Approach to monitor large two-phase LNG flows

A new version of a system to monitor the average void fraction, φ, the quality, x, and the mass flow rate, G, of two-phase liquefied natural gas (LNG) flows is offered. It is based on a combination of a gamma-densitometer with a Cs-137 radioactive source and a narrowing device. The metrological characteristics of this system are estimated and its practical realization is substantiated. A model of ID =100 mm has been manufactured and tested at the State Primary Special Standard of the Unit of Mass Flow Rate of Gas-Liquid Mixtures GET 195-2011 (Kazan, Russia) with simulated two-phase flows “Exxsol - compressed air”. The offered system can be used for pipelines up to ID =500 mm by applying a gamma source with the necessary activity. The experiments on GET 195-2011 have shown that the void fraction error and the relative mass flow rate error for Exxsol do not exceed 5% and 2%, respectively, at φ<50%. It appears to be suitable for practical application. If one adds a second gamma-source (for example, Am-241) to the proposed system, it can serve as a separationless three-phase flow-meter for mixtures “oil-gas-formation water”.