The constraints of transfer lines for LNG sampling

Inthe liquefied natural gas sampling lines, the transfer lines must make it possible to transport the vaporized LNG sample to the analyzer without changing its representativeness. The constraints are the same as for the transfer of the natural gas sample to the analyzer.

In case of a risk of condensation or adsorption (this risk depends on the composition of the gas and the temperatures that the line will undergo), the transfer line must be heated at a temperature of at least 10°C above the condensing temperature. For measurements concerning water content and trace-state compounds, the lines will be heated or insulated according to ambient conditions.

The transfer line should be as short as possible and its diameter as small as possible in order to reduce transit time. As a general rule, the length of the sampling line should not exceed a few tens of metres and its diameter should be between 3 and 6 mm (1/8 to 1/4 inch).
316L stainless steel must be used for the vaporized LNG transfer line.

Various applications for all LNG sampling lines

When it comes to analysis of sulphur compounds such as H2S and THT, a complementary treatment to electro-polishing is recommended: SilcoNertTM2000. The latter inhibits the remaining adsorption sites. It is then necessary to use the TrueTube EPS (316L seamless drawn, electropolished, treated and coated tube) SilcoNert™ 2000) from TRACEPAK suitable for critical measures at low ppm and ppb.

However, in the case of a sampling line with a fast loop (continuous), if the sulphur compound contents are likely to vary slightly (as is the case for the THT content), the Silconert treatmentTM2000 is not necessary, but electro-polishing is still necessary.

With TRACEPAK, SOCLEMA offers you all these alternatives: welded or seamless stainless steel 316 L tube, 316 L seamless tube with chemically polished (TrueTube CP), seamless 316 L tube, chemically polished and coated with SilcoNert ™ 2000 (TrueTube FS), seamless 316 L tube, polished and chemically cleaned (TrueTube EP), seamless 316 L tube, treated and coated with SilcoNert ™ 2000 (TrueTube EPS). These tubes can be insulated or equipped with electrical or steam tracing to ensure that the installations are frost-proof or kept at a constant temperature.

SOCLEMA supports you to help you determine which tube is suitable for your application.