Patent ID: 8347694
Filing Date: 2013-01-08
Classification: F16K,G01N,Y10T

Abstract:
1. A method of measuring the BTU content of an LNG sample from a source of LNG to prevent backflow of portions of the sample through a probe and back into the source which disrupts the integrity of the LNG sample, said method comprising: positioning at least a portion of a probe in a source of LNG, where LNG in said source is stored at about −250° F., said probe defining a sample flow path for the LNG; extracting an LNG sample through a pressure responsive check valve in the sample flow path of the probe, said pressure responsive check valve having a valve seal in the form of an annular ring having two generally opposing planar surfaces with a centrally located aperture that further defines the sample flow path; passing the LNG sample from the probe through a piping system and a second check valve to a vaporizer unit where the LNG sample is warmed and changed from a liquid phase to a gas phase natural gas sample, the second check valve preventing reverse flow of the gas phase natural gas sample from the vaporizer unit into said piping system; passing the gas phase natural gas sample through an accumulator and warming the gas phase natural gas sample to a temperature above 32° F.; passing the gas phase natural gas sample into an analyzer where the BTU content of the gas phase natural gas sample is determined; and preventing backflow of any components from said piping system back to the LNG source in the event of an unwanted vaporization of at least a portion of the LNG sample in said piping system by selective closing of the pressure responsive check valve, which exposes one of the two generally opposing planar surfaces of the valve seal to liquid phase LNG and the opposing planar surface to the gas phase of the components during an unwanted vaporization of at least a portion of the LNG sample in said piping system.