Portable Moisture Measurement Ensures Safe and Efficient Operation of LNG Plants
Summary
The LNG value chain — extraction and pre-treatment, transport to a processing facility, liquefaction, and distribution to end users — depends on tight moisture control at every stage. Excess moisture corrodes pipelines, damages compressors and cryogenic heat exchangers, and threatens product quality. A portable aluminum oxide moisture analyzer gives plant staff a practical way to check moisture levels throughout the process, especially during start-ups and maintenance.
Application
Portable analyzers are used to check online instruments and take spot measurements during normal operation and start-ups. Key measurement points across the LNG value chain include:
| Extraction & Drying | TEG (triethylene glycol) contactors at onshore and offshore platforms |
|---|---|
| Processing | Fuel gas dryers and LNG molecular sieve dryer bed outlets |
| Purging | Nitrogen purging of the metal infrastructure to remove ambient moisture |
| Transportation | Metering skids monitoring moisture levels during transport |
| Utilities | Instrument air, nitrogen and other utility gases |
Benefits:
- Improved start-up efficiency
- Enhanced equipment protection
- Accurate and reliable measurement
Challenge
LNG plants must keep moisture under tight control even though conditions are demanding. Moisture levels vary during start-up sequences and after maintenance, and excess moisture accelerates corrosion and damages equipment, driving up maintenance and repair costs. Measuring accurately is itself a challenge in the extreme temperatures and pressures typical of LNG service. Left unchecked, moisture can freeze in the cryogenic section of the plant, causing hydrate formation, flow blockages and higher energy consumption. Because of this, start-up nitrogen purging of the LNG train’s metal infrastructure has to run long enough to remove residual moisture and keep wet gas out of the cryogenic section — but running it longer than necessary costs valuable production time.
Solution
Panametrics PM880 portable aluminum oxide analyzers measure moisture content at various points across the LNG value chain, particularly during start-ups and maintenance, directly at line pressure — so operators see actual process conditions rather than lab estimates. During nitrogen purging, the PM880 is used to confirm in real time when moisture has dropped below approximately 10 ppm, the threshold at which the purge can be considered complete and the LNG process safely started. The analyzer is built to withstand the extreme temperatures and pressures typical of LNG plants and reports moisture as water dew point or in parts per million (ppmv).
Source: Panametrics Application Note PANA004AN (panametrics.com) — © Panametrics LLC. Localized and prepared by INTECH CONTROL, the official Panametrics representative in Slovakia and Hungary.