Composite Gas Sampling System for LNG Transfer
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Solution Overview
Problem
Conventional composite sampling technologies for liquefied natural gas (LNG) face issues such as contamination from fluid seals, mechanical parts leakage, and dew point dropout, which affect the accuracy and reliability of gas sampling during transfer processing.
Innovation Solution
A novel gas sampling system with a minimum of moving parts, utilizing a programmable logic controller (PLC) to manage solenoid-controlled valves and high-pressure pumps for real-time, periodic analysis of non-composite samples and composite sample creation, maintaining pressure to prevent dew point dropout, and using accumulator lines for selective gas sample storage and analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dome systems are used for composite sampling, then sample collection is achieved, but water seals contaminate the composite sample
Solution Approach 1:
The patent removes the water seal component entirely from the sampling system, replacing it with a diaphragm seal that uses a gas-permeable membrane. This extraction of the harmful water element eliminates contamination while maintaining the pressure isolation function needed for composite sampling.
Solution Approach 2:
The patent introduces a diaphragm membrane as an intermediary between the sampling chamber and the external environment. This membrane allows pressure transmission while blocking water and other contaminants, serving as a mediator that preserves sample purity without compromising system functionality.
2Reliability
If floating piston systems are used, then water contamination is avoided, but mechanical seals and movable parts introduce leakage and contamination
Solution Approach 1:
The patent eliminates all movable parts and mechanical seals from the sampling system by using a static diaphragm-based design. The diaphragm remains stationary while still providing pressure isolation, removing the sources of mechanical failure and contamination associated with moving components.
Solution Approach 2:
The patent replaces the mechanical seal system with a membrane-based sealing approach. Instead of using mechanical floating pistons with seals, the system uses a flexible diaphragm that provides pressure isolation through material properties rather than mechanical contact, reducing wear and contamination risks.
3Productivity
If high pressure is used to evacuate sample chamber, then sampling efficiency is improved, but sample contamination from leakage increases
Solution Approach 1:
The patent pre-pressurizes the sampling chamber with inert gas before initiating the sampling process. This cushioning pressure prevents vacuum formation during sample collection, eliminating the pressure differential that would drive leakage and contamination while maintaining efficient sampling throughput.
4Loss of time
If periodic direct sampling is used, then immediate analysis is enabled, but accurate portrayal of entire transfer process requires extrapolation
Solution Approach 1:
The patent merges periodic direct sampling with continuous composite sampling into a unified system. Samples are collected at regular intervals and automatically combined in a single accumulation chamber, creating a true composite representation of the entire transfer process while maintaining the timing benefits of periodic sampling.
Data Source
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AI summary
A sampling system for collecting periodic composite and/or non- composite samples of vaporized gas during a transfer process from a vaporizer of a cryogenic hydrocarbon liquid including 1) a direct sample pathway to a gas analyzer for instantaneous, real-time vaporized gas analysis, 2) a speed loop pathway for directly collecting fresh vaporized gas samples for subsequent analysis, and 3) a composite sample pathway including a pressurized sample accumulator for collecting a plurality periodically obtained samples of a select volume during the transfer process to create a composite sample of the vaporized gas.