Nitrogen seal valve

There’s a lot of information on this topic at 100 degrees: http://baike.baidu.com/link?url=AGVA1NvN-ZUoFJ5Y8YLbfHsWb6QNILociBUHbju_DEn1Ljt_KABKKKqPrbtCK_W7YjmbXh-G1MvpQUOsyiM0iF5adyJ-gCgph--Wc7AFh_FhNkONPUJ64L0e2PkmTgFRHExEaqcprzcGikyj4bFOJa. There are many explanations available on Baidu Baike as well as in Baidu Wenku

There are many on Baidu; you can look up specific information to take a look – there’s a lot of content available on this topic

I don’t know the principle behind it, but it works well

The pressure behind the valve is controlled by springs; generally, the pressure behind domestic valves is kept at around 2 KPa, while imported nitrogen seal valves maintain a pressure of less than 500 Pa

It is the internal spring that controls the amount of air intake

Working principle of the nitrogen sealing system: When the liquid discharge valve of the storage tank is opened and the user releases liquid, the liquid level drops, the volume of the gas phase increases, and the pressure of nitrogen inside the tank decreases. As a result, the nitrogen supply valve opens, allowing nitrogen to be injected into the tank; this raises the nitrogen pressure inside the tank. When the pressure inside the tank reaches the set value specified for the nitrogen supply valve, it automatically closes. When the liquid inlet valve of the tank is opened to add material to it, the liquid level rises, the volume of the gas phase decreases, and the pressure increases. When this pressure exceeds the set value of the nitrogen release valve, the valve opens and releases nitrogen to the outside, causing the nitrogen pressure inside the tank to drop. Once the pressure falls to the set value of the nitrogen release valve, the valve closes automatically. Instructions for selecting valves: The nitrogen seal valves manufactured by Fuyang Paiwo Valve Industry are designed to operate with a nitrogen supply pressure of around 300–800 KPa. The set pressure for the nitrogen seal is 1 KPa, the nitrogen release pressure is 3 KPa, the exhaust pressure of the breather valve is 5 KPa, and the intake pressure is –0.8 KPa. (Note: The nitrogen pressure at the inlet of the nitrogen supply valve must be ≥300 KPa) ； When it is below 300 KPa, the nitrogen supply valve does not function ； When the inlet pressure of the nitrogen supply valve is zero, the nitrogen supply valve is in the open state. For the nitrogen supply valve, the inlet nitrogen pressure must be ≤1 MPa. When the nitrogen pressure is ≥1 MPa, a ZZY type self-acting pressure reducing valve should be installed in front of the nitrogen supply valve to reduce the pressure. The roof vent valve serves only a safety purpose; it comes into action when the main valve fails, causing the pressure inside the tank to become too high or too low. It does not function under normal conditions ； The nitrogen release valve is installed on the top of the tank, and its diameter is generally the same as that of the liquid inlet valve ； Generally, the ZZDG type is used for nitrogen supply valves, the ZZDX type for nitrogen release valves, and the ZZFX type of explosion-proof flame-retardant breather valve is used for breather valves.