What are the filling conditions for liquid ammonia trucks after annual inspection?
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Liquid ammonia tank trucks are regularly subjected to annual inspections by the relevant authorities. After the annual inspection, the pressure in such tank trucks is generally around 0.02 MPa, and the oxygen content during gas composition analysis is about 2.3%. I would like to ask the experts: for tank trucks that have undergone such annual inspections, do the aforementioned conditions meet the requirements for refilling with liquid ammonia?
Additional note: The annual inspection for tank trucks is carried out by the only designated agency at the provincial level. After the inspection, nitrogen is used to purge the tanks; however, the purity of this nitrogen may not be very high, with an oxygen content of around 2.3%.
Paragraph 6 of Article 50 of the \"Regulations on Safety Inspection of Liquefied Gas Road Tankers\" stipulates that: \"Newly manufactured road tankers or those that have been overhauled and filled for the first time must be subjected to vacuum treatment, or nitrogen purging, before being filled with flammable or explosive substances. The vacuum level required is not less than 650 mmHg (86.6 kPa), or the oxygen content in the gas inside the tank must not exceed 3%.\" Paragraph 12 of Article 50 states that: \"A residual pressure of not less than 0.1 MPa should be maintained in the tank after gas is unloaded, in order to prevent air from entering the tank.\" Since vacuuming truck-cars requires high-capacity vacuum equipment, the initial investment is large and the operating costs are high. Therefore, in practical operations, three methods are generally used to replace the air inside the tank: evacuating first and then filling with nitrogen; filling directly with nitrogen; or not evacuating and instead exhausting air while filling with nitrogen.