Natural Gas Liquefied NGL Sampling System and Analysis
SUBCOOLED SAMPLE TAKE-OFF PROBE
On NGL applications where the two phases envelope calculated diagram demonstrates a liquid sample at saturated conditions (i.e. already at bubble point) in process line or in a vessel, the light ends will be evolving in sample probe as soon as the system pressure is decreased and/or the system temperature is increased from the point where the sample is taken, such as liquid exiting the vessel where pressure will be reduced due to line losses or pressure drop.
The “Subcooled ISOPROBE 1100” developed for this type of application integrates a chiller for subcooling the first segment probe inside of the vacuum jacket below the bubble point temperature at the process pressure less 0.5 bar.
The SUBCOOLED ISOPROBE 8100 has been designed to cool the sample from inlet to the outlet of first segment with providing an external thermal insulation from atmosphere by high vacuum.
With the conjunction of this high vacuum minimizing heat leak by conduction/convection and the first segment probe temperature cooling, the enthalpy rise can be controlled to be inferior of the subcooling degree and fractionation will not occur in the sampling line even for saturated conditions in the process line or vessel.
Downstream to the subcooled first segment, the LNG sample is vacuum insulated in the second segment up to the sample vaporizer coil exchanger sealed in calorific block temperature controlled. At this critical point, represented on diagram, a small internal volume pressure relief valve is operating the sample transformation of LNG into Natural gas in supercritical state (sample is flashing) to eliminate any fractionated distillation. Inlet / outlet temperatures are monitored with flow control and interlock shut-off system