Gas was detected in the interlayer of the LNG storage tank – how to address this?
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Flammable gas was detected in the interlayer of the LNG storage tank. A combustible gas detector is used at the sampling port in the LNG tank interlayer to provide immediate alarm. Subsequent sampling and analysis revealed that the interlayer contained 0.1% methane, over 98% nitrogen, and slightly 1% oxygen. . . To solve this problem, it is necessary to remove the interlayer pearlescent sand and then empty the large tanks in the plant. The key issue is that the LNG storage tanks are fully welded, so how can the leakage point be located?
It is recommended to analyze after replacement; one should not jump to the conclusion that there is a leak. It is necessary to analyze the methane content and nitrogen purity of nitrogen before displacement,,,,. Also, to check if there is a problem with the pressure in the interlayer, start by examining the exterior. After confirmation, even if it’s unnecessary, a disassembly inspection must be carried out.
Thank you; it’s great that this approach was brought to my attention. Thank you so much
I would like to ask, in a vacuum environment, what technique do you use for sampling the interlayer?
Isn’t there a sampling port at the bottom of the large tank?
A vacuum can only be used to measure the vacuum level; sampling is not possible. Ours uses pearlescent sand and a nitrogen interlayer; all of them are equipped with sampling ports
Understood: handshake
It is recommended to increase the nitrogen flow rate in the interlayer, and then continue to take samples for analysis over a few days. A methane level of 0.1% does not necessarily indicate a leak; moreover, if there is a sand hole, it may not be possible to detect it even if the storage tank is emptied. It’s sufficient to take samples and monitor daily
There are two considerations: one is nitrogen protection, as flammable gases can enter the nitrogen system and then proceed to the interlayer of the cryogenic tank. On the other hand, if there is a leak in the inner lining of the storage tank, observing the outer wall of the tank shows that such a leak usually causes frosting or sweating on the outer wall of the tank.