Selection of breather valves for nitrogen-sealed tanks
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For tanks that require nitrogen sealing (storage tanks or intermediate tanks), should the breather valve be unidirectional or bidirectional?
It is best to have bidirectional functionality, in order to avoid vacuum formation in the storage tank due to material discharge
{:3_49:} Since it’s nitrogen-sealed, it’s one-way flow anyway, right? As long as it can release gas, that’s fine; what gets drawn in is nitrogen
If a self-acting control valve fails, then no gas can flow in.
Air can be allowed to enter the tank in both directions, or only in one direction. If concerned about nitrogen seal failures, a dual gas supply can be installed
A unidirectional, open system is bidirectional
With a breathing valve + nitrogen seal, only exhaust occurs; nitrogen is injected when pressure drops
It is best to install a one-way valve, along with a breathing valve that has a slightly higher activation pressure； When the pressure reaches the set pressure of the one-way valve, it is discharged to the exhaust gas absorption system through the one-way valve ； If the single vent valve fails and the pressure continues to rise to the set pressure of the breathing valve, it is discharged through the breathing valve, ensuring that the pressure inside the storage tank remains below its design pressure. When discharging material outward, the nitrogen sealing system supplies nitrogen gas into the tank. If the nitrogen sealing control valve fails and nitrogen gas cannot be supplied properly, as the material continues to leave the tank, the pressure inside the tank drops to the set pressure of the breather valve; at that point, the breather valve draws in air to prevent the storage tank from collapsing.
When a nitrogen sealing system is installed, it is typically equipped with a nitrogen release valve, a nitrogen sealing valve, and an exhaust valve; the nitrogen sealing valve is used to supply nitrogen when the system is under negative pressure； The nitrogen release valve is used to discharge gas from the system when it is overpressured ； The operating pressure of the exhaust valve is slightly higher than that of the nitrogen release valve, serving to provide a secondary pressure relief mechanism ；