally increasing device complexity, as the additional measurement capability leverages existing pressure sensors and tap structures.
Solution Approach 2:
The patent implements feedback by using the third tap differential pressure measurement to provide information about liquid presence back to the gas flow rate calculation process. When the pressure loss ratio indicates liquid presence, the system adjusts the gas flow rate measurement accordingly. This feedback mechanism ensures that the measurement system adapts to changing flow conditions and maintains reliability by compensating for liquid effects rather than requiring completely separate detection and measurement systems.
3Measurement precision
If liquid presence is detected and correction is applied, then the measurement precision is improved, but the device complexity increases due to additional measurements and calculations
Solution Approach 1:
The patent applies preliminary action by pre-calculating the pressure loss ratio relationship between the third tap differential pressure and flow restriction differential pressure under known conditions. This allows the system to have correction factors or lookup tables prepared in advance, so when liquid presence is detected during operation, the correction can be applied quickly without requiring complex real-time calculations. The preliminary characterization of pressure loss behavior reduces the computational burden during actual measurement and correction operations.
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
Accurately quantifies liquid flow and corrects gas flow rate measurements, enabling precise revenue calculations and reducing the need for costly multi-component wet gas meters.
Implementation Method 1
The flow restriction differential pressure information may define a flow restriction differential pressure between a first point along the pipe and a second point along the pipe
Implementation Method 2
A pressure loss ratio may be determined based on the flow restriction differential pressure, the third tap differential pressure, and/or other information. Whether liquid is present in the pipe may be determined based on the pressure loss ratio
Data Source
AI summary
Flow restriction differential pressure and a third tap differential pressure for a pipe are used to determine a pressure loss ratio for the pipe/system that includes a flow restriction. The pressure loss ratio is used to determine whether liquid is present in the pipe. If liquid is determined to be present in the pipe, overread or underread of gas flow rate measurement in the pipe is determined and used to correct gas flow rate measurement for the pipe. The liquid flow rate in the pipe is determined.