Facility Diagnostics for LNG TerminalsTokyo has been using LNG as feedstock for city gas for more than 40 years, ever since Japan’s first imports arrived at the Negishi LNG Terminal in Yokohama in 1969. In that time, we have become experienced at operating and maintaining a range of city gas production facilities at several LNG terminals, and have used this extensive experience to develop and introduce facility diagnostics suited to LNG facility maintenance. Here are some examples of the technologies developed.
SCC inspection technology for stainless steel pipes
LNG terminals use pipes and containers made of stainless steel (18Cr-8Ni stainless steel). As this material is subject to stress corrosion cracking (SCC), many facilities have to be regularly inspected, which is expensive. Based on our maintenance experience, therefore, we optimized procedures such as the following to ensure safety while reducing the cost of SCC inspections:
- Identification and targeted inspection of parts prone to SCC
- Non-destructive methods of testing each part inspected
- Response grading and continuous monitoring methods
Management of operational life of LNG pumps
LNG pumps play a crucial role in sending out city gas at high pressure. As they operate non-stop throughout the year, the vibration of their bearings is continuously monitored to detect abnormalities caused by pump degradation and failure. The vibration data obtained is analyzed using a database that correlates past vibration data with abnormalities so as to determine whether pump maintenance is required. This makes it possible to determine the best time for maintenance based on the state of each pump, allowing pumps to be overhauled before they fail and so bringing down maintenance costs and contributing to the stable supply of city gas.
Inspection for crevice corrosion of stainless steel piping
Depending on the operating conditions, crevice corrosion can occur on the external surfaces between stainless steel pipes and their supports. However, pipes in confined spaces cannot normally be easily inspected. Tokyo Gas has therefore developed and introduced a stainless steel pipe crevice corrosion inspection device to check on the state of corrosion.
〔Probe for inspection device〕
Internal observation of LNG tanks
LNG is a very low temperature (-160℃) flammable liquid, and is stored in tanks in complete isolation from the atmosphere. Conventionally, therefore, their interiors have been hard to observe. Now, however, Tokyo Gas has developed the world’s first submersible LNG tank observation device in a compact, lightweight package, which enables visual inspection of the inside of the tank. This has been deployed at Tokyo Gas’s Sodegaura and Negishi LNG Terminals.
〔Submersible observation system〕