119、2000m ³ pre cooling scheme of lng atmospheric tank (3) - doer equipment
classification：industry publishtime：2019-12-17 14:52:40
2000m ³ pre cooling scheme of lng atmospheric tank (3)
main steps of precooling
1. the liquid nitrogen tank car and the low temperature atmospheric pressure tank are connected properly with metal hose, and the tank car is pressurized by self pressurization;
2. the low-temperature nitrogen at the top of the tank car is slowly flushed into the atmospheric tank. at this time, the gas-phase manual and automatic vent valves of the atmospheric tank should be opened to empty the nitrogen;
3. slowly open the liquid valve of the tank car to a smaller opening, close the gas valve of the tank car, and use low-temperature liquid nitrogen for precooling. a small amount of liquid nitrogen should enter from the liquid inlet valve on the atmospheric tank (note: the opening of the valve should be small, because the tank is a "hot tank" for the first filling. if the opening of the valve is large, the pressure of the tank may rise rapidly and cause damage to the tank). in this process, the gas should be continuously discharged to the top gas-phase pipe, and the pressure of the inner tank should not exceed 12kpa.
4. as the precooling process goes on, the temperature of the inner tank decreases continuously until the temperature of the lower part of the inner tank drops below - 100 ℃. the liquid inlet can be appropriately increased to fully precooling the tank.
5. in the process of liquid feeding, the pressure of the storage tank shall be closely observed and recorded to prevent the pressure from rising. close the inlet valve in time when the pressure rises.
6. in the above process, the refilling procedure of re feeding liquid after unloading liquid of a tank car should be carried out according to the above procedure (omitting the preliminary precooling procedure of low temperature gas).
7. when the tank is precooled to a certain extent, liquid will start to accumulate in the tank, leaving a small amount of liquid to fully precooling the pipelines in the system.
8. at the end of the above process, stop feeding liquid and precooling.
what should be checked during precooling
1. check the material and weld of the outer pipeline for cracks and other damage;
2. because the bolt may reduce the preload doer to cold shrinkage, there will be leakage at the flange connection. therefore, it is necessary to focus on leak detection and cold tighten the flange;
3. check the sealing and flexibility of low temperature valve, and check whether it is frozen;
4. fastening pipe support;
5. after precooling and cold tightening are completed and qualified, the external pipeline can be insulated and wrapped.
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