Gas-Buffered Pressure Sensing for Corrosive Hot Liquid Flow
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Solution Overview
Problem
Conventional sensors are unsuitable for measuring the pressure and flow rate of high temperature and/or corrosive process liquids due to damage risks from thermal and chemical effects.
Innovation Solution
A pressure sensor is connected via a vertical tube with a buffer gas column that isolates it from the corrosive liquid, using nitrogen gas to maintain a stable interface and protect the sensor, allowing pressure and flow rate measurements through gas-buffered sensors upstream and downstream of a valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensors are directly exposed to the process liquid for measurement, then measurement precision is improved, but the sensor reliability deteriorates due to high temperature and corrosive damage
Solution Approach 1:
A buffer gas (nitrogen or other inert gas) is introduced as an intermediary substance between the process liquid and the pressure sensor. The buffer gas fills the vertical tube connecting the process liquid to the sensor, creating a protective barrier that transmits pressure while isolating the sensor from direct contact with corrosive and high-temperature process liquid, thus maintaining both measurement accuracy and sensor reliability
Solution Approach 2:
The measurement system is segmented into distinct zones: the process liquid zone, the buffer gas zone, and the sensor zone. The vertical tube creates a physical separation where the buffer gas column acts as an intermediate layer, allowing the sensor to measure pressure indirectly without being exposed to harmful conditions
2Reliability
If the sensor is thermally isolated from the process liquid, then the sensor is protected from high temperature damage, but the measurement capability deteriorates due to temperature differences
Solution Approach 1:
The buffer gas serves as a thermal intermediary that allows pressure transmission while providing thermal isolation. The gas column transmits the pressure signal from the process liquid to the sensor but prevents direct thermal contact, protecting the sensor from high temperature damage while maintaining measurement capability through pressure equilibrium
Solution Approach 2:
The system uses pneumatic principles by introducing a compressible gas medium (buffer gas) into the vertical tube. The gas column responds to pressure changes in the process liquid and transmits these changes to the sensor, utilizing gas compressibility and elasticity to maintain pressure equilibrium while providing thermal and chemical isolation
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
Enables accurate measurement of pressure and flow rate of high temperature and corrosive liquids by thermally and chemically protecting the sensor, ensuring reliable operation and real-time reporting.
Implementation Method 1
establishing and regulating column of buffer gas in the vertical tube that isolates the pressure sensor from any corrosive effects of the process liquid
Implementation Method 2
the much lower heat capacity and thermal conductivity of the buffer gas protects the pressure sensor from being damaged by the high temperature of the process liquid
Implementation Method 3
measuring the pressure both upstream and downstream of the valve, using gas-buffered pressure sensors
Data Source
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AI summary
An apparatus for measuring a pressure of a corrosive or high temperature process liquid includes a pressure sensor in communication with the process liquid via a vertical tube. A buffer gas injected into the vertical tube forms a liquid/gas interface at a desired height. The buffer gas supply is then either isolated or regulated so as to cause the buffer gas pressure within the vertical tube to remain equal with the process liquid pressure. The pressure sensor indirectly measures the process liquid pressure by measuring the buffer gas pressure within the vertical tube, while remaining chemically and thermally protected from the process liquid. In embodiments, pressure measurements from a pair of gas buffered pressure sensors located upstream and downstream of a valve are combined with measurements of the process liquid temperature to determine a flow rate of the process liquid through the valve.