TOKYO GAS TOP > Technical development > For the stable production of city gas > Waterless LNG Sampling System

Waterless LNG Sampling System


Tokyo Gas has developed, and was the first in the world put into use, a new type of gas sampling system featuring a waterless holder as a replacement for the conventional, widely used water-sealed type used to collect gas samples for analyzing the composition of LNG. The system consists principally of an electrically heated vaporizer and waterless-type holder containing an elastic membrane, and is designed to automate the sampling process without the need for steam.
Waterless-type test unit



Conventional sampling process
New sampling process

Comparison with conventional water-sealed holder system
Item Conventional system New system
Vaporizer type Hot water bath Electric heater
Holder type Water-sealed Waterless(using elastic membrane)
Purging Submersion and bubblin Vacuum
Filling Compressor N2pressure



Performance compared with conventional water-sealed holder type
Item Water-sealed holder type Waterless holder type
  • Melting into water seal is dealt with by bubbling.
  • On a par for precision, with tests revealing no significant difference.
  • Despite possible effects of corrosion due to water use and friction caused by vertical movement of holder, no particular issues even after prolonged use.
  • Intrinsically corrosion-free as waterless
  • Durability tests on the bladder membrane produced good results.
Check Function
  • Sample collection (holder flow and fluid level checked)
  • Sample collection (holder flow and pressure checked)
  • Vacuum level (checks for completion of evacuation and absence of leaks)
  • Difficult to automate handling of water
  • Numerous tasks have to be performed manually
  • Easy to automate
  • Only requires operation via CRT
Ease of maintenance
  • Compressor: once/year Agitator functioning: once/year
  • Vacuum pump: once/year
  • Large water-sealed holder, etc.
  • Need for after-cooler, drain separator, etc. as gas is water saturated
  • Compact
  • Layout configurable according to installation space
  • Steam, industrial water, electricity
  • Electricity, N2
Overall assessment The waterless holder type proves that it is superior to the water-sealed holder type.

Page Top