LNG Terminal Sample Probes — Liquefaction, Storage, and Regas
Sample probe assemblies for LNG liquefaction trains, cryogenic storage, regasification terminals, and bunkering. Cryogenic-rated materials, BOG sampling, and custody transfer in international LNG trade.
Overview
LNG terminal sampling sits at the intersection of custody transfer accuracy, cryogenic material limits, and the safety regime of international gas trade. The probe must work at -162 °C liquid temperatures, survive thermal cycling between cryogenic and ambient, and deliver a sample that vaporizes representatively for downstream BTU and composition analysis.
Unit-by-Unit
| Unit | Service | Probe consideration |
| Liquefaction train | Hot pretreatment, cold dehydration, cryogenic exchanger | Material grade by temperature zone |
| Storage tank | -162 °C LNG, BOG vapor | Cryogenic 316L or Invar |
| Loading arm | LNG transfer | Insulated cryogenic probe |
| Vaporizer outlet | Warmed natural gas | Standard 316L |
| Bunkering | LNG fuel transfer | Same as loading arm |
Cryogenic Material Selection
At LNG temperatures, ferritic and martensitic steels become brittle. Acceptable materials:
- 316L SS — austenitic structure remains tough at -196 °C; standard cryogenic choice
- 304L SS — also acceptable; slightly lower cost
- Invar 36 — used where thermal contraction must match adjacent materials
- 9% Ni steel — used for tank shells, not for probes
- Aluminum 5083 — used for some cryogenic connectors, not probe tubes
The Vaporization Problem
LNG sampling cannot deliver a representative composition unless the liquid is vaporized completely before reaching the analyzer. Partial vaporization (flashing) preferentially releases methane and ethane, leaving the heavier components in the residual liquid. The composition reaching the analyzer is then biased light, and the BTU is biased low.
The standard solution is a direct-vaporizer probe that:
1. Aspirates LNG into a heated chamber at the probe head
2. Vaporizes the entire aliquot in one pass
3. Delivers warm gas to the sample line at constant pressure
The vaporizer power and flow are sized for complete vaporization at the maximum expected flow.
Standards
- ISO 8943: Sampling of LNG (international)
- GIIGNL Custody Transfer Handbook: Industry consensus practice
- ISO 10715: Natural gas sampling, applies after vaporization
- EN 12838: LNG sampling for analysis
Configurator Defaults for LNG
The SPA Configurator supports cryogenic-rated 316L probes with:
- Vaporizer head option
- Cryogenic-rated PG packing gland sealant
- Insulated jacket option
- ISO 8943 documentation package