The LNG storage tank is a double-walled structure, comprising an inner tank, outer tank, internal and external supports, insulation layer, pressure safety system, vacuum pump, piping system, and more. All vacuum-type insulation structures rely on vacuum. Due to the high degassing rate and suction resistance of the insulation space materials, and the limitation that the baking temperature of the sealing materials cannot be too high and the degassing must be slow, suction is challenging. To achieve the required vacuum level within the design-specified suction time, in addition to the vacuum pump and suction process, it also depends on the flow area of the annular suction pipes. To ensure a high vacuum level and improve the suction rate, a vacuum pump is installed at both ends of the equipment. One vacuum pump consists of three suction pipes, placed in the lower annular space and leading out from the bottom, while the other vacuum pump, also with three suction pipes, is positioned in the upper annular space and leads out from the top. The two sets of suction pipes cross and overlap along the length of the tank. By increasing the flow area of the suction pipes and using various auxiliary methods such as heating and nitrogen displacement, the vacuum achievement time for the annular insulation space with a volume of 100m³ is reduced to one-third of the time required for conventional structures.
When the low-temperature storage tank is in operation, there are potential dangers such as leaks, overpressure, and explosions. If the hidden dangers before these accidents are not discovered and addressed in time, they can escalate into severe incidents. Therefore, establishing a comprehensive inspection system and strictly enforcing it is crucial for ensuring the safe operation of the low-temperature storage tank.
When the low-temperature storage tank is in operation, there are potential hazards such as leaks, overpressure, and explosions. If the hidden dangers before these accidents are not discovered and addressed in time, they can escalate into severe incidents. Therefore, establishing a comprehensive inspection system and strictly enforcing it is crucial for ensuring the safe operation of the low-temperature storage tank. Daily inspections of the low-temperature storage tank mainly include the following:
1. Are there any leaks in the valves and piping, and is there any frosting or sweating on the casing?
2. Are all valves in normal open/close status?
3. Are the instruments (level gauges, pressure gauges) functioning properly, and do the DCS display parameters match the field primary meters?
4. Ensure the storage tank pressure is normal. Release pressure by opening the vent valve when the pressure approaches or equals the maximum pressure.
5. Is the liquid fill rate over 95%?
6. Is the sealed gas normal for atmospheric pressure powder insulation storage tanks? (50mmH2O)
7. No flammable, explosive materials or any debris shall be placed near the liquid oxygen storage tank, with clear signage.
8. No smoking or open flame near the liquid oxygen storage tank.
9. Test the acetylene and total hydrocarbon content in the liquid oxygen storage tank at least once a week. The acetylene content must not exceed the specified process standards; if it does, liquid oxygen must be discharged and replaced immediately for treatment.
10. Is the liquid oxygen storage tank properly grounded?
11. Ensure there is a certain amount of liquid inside the drum if it's not to be left unused for long periods, to avoid spending a significant amount of time re-cooling and replacing the drum.
12. Check for leg damage, foundation settlement, tilt, or cracking, the condition of the fastening bolts, and whether the tank has deformed.
13. Regularly check the vacuum level of the storage tank.
