TOKYO GAS TOP > Technical development > Earthquake disaster prevention & stable supply > Compact, Lightweight Submergible Observation Device for LNG Tanks

Compact, Lightweight Submergible Observation Device for LNG Tanks

This small-size and lightweight observation device enables remote “eyeball” inspection of the inside of LNG storage tanks, and is capable of operating at minus 162 degree C while submerged in LNG. It was awarded the Japan Gas Association Technical Prize in 2001.



Tokyo Gas first introduced LNG from Alaska into Japan in 1969. Since then, not only Tokyo Gas but also lots of gas and power companies constructed inground LNG tanks and/or above-ground ones and they have been operating them so far. Some of the tanks, however, have been getting older. For use in such tanks, Tokyo Gas developed and introduced the world's first small-size and lightweight submergible observation device for visual checks of inside of the tanks.



  • It is so small and lightweight that it can be handled using human power alone.
  • Only one week is required for observation (including preparation and restoration works).
  • It has sufficient durability to withstand the heat cycle from normal temperature to the temperature of LNG (-162°C).
  • It can record observation date, time, position identification, etc. on screen for data analysis.


This device mainly consists of a camera unit, lighting unit, and control unit. The camera unit and lighting one are hung in a tank with cables through spare nozzles of the tank, and the cables made to go up and down by human power for the purpose of vertical positioning. For directional control during observations, the entire camera unit can be panned to view the circumference of the tank, while a mirror with a tilt mechanism is used for vertical observation adjustments. The control unit and cable receipt stands are set outside the tank. Monitoring of the image and operation adjustments of the camera unit and lighting unit are performed using this control unit.
System overview
System of submergible observation device
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This device has been introduced and is being used in maintenance work at Tokyo Gas’s Sodegaura and Negishi LNG Terminals. It is also being used during cooldown of new tanks at the Ohgishima LNG Terminal, where it is helping to make startup work safer and more reliable.

Appearance of main unit

Observation image (in LNG)

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