The issue of nitrogen purging or vacuuming for liquefied gas transport vehicles prior to leaving the factory
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The technical specifications state that: 1) when nitrogen displacement is used, the oxygen content after treatment is less than 3%, with a residual pressure of 0.05 MPa to 0.1 MPa maintained； 2) When vacuum treatment is used, the vacuum level after treatment should be no less than 0.086 MPa. The transfer gauge also follows the same requirements as the above two points. What is the purpose of nitrogen purging or vacuum treatment before leaving the factory?
The nitrogen purging or vacuuming before leaving the factory is intended to test the sealing performance
I asked two people from the department; one said that vacuuming is done to prevent corrosion and to test the sealing quality, while the other said it is intended to reduce the oxygen level inside the tank in order to avoid explosions. I also checked the regulations regarding mobile pressure vessels, which state that they should be used for storing flammable and explosive substances. Given the toxic properties of liquid ammonia, the technical specifications require that the tank be filled with nitrogen or evacuated
Nitrogen filling is definitely done for explosion prevention; the pressure used in the sealing test is much higher than this
Nitrogen filling or vacuuming are both done to reduce the oxygen content for explosion prevention, right?
When mixed with air, it can explode at a certain concentration; nitrogen is introduced for this reason. Evacuating the air is also done to allow nitrogen to be introduced, as well as to reduce the amount of air inside the tank vehicle – that is, to lower the oxygen level……
That’s right; all tank trucks have this requirement – the filling unit must measure the oxygen content before filling them
Thanks. What is the purpose of measuring the oxygen content, given that the properties of liquid ammonia as a medium represent a moderate level of hazard?
.....Filling is mainly done to prevent air from entering, (as there is pressure inside, higher than atmospheric pressure). 1. Air contains moisture, which can cause rusting inside the tank (this is the case in most situations). 2. For flammable and explosive media, if air gets mixed in—and air contains oxygen—there is a slight safety risk.