Some questions regarding the openings of LNG storage tanks
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This is my first time dealing with LNG storage tanks (double-layer, low-temperature, at normal pressure, with a capacity of 10,000 cubic meters), and I have some questions I’d like to ask the experts out there. My QQ number is 996479994. 1. Pressure relief valves and guide ports for these valves are installed on the top of the LNG storage tank. Does this mean that pilot-operated pressure relief valves should be used? I’ve never seen pilot-operated pressure relief valves with a DN600 size 2. Can the gas returned by the loading system go directly to the inlet of the cryocooler for compression and liquefaction before being sent back to the storage tank? Is it still necessary to return directly to the LNG tank? 3. What is the purpose of the air outlet installed on the pump well? 4. The outer tank of the LNG tank is equipped with pressure equalization ports at its top and bottom – is this done to ensure that the pressures on the upper and lower sides are equal? 5. Is it necessary to install differential pressure gauges on the inner and outer tanks? To monitor the pressure difference between the inner and outer tanks.
1. A normal pilot-operated setup is fine; it seems that in the past there were issues with the pressure control valve. 2. Regarding this chiller inlet, you are referring to the BOG compressor, right? Generally, it goes back to the storage tank and then the BOG is processed further. The exact principle isn’t clear, but when parking, you can only return to the storage tank and empty it. 3. I hadn’t noticed this; could you provide the drawings? 4. It’s probably to take into account layering and stirring. 5. A dedicated differential pressure gauge might not be necessary; there must be a pressure gauge inside, and nitrogen is likely used on the outside, so the pressure should be visible as well. Could you please send a private message to let me know which project it is? It feels like there’s a connection.
1. The pressure relief valves and the guide ports for these pressure relief valves located on the top of the LNG storage tank are actually vent holes. 2. Part of it returns to the LNG tank via reflux, while part is supplemented to the pipeline through a BOG compressor to be circulated and compressed. 3. A gas outlet is provided on the pump well; it serves as the inlet for air to enter the pipeline, and there is also a small exhaust outlet. 4. A pressure balance valve is installed at the bottom of the LNG tank, used to control and balance the pressures at different liquid levels. 5. Differential pressure gauges equipped with nitrogen are used for insulation of the inner and outer tanks, primarily to monitor the nitrogen pressure. Upon detecting a pressure difference in the nitrogen within the insulation layer in the control room, it began to replenish nitrogen into the nitrogen generation system.
May I ask why, in some tanks, the inner and outer tanks are connected via a gas phase, and why there is even a pressure difference gauge?